JPH0667879B2 - Liquid crystalline compound, composition thereof and optical switching device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound, a liquid crystal composition and an optical switching element, and more particularly to an optical switching element having ferroelectricity. The present invention relates to a material which is most suitable for displaying a high-speed moving image such as a television because it has applicability to a liquid crystal display element which is particularly excellent in responsiveness and memory property as compared with the liquid crystal material.

[Prior Art] Liquid crystal display elements are widely used as various display elements because they have excellent features such as low voltage drivability, low power consumption, thin display capability, and light-receiving type that do not cause eye strain. It is used.

At present, the most commonly used display system uses a nematic liquid crystal called Twisted Nematic type (TN type) as a material. However, this TN type liquid crystal display element has the drawback that the response speed is slower than that of a light emitting diode, electroluminescence, etc. while having the above-mentioned excellent characteristics, and thus there is a limitation in application. However, as described above, a new display system has been developed which utilizes the characteristics of light receiving type and low power consumption and has a high-speed response.

In recent years, ferroelectric liquid crystals have been attracting attention for meeting this purpose. A display element using this ferroelectric liquid crystal has a high-speed response of about several hundred times compared to the conventional TN type liquid crystal, and since it can also obtain bistability, it can be used for moving images such as television and It can be expected to be applied to various display devices such as high-speed optical shutters.

Ferroelectric liquid crystals have been found and reported by Mayer et al. (Journal de Physique, 36 (1975) L-6.
9), it was announced by NAClark et al. That it is possible to make a display element with a response speed of the order of microseconds (Clark et al., Applied Physics Letters, 36 (1980). Since 899), it has become a very noticeable entity.

Ferroelectric liquid crystal belongs to a class of smectic liquid crystals, and is classified as a compound having a chiral smectic phase, which is represented by a compound having an asymmetric carbon in the molecule.
Chiral smectic C is included in the chiral smectic phase.
Phase, chiral smectic G phase, chiral smectic H phase and many other chiral smectic phases exist, but from the viewpoint of practicality, the chiral smectic C phase (hereinafter, SC ^*
Abbreviated as phase. ) Is desirable, including in terms of handling.

Many liquid crystal compounds exhibiting the SC ^* phase have been published so far, and are characterized by having an asymmetric carbon atom in part of their molecular structure. Known as ferroelectric liquid crystal (S)-
2-Methylbutyl p-decyloxybenzylidene aminocinnamate (abbreviated as DOBAMBC) and a series of Schiff base type liquid crystals are listed. However, since Schiff bases are generally unstable to moisture, light, etc., there is a big problem in terms of practicality. (Keller et al.
Journal of Physics, 37 C3-129: Yoshino et al. Japanese Journal of Applied Physics, 23 L175 (1984); Isogai et al., JP 59-98051.

Further, as a halogen-substituted ferroelectric liquid crystal, JP-A-60-
Although described in 193947, it is a compound showing a narrow SC ^* phase temperature range.

[Problems to be Solved by the Invention] In consideration of the above problems, the inventors of the present invention contain a liquid crystal compound and a liquid crystal compound which are excellent in stability against moisture, light, etc. and have a SC ^* phase in a wide range. A liquid crystal composition is provided.

[Means for Solving Problems] The first point of the present invention is to provide a liquid crystal compound represented by the general formula (I).

(In the formula, R represents an alkyl group having 20 or less carbon atoms,
Q ^* represents an optically active alkyl group having an asymmetric carbon atom, and X represents a fluorine atom or a chlorine atom bonded at the ortho or meta position with respect to the RO-group. The second point is to provide a liquid crystal composition comprising at least two kinds of liquid crystal compounds and containing the compound represented by the general formula (I).

In general, when a liquid crystal has a layer structure and the constituent molecules are tilted with respect to the layer normal, and the constituent molecules have an asymmetric carbon atom, the tilt directions of the molecules are gradually increased between layers. It becomes twisted and shows a helical structure. When the spontaneous polarization is oriented in the direction perpendicular to the spiral axis, the liquid crystal exhibits ferroelectricity.

Therefore, the present inventors have earnestly studied a liquid crystal compound having an asymmetric carbon atom in the molecule, and as a result, obtained the compound represented by the general formula (I). Here, it can be said that the obtained compound is stable to moisture, light and the like and has a great advantage in terms of practicality as described above.

The compound represented by the general formula (I) of the present invention has various characteristics, for example, R = n-C ₁₂ H in the general formula (I).
₂₅ , Q ^* =-CH ₂ C ^* HCH ₃ (C ₂ H ₅ ), when X is a fluorine atom and is in an alkoxy ortho position, for example, X
When is a hydrogen atom, the performance is significantly different, and when X is a fluorine atom, it shows the SC ^* phase. For example, when X is a hydrogen atom,
It only shows liquid crystal phases other than SC ^* phase.

Moreover, the general formula R in _{(I) = n-C 10} H 21, Q * = -
In the case of CH ₂ C ^* HCH ₃ (C ₂ H ₅ ), when X is an ortho position of alkoxy, X = SC due to the difference between hydrogen atom, fluorine atom and chlorine atom.
^* The temperature range and temperature range of the phases differ greatly, and it is difficult to easily predict the difference in performance between them, and each has the property of being effectively utilized depending on the purpose of use.

Further, the compound of the present invention is a compound of Japanese Patent Application No.
It contains a group of compounds having an SC ^* phase over a wider temperature range than the compounds described in 60-98712, in which the compound of the general formula (I) is an optically active carboxylic acid monoester type of hydroquinone. It is thought that this is due to the fact that it has a molecular structure of, which is an effect not seen in the past.

Further, JP-A-60-32748 discloses a phase transition temperature of the following compounds.

Phase transition temperature (° C) C55 SC ^* 126 SA171 I In contrast, the corresponding transition temperature of the compound of the present invention is
It is as follows.

Phase transition temperature (° C) C80.2 SC ^* 153.6 SA168.5 Ch171.8 I From this, the compound described in JP-A-60-32748 is Ch
It shows no phase at all, and it is very difficult to obtain the (I → Ch → SA → SC ^* ) phase sequence necessary for obtaining a good cell, whereas the compound of the present invention is difficult to obtain. On the contrary, it is obvious that it can be easily obtained. In addition, the temperature range of the SC ^* phase is slightly widened, and it can be understood that this is a very preferable compound for obtaining a practical composition and device.

Further, various compounds contained in the general formula (I) can lead to a liquid crystal composition in which the temperature range showing the SC ^* phase is lower than that of each compound by mixing various compounds.

Further, although the compound of the present invention may be a compound which exhibits ferroelectricity alone, it may be used as a mixture with another ferroelectric liquid crystal compound. Furthermore, among the compounds of the present invention,
A compound exhibiting ferroelectricity may exhibit ferroelectricity even when mixed with another liquid crystal compound. As described above, the compound of the present invention can be used as a display device by blending various liquid crystal compounds or used alone to form an optical switching device utilizing the optical switching phenomenon of a ferroelectric liquid crystal. Is available.

Next, a method for producing the compound represented by formula (I) will be described.

The compound of general formula (I) can be produced by a condensation reaction of two compounds represented by the following general formula (IV) and general formula (V).

(In the formula, R and X have the same meanings as in formula (I).) (In the formula, Q ^* has the same meaning as in formula (I).) Next, a method for producing the compound of formula (IV) is schematically shown.

That is, it can be produced by using the halogen substitution product of 4'-alkoxy-4-biphenylcarboxylic acid by the method schematically shown in the following process drawing 1.

The functional groups R and Q ^* in the general formula (I) may have a hydrogen atom substituted with a halogen atom or other substituents as long as the identity of the compound of the general formula (I) is not impaired. Add note.

That is, the halogen-substituted 4'-alkoxy-4-biphenylcarboxylic acid of the compound of the general formula IV is prepared by converting halogen-substituted 4-methoxybrombenzene into the corresponding magnesium bromide with magnesium, and then reacting with iodobenzene in the presence of palladium chloride. To give the corresponding 4-methoxybiphenyl. Subsequently, the corresponding 4-acetyl-4'-methoxybiphenyl is obtained by Friedel-Crafts reaction with acetyl chloride in the presence of aluminum chloride. Subsequently, the acetyl group was converted to a carboxyl group by an oxidation reaction with an aqueous solution of sodium hypochlorite, and 48%
Demethylation in an aqueous solution of hydrogen bromide gives halogen-substituted or unsubstituted 4'-hydroxy-4-biphenylcarboxylic acid. Then, the compound of general formula IV can be obtained by alkoxylation with an alkyl halide.

Next, the compound of general formula V can be prepared by ester condensation reaction of hydroquinone and an optically active carboxylic acid using N, N'-dicyclohexylcarbodiimide, or condensation of an acid halide of optically active carboxylic acid and hydroquinone. it can.

The compound of the general formula IV and the compound of the general formula V thus obtained are used to produce a compound of the general formula I. The production method is as follows: ester condensation using N, N'-dicyclohexylcarbodiimide, Alternatively, it can be easily produced by preparing the corresponding acid halide of the compound of the general formula IV and then conducting the condensation reaction with the compound of the general formula V.

The liquid crystalline compound thus obtained or a composition using the same is formed into a thin film having a uniform thickness (1 to 20 μm) between two transparent electrode plates so that optical switching of a liquid crystal display cell or the like can be achieved. It can be used as an element.
In the display cell, the liquid crystal molecules need to be monodomains in which the long axes of the molecules are so-called homogeneous and have a uniform orientation. For this reason, the isotropic liquid phase is subjected to an orientation treatment such as rubbing or vapor deposition on the cell surface, or a method of applying an electric field, a magnetic field or the like, further, a temperature gradient method, or a method of combining these methods. Generally, a method of gradually cooling to a liquid crystal phase to orient is used, and even in the compound or composition of the present invention, a uniformly oriented monodomain cell can be obtained by such a method.

[Effect of the Invention] The group of compounds represented by the general formula I according to the present invention is DOBAMB, which is conventionally known as a typical ferroelectric liquid crystal compound.
Compared and C, also including comparison also extensively to other so far published in which ferroelectric liquid crystal compounds, and the enantiomerically tropic include compounds exhibiting SC ^* phase, SC ^* phase at even lower temperature region It also includes a compound showing.

As described above, the compound represented by the general formula I constitutes a useful compound group capable of largely changing the properties of the compound due to the effect of the halogen substitution. In addition, the general formula I
In even compositions using compounds represented, SC ^*
It has the effect of greatly changing the temperature range having a phase. The compounds of general formula I are also extremely reliable in terms of stability to light and moisture in practical use.

[Examples] The present invention will be specifically described below with reference to Examples and Production Examples, but of course the gist and scope of the present invention are not limited to these Examples. In the following examples, the value of the phase transition temperature may be slightly different depending on the measuring method and the purity.

Examples 1 to 8 Table 1 shows the phase transition temperatures of the compounds represented by the general formula I.

In Table 1, 3F 'in the designation of X indicates that a fluorine atom is substituted at the ortho position of the biphenyl ring alkoxy group. Similarly, for 3'Cl, it is shown that the chlorine atom is substituted.

A means a ^{_{-CH 2 C * H (CH 3}} ) C 2 H 5 in Q ^*,
B is, ^-C * H (CH ₃₎ means a C ₂ H _5.

At the phase transition temperature, C is a crystalline phase, SX is a smectic phase with undetermined phase, SA is a smectic A phase, Ch is a cholesteric phase, and I is an isotropic liquid phase, and · indicates that the phase exists. The-indicates that the phase does not exist. In addition, what is shown in parentheses indicates that the phase exists monotropically, that is, under supercooling.

Production Example 1 Production of compound of general formula IV (3'-fluoro-4'-alkoxy-4-biphenylcarboxylic acid) A 500 ml five-necked flask was equipped with a stirrer, a cooling condenser, a nitrogen gas introducing tube, a thermometer, and a dropping funnel. Attach to the device that can release nitrogen gas from the top of the cooling condenser, 2.
5 g of scrap metal magnesium and 120 ml of dehydrated tetrahydrofuran are charged, and 20.5 g of 3-fluoro-4-methoxybromobenzene dissolved in 50 g of dehydrated tetrahydrofuran is charged to the dropping funnel. Under nitrogen gas flow,
The flask was heated while dropping 3-fluoro-4-methoxybromobenzene little by little from the dropping funnel, and 3-fluoro-4-methoxybromobenzene was dropped for 30 minutes while gradually reacting. When the reaction is in progress during the dropping, heating from the outside is not necessary due to heat generation. After the dropping is completed,
3-Fluoro-4-methoxyphenylmagnesium bromide which was further heated under reflux for 1 hour was produced. Then 2
In a flask charged with 0.3 g of iodobenzene, 0.20 g of palladium chloride and 100 ml of dehydrated tetrahydrofuran,
Under a nitrogen stream, the above tetrahydrofuran solution of 3-fluoro-4-methoxyphenylmagnesium bromide is added dropwise to the iodobenzene solution while stirring. After dropping at 40 minutes, the mixture was heated under reflux for 2 hours. Then, the reaction solution was returned to room temperature, 10% hydrochloric acid was added and stirred, and then hexane was added and sufficiently stirred to separate the organic layer. The organic layer was further washed with water and then concentrated, and the resulting residue was separated from impurities of the desired product 3-fluoro-4-methoxybiphenyl by a silica gel column chromatography method. Yield 11.2g, yield 55
% Next, 11.2 g of 3-fluoro-4-methoxybiphenyl obtained here was charged into a reaction flask equipped with a cooling tube together with 4.3 g of acetyl chloride and 100 ml of carbon dicarbide, and an anhydrous calcium chloride tube was placed at the top of the flask. Moisture was cut off. While cooling the flask with ice, 9.0 g of anhydrous aluminum chloride is added here.
After addition, the mixture was stirred for 2 hours, and then gently heated to reflux for 5 hours.

After the reaction is completed, the reaction solution is poured into a large amount of 10% hydrochloric acid aqueous solution,
Stir well. The resulting precipitate was collected by filtration to give 9.1 g. Recrystallization from isopropyl alcohol gave 7.2 g of the desired product, 4-acetyl-3'-fluoro-4'-methoxybiphenyl. Yield 53% 4-acetyl-3'-fluoro-4'-obtained here
Dissolve 7.2 g of methoxybiphenyl in 300 ml of dioxane and add 360 ml of sodium hypobromite solution (caustic soda 7
5 g, adjusted from 78 g of bromine) was added at 0 to 5 ° C over about 40 minutes, and then stirred at 30 to 35 ° C for 2 hours. Next, after decomposing excess sodium hypobromite with a saturated aqueous solution of sodium hydrogen sulfite, 10% hydrochloric acid aqueous solution is added to adjust the pH to 3 to 4, and the pH is adjusted to 2 at 10 ° C.
It was left to stand for 0 hour to be crystallized. The crystals formed are filtered off, 7.2
g of 3'-fluoro-4'-methoxy-4-biphenylcarboxylic acid was obtained. Recrystallization from isopropylate alcohol gave 6.8 g of the desired product. Yield 94%, followed by 6.8 g of 3'-fluoro-4'-methoxy-4.
Biphenylcarboxylic acid was heated to reflux in 150 ml of 48% aqueous hydrobromic acid and 80 ml of dioxane for 14 hours. Then, the volatile matter was distilled off with an evaporator, and the residue was washed several times with water and recrystallized from isopropyl alcohol to obtain 6.10 g of the target product 3′-fluoro-4′-hydroxy-4-biphenylcarboxylic acid. . Yield 95% With respect to the 3'-fluoro-4'-hydroxy-4-biphenylcarboxylic acid thus obtained, 1.2 times mol of alkyl bromide and 1.95 times mol of caustic soda are used, and heated under reflux in water-containing ethanol for 10 hours. After that, 10% hydrochloric acid aqueous solution was added to adjust the pH of the solution to 2-3, and the mixture was heated under reflux for 1 hour. After cooling, the organic matter was extracted with chloroform, the chloroform layer was washed with water and dehydrated with sodium sulfate. The chloroform layer is concentrated to obtain crude crystals. Recrystallized from ethanol, 3'of target
-Fluoro-4'-alkoxy-4-biphenylcarboxylic acid was obtained. Although the yield in this alkoxylation reaction varies slightly depending on the type of alkyl bromide used,
60-80%.

Production Example 2 (Compound of Example 3) By the method shown in Production Example 1, 3'-fluoro-4'-
Producing dodecyloxy-4-biphenylcarboxylic acid,
used.

To 4.0 g of 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylic acid was added 8.5 g of thionyl chloride, 1 drop of pyridine was added, and the mixture was heated under reflux for 6 hours. The volatile components were distilled off with an evaporator, and 20.8 g of hydroquinone-mono (S) -3-methylpentanoate was added,
The reaction was carried out at -50 ° C for 7 hours. After the reaction, the reaction solution was poured into a large amount of ethyl acetate, washed with diluted hydrochloric acid 3 times, and then washed with water 3 times. The ethyl acetate layer is dehydrated with Glauber's salt, and then ethyl acetate is concentrated to obtain a residue.
3.83 g of -oxycarbonyl- (S) -2-methylbutyl) phenyl 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylate was obtained. Yield 65% The obtained target product was confirmed by a nuclear magnetic resonance spectrum, an infrared absorption spectrum and a mass spectrum.

Nuclear magnetic resonance spectrum (CDCl ₃ ) δ value (proton) 0.82 to 2.25 (32H); 2.43 to 2.72 (2H) multiplet; 4.00 to 4.1
5 (2H) triplet; 7.01 ~ 8.30 (11H) infrared absorption spectrum (cm ^-1 ) (main absorption value) 2930,2850,1750,1730,1610,1515,1285,1190,1090,815,7
65 Mass spectrum M / e = 590 (CI method) Production Example 3 (compound of Example 6) 4.00 g of 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylic acid and hydroquinone-mono- (S)
The reaction and post-treatment were carried out in exactly the same manner as in Production Example 1, except that 1.94 g of 2-methylbutanoate was used (4)
There was obtained 3.92 g of -oxycarbonyl- (S) -1-methylpropyl) phenyl 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylate. Yield 68% Nuclear magnetic resonance spectrum (CDCl ₃ ) δ value (proton) 0.80 to 1.95 (23H); 2.50 to 2.83 (1H) multiplet; 4.00 to 4.1
5 (2H) triplet; 7.03 to 8.30 (11H) infrared absorption spectrum (cm ^-1 ) (main absorption value) 2930,2860,1750,1730,1610,1515,1285,1190,1090,815,7
15 Mass spectrum M / e = 576 (CI method) Production Example 4 (compound of Example 7) 3.90 g of 3'-chloro-4'-decyloxy-4-biphenylcarboxylic acid was added to 10.0 g of thionyl chloride, and another drop was added. Pyridine was added and the mixture was heated under reflux for 6 hours. Then, post-treatment was carried out in the same manner as in Production Example 1, and 2.08 g of hydroquinone-mono-
Production Example 1 using (S) -3-methylpentanoate
The reaction and post-treatment were carried out in exactly the same manner as in (1) to give the desired (4-oxycarbonyl- (S) -2-methylbutyl) phenyl 3'-fluoro-4'-dercioxy-4-biphenylcarboxylate (4.16 g). Yield 72% Nuclear magnetic resonance spectrum (CDCl ₃ ) δ value (proton) 0.86 to 2.22 (28H); 2.33 to 2.66 (2H) multiplet; 3.94 to 4.0
9 (2H) triplet; 6.89-8.17 (11H) infrared absorption spectrum (cm ^-1 ) (main absorption value) 2950,2880,1765,1735,1610,1520,1265,1175,1080,850,7
65 Mass spectrum M ⁺ = 578 (CI method) Production Example 5 Preparation of liquid crystal composition Compound of Example 3 (4-oxycarbonyl (S) -2-
Methylbutyl) phenyl 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylate 1.8 parts by weight and compound (4-oxycarbonyl- (S) -1-methylpropyl) phenyl 4-decyloxybenzoate 1.0
Parts by weight were mixed, heated and melted, and sufficiently stirred. This mixture is enantiotropically SC at temperatures between 38 ° C and 66 ° C.
^* A mixed liquid crystal having a phase was obtained, and a useful composition could be obtained.

Production Example 6 Preparation of Liquid Crystal Composition The compound of Example 3 (4-oxycarbonyl- (S) -2
-Methylbutyl) phenyl 3'-fluoro-4'-dodecyloxy-4-biphenylcarboxylate 36 parts by weight, the compound of Example 2 (4-oxycarbonyl- (S)
2-Methylbutyl) phenyl 3'-fluoro-4'-
20 parts by weight of decyloxy-4-biphenylcarboxylate, the compound of Example 6 (4-oxycarbonyl- (S)
-1-Methylpropyl) phenyl 3'-fluoro-4 '
-Dodecyloxy-4-biphenylcarboxylate 12
Parts by weight and compound (4-oxycarbonyl- (S) -1
-Methylpropyl) phenyl 4-dodecyloxybenzoate (32 parts by weight), mixed by heating and sufficiently stirred,
A liquid crystal composition was prepared.

This composition became a mixed liquid crystal having an enantiotropic SC ^* phase in the range of 34 ° C. to 110 ° C., and a useful composition could be obtained.

Production Example 7 Production of Liquid Crystal Display Device The liquid crystal composition obtained in Production Example 6 was used, and a thin film was filled as an isotropic liquid between two glass rubbing orientation-treated transparent electrodes using a spacer having a thickness of 3 μm. A cell was prepared. The cell was cooled at a rate of 0.5 degree per minute to obtain a chiral smectic phase as a uniform monodomain. When an electric field of 5 V and 0.1 Hertz was applied to this cell at 55 ° C. and an optical switching operation was detected by a photomultiplier, the response speed was about 450 μsec. As a result, a liquid crystal display device having a fast response speed was obtained.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroshi Ogawa 246-4 Ikari, Kawaguchi City, Saitama Prefecture (72) Inventor Yoshiyoshi Arai 5-8-6-402 Higashi, Hasuda City, Saitama Prefecture (72) Inventor Mio Kurokawa Omiya, Saitama Prefecture 2-39, Yoshino-cho, Yokohama

Claims (3)

[Claims] 1. A general formula (I) (In the formula, R represents an alkyl group having 20 or less carbon atoms,
Q ^* represents an optically active alkyl group having an asymmetric carbon atom, and X represents a fluorine atom or a chlorine atom bonded at the ortho or meta position with respect to the RO-group. ) A liquid crystal compound represented by: Wherein Q ^* is first appended claims is an optically active 2-methylbutyl group or an optically active 1-methylpropyl group
The liquid crystalline compound according to the item. 3. A liquid crystal composition comprising at least two kinds of liquid crystalline compounds, wherein (In the formula, R represents an alkyl group having 20 or less carbon atoms,
Q ^* represents an optically active alkyl group having an asymmetric carbon atom, and X represents a fluorine atom or a chlorine atom bonded at the ortho or meta position with respect to the RO-group. ) A liquid crystal composition containing a compound represented by: