JPH0739579B2 - Liquid crystal material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a novel liquid crystal material, and more particularly to a liquid crystal material suitable for a ferroelectric liquid crystal having a chiral smectic C phase.

(Prior Art) Liquid crystals have been widely used in calculators, watches, etc. as a favorite of small sized plat panel displays. Further, recently, it has been used as a display for automobiles and a display for personal computers. Furthermore, it has been applied to motion picture displays such as small LCD TVs.

By the way, conventionally, a twist nematic liquid crystal is known as a liquid crystal used for a calculator, a clock and the like. However, the display method using the liquid crystal has problems such as insufficient response speed and occurrence of crosstalk. Therefore, it is difficult to apply such a display system to a large-screen display for moving images or the like that requires a fast response speed. To solve these problems thin f
A method such as an active matrix using an ilm transistor (TFT) has also been developed, but there were problems such as high manufacturing cost.

From this, a display system using a ferroelectric liquid crystal is drawing attention as an alternative to the display system using the twisted nematic liquid crystal. This method was announced by RB Mayer et al. In 1975, and has features such as faster response speed and memory effect than the conventional method. The ferroelectric liquid crystal has a chiral smectic C phase in the liquid crystal form. As a liquid crystal material that can be such a ferroelectric liquid crystal, many materials have been known in the past. However, the conventional liquid crystal materials are unstable with respect to moisture and light in the air, and have a narrow temperature range in which the chiral smectic C phase is obtained, which poses a problem that there is a large restriction in use.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and expands the temperature range of the chiral smectic C phase required for application to ferroelectric liquid crystals. An object of the present invention is to provide a liquid crystal material that can be manufactured and is excellent in thermodynamic stability.

[Structure of the Invention] (Means and Actions for Solving Problems) [Wherein R is an alkyl group and R ^* is an optically active group having a mismatched carbon atom], and is a liquid crystal material composed of a 7-alkoxyfluorene-2-carboxylic acid ester.

From the viewpoint of expanding the temperature range of the chiral smectec C phase, R in the general formula (A) is preferably selected from a linear alkyl group having 3 to 18 carbon atoms, and more preferable R is 4 carbon atoms.
~ 14 straight chain alkyl groups.

R ^* in the general formula (A) is a general formula from the viewpoint of expanding the temperature range of the chiral smectec C phase. (However, R _{1 to} R ₃ in the formula are any of an alkyl group, a halogen group, a cyano group, a trifluoroalkyl group, and a hydrogen atom, and R ₁ ≠ R ₂ , R ₂ ≠ R ₃ , and R ₃ ≠ R ₁ And n represents an integer of 0 to 15 (preferably an integer of 0 to 8)]. It is desirable to use an alkyl group having an asymmetric carbon atom. More preferable R ^* is an optically active 2-methylbutyl group or 2-octyl group.

7-Alkoxyfluorene-2 as the liquid crystal material of the present invention
-The carboxylic acid ester is produced by the synthetic method described below.

In the above synthesis method, the production of the raw material (I) and (I) to
The reactions up to (III) are known methods. That is, the raw material (I) can be obtained from commercially available fluorene through a three-step reaction as disclosed in, for example, Org.Synth.1933, 13 , 74. In addition, the above reactions (I) to (II) are CHCoak
J. Org. Chem. 1954, 19 , 626 by J. Org.
The methods announced in 57,3228, respectively. On the other hand, (I
The 7-alkoxyfluorene-2-carboxylic acid ester of V) is obtained by converting (III) into an acid chloride with thionyl chloride and then reacting with an optically active alcohol in pyridine.

Therefore, the liquid crystal material of the present invention, 7-alkoxyfluorene-2-carboxylic acid ester represented by the general formula, has an expanded temperature range of the chiral smectec C phase and is excellent in thermodynamic stability. Therefore, a ferroelectric liquid crystal having a chiral smectic C phase can be realized in a wider temperature range than conventional by mixing two or more of these or a compound having another chiral smectic C phase. .

(Examples of the Invention) Hereinafter, synthesis examples and examples of the present invention will be described in detail.

Synthesis Example 1 First, 38.2 g (0.1 mol) of 7-heptyloxy-fluorene-2-carboxylic acid synthesized by a known method and 60 ml of thionyl chloride were refluxed for 5 hours while stirring. Subsequently, excess thionyl chloride was distilled off, and the residue was recrystallized with n-hexane to obtain 26.4 g (yield 80%) of white crystals (acid chloride).

Then, 4.8 g of (−)-2-methyl-1-butanol was added to a solution of 20 g (0.06 mol) of the above acid chloride in 80 ml of pyridine.
ol) was added dropwise in 10 ml of pyridine solution over 10 minutes, and the mixture was heated with stirring in an oil bath at 90 ° C. for 4 hours. Subsequently, after cooling to room temperature, the resulting pyridine solution was added to 500 m.
The resulting precipitate was collected by filtration. Subsequently, this precipitate was recrystallized twice with ethanol to obtain 19.5 g of white crystals (yield 85%).

When the obtained white crystals were dissolved in heavy acetone and analyzed by NMR, the NMR spectrum shown in the drawing was obtained. Furthermore, when an elemental analysis of white crystals was performed, C: 79.4, H:
It was 8.3, O: 12.2 (calculated value C: 79.19, H: 8.63, O: 12.18). From these illustrated NMR spectra and elemental analysis, white crystals were identified as R in the above general formula A by C ₇ H ₁₅ , R ^* . Was confirmed to be 7-heptyloxyfluorene-2-carboxylic acid-2-methylbutyl ester.

Synthesis Examples 2-5 7-octyloxy-fluorene-2-carboxylic acid, 7
0.1 mol of nonyloxy-fluorene-2-carboxylic acid, 7-decyloxy-fluorene-2-carboxylic acid and 7-undecyloxy-fluorene-2-carboxylic acid, respectively.
Prepared and carrying out the same reaction as in Synthesis Example 1 to obtain optically active 7-octyloxyfluorene-2-carboxylic acid-2-methylbutyl ester, 7-nonyloxyfluorene-2-carboxylic acid-2- Methyl butyl ester, 7-decyloxyfluorene-2-carboxylic acid-
2-Methylbutyl ester and 7-undecyloxyfluorene-2-carboxylic acid-2-methylbutyl ester were obtained. It was confirmed that these compounds had the above structure by NMR spectrum analysis and elemental analysis.

Then, the melting point and each phase transition temperature of the compounds obtained in Synthesis Examples 1 to 5 were examined. The results are shown in the table below.

In the above table, C is a crystalline phase, SmC ^* is a chiral smectec C phase, SmA is a smectec A phase, and I is an isotropic liquid phase. Further, () indicates a monotropic phase transition temperature.

Example 1 Optically active 7-heptyloxyfluorene-2-carboxylic acid-2-methylbutyl ester and 7-octyloxyfluorene-2-carboxylic acid-2-methylbutyl ester obtained by the above-described synthetic method were prepared at a ratio of 1: 1. A mixture was prepared by mixing in proportions.

When each phase transition temperature of the obtained mixture was measured, C →
The values were SmC ^* 35.5 ℃, SmC ^* → SmA 42 ℃, SmA → 170.5 ℃.
From this result, it was found that a liquid crystal composition in which SmC ^* was stabilized was obtained by mixing the above compounds.

Example 2 Optically active 7-heptyloxyfluorene-2-carboxylic acid-methylbutyl ester synthesized by the above method,
7-octyloxyfluorene-2-carboxylic acid-2-
Methyl butyl ester, 7-decyloxyfluorene-
A mixture was prepared by equimolar mixing 2-carboxylic acid-2-methylbutyl ester.

When each phase transition temperature of the obtained mixture was measured, C →
The values were SmC ^* 27.5 ℃, SmC ^* → SmA 44 ℃, SmA → I 75 ℃.
From this result, it was found that the liquid crystal composition in which the SmC ^* was stabilized was obtained by mixing the respective compounds, as in Example 1.

[Effects of the Invention] As described in detail above, according to the present invention, a liquid crystal material comprising a compound represented by the general formula (A), in which the temperature range of the chiral smectic C phase is widened and thermodynamic stability is excellent. It is possible to obtain a ferroelectric liquid crystal having a chiral smectic C phase stably in a wide temperature range by mixing these liquid crystal materials or another liquid crystal material showing a chiral smectic C phase. Has a remarkable effect.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing shows the 7-heptyloxyfluorene-2-carboxylic acid-2-methylbutyl ester synthesized in Synthesis Example 1.
It is a figure which shows NMR-spectrum.

Claims (4)

[Claims] 1. A general formula A liquid crystal material comprising a 7-alkoxyfluorene-2-carboxylic acid ester represented by the formula [wherein R represents an alkyl group and R ^* represents an optically active group having an asymmetric carbon atom]. 2. R in the general formula (A) is a straight chain alkyl group having 3 to 18 carbon atoms.
The liquid crystal material according to the item. 3. A general formula Claims first, characterized in that (A) in the R ^* is an optically active 2-methylbutyl group
The liquid crystal material according to the item. 4. The liquid crystal material according to claim 1, wherein R ^* in the general formula (A) is an optically active 2-octyl group.