JPS58164676A - Over-coolable nematic liquid crystal composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to supercoolable nematic liquid crystal compositions for electro-optical structural elements for modulating transmitted or reflected light and for displaying numbers, symbols and figures.

Nematic liquid crystals can be used as electro-optical structural elements, especially cells with twisted nematic structure
Cell (8chadt-Helfrlah-2・11en
)) is known for use in

For practical use in various fields, depending on the field of application, the above-mentioned components and therefore liquid crystals have to be characterized by their melting and clearing points, threshold and operating voltages, decay onset and decay times, and thermal and chemical stability. There are various requirements regarding Hitherto, there are no compounds that substantially satisfy the above requirements in a pure state. Therefore, mixtures consisting of at least 3 to 6 components of various properties are invariably used. New applications, for example in electro-optical components of vehicles, require low operating temperatures and storage at which liquid crystal mixtures, which are in the thermodynamically metastable nematic state in most cases at temperatures below o'c, do not crystallize. temperature is required.

However, due to their good properties, many mixtures are suitable for practical use, such as various 4-n-alkylcyclohexane-carboxylic acids-4'-'/77 phenyl esters Incense 11-1'-
Mixtures of cyanophenyl esters cannot be used at low temperatures.

This is because they crystallize at temperatures below 0°C, and therefore the required orientation of the nematic liquid crystals by the electrodes is no longer guaranteed even after the cough mixture has been melted into the liquid. .

The object of the invention is a new nematic liquid-crystal mixture for electro-optical components that does not crystallize at temperatures below 0.degree.

The object of the present invention is to find suitable liquid crystal compounds which, when added to nematic liquid crystals, which can be one compound or a mixture of many compounds, significantly reduce the possibility of supercooling.

The inventors were surprised by the addition of a novel liquid crystalline 6-alkylnaphthalene-2-carboxylic acid-(lance-4-alkylcyclohexyl ester) to a liquid-crystalline nematic mixture suitable for use in electro-optical structural elements. It has been found that over time the supercooling potential is significantly reduced and crystallization of the mixture at temperatures below 0° C. is avoided for a long time.

Novel liquid crystal 6-alkylnaphthalene-2-carbon a
The l-(trans-V dialkylcyclohexyl ester) is colorless, thermally and chemically stable and already in its pure state the invention is illustrated in more detail by the following examples.

Example 1 Novel liquid crystal 6-alkylnaphthalene-2-carvone I
I() lance-4-furkylcyclohexyl ester)
from 6-alkylnaphthalene-2-carboxylic acid chloride and toran J-4-alkylcyclohexalne:
) according to the following general formula: Example 2 Preparation of 6-n-butylnaphthalene-2-carboxylic acid-[trans-4-n-butylcyclohexyl ester]: t trans-4-n-butylcyclo 121111F ((18
Add 4-n-butylphenol from mob) and add the solution.
1st Raney nickel and 60 to 90
Shake until the predetermined pressure drop occurs after minutes. The catalyst is then stripped off and, after removal of the solvent, the residue is fractionated under reduced pressure.

Main fraction (boiling point: 110-116℃/t5K Pm
) contains a theoretical amount of 8096 4-n-butylcyclohexanol (cis-trans mixture). Engineering R
- Spectral analysis confirms complete hydrogenation and absence of cyclohexanone. Separation of isomers was performed using a Normag micro-rotating belt column (Normag-M
Lkro-Drsh-bandkolonno)
Column charge for 1-7 minutes using (55O11 plates), 1
:50 reflux ratio and a distillation rate of 1 #l/min.

Yield of F lance type product: 313-57.5 F (theoretical value 25-5 ol): Boiling point: 69-70°C/α65
1CPa02, 7.8 f (α05 mob
) of trans-4-n-butylcyclohexanol was dissolved in 6 of 12.32 (α05 mob ).
-n-Butylnaphthalene-2-carboxylic acid chloride is added dropwise at 0°C. The reaction mixture is heated at room temperature for 24 hours and then heated to 70° C. for 1 hour. The cold reaction mixture is then shaken over 50 ml of ice and 150 ml of concentrated sulfuric acid mixture. It is then treated several times with ether, the ether extract is washed with 5es NaHCO3 bath, dilute hydrochloric acid and thoroughly with water, the solvent is distilled off and the residue is washed several times with methanol or L ethanol. Recrystallize twice.

Yield: 9.15 ? (Theoretical value 5o96): Crystalline solid state (K) 54.5, nematic state M (16g
Isotropic liquid.

Example 3 Examples of the compounds of the present invention are shown in the table below.

In the table: X-crystalline solid state N-nematic state S-smectic state 1-unidirectional liquid
Lance-4-n-alkyl-cyclohexyl ester] ” C4Hs 0mlli
-3t5 - -
37 ・lb a4a @ 1m
! sH, -44--71s @jC04B1
O4Hg '345'!
8”1d 04B, am)iH
-57--77-Ie 04H嘗C@H1l
'5 & 5-・6L5 "2a (4HH
0111B ・51 (・44
) ・2b 0aH1, away -9
15-(-7A5)-2a (4H17,04
Book H 52-1147.5 '2dO Hatake H1,O,
H, 1-44, 5-65-84・2e O12
Yes, O, Hll -445(-37) -
69,5.

Example 4 Twisted nematic liquid crystal structure [Shaded-Helfrioh-Zssle
) In a cell of type J, a mixture M1 of the following composition is used: 'This mixture exhibits the following properties.

[10~1411721g Layer thickness: d-19,8PM1 Threshold voltage: Uo-t77 (20℃) Start time: tlso-560ms (20℃) Extinction time: tm5o-180mm (20℃) Long time The melting point, particularly of 10-14° C., which cannot be significantly supercooled throughout, precludes its use at low temperatures.

By adding the compound Na1C, which has an enthalpy of fusion of 25500 J/ll01, can be significantly supercooled and is very thermally stable, a mixture MiB is obtained with the following properties:

Composition of MiB: A mixture of 80 mol 9 of M1 and 20 mol % of the compound-10. No crystallization occurred after 4 weeks, and no crystals formed even after a small amount of the sample was weighed on a microscope cooling table for 8 hours at -20°C. As a result, this stable melting point could not previously be confirmed due to the high possibility of supercooling.

Electro-optical parameters at 20°C: Bite thickness: 21
μOtori threshold voltage: U, -tav/s o OH1 start time:
(son)t, -1q 40 rna extinction time: (5
0ch) tA -575188Continued from page 10Inventor Hans-Joachim Deutschell, German Democratic RepublicHalle, Feszpremelstrasse15 0Inventor Sabine SchuleGerman Democratic RepublicStendal am Mühlenberg6 0 Inventor Wolfgang Schiefel Boddam Allaf der Kiewitz 31, German Democratic Republic

Claims (1)

[Claims] A supercoolable nematic liquid crystal composition for electro-optical structural elements, characterized in that it contains liquid crystals and 6-alkylnaphthalene-2-carboxylic acid (lance-4-alkylcyclohexyl ester).