JPS59134767A - Ester compound having negative dielectric anisotropy - Google Patents

Abstract

NEW MATERIAL:The 2-cyano-4-fluorophenol ester derivative of formula I (the ring X is group of formula II or III; R is 1-10C alkyl or alkoxy). EXAMPLE:trans-4-Propylcyclohexanecarboxylic acid 2-cyano-4-fluorophenyl ester. USE:A liquid crystal substance having negative dielectric anisotropy. It is useful for a guest-host display element. PROCESS:The compound of formula I can be prepared by reacting the corresponding carboxylic acid chloride of formula IV with 2-cyano-4-fluorophenol of formula V in the presence of pyridine. The compound of formula III is obtained by dehydrating 5-fluorosalicylaldehyde oxime with acetic anhydride.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel liquid crystal compound having negative dielectric anisotropy and a liquid crystal composition containing the same.

Liquid crystal display crystals utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, but depending on the display format, TN
It is divided into various types such as type (twisted nematic type), DS type (dynamic scattering type), guest-host type, and DAP type.
The properties of liquid crystal materials suitable for each use vary. However, all seven liquid crystal materials share the need to be stable against moisture, air, heat, light, etc., and they are also required to exhibit a liquid crystal phase over as wide a temperature range as possible, centered around room temperature. It is being However, at present, there is no single compound that satisfies these conditions, and the current situation is to use liquid crystal compositions obtained by mixing several types of liquid crystal compounds and non-liquid crystal compounds.

Recently, guest display, which is a color LCD display method, has been
Host-type liquid crystal display devices have started to attract attention. This uses a mixture of liquid crystal and dye, but a liquid crystal with negative dielectric anisotropy is used for the positive guest/host type display element. Therefore, there is a need for liquid crystal compounds or liquid crystalline compounds having various properties, good compatibility, and negative dielectric anisotropy that can be used as constituent components of liquid crystals.

An object of the present invention is to provide a novel compound constituting a liquid crystal composition suitable for such uses.

That is, the present invention e is a general formula (in the above formula, y is either -0- or -0-,
and R represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms) and a liquid crystal composition containing at least one ester derivative of 2-cyano-4-fluorophenol. The compound of the present invention itself does not exhibit a liquid crystal phase, but since its dielectric anisotropy value is about 14% false, other nematic liquid crystals, such as biphenyl, ester, cyclohexane carboxylic acid ester, phenylcyclohexane, etc. By mixing with one type or several types of liquid crystal compounds such as phenylmetadioxane type and phenylmetadioxane type, guest
A liquid crystal composition having negative dielectric anisotropy that can be used for host-type display devices can be obtained. It can also be used in the two-frequency method, which has been attracting attention recently.

Next, the method for producing the compound of the present invention will be described. First, the desired compound is obtained by reacting the corresponding carboxylic acid acid chloride with 2-cyano-4-fluorophenol in the presence of pyridine. The 2-cyano-4-fluorophenol used here was prepared by dehydrating the oxime of 5-fluorosalicylaldehyde with acetic anhydride. The compound of the present invention will be explained in more detail by using the following examples, which are represented by a chemical formula.

Example [trans-4-zorobylcyclohexanecarboxylic acid]
Production of 2-cyano-4-fluorophenyl ester] (1) Production of 2-cyano-4-fluorophenol,
5-fluorosalicylaldehyde oxime 20.29 (
1J, 18 mol) was dissolved in 100 ml of acetic anhydride and refluxed for 5 hours. After the reaction was completed, acetic anhydride was distilled off under reduced pressure, and a solution of 20 f of potassium hydroxide dissolved in 100*J of water and 100 vtl of ethanol were added to the remaining oil at 80°.
Warm at C for 2 hours. Cool to room temperature and add 6N-HCl
When 20 ynl and 200πl of water are added, crystals are precipitated. The crystals were filtered and dried. Harvest 15.611
, m, p, 121-122°C. This was used as it was in the next reaction - (2) 1.5 g (0,011 mol) of esterification/ζ2-cyano-4-fluorophenol obtained in (1) was dissolved in 20 rst of pyridine, and trans -4-propylcyclohexanecarboxylic acid chloride 2,1f (0,011 mol)
'5 =) Add 20 txtK dissolved fc solution of toluene,
React at 60'C for 3 hours. After the reaction, 100 pots of water?
Separate the toluene layer and add 6N hydrochloric acid and 2N sodium hydroxide solution.

It is then washed with water and finally dried over anhydrous sodium sulfate. Toluene is distilled off and the remaining crystals are recrystallized from 10 trtl of ethyl alcohol to obtain the desired trans-4-
Propylcyclohexanecarboxylic acid-2-cyano-4-
Fluorophenyl ester 2.1f (yield 65%) was obtained. This material had a melting point of 722-72.8°C.

Examples 2 to 10 Transformer-4- in Example 1 in the same manner as Example 1
The desired compounds were prepared using the corresponding carboxylic acid chlorides in place of propylcyclohexanecarboxylic acid chloride. These results are combined with the results of Example 1 in the first
Shown in the table.

Table 1 Example 11 (Usage Example) The ester-based nematic liquid crystal composition A having the above proportions had an IN~■ point of 62.8°C1Δε of -i.

The viscosity at 20°C is 18.5 cp. A guest-host type liquid crystal cell was prepared by adding 1% of commercially available dye G-224 manufactured by Merck & Co., Ltd. to this mixture and sealing it in a cell.The threshold voltage of the cell was measured and found to be 3.80V. Next, the compound of the present invention, trans-4-propylcyclohexanecarboxylic acid-2-cyano-4-fluorophenyl ester 5i1S,) 5 parts of trans-4-butylcyclohexanecarboxylic acid-2-cyano-4-fluorophenyl ester, ) lance-4-hentylcyclohexanecarvone v-2-cyno-4-fluorophenyl ester l,=e A liquid crystal composition was prepared by adding to 75 parts of the above liquid crystal composition A. The N-I point is 47C9△ε is -2,
The viscosity at 7°20°C was 24.7 cp, and when a guest-host type liquid crystal cell was made with the same 1% dye G-224 as before and the threshold voltage was measured, it was 8.10V. It decreased significantly.

that's all Patent applicant: Chisso Corporation Representative Patent Attorney Yatabe Sasai

Claims (2)

[Claims] (1) 2-cyano- represented by the general formula (in the above formula, Yaken is -0-, (), and R represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms) Ester derivative of 4-fluorophenol. (2) 2-cyano represented by the general formula (in the above formula, "Yahe" is either -0- or -0-, or R represents an alkyl group or an alkoxy group having 1 to 10 carbon atoms) - A liquid crystal composition containing at least one ester derivative of 4-fluorophenol.