JPS59161349A - Liquid crystal compound with negative dielectric anisotropy - Google Patents

Abstract

NEW MATERIAL:A compound of formula I (R is 1-8C alkyl, alkoxy; ring A and ring B are formula II and III). EXAMPLE:Trans-4-(trans-4'-propylcyclohexyl)cyclohexanecarboxylic acid 2-cyano- 4-fluorophenyl ester. USE:A liquid crystal composition: it has negative anisotropy and its mixing with other nematic liquid crystals gives a liquid crystal composition which has negative anisotropy and can be used in guest-host type display elements. PREPARATION:The reaction of a carboxylic acid chloride of formula IV with 2-cyano-4-fluorophenol of formula V in the presence of pyridine gives the compound of formula I . The compound of formula V is obtained by dehydration of 5-fluorosalicyl aldehyde oxime with acetic anhydrice.

Description

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

Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal materials, but depending on the display format, TN
type (twisted nematic, J)m), DS type (dynamic scattering type)
It is divided into various types such as , guest-host type, and DAP type, and products '4! are suitable for each type of use. /J The nature of quality is different. It is common that F-quality substances need to be stable against moisture, air, heat, and sources, and they are also required to exhibit a liquid crystal phase over as wide a temperature range as possible, centered around room temperature. . 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
Host-type crystalline display devices have started to attract attention. This uses a mixture w of liquid crystal and dye, but a liquid crystal having negative dielectric anisotropy is used for a positive guest-host type display element. Therefore, there is a need for a liquid crystal compound having various properties and having good compatibility with negative dielectric properties as a constituent component of the liquid crystal.

The present invention has been made in view of the above points.

The purpose of the present invention is to provide a compound having a V-type that constitutes a liquid crystal composition exhibiting negative dielectric anisotropy.

That is, the present invention provides a 2- A liquid crystal composition comprising a carbon ester derivative of cyano-4-fluorophenol and at least one thereof.

The compound of the present invention has several practical temperature ranges, and its dielectric anisotropy is about 14. By mixing with metadioxane, phenylpyrimidine threads, or other nematic crystals, it is possible to obtain liquid crystal compositions with negative dielectric anisotropy that can be used for guest-host display devices. 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 corresponding carbonyl chloride is added to 2-cyano-4-
The desired compound can be obtained by reacting with fluorophenol. This can be expressed as a chemical formula as follows.

(In the above formula, R, -()- and -σX represent the same as above.) The 2-noano-4-fluorophenol used here is 5
-Produced by dehydrating the oxime of fluorosalicylaldehyde with acetic anhydride. This can be expressed as a chemical formula as follows.

The compounds of the present invention will be explained in more detail with reference to the following examples. In each example, the crystalline phase is abbreviated as 01, the nematic phase as N, the melting point as m4+, and the transparent phase as N.

[Example 1] Production of trans-4-(trans-4'-propylcyclohexyl)cyclohexanecarboxylic acid-2-Schiff/-4-fluorophenyl ester (1) Production of 2-cyano-4-fluorophenol 5-fluoro Salicylaldehyde oxime 20.2f
(0.13 mol) was dissolved in 100 d of acetic anhydride and flowed at a rapid rate for 5 hours. After the reaction is complete, the anhydrous vinegar is distilled off under reduced pressure, and the remaining oil is mixed with 209 g of potassium hydroxide and 101 m7 of water! A 100% solution of ethanol was added to the mixture, and the mixture was heated at 80°C for 2 hours. Leave to cool to room temperature, add 50 g of 6N hydrochloric acid and 2 g of water.
00rnt was added to precipitate crystals. The crystals were filtered and recrystallized from 30 g of methanol to obtain needle-shaped crystals of 15.6 f.

The melting point was 121-122°C.

(2) Esterification (1) 1.7 M (0,011 mol) of the 2-cyano-4-fluorophenol obtained in 2-cyano-4-fluorophenol was dried in 20 y of pyridine.
I7! Trans-4-(trans-4',7'ropylcyclohexyl)cyclohexanecarboxylic acid chloride 3. A bath solution in which Of (0,011 mol) was dissolved in dry toluene 20°C was added, and the mixture was heated at 60°C for 3
Allowed time to react. After the reaction is completed, the reactant is poured into 1 glass of water, the toluene layer is separated, and washed with 6R salt and 2N sodium hydroxide solution, then water. Dry over sodium. The remaining crystals were re-crystallized from 1 mol of acetate ethyl chloride under heavy toluene, and the desired product was cyclohexanecarbo7z-2.
-77/'-4-fluorophenyl ester 2゜7y(
A yield of 68 cm) was obtained.

This product has an O-N point; 108.7°C, 11-1 point; 15
0.L1°C.

Examples 2 to 11 All operations were carried out according to Example 1, except that the corresponding carboxyl chloride was used in place of the trans-4-(trans-l-propylcyclohexylcocyclohexane carbonyl chloride) in Example 1. Go to the desired compound ′+g
was manufactured. These results are combined with the results in the example.
Shown in the table.

(・) indicates a Notrovitsk-style item.

Example 12 (Application example) The N-1 point of weight-cracked ester-based nematic liquid crystal composition A is 74
．． At 5°C, the dielectric constant anisotropy Δε was -1,420°C, the viscosity was 20.3 cp. A guest host cell was prepared by adding 1% of commercially available dye G-224'fr manufactured by Merck & Co., Ltd. to this mixture and sealing it in a cell, and the threshold voltage was determined to be 3.7V. Next, a liquid crystal composition was prepared by adding the compound trans-4-(tra/su-4'-propylcyclohexyl)cyclohexanecarboxylic acid-cyclohexyl)cyclohexane/carbopentylcyclohexyl)cyclohexane. This B1-4 point is 79.2℃, the dielectric constant anisotropy Δε is -2,
The viscosity at 4.20°C is 27 cp, and 1% of the dye (1-224'i) was added to this as before (I made a guest-host type late crystal cell and measured its threshold voltage, and it was 2.9V). It decreased significantly.

that's all

Claims (1)

[Claims] (]) General formula (in the above formula, R is alkyl having 1 to 8 carbon atoms, 2
- A liquid crystal compound having negative dielectric anisotropy due to a carbonyl ester derivative of cyano-4-fluorophenol. (2) 2-cyano- represented by the general formula (in the above formula, R represents an alkyl group or alkoxy group having 1 to 8 carbon atoms, -σX, and each symbol represents -()- or +) A liquid crystal composition containing at least one liquid crystal compound having negative dielectric anisotropy due to a carboxylic acid ester conductor of 4-fluorophenol.