Liquid-crystalline medium

• US 5,744,060 A
• Filed: 08/02/1996
• Issued: 04/28/1998
• Est. Priority Date: 08/04/1995
• Status: Expired due to Term

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Pauluth, Detlef, Schuler, Brigitte, Tarumi, Kazuaki, Bartmann, Ekkehard
• Primary Examiner(s): Kelly, C. H.
• Application Number:
  US08/691,234
• Time in Patent Office: 634 Days
• Field of Search: 252/299.63, 252/299.66
• US Class Current: 252/299.63
• CPC Class Codes: C09K 19/30 containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
• CPC Class Codes: C09K 19/3098 Unsaturated non-aromatic rings, e.g. cyclohexene rings

Abstract

A liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, characterized in that it comprises one or more compounds of the general formula I ##STR1## in which R, Y, L¹ and L² are as defined in claim 1.

Claims

1. A liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, comprising one or more compounds of the formula I, ##STR48## in which R is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF₃ or monosubstituted to perhalo-substituted by halogen, it also being possible for one or more CH₂ groups in these radicals to be replaced, in each case independently of one another, by --O--, --S--, --O--, --CO--, --CO--O--, --O--CO-- or --O--CO--O-- in such a way that O atoms are not linked directly to one another,

Y is F, Cl or halogenated alkyl, alkenyl or alkoxy having 1 to 6 carbon atoms, and

L¹ and L² are each, independently of one another, H or F;

additionally comprising one or more compounds selected from the group consisting of those of the formulae II, III, IV, V, VI and VII;

##STR49## in which the individual radicals having the following meanings;

R⁰ ;

n-alkyl, oxaalkyl, fluoroalkyl or alkenyl in each case having 1 to 7 carbon atoms,

X⁰ ;

F, Cl or halogenated alkyl, alkenyl or alkoxy having 1 to 6 carbon atoms.

Y¹ and Y² ;

in each case independently of one another H or F,

Z;

single bond or ##STR50## and r;

0 or 1.

2. Medium according to claim 1, wherein the proportion of compounds of the formulae I to VII together is at least 50% by weight of the total mixture.

3. Medium according to claim 1, wherein the proportion of compounds of the formula I is from 3 to 80% by weight in the total mixture.

4. Medium according to claim 1, wherein the proportion of compounds of the formulae II to VII is 20 to 80% by weight of the total mixture.

5. Medium according to claim 1, additionally comprising a compound of the formula ##STR51## in which R⁰ :

n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having 1 to 7 carbon atoms,

X⁰ ;

F, Cl or halogenated alkyl, alkenyl or alkoxy having 1 to 6 carbon atoms, and

Y² ;

H or F.

6. Medium according to claim 5, wherein X⁰ is F or OCF₃, and Y² is H or F.

7. Medium according to claim 1, wherein, in the compound of the formula I, Y is F or OCF₃, and L¹ and L² are H or F.

8. Medium according to claim 1, additionally comprising one or more compounds of the formula ##STR52## in which X⁰ is F, OCHF₂ or OCF₃,

Y¹ and Y² are each, independently of one another, H or F,

Z is a single bond or ##STR53## and R⁰ is n-alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having 1 to 7 carbon atoms.

9. Electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 1.

10. The medium of claim 1, wherein the mixture contains a compound of the formula IV which is of one of the following subformulae IVa to IVe:

##STR54##

11. The medium of claim 1, which additionally comprises one or more compounds selected from those of the following formulae VIII to XIII:

##STR55## in which R⁰, X⁰, Y¹ and Y² are independently as defined.

12. The medium of claim 1, which contains at least one compound of one of the formulae II to VII wherein ##STR56##

13. The medium of claim 1, which consists essentially of compounds of the formulae I to VII.

14. The medium of claim 11, which consists essentially of compounds of the formulae I to XIII.

15. A medium according to claim 1, which has a clearing point above 80°

C., a dielectric anisotropy value of ≧

6 and a nematic phase down to -20°

C.

16. A medium according to claim 1, which has a TN threshold of below 2.0 V.