JP2510668B2 - Liquid crystalline compound, liquid crystal composition containing the same, and liquid crystal device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal composition containing a novel liquid crystal compound and a liquid crystal device using the liquid crystal composition.

[Conventional technology]

As a conventional liquid crystal element, for example, M.Chat (M.
Schadt) and W. Helfrich,
"Applied Fusion Letters"("Applied
Physics Letters ") Volume 18, Issue 4 (Published February 15, 1971), pages 127-128," Voltage Day Pendant Optical Activity of a Twisted Nematic Liquid Crystal ". (“Volt
age Dependent Optical Activity of a Twisted Nemati
It is known to use Twisted Nematic liquid crystal shown in "C Liquid Crystal"). However, this TN liquid crystal is used for time-division driving using a matrix electrode structure with high pixel density. However, the number of pixels is limited because of the problem of crosstalk.

Further, since the electric field response is slow and the viewing angle characteristic is poor, its use as a display is limited.

Further, since the electric field response is slow and the viewing angle characteristic is poor, the use as a display is limited.

Further, there is known a display element of a system in which a switching element formed of a thin film transistor is connected to each pixel, and each pixel is switched.However, the step of forming the thin film transistor on the substrate is extremely complicated, and a large area display element is used. There are problems that are difficult to create.

In order to improve the drawbacks of the conventional liquid crystal device, the use of a liquid crystal device having bistability has been proposed by Clark and Lagerwall (Japanese Patent Laid-Open No. 56-107216). U.S. Patent No. 4,367,9
24, etc.). A liquid crystal having bistability is generally a chiral smectic C phase (SmC ^* ) or H phase (Sm
Ferroelectric liquid crystals with H ^* ) are used.

This ferroelectric liquid crystal has a very fast response speed due to its spontaneous polarization, and can express a bistable state with a memory property, and is also excellent in viewing angle characteristics. Suitable as a display material for screens.

Since the material used as the ferroelectric liquid crystal has asymmetric carbon, it is used not only as the ferroelectric liquid crystal utilizing its chiral smectic phase but also as the following optical element. be able to.

1) Using the cholesteric / nematic phase transition effect in the liquid crystal state [JJWysoki, A.Adams and W.Haas; Ph]
ys.Rev.Lett.), 20,1024 (1968)], 2) Utilizing the White-Taylor type guest-host effect in the liquid crystal state [DL White, GM Taylor, “Journal of Applied”]
Wikis "(DL White and GNTaylor; J.Appl.Ph
ys.), 45 , 4718 (1974)], etc. are known. Although detailed description of each method is omitted, it is important as a display element or a modulation element.

In the method using the electric field response optical effect of the liquid crystal, it is considered preferable to introduce a polar group in order to enhance the response of the liquid crystal. In particular, in a ferroelectric liquid crystal, it is known that the response speed is proportional to the spontaneous polarization, and it is desired to increase the spontaneous polarization for speeding up. From such a point, P. Kelle
r) et al. showed that by introducing a chlorine group directly into the asymmetric carbon, the spontaneous polarization can be increased and the response speed can be increased [CR Academy Science (CRAc
ad.Sc.Paris), 282 C, 639 (1976)].

However, the chlorine group introduced into the asymmetric carbon is chemically unstable and has a drawback that the stability of the liquid crystal phase is deteriorated due to its large atomic radius, and improvement thereof is desired. There is.

On the other hand, a functional material required for an optical element characterized by having optical activity is often synthesized through an optically active intermediate itself, but as an optically active intermediate used conventionally, 2 -Methyl butanol, 2-octyl octyl alcohol, secondary butyl alcohol, p- (2-methylbutyl) benzoic acid chloride, secondary phenethyl alcohol, amino acid derivatives, camphor derivatives, cholesterol derivatives, etc. The polar group was rarely introduced into the intermediate. For this reason, the method of increasing spontaneous polarization by directly introducing a polar group into an asymmetric carbon atom has not been used very effectively.

[Problems to be solved by the invention]

The present invention has been made in view of the above points. That is, the present invention is directed to a liquid crystal compound whose polarity is enhanced by directly introducing a fluorine group which is stable and has a large dipole moment into an asymmetric carbon atom, and an electric field responsiveness of a liquid crystal by containing at least one thereof. An object of the present invention is to provide a liquid crystal composition having improved liquid crystal and a liquid crystal device using the liquid crystal composition.

[Means for Solving Problems] and [Operation] The present invention has been made to achieve the above object, and the first invention is represented by the following general formula (1). (In the formula, R ₁ is an alkyl group having 1 to 18 carbon atoms, R ₂
Is an alkyl group having 5 to 12 carbon atoms, X is a single bond,
-O-, Selected from, Y is a single bond, -CH ₂ O-or -OCH ₂ - it is either.

, K and mn are independently selected from 0 or 1,2, and k + m + n is a number of 2 or 3. C ^* represents an asymmetric carbon atom) and is a liquid crystal compound represented by the formula.

The second invention relates to a liquid crystal composition containing at least one liquid crystalline compound represented by the general formula (1).

Furthermore, the third invention relates to a liquid crystal element characterized by using a liquid crystal composition containing at least one liquid crystalline compound represented by the general formula (1).

 Hereinafter, the present invention will be described in detail.

The liquid crystal compound represented by the above general formula (1) of the present invention is preferably shown in the specification of the application filed by the present applicant on April 14, 1988.

It is synthesized from an optically active 2-fluoroalkanol represented by the following general formula (2).

(In the formula, R ₂ and C ^* are as defined above.) Next, the main synthetic routes thereof are shown.

When Y is a single bond Y is Or for -CH ₂ O- However, in the above formula, R ₁ , R ₂ , Is as defined above.

 Examples of compounds that can be produced as described above are shown below.

The liquid crystal compound of the present invention is characterized in that the fluoroalkane of the optically active group in the general formula (1) contains an ether bond. Therefore, when the liquid crystal composition is prepared, the ether bond is different from that in the optically active group portion. Sc ^{* in the} area
The temperature range of the phase is widened, and a liquid crystal composition having a fast electric field response speed even near room temperature can be obtained.

The liquid crystal composition of the present invention contains at least one liquid crystalline compound represented by the general formula (1) as a blending component. For example, the liquid crystalline compound
When combined with a ferroelectric liquid crystal represented by the following formulas (1) to (13), the spontaneous polarization is increased and the response speed can be improved.

In such a case, the liquid crystal compound represented by the general formula (1) of the present invention is added to the obtained liquid crystal composition in an amount of 0.1 to 9
It is preferably used in a proportion of 9% by weight, particularly 1 to 90% by weight.

Further, by mixing the liquid crystalline compound represented by the general formula (1) of the present invention with a smectic liquid crystal which is not itself chiral as shown by the following formulas (14) to (18), ferroelectricity can be improved. A liquid crystal composition that can be used as a liquid crystal is obtained.

In this case, the liquid crystal compound represented by the general formula (1) is
It is preferable to use 0.1 to 99% by weight, particularly 1 to 90% by weight of the obtained liquid crystal composition.

Such a liquid crystal composition can obtain a large spontaneous polarization resulting from the content of the liquid crystal compound of the present invention.

Here, the symbols indicate the following phases, respectively.

Cryst .: crystalline phase, SmA: smectic A phase, SmB: smectic B phase, SmC: smectic C phase, N: nematic phase, Iso: isotropic phase, and the liquid crystalline compound represented by the general formula (1) of the present invention By using a liquid crystal composition containing at least one of the above, it is possible to obtain a liquid crystal element such as a ferroelectric liquid crystal element or a twisted nematic liquid crystal element.

〔Example〕

 The present invention will be described in more detail with reference to the following examples.

Example 1 Optically active 5-dodecyl-2- [4 '-(2 "
Preparation of -Fluoro-3 "-pentyloxypropyloxy) phenyl] pyrimidine Optically active 5-dodecyl-2- [4'- according to the following steps
(2 "-Fluoro-3" -pentyloxypropyloxy) phenyl] pyrimidine was prepared.

Step 1) Preparation of (+)-p-toluenesulfonic acid 2'-fluoro-3'-pentyloxypropane (-)-2-Fluoro-3-pentyloxypropanol 0.32 g and pyridine 0.5 ml are stirred in a Nasflask. ,
Add 0.27 g of p-toluenesulfonic acid chloride and add 20 ° C.
After reacting by stirring for 6 hours below, diluted hydrochloric acid was added to make an acidic solution, which was then extracted with diethyl ether. The obtained ether solution was washed with water and then dried over sodium sulfate. After distilling off the solvent, the residue was purified by thin film chromatography (developing solvent: benzene) to give 0.14
g of (+)-p-toluenesulfonic acid 2'-fluoro-
3'-Pentyloxypropane was obtained.

NMR spectrum 0.5-2.0ppm m. (9H), 2.4ppm s. (3H) 3.3-5.3ppm m. (7H), 7.2-7.8ppm q. (4H) Step 2) (+)-5-dodecyl-2 -[4 '-(2 "-
Preparation of fluoro-3 ″ -pentyloxypropyloxy) phenyl] pyrimidine Sodium hydride (60%) 0.02 g 5-dodecylpyrimidyl-2- (p-phenol) 0.16 g, (+)-
0.14 g of p-toluenesulfonic acid 2'-fluoro-3'-pentyloxypropane was placed in a round-bottomed flask and heated under reflux in dimethylformamide for 4 hours. After completion of the reaction, hydrochloric acid was added to acidify the mixture and diethyl ether was used. Extracted. The obtained ether layer was washed with water and then dried over sodium sulfate. After the solvent was distilled off, the residue was purified by thin layer chromatography (developing solvent: dichloromethane), 0.16
g of (+)-5-dodecyl-2- [4 '-(2 "-fluoro-3" -pentyloxypropyloxy) phenyl] pyrimidine was obtained.

NMR spectrum 0.7-2.0ppm m. (30H), 2.4-2.7kppm t. (2H) 3.3-5.3ppm m. (7H), 6.8-8.5ppm q. (4H) 8.5ppm s. (2H) Specific rotation ▲ [α] ²³ _D ▼ ＋ 1.3, ▲ [α] ²³ ₄₃₅ ▼ ＋ 2.9
(C0.91CHCl ₃ ) Phase transition temperature (℃) However, S1, S2, S3, S4, and S5 are unidentified liquid crystal phases, Cryst is a crystal, and Iso is an isotropic liquid.

Example 2 Optically active 4-dodecyloxybenzoic acid 4'-
Production of [2 ″ -fluoro-3 ″ -hexyloxy) propyloxy] phenyl ester Optically active 4-dodecyloxybenzoic acid 4 ′-[(2 ″ -fluoro-3 ″ -hexyloxy) propyloxy according to the following steps: ] The phenyl ester was prepared.

Step 1) Production of (+)-p-toluenesulfonic acid 2'-fluoro-3'-hexyloxypropane (-)-2-fluoro-3-hexyloxypropanol 1.2 g and pyridine 2 ml are stirred in a round bottom flask. Then, 1.3 g of p-toluenesulfonic acid chloride was added thereto, and the mixture was stirred at 20 ° C. or lower for 2 hours to cause a reaction, then diluted hydrochloric acid was added to form an acidic solution, and the mixture was extracted with diethyl ether. The obtained ether solution was washed with water and then dried using sodium sulfate. After the solvent was distilled off, the residue was purified using silica gel column chromatography (mobile phase: CH ₂ Cl ₂ / hexane = 1/1 mixed solvent). As a result, 0.26 g of (+)-p-toluenesulfonic acid 2 ′ was obtained. -Fluoro-3'-hexyloxypropane was obtained.

NMR spectrum 0.7-1.8ppm m. (11H), 2.5ppm s. (3H) 3.2-5.1ppm m. (7H), 7.2-7.8ppm q. (4H) Specific rotation ▲ [α] ³¹ _D ▼ + 6. 8, ▲ [α] ³⁰ ₄₃₅ ▼ (c2, diethyl ether) Step 2) Production of Optically Active p-Benzyloxy [(2'-fluoro-3'-hexyloxy) propyloxy] phenyl Phosphorus sodium hydroxide 0.034 g, p-benzyloxyphenol 0.160 g, and ethanol 1 ml were added, and the solution was dissolved into 1 ml ethanol (+)-p-toluenesulfonic acid 2'-fluoro-3'-.
Hexyloxypropane (0.26 g) was added, and the mixture was heated under reflux for 5.5 hr to cause a reaction, and then 2N HCl poured into ice water was added to acidify the mixture, followed by extraction with diethyl ether. The obtained ether layer was washed with 5% saline and then dried over sodium sulfate. The solvent was distilled off, and the residue was purified by silica gel column chromatography (mobile phase: CH ₂ Cl ₂ ).
The desired optically active p-benzyloxy [(2'-fluoro-3'-hexyloxy) propyloxy] phenyl is
0.23 g (yield 80%).

Step 3) Production of optically active p-[(2'-fluoro-3'-hexyloxy) propyloxy] phenol Optically active p-benzyloxy [(2'-fluoro-
3'-hexyloxy) propyloxy] phenyl 0.23
Dissolve g in 3 ml of ethanol and add 5% palladium /
After adding 40 mg of activated carbon, reduction was carried out by stirring with a catalytic hydrogenation device at 30 ° C. for 3 hours. After the reaction was completed, palladium / activated carbon was removed by fold filtration, and the solvent was distilled off to obtain 65 mg of the desired product, optically active p- [2'-fluoro-3'-hexyloxy) propyloxyphenol.

Step 4) Optically active 4-dodecyloxybenzoic acid 4'-
Preparation of [(2 "-fluoro-3" -hexyloxy) propyloxy] phenyl ester 85 mg p-dodecyloxybenzoic acid and 1 ml thionyl chloride
By heating under reflux for 2 hours, p-dodecyloxybenzoic acid chloride was obtained. After distilling off excess thionyl chloride, the optically active p-[(2'-fluoro-
3'-hexyloxy) propyloxy] phenol 65
g and 62 mg of triethylenediamine were added dropwise to a solution of 1 ml of dry benzene. 50 ° C
After stirring for 2 hours, 15 mg of sodium hydroxide (60%)
In addition, the mixture was heated and refluxed for another 2 hours. After completion of the reaction, the mixture was poured into cold water, acidified with dilute hydrochloric acid and then extracted with diethyl ether. The obtained organic layer was washed with brine, dried by adding sodium sulfate, and the solvent was distilled off. Purification using thin layer chromatography (developing solvent: dichlorohetane), recrystallization with a mixed solvent of hexane and ethanol, and the desired product of optically active 4-dodecyloxybenzoic acid 4 '-[(2 "-fluoro -3 ″ -hexyloxy) propyloxy] phenyl ester was obtained in a yield of 35 mg.

Phase transition temperature (℃) However, Sc ^* represents a chiral smectic C phase, and the others are as defined above.

Spontaneous polarization (nC / cm ² ) 15.4 [59 ° C.] 21.9 [58 ° C.] Example 3 The compound of Example 1 and the following liquid crystal compound A were mixed at a ratio of 2: 8 to obtain a liquid crystal composition. .

Covering the electrodes with the above liquid crystal compound A and the liquid crystal composition,
A liquid crystal element having a liquid crystal layer thickness of 5 μm was produced by sandwiching the polyimide coating between a pair of electrode substrates that were rubbed. Using this liquid crystal element, a peak-to-peak voltage of 8 V was applied to detect the optical response under orthogonal Nicols, and the response speed was measured.

The results of the phase transition temperature and the response speed of the liquid crystal compound A and the liquid crystal composition are shown below.

Liquid crystal compound A Response speed 12.5μs (55 ℃) (| Tc -T | = 7 ℃) ※ | Tc-T | is obtained taking the difference between the actual temperature and S _A -Sc ^* transition temperature.

Liquid crystal composition I Response speed 10.5 μs (49 ° C.) (| Tc−T | = 7 ° C.) From the above results, by mixing the liquid crystal compound of Example 1 with the liquid crystal compound A, the temperature range of Sc * was close to room temperature. It was found that it spreads and the response speed also improves.

Example 4 Using the liquid crystal compound A and the liquid crystal composition I of Example 1,
A liquid crystal element was produced under exactly the same conditions as in Example 1 except that the cell thickness was 10 μm.

When the temperature of each liquid crystal element was lowered from the isotropic phase at 1 ° C./min and the temperature was set to | Tc−T | = 10 ° C. and observed by a polarizing microscope, both liquid crystal compound A and liquid crystal composition I were observed. The orientation of the monodomain was uniform.

Next, when a pulse having a pulse width of 1 ms and a voltage of 20 V was applied to each element, in the case of the liquid crystal compound A, a bistable state was not obtained, and crystallization occurred immediately after the pulse application.

On the other hand, in the case of the liquid crystal composition I, a bistable state is obtained,
When the tilt angle was measured, it was 12 °.

Further, when the same operation was performed for the liquid crystal composition I at a temperature of | Tc−T | = 15 ° C., a good bistable state was obtained. When the tilt angle was measured, it was as large as 20 ° and a high contrast state was obtained.

From this, it was found that the liquid crystal composition I can obtain a good bistable state and a high contrast ratio even when a liquid crystal device having a cell thickness as thick as 10 μm is formed.

Example 5 The following compounds were mixed in the following composition ratio to obtain a liquid crystal composition II.

Next, the above composition II and the compound of Example 2 were mixed at a ratio of 95: 5 to obtain a liquid crystal composition III.

Liquid crystal compositions II and III were used, and under the same conditions as in Example 3, except that the cell thickness was set to 2 μm, liquid crystal elements were produced, and the peak to peak voltage was set to 20 V. The response speed was measured.

 The response speed measurement results at 25 ° C are shown below.

Liquid Crystal Composition II 250 μs Liquid Crystal Composition III 197 μs Based on the above results, the compound of the present invention, 4-dodecyloxybenzoic acid-4 ′-[(2 ″-
It was found that the response characteristics were improved by mixing the fluoro-3 ″ -hexuloxy) propyloxy] phenyl ester.

Examples 6 to 10 Liquid crystal compositions II and the following compounds were mixed at a ratio of 95: 5 to obtain liquid crystal compositions. Using these liquid crystal compositions,
A liquid crystal element was prepared in the same manner as in Example 5, and the response speed was measured at 25 ° C. in the same manner. The results are shown below.

From the above results, it was found that the response characteristics were improved by mixing the compound of the present invention with the liquid crystal composition II.

Example 11 As a transparent electrode, using a polyimide resin precursor (Toray Industries, Inc. SP-510) on a glass substrate on which an ITO film was formed,
After forming a film by spinner coating, it was baked at 300 ° C. for 60 minutes to form a polyimide film. Next, this coating was subjected to orientation treatment by rubbing, and cells were prepared so that the rubbing treatment axes were orthogonal to each other (cell spacing 2 μm).

A nematic liquid crystal composition [Rixon GR-63: manufactured by Chitso Corp., biphenyl liquid crystal mixture] was injected into the above cell, and TN was injected.
A (twisted nematic) cell was observed with a polarizing microscope, and it was found that a reverse domain (striped pattern) was generated.

When a liquid crystal mixture obtained by adding the fluoroalkane derivative (1 part by weight) of Example 2 of the present invention to Rixon GR-63 (99 parts by weight) was observed as a TN cell in the same manner as above, a reverse The domain was not seen and the nematic phase had good homogeneity. From this, it was confirmed that the liquid crystal compound of the present invention is effective in preventing the reverse domain.

〔The invention's effect〕

As described above, according to the present invention, the polarity can be enhanced by directly introducing the fluorine group into the asymmetric carbon atom of the liquid crystal compound. Furthermore, since the optically active group has an ether bond, the temperature range of the Sc ^* phase of the liquid crystal composition containing it extends to the low temperature side. Therefore, a liquid crystal element using the liquid crystal composition can be driven near room temperature and has a high response speed.

Further, by incorporating the liquid crystal compound of the present invention into the liquid crystal composition, it is possible to prevent the occurrence of reverse domains in nematic liquid crystals.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C07C 69/96 9546-4H C07C 69/96 Z C07D 239/26 C07D 239/26 C09K 19/12 9279-4H C09K 19/12 19/20 19/20 19/30 19/30 19/34 19/34 G02F 1/13 500 G02F 1/13 500 // C07M 7:00 C07M 7:00

Claims (3)

(57) [Claims] 1. A liquid crystal compound represented by the following general formula (1): (However, in the above formula, R ₁ is an alkyl group having 1 to 18 carbon atoms, R ₂ is an alkyl group having 5 to 12 carbon atoms, X
Is a single bond, -O-, Selected from, Y is a single bond, -CH ₂ O-or -OCH ₂ - it is either. , K, m, n are independently selected from 0 or 1,2, and k + m
+ N is a number that becomes 2 or 3. C ^* represents an asymmetric carbon atom) 2. A liquid crystal composition containing at least one liquid crystal compound represented by the following general formula (1). (However, in the above formula, R ₁ is an alkyl group having 1 to 18 carbon atoms, R ₂ is an alkyl group having 5 to 12 carbon atoms, X
Is a single bond, -O-, Selected from, Y is a single bond, -CH ₂ O-or -OCH ₂ - it is either. , K, m, n are independently selected from 0 or 1,2, and k + m + n is a number 2 or 3. C ^* represents an asymmetric carbon atom) 3. A liquid crystal device using a liquid crystal composition containing at least one liquid crystal compound represented by the following general formula (1). (However, in the above formula, R ₁ is an alkyl group having 1 to 18 carbon atoms, R ₂ is an alkyl group having 5 to 12 carbon atoms, X
Is a single bond, -O-, Selected from, Y is a single bond, -CH ₂ O-or -OCH ₂ - it is either. , K, m, n are independently selected from 0 or 1,2, and k + m + n is a number 2 or 3. C ^* represents an asymmetric carbon atom)