JPH0714899B2 - Liquid crystal compound and liquid crystal composition - Google Patents

Description

The present invention relates to a novel liquid crystal compound, and provides a liquid crystal material having ferroelectricity, particularly a material having applicability to a liquid crystal display device.

Liquid crystal display devices are widely used as various display devices because of their excellent features such as low voltage operability, low power consumption, thin display capability, and light-receiving type that prevent eye strain.

At present, as a display method, a nematic liquid crystal called Twisted Nematic type is most often used as a material. However, this twisted nematic 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 excellent characteristics as described above, and therefore the application limitation was there. However, as described above, a new display system has been developed which has a light receiving type and low power consumption and has a high-speed response.

Ferroelectric liquid crystals have recently attracted attention as a material for this purpose. The display using this ferroelectric liquid crystal has a high-speed response of about several hundred times compared to the conventional twisted nematic liquid crystal, and can also obtain bistability. It can be expected to be applied as a display device in various fields including images and high-speed optical shutters.

Ferroelectric liquid crystals have been found by RB Meyer et al. (RB Meyer et al., J. Physique, 36 (1975) 2-
69), it was announced by NA Clark et al. That it is possible to make a display element with a response speed on the order of microseconds and with a memory effect (NA Clark et al., Appl.Phys.Lett., 36 . (1980) 899) has received much attention.

Ferroelectric liquid crystals belong to a class of smectic liquid crystals, and are classified into a chiral smectic phase represented by a compound having an asymmetric carbon in the molecule. The chiral smectic phase has many chiral smectic phases such as chiral smectic C phase, the same G phase, and the same H phase, but from the viewpoint of practicality, the chiral smectic C phase (hereinafter Sc ^* (Abbreviated as “phase”) is considered to be the most desirable phase in terms of performance including handling.

There have been many publications on liquid crystalline compounds exhibiting the Sc ^* phase, and a typical example is (s) -2-methylbutyl p-, which is the first known ferroelectric liquid crystal to be synthesized.
Decyloxybenzylidene aminocinnamate (DOBAMB
Abbreviated as C) and a series of Schiff base liquid crystals. However, since Schiff bases are generally unstable to water, light, etc., there is a big problem in terms of practicality (p. Keller et al., J. Physique, 37 C3-129; K. Yosh.
ino et al., Japanese J. of Appl. Phys. 23 L175 (1984); JP-A-59-98051).

Further, in JP-A-60-32748, the general formula II (In the general formula II, R represents an alkyl group or an alkoxy group having 20 or less carbon atoms), but there is a tendency that the temperature range showing the Sc ^* phase is narrow and the melting point is high. Therefore, the composition showing the Sc ^* phase at room temperature tends to be extremely difficult.

The present invention provides a liquid crystal compound having excellent stability against moisture, light, etc. as described above, and a liquid crystal compound having a Sc ^* phase in a wide temperature range, and a liquid crystal composition containing the liquid crystal compound. It is intended to be applied.

The invention has the general formula I (In the formula I, R represents an alkyl group or an alkoxy group having 20 or less carbon atoms, X represents a halogen atom or a hydrogen atom, and R ^* represents a branched alkyl group having an asymmetric carbon atom at the 1-position or 2-position. The present invention provides an optically active liquid crystalline compound represented by.

The present invention also provides a liquid crystal composition containing a compound represented by the general formula I in a liquid crystal composition comprising at least two kinds of liquid crystal components.

When the liquid crystal has a layered structure and is tilted with respect to the layer normal, when the liquid crystal constituent compound has an asymmetric carbon atom, the layers are twisted little by little, and a helical structure is exhibited. When the spontaneous polarization is oriented in the direction perpendicular to the spiral axis, the liquid crystal exhibits ferroelectricity. From such a viewpoint, the inventors of the present invention diligently studied a liquid crystal compound having a chiral carbon atom in the molecule, and obtained a compound represented by the general formula I.

It was found that the compound of the general formula I has a temperature range showing the S _c ^* phase in the range of 30 to 50 ° C., and above all, the melting point is 20 ° C. or more lower than that of the halogen-unsubstituted compound, and a practical compounding composition is obtained It turned out to be a real advantage. That is, Japanese Patent Application Sho 60-90
It was found that the combination of 676 with a series of compounds can bring the S _c ^* phase down to room temperature. These effects are
It is generated by substituting the aromatic nucleus of the compound of general formula I with halogen, and a halogen, particularly a fluorine-substituted biphenyl skeleton in which a fluorine atom is introduced, exhibits an effective action. In this case, a compound exhibiting an S _c ^* phase can still be obtained by introducing a chlorine atom instead of a fluorine atom, but a chlorine-substituted biphenyl compound generally tends to exhibit an S _c ^* phase in monotropic.

From the above, it can be said that the compound represented by the general formula I has good performance, is stable to moisture and light, and has a great advantage in terms of practicality.

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

Compounds of general formula I can be prepared by ester condensation of compounds of general formula III with compounds of general formula IV.

(In the general formula III, R represents an alkyl group or an alkoxy group having 20 or less carbon atoms. X represents a halogen atom or a hydrogen atom.) (In the general formula IV, R ^* represents a branched alkyl group having an asymmetric carbon atom at the 1-position or 2-position.) The compound represented by the general formula III is a halogen-substituted or unsubstituted alkylbenzene or alkoxybenzene converted to acetyl chloride. , Acetylation with a reaction reagent such as aluminum chloride, followed by reaction with an aqueous solution of sodium hypobromite.

In addition, among the compounds of the general formula III, compounds in which R is an alkoxy group are compounds in which halogen-substituted or unsubstituted anisole is brominated and reacted with magnesium to form a Grignard reagent, and then carbon dioxide gas is reacted to form a carboxylic acid, and then 48 % Hydrobromic acid aqueous solution to demethylate to a halogen-substituted or unsubstituted parahydroxybenzoic acid, and this compound can be alkoxylated with an alkyl bromide to obtain the compound.

Next, the compound represented by the general formula IV is prepared as 3-fluoro-4-methoxybiphenyl by bromination of 2-fluoroanisole, adjustment of Grignard reagent by reaction with magnesium, and coupling reaction with iodobenzene. ,
Sequentially, acetylation with acetyl chloride and aluminum chloride and carboxylation of the acetyl group with an aqueous solution of sodium hypobromite were performed, followed by demethylation with 48% hydrobromic acid to give 3'-fluoro-4'-hydroxyl. It can be obtained by preparing -4-biphenylcarboxylic acid and subjecting this to ester condensation with an optically active alcohol.

Thus obtained compound of general formula III and general formula IV
By subjecting the compound of formula (1) to ester condensation, the target compound of general formula I is obtained.

The liquid crystalline compound thus obtained or a composition using them is used as a liquid crystal display cell by forming a thin film having a uniform thickness (1 to 20 μm) between two transparent electrode plates. be able to.

In the display cell, the liquid crystal molecules are required to be monodomains in which the long axes of the molecules are arranged in parallel to the electrode surface, that is, a so-called homogeneous and uniform orientation. In order to achieve such orientation, rubbing, resinous material, vapor deposition of an inorganic substance, etc. on the cell surface, and further rubbing treatment after vapor deposition, or by an electric field, magnetic field or temperature gradient method as an alternative method, or these A method is generally used in which the cell surface treatment is performed by a combination of the methods, and a liquid crystal compound or a liquid crystal composition in this cell is gradually cooled from an isotropic liquid to a liquid crystal phase to be aligned. A monodomain cell can be obtained by the same method in the composition.

This mono-domain cell is installed in two polarizing plates, and it is possible to observe the optical switching operation by applying rectangular waves of various voltages and frequencies. Therefore, the optical switching element is manufactured in this way. be able to.

The compound represented by the general formula I according to the present invention is further compared with DOBAMBC, which is known as a typical representative ferroelectric liquid crystal compound, as compared with the ferroelectric liquid crystal compounds previously announced. By comparison, it also includes a compound having a low melting point compound and having an S _c ^* phase in a wide temperature range. Furthermore, as shown in Example 14, the chiral smectic C was widely spread over the room temperature including the liquid crystal compound.
It contains a useful compound that can be a material for obtaining a composition having a phase.

Hereinafter, the present invention will be specifically described with reference to Examples and Production Examples, but of course, the gist and the scope of application 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 12 Table 1 shows the phase transition temperatures of the compounds represented by the general formula I.

In Table 1, H in X means hydrogen, 2-F, 3-
F and 2-Cl mean that the R group is substituted with fluorine (F) or chlorine (Cl) at the 2- and 3-positions. In R ^* , 2MB is an optically active 2-methylbutyl group, 2B is an optically active 2-methylbutyl group.
A butyl group is shown. C at the phase transition temperature indicates the melting point of the crystalline phase, SA indicates the smectic A phase, Ch indicates the cholesteric phase, and I indicates the isotropic liquid. The-mark in each phase means that the phase exists, and the-mark indicates that the phase does not exist. The parenthesized symbols and numbers indicate the presence of the phase in monotropics, ie only under supercooling.

Production Example 1 [(s) -2-methylbutyl 3'-fluoro-
Production of 4'-Hydroxy-4-biphenylcarboxylate] 2.43 g of shaving metal magnesium was added to 150 ml of tetrahydrofuran, and 20.5 g of 4-bromo-dissolved in 100 ml of tetrahydrofuran under a nitrogen stream while heating. A tetrahydrofuran solution of 3-fluoro-4-methoxyphenylmagnesium bromide was prepared by a conventional method in which 2-fluoroanisole was added dropwise little by little. This Grignard reagent was gradually added dropwise to 100 ml of a tetrahydrofuran solution containing 20.4 g of iodobenzene and 0.1 g of palladium chloride while maintaining the temperature at 50 ° C to 60 ° C, and about 30% of the Grignard reagent was added dropwise. By the way,
It was confirmed that the reaction had occurred. Then, the remaining Grignard reagent was added dropwise at the reflux temperature of tetrahydrofuran. After completion of the dropping, the mixture was heated under reflux for 2 hours to complete the reaction. After completion of the reaction, post treatment was carried out by a conventional method to obtain 35 g of a crude product. The target product was separated and purified from the crude product by silica gel column chromatography (ethyl acetate-hexane eluent), and 12.0 g of the target product 3-
Fluoro-4-methoxybiphenyl was obtained (yield 59.4
%). Next, 11.2 g of 3-fluoro-4-methoxybiphenyl obtained here was acetylated using 4.3 g of acetyl chloride, 9.0 g of aluminum chloride and 100 ml of carbon disulfide. That is, 4.3 g of acetyl chloride was added to 9.0 g of aluminum chloride and 100 ml of carbon disulfide under ice cooling, and after well stirring, 11.2 g of 3-fluoro-4-methoxybiphenyl was added and the mixture was cooled under ice cooling to 30%. Stir well for 2 minutes, then at room temperature for 2
After stirring for an hour, the mixture was heated to reflux for another 2 hours. After the reaction, the reaction solution was added to a mixture of ice and concentrated hydrochloric acid by a conventional method, and the mixture was stirred well and the resulting precipitate was filtered to obtain 9.0 g of a product. This was recrystallized from isopropyl alcohol to obtain 7.2 g of the target product 4-acetyl-3'-fluoro-4'-methoxybiphenyl (yield 53%).

7.2 g of 4-acetyl-3'-fluoro-4'-methoxybiphenyl obtained here was dissolved in 300 ml of dioxane,
60 ml sodium hypobromite aqueous solution (caustic soda 75 g, bromine 7
(Prepared from 8 g) was added dropwise at 0 to 5 ° C. in about 40 minutes and then stirred at 30 to 35 ° C. for 2 hours. Next, excess sodium hypobromite was decomposed with a saturated aqueous solution of sodium hydrogen sulfite, 10% aqueous hydrochloric acid solution was added to adjust the pH to 3 to 4, and the mixture was allowed to stand at 10 ° C. for 20 hours for crystallization. The resulting precipitate was passed through to obtain 7.2 g of 3'-fluoro-4'-methoxy-4-biphenylcarboxylic acid. Recrystallize from isopropyl alcohol 6.
8 g of purified product was obtained (94% yield). Continued, 6.8g 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, the residue was washed with water several times, and recrystallized from isopropyl alcohol to obtain the desired product 3'-fluoro-4 '.
6.1 g of -hydroxy-4-biphenylcarboxylic acid was obtained (yield 95%).

3'-Fluoro-4'-hydroxy-4-obtained here
6.1 g of biphenylcarboxylic acid was added to 50 ml of toluene,
Further 4.0 g of (s) -2-methylbutanol and 1-2
Add a drop of concentrated sulfuric acid and use the GeneStark trap to
Heated to reflux for hours. After completion of the reaction, the reaction mixture was diluted with chloroform, washed with an aqueous sodium hydrogen carbonate solution and washed with water, and the organic layer was taken out. The organic layer was dehydrated with sodium sulfate and concentrated to obtain 9.0 g of a crudely purified product. This was recrystallized from ethanol to give the desired product (s) -2-methylbutyl 3'-fluoro-
4'-Hydroxy-4-biphenylcarboxylate 6.0g
Was obtained (yield 75%).

Production Example 2 (Compound of Example 2) 8 g in 2.68 g of 3-fluoro-4-n-octyloxybenzoic acid
Of thionyl chloride was added and the mixture was heated under reflux for 3 hours. Then, excess thionyl chloride was distilled off, and 10 ml of pyridine was added thereto,
Furthermore, (s) -2-methylbutyl 3'-fluoro-4 '
After adding 3.04 g of -hydroxy-4-biphenylcarboxylate and reacting at 60 to 70 ° C for 3 hours, the mixture was left at room temperature overnight. The reaction product was poured into diluted hydrochloric acid aqueous solution and extracted with ethyl acetate. The ethyl acetate layer was washed with water, dehydrated with sodium sulfate and concentrated to obtain 5.5 g of crude crystals. This was subjected to silica gel column chromatography (ethyl acetate-hexane eluent) method to obtain the target fraction 3'-fluoro-4-((s) -2-methylbutyloxycarbonyl) biphenyl-3-fluoro-4-n-. 4.8 g of octyloxybenzoate was obtained (yield 86.6%). The structure of 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): 0.85
~ 2.05 (24H), 4.02 ~ 4.23 (4H), 6.90 ~ 8.15 (10H) Infrared absorption spectrum (cm ^-1 ) (main absorption value): 2940, 2
860, 1735, 1710, 1615, 1280, 1185, 1145 Mass spectrum: M ⁺ = 552 (CI method) Production Example 3 (Compound of Example 7) 2.78 g of 4-n-decyloxybenzoic acid in 8 g of thionyl chloride Was added and the mixture was heated under reflux for 3 hours, then excess thionyl chloride was distilled off, 10 ml of pyridine was added thereto, and (s) was added.
-2-Methylbutyl ・ 3'-fluoro-4'-hydroxy-4-biphenylcarboxylate 3.04g added to 60 ~ 70
After reacting for 3 hours at ℃, it was left overnight. Thereafter, post-treatment was carried out in the same manner as in Production Example 2 to obtain the desired product 3'-fluoro-4-.
4.5 g of ((s) -2-methylbutyloxycarbonyl) biphenyl-4-n-decyloxybenzoate was obtained (yield 8
0.0%).

Nuclear magnetic resonance spectrum (CDCl ₃ ) δ value (proton): 0.85
~ 1.10 (9H) (methyl proton), 1.10 ~ 2.05 (19H),
4.00-4.27 (4H), 6.93-8.30 (11H) (aromatic nucleus) Infrared absorption spectrum (cm ^-1 ) (main absorption value): 2940, 2870, 1735, 1710, 1610, 1510, 1270, 1205, 10
80 Mass spectrum: M ⁺ = 562 (CI method) Production Example 4 (Compound of Example 12) 2.32 g of 3′-fluoro-4′-hydroxy-4-biphenylcarboxylic acid was dissolved in 20 ml of dehydrated pyridine, 0-5 ° C
Cooled to 10 ml of dehydrated pyridine and a solution of 3.0 g of 4-decyloxybenzoic acid chloride dissolved in 10 ml of methylene chloride, while keeping the reaction liquid temperature at 5 to 10 ° C.
The mixture was added dropwise over time and then stirred overnight at room temperature. The reaction solution was diluted with a large amount of ethyl acetate, washed twice with a dilute hydrochloric acid aqueous solution, then washed with water, dehydrated, and the solvent was concentrated under reduced pressure. The resulting crude crystals were separated by silica gel column chromatography with ethyl acetate-hexane-ethanol to give the desired 3'-fluoro-4 '-(4-decyloxyphenylcarbonyloxy) -4-biphenylcarboxylic acid. Was obtained 3.40 g (yield 69%). Then, 3.4 g of 3'-fluoro-
4 '-(4-decyloxyphenylcarbonyloxy)-
Add 10 g of thionyl chloride to 4-biphenylcarboxylic acid and add 6
After reacting at 0-70 ° C for 5 hours, excess thionyl chloride was distilled off, and 0.6 g of (s)-(t) -2-butanol was removed.
Was added, 10 ml of pyridine was further added, and the mixture was stirred at room temperature for 20 hours. This pyridine solution was diluted with ethyl acetate, washed twice with a dilute aqueous hydrochloric acid solution, washed with water, dehydrated, then concentrated under reduced pressure and separated and purified by a silica gel column chromatography method using a hexane-ethyl acetate system. 3.2 g of crystals were obtained. The crystals were recrystallized from ethanol to give 2.9 g of the desired product (s) -2-butyl.3'-fluoro-4 '-(4-
Decyloxyphenylcarbonyloxy) -4-biphenylcarboxylate was obtained (yield 76%). The structure of 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): 0.80
~ 1.10 (9H) (methyl proton), 1.15 ~ 1.95 (18
H), 3.91 to 4.10 (2H) (triplet, methylene),
5.0-5.30 (1H) (Multiple, methine), 6.90-
8.25 (11H) (aromatic nucleus) Infrared absorption spectrum (cm ^-1 ) (main absorption value): 2950, 2870, 1750, 1715, 1610, 1260, 1180, 1060 Mass spectrum: M ⁺ = 548 (CI method) Example 13 The liquid crystal compound obtained in Example 3 was filled as an isotropic liquid between two rubbing-aligned glass transparent electrodes using a spacer having a thickness of 2.2 μm to prepare a thin film cell. This cell was cooled at a rate of 0.5 ° C. for 1 minute to obtain a chiral smectic C phase as a uniform monodomain.
A rectangular wave of 30 V and 50 Hz was applied to this cell at 50 ° C., and the optical switching operation was detected. The response speed was 700 microseconds. As a result, a liquid crystal display device having a high response speed was obtained. The spontaneous polarization was measured from the polarization reversal current generated by applying a triangular wave to this cell, and it was 5.0 nC / cm ² at 50 ° C.

Example 14 50% by weight of the compound obtained in Example 7 and (s) -2-methylbutyl-4- (3'-fluoro-4'-decyloxybiphenyl-4-carbonyloxy) benzoate [Japanese Patent Application No.
See -90676; Phase change: A phase transition from the crystalline phase to the S _c ^* phase at 54.0 ° C, a transition from the S _c ^* phase to the SA phase at 124.2 ° C, and an isotropic liquid at 156.6 ° C. ] A mixture with 50% by weight was prepared and this phase change was observed. At 13.8 ℃, the crystalline phase transformed into S _c ^* phase, at 98.3 ℃ became SA phase, and at 146.5 ℃ became an isotropic liquid.

Further, this mixture was sealed in the same cell as in Example 13,
When the optical switching operation was detected by the same operation, the response speed was 550 μs at 65 ° C.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Nobu Fujisawa 4-14-22 Namiki, Kawaguchi City, Saitama Prefecture (72) Inventor Hiroshi Ogawa 246-4 Ikari, Kawaguchi City, Saitama Prefecture

Claims (2)

[Claims] 1. A general formula I (In the formula, R represents an alkyl group or an alkoxy group having 20 or less carbon atoms. X represents a halogen atom or a hydrogen atom. R ^* represents a branched alkyl group having an asymmetric carbon atom at the 1-position or 2-position. An optically active liquid crystalline compound represented by. 2. The general formula I (In the formula, R represents an alkyl group or an alkoxy group having 20 or less carbon atoms. X represents a halogen atom or a hydrogen atom. R ^* represents a branched alkyl group having an asymmetric carbon atom at the 1-position or 2-position. A liquid crystal composition comprising an optically active liquid crystalline compound represented by