JPH0572911B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a ferroelectric liquid crystal compound useful as a display element with excellent image display responsiveness and a liquid crystal composition containing the same. Currently, display elements using liquid crystal materials are of a light-receiving type, and are widely used in practical use because of their low power consumption and ability to create thin display devices. On the other hand, EL (electroluminescence) is a light-emitting display system that features high-speed response.
There is also active development of plasma displays. [Prior Art] Most of the liquid crystals that have been used for display elements so far are nematic liquid crystals, and the mainstream is the TN (twisted nematic) type. Although this TN display method has advantages such as small size and low power consumption, it also has the disadvantage of slow response speed for image display. Various attempts have been made to improve this point, including the Molecular Crystals and Liquid Crystals.
The results only demonstrate the theoretical limit values shown in Vol. 94, pages 155-165, and it appears that the development of materials for TN type displays has almost reached its limit. Therefore, in order to overcome the above-mentioned drawbacks, interest has recently shifted to the development of chiral liquid crystals in place of nematic liquid crystals, and considerable progress has been made in particular with respect to ferroelectric liquid crystals. The first ferroelectric liquid crystal developed was

It is a compound (hereinafter abbreviated as DOBAMBC) represented by [C] (in the formula, 〓 represents an asymmetric carbon atom), and its liquid crystal phase series and phase transition temperature (°C) are as follows.

[C] (In the formula, C is the crystalline phase, S _A is the smectic A phase,
S _C ^* represents chiral smectic C phase, S _H ^* represents chiral smectic H phase, and I represents isotropic liquid.) Ferroelectricity is classified into chiral smectic C phase (hereinafter abbreviated as S _C ^* ) or chiral smectic H phase (hereinafter abbreviated as S _H ^* ), which are classified and named based on the molecular arrangement.
R.B. Meyer and others reported in the Journal of Physics France that using this method it is possible to obtain a display element with a response of up to 1 μs.
Physics France, Volume 36, Page 69 (1975). Since then, various analogs of DOBAMBC have been synthesized, but at present, the lower limit of the temperature range belonging to S _C ^* or S _H ^* is higher than room temperature, and the compound itself is unstable to moisture and light. The focus of research shifted to ester-based ferroelectric liquid crystal compounds shown in Table 1 below (Liquid Crystals and Ordered Fluids).
and Ordered Fluids, 4 , 1-32 (1982)].

【table】

【table】 ^{* *
*}
[Problems to be solved by the invention] As a result, chemically stable compounds were obtained, but as shown in Table 1, these liquid crystal compounds alone exhibit ferroelectricity in a temperature range higher than room temperature. Not practical. Furthermore, when the compounds shown in Table 1 are mixed together, a large decrease in melting point as shown in Table 2 has not been found because their molecular structures are similar.

[Means for solving problems]

As a result of intensive research from the above viewpoint, the present inventors have found that
The present inventors have discovered a ferroelectric liquid crystal compound and a liquid crystal composition containing the same that have excellent stability and whose temperature range in the S _C ^* phase or S _H ^* phase is around room temperature, and have arrived at the present invention. That is, the present invention provides general formula []

[Formula R is an alkyl group having 1 to 18 carbon atoms, m
is 1 or 5, n is an integer of 0 to 5, and 〓 is an asymmetric carbon atom). The present invention also provides a chiral smectic liquid crystal composition containing at least one compound represented by the above general formula []. In the general formula [], the boron-containing skeleton is named as follows.

In the general formula [], R represents an alkyl group having 1 to 18 carbon atoms, preferably a linear alkyl group having 8 to 16 carbon atoms. Therefore, the compound represented by the above general formula [] is 2-(4'-alkoxyphenyl)-5-alkyl-1,3,2-
It can be named dioxaborinane. The method for producing the compound represented by the general formula [] will be described in detail below, and an optically active alcohol is used as one of the raw materials for production. Optically active alcohols include 2-methylbutanol, 3-methylpendanol, 4-methylhexanol, 5-methylheptanol, 6-methyloctanol, and 1-methylhexanol, which are available at low cost in view of industrial versatility.
-Methylpropanol etc. are often used. An outline of the method for producing the compound represented by the general formula [] is as shown in the following formula.

[ka]

[In the above formula, R ^* is a group]

[Effect]

The compounds of the present invention exhibit the following actions and features. First, groups that can be decomposed in an atmosphere containing moisture, carboxylic acid ester groups, etc.

Since it does not have [Formula] and the conjugated system based on double bonds is an extremely short system with one benzene ring,
Very stable against moisture and light. Next, the dioxaneborinane ring

Contains [formula], geoki Sankan

〔Example〕

The present invention will be explained below by way of examples.
% in the examples indicates weight %. Production Example 1 Synthesis of 4-alkoxybromobenzene In a 300 c.c. four-necked flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 35.7 g (0.206 mol) of bromophenol and 8.24 g of sodium hydroxide were added.
(0.206 mol) and 200 ml of absolute ethanol,
The mixture was stirred to form a solution, and 0.206 mol of an optically active alkyl p-toluenesulfonic acid ester prepared in advance from an optically active alcohol and p-toluenesulfonic acid was added dropwise to this solution at room temperature. After the dropwise addition, the mixture was further reacted under reflux for 10 hours, the precipitate was separated, the ethanol was distilled off, and the residue was extracted with ether. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and then the organic solvent was distilled off. The obtained oil was subjected to vacuum distillation or silica gel column chromatography (developing solvent: hexane) and the third
The 4-alkoxybromobenzene shown in the table was obtained in a yield of 87-94%. Its structure was confirmed by IR and NMR spectra. The results are shown in Table 3.

[Table] Production Example 2 Synthesis of 4-alkoxyphenylboronic acid 10 g (0.10 mol) of trimethyl borate was placed in a 300 c.c. three-necked flask equipped with a stirrer, thermometer, dropping funnel, and nitrogen gas inlet tube under a nitrogen stream. and 60 ml of anhydrous tetrahydrofuran, stirred to form a solution, kept the internal temperature below -60°C in a dry ice tank, and added 4-alkoxybromobenzene prepared from 4-alkoxybromobenzene synthesized in Production Example 1 and magnesium to this solution. 70 ml of anhydrous tetrahydrofuran solution containing 0.09 mol of alkoxyphenylmagnesium bromide was added dropwise over about 10 minutes with stirring. After stirring at -60°C for 2 hours, 10 ml of water was added dropwise, and using the heat of reaction, the internal temperature was gradually raised to -30°C. Next, remove the dry ice bath and add 55 mL of an aqueous solution containing 3 ml of concentrated sulfuric acid.
ml was added dropwise, the temperature was raised to room temperature to complete the reaction. Tetrahydrofuran was distilled off under reduced pressure,
200 ml of ether was added to extract the target product. A white solid was obtained after distilling off the ether. 20 of this
It was dissolved in n-hexane at a temperature of ~30°C, recrystallized by cooling to -30°C, and after air drying, the 4-alkoxyphenylboronic acids shown in Table 4 below were obtained. Its structure was confirmed by IR and NMR spectra. The results are shown in Table 4.

[Table] Production Example 3 Synthesis of 2-alkyl-1,3-propanediol Into two three-necked flasks equipped with a stirrer, thermometer, dropping funnel, and reflux condenser, 15 g (0.4 mol) of lithium aluminum hydride and anhydrous were added. ether 600ml
0.2 mole of 2-alkylmalonic acid was added to the suspension in anhydrous ether with vigorous stirring.
A solution dissolved in 20 ml was added dropwise at an internal temperature of 5°C. After the dropwise addition was completed, the reaction was carried out at reflux temperature for 6 hours. After the reaction was completed, the reaction product was ice-cooled, and in order to decompose excess lithium aluminum hydride, 50 ml of water-saturated ether and then 10 ml of a 5% aqueous sodium hydroxide solution were added dropwise, followed by stirring at 25°C overnight. The white inorganic matter produced was removed and a white solid was obtained after concentrating the mother liquor. Recrystallization was performed with n-hexane to obtain 2-alkyl-1,3-propanediol shown in Table 5 below.

[Table] Example 1 2-(4'-alkoxyphenyl)-5-
Production of alkyl-1,3,2-dioxaborinane 0.01 mol of phenylboronic acid and 0.01 mol of 2-alkyl-1,3-propanediol obtained in Production Example 3 were charged together with 50 ml of toluene, and azeotropic dehydration was carried out at reflux temperature. The reaction was completed in about 1 to 2 hours, toluene was distilled off under reduced pressure, and the residue was isolated and purified by silica gel column chromatography (40 g of 200 mesh silica gel, developing solvent: dichloromethane). -(4'-alkoxyphenyl)-5-alkyl-1,3,2
-Dioxaborinan was obtained with a yield of 90-96%. A compound with even higher purity can be obtained by recrystallization from petroleum ether. The results are shown in Tables 6-1 and 6-2 together with the phase transition temperature of each compound obtained. The symbols in the table below represent the following: C: crystalline phase, S _C ^* : chiral smectic C phase,
S _A : Smectic A phase, I: Isotropic liquid phase

【table】

【table】

[Table] Example 2 The liquid crystal compositions shown in Table 7 below were prepared using the compounds of the present invention obtained in Example 1, and the phase transition temperatures thereof were measured, and the results were as shown in Table 7. .

〔Effect of the invention〕

As shown in Example 1 above, the compound of the present invention exhibits an S _C ^* phase near room temperature and is a ferroelectric compound, and the results of Examples 2 and 3 indicate that the compound of the present invention has a wide temperature range including room temperature. It is clear that it will be an effective component in obtaining a chiral smectic liquid crystal composition. Such effects are achieved for the first time by the present invention.

Claims (1)

[Claims] 1 General formula:
is 1 or 5, n is an integer of 0 to 5, and 〓 is an asymmetric carbon atom). 2 General formula: (In the formula, R represents an alkyl group having 1 to 18 carbon atoms, m
is 1 or 5, n is an integer of 0 to 5, and 〓 is an asymmetric carbon atom.