Liquid crystal medium

• US 6,793,983 B1
• Filed: 06/21/2001
• Issued: 09/21/2004
• Est. Priority Date: 12/22/1998
• Status: Expired due to Fees

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Reiffenrath, Volker, Schuler, Brigitte, Heckmeier, Michael, Kirsch, Peer, Tarumi, Kazuaki
• Primary Examiner(s): WU, SHEAN CHIU
• Application Number:
  US09/868,866
• Time in Patent Office: 1,188 Days
• Field of Search: 428/1.1, 252/299.61, 252/299.63, 252/299.66, 252/299.67
• US Class Current: 428/1.1
• CPC Class Codes: C09K 19/3001 Cyclohexane rings
• CPC Class Codes: C09K 19/3003 Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
• CPC Class Codes: C09K 19/3028 in which at least two rings are linked by a carbon chain containing carbon to carbon single bonds
• CPC Class Codes: C09K 19/3066 in which the rings are linked by a chain containing carbon and oxygen atoms, e.g. esters or ethers
• CPC Class Codes: C09K 19/3402 having oxygen as hetero atom sugars C09K19/0422
• CPC Class Codes: C09K 19/42 Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40
• CPC Class Codes: C09K 2019/3422 the heterocyclic ring being a six-membered ring
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition

Abstract

The invention relates to a liquid-crystalline medium based on a mixture of polar compounds of positive dielectric anisotropy, characterized in that it comprises one or more compounds of the general formula I

and at least one compound of the formula

in which the substituents are as defined in claim 1.

Claims

1. Liquid-crystalline medium comprising a mixture of polar compounds of positive dielectric anisotropy, wherein the medium comprises one or more compounds of formula I

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 at least monosubstituted by halogen, where one or more CH₂ groups in these radicals are optionally, in each case independently of one another, replaced by —

O—

, —

S—

,

 

—

CO—

, —

CO—

O—

, —

O—

CO—

or —

O—

CO—

O in such a way that O atoms arc not linked directly to one another,

 

is a trans-1,4-cyclohexylene ring, in which one or two CH₂ groups are optionally replaced by —

O— and

/or —

S—

, or a cyclohexenylene ring,

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

Z is —

CH₂O—

, —

OCH₂—

, —

CH₂CH₂—

, —

CH═

CH —

, —

CF₂O —

, —

OCF₂—

, —

C₂F₄—

or a single bond, and

n is 1 or 2, and

the medium comprises one or more compounds of the formula

 

in which

R⁰;

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

X⁰;

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

Y²;

H or F.

2. Medium according to claim 1, which additionally comprises one or more compounds selected from the group consisting of compounds of the formulae II to VIII:

in which the individual radicals have the following meanings;

R⁰;

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

X⁰;

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

Z⁰;

—

C₄H₈—

, —

CF₂O—

, —

OCF₂—

, —

C₂F₄—

, —

CH₂O—

, —

OCH₂—

or —

COO—

;

Y¹, Y², Y³ and Y⁴;

each, independently of one another, H or F, and

r;

0 or 1.

3. Medium according to claim 2, wherein the proportion of compounds of the formulae I to VII in the mixture as a whole is at least 50% by weight.

4. Medium according to claim 1, wherein the proportion of compounds of the formula I in the mixture as a whole is from 5 to 50% by weight.

5. Medium according to claim 2, wherein the proportion of compounds of the formulae II to VIII in the mixture as a whole is from 20 to 80% by weight.

6. Medium according to claim 2, wherein the medium comprises at least one compound of formulae II to VIII, wherein X⁰ is F or OCF₃, and Y² is H or F.

7. Medium according to claim 1, wherein the medium comprises at least one compound of the formula I wherein Y is OCF₃ or CF₃.

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

10. Medium according to claim 1, wherein the medium comprises one or more compounds of the formula I having at least one ring A which is trans-1,4-cyclohexane or dioxane.

11. Medium according to claim 1, wherein the medium comprises one or more compounds of the formula I wherein Z is a single bond, —

COO—

or —

CH₂CH₂—

.

12. Medium according to claim 1, wherein the medium retains a nematic phase down to −

20°

C. or less, has a clearing point above 80°

C., and has a birefringence of ≦

0.08.

13. Medium according to claim 1, wherein the medium retains a nematic phase down to −

30°

C. or less, has a clearing point above 90°

C., has a birefringence of ≦

0.07.

14. Medium according to claim 1, wherein the medium has a TN threshold below 1.9 V.

15. Medium according to claim 1, wherein the medium has a TN threshold below 1.7 V.

8. Liquid-crystalline medium comprising a mixture of polar compounds of positive dielectric anisotropy, wherein the medium comprises at least one compound selected from the group consisting of the compounds of formulae Ia to In.

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 at least monosubstituted by halogen, where one or more CH₂ groups in these radicals are optionally, in each case independently of one another, replaced by —

O—

, —

S—

,

 

—

O—

, —

CO—

O—

, —

O—

CO—

or —

O—

CO—

O in such a way that O atoms are not linked directly to one another, and

the medium comprises one or more compounds of the formula

 

in which

R⁰;

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

X⁰;

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

Y²;

H or F.

16. Medium according to claim 8, wherein the medium comprises one or more compounds of each of the formulae Ib and Ie.

17. Medium according to claim 8, wherein the medium comprises one or more compounds of each of the formulae Ij and Ik.

19. Medium according to claim 8, which additionally comprises one or more compounds selected from the group consisting of compounds of the formulae II to VIII:

in which the individual radicals have the following meanings;

R⁰;

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

X⁰;

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

Z⁰;

—

C₄H₈—

, —

CF₂O—

, —

OCF₂—

, —

C₂F₄—

, —

CH₂O—

, —

OCH₂—

or —

COO—

;

Y¹, Y², Y³ and Y⁴;

each, independently of one another, H or F, and

r;

0 or 1.

20. Medium according to claim 8, wherein the proportion of compounds of the formulae Ia-In and formulae II to VIII in the mixture as a whole is at least 50% by weight.

21. Medium according to claim 8, wherein the proportion of compounds of the formulae Ia-In the mixture as a whole is from 5 to 50% by weight.

22. Medium according to claim 19, wherein the proportion of compounds of the formulae II to VIII in the mixture as a whole is from 20 to 80% by weight.

23. Medium according to claim 19, wherein the medium comprises at least one compound of formulae II to VIII, wherein X⁰ is F or OCF₃, and Y² is H or F.

24. Electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 8.

25. Medium according to claim 8, wherein the medium retains a nematic phase down to −

20°

C. or less, has a clearing point above 80°

C., and has a birefringence of ≦

0.08.

26. Medium according to claim 8, wherein the medium retains a nematic phase down to −

30°

C. or less, has a clearing point above 90°

C. has a birefringence of ≦

0.07.

27. Medium according to claim 8, wherein the medium has a TN threshold below 1.9 V.

28. Medium according to claim 8, wherein the medium has a TN threshold below 1.7 V.

18. A liquid-crystalline medium comprising a mixture of polar compounds of positive dielectric anisotropy, wherein the medium comprises one or more compounds of formula I

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 at least monosubstituted by halogen, where one or more CH₂ groups in these radicals are optionally, in each case independently of one another, replaced by —

O—

, —

S—

,

 

—

CO—

, —

CO—

O—

, —

O—

CO—

or —

O—

CO—

O in such a way that O atoms are not linked directly to one another,

 

is a trans-4,1-cyclohexylene ring, in which one or two CH₂ groups are optionally replaced by —

O— and

/or —

S—

, or a cyclohexenylene ring,

Y is halogenated alkyl, halogenated alkenyl, halogenated alkoxy or halogenated alkenyloxy having 1 to 6 carbon atoms,

Z is —

CH₂O—

, —

OCH₂—

, —

CH₂CH₂—

, —

CH═

CH—

, —

CF₂O—

, —

OCF₂—

, —

C₂F₄—

or a single bond, and

n is 1 or 2, and

the medium comprises one or more compounds of the formula

 

in which

R⁰;

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

X⁰;

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

Y²;

H or F, and

the medium additionally comprises one or more compounds selected from the group consisting of compounds of the formulae II to VIII;

 

in which the individual radicals have the following meanings;

R⁰;

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

X⁰;

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

Z⁰;

—

C₄H₈—

, —

CF₂O—

, —

OCF₂—

, —

C₂F₄—

, —

CH₂O—

, —

OCH₂—

or —

COO—

;

Y¹, Y², Y³ and Y⁴;

each, independently of one another, H or F, and

r;

0 or 1,

provided that the medium comprises at least one compound of the formula IV wherein r is 1, Y¹, Y² and Y³ is F and Y⁴ is H.

29. Medium according to claim 18, wherein the proportion of compounds of the formulae I to VIII in the mixture as a whole is at least 50% by weight.

30. Medium according to claim 18, wherein the proportion of compounds of the formulae II to VIII in the mixture as a whole is from 20 to 80% by weight.

31. Medium according to claim 18, wherein the medium comprises at least one compound of formulae II to VIII, wherein X⁰ is F or OCF₃, and Y² is H or F.

32. Electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 18.

33. Medium according to claim 18, wherein the medium retains a nematic phase down to −

20°

C. or less, has a clearing point above 80°

C., and has a birefringence of ≦

0.08.

34. Medium according to claim 18, wherein the medium retains a nematic phase down to −

30°

C. or less, has a clearing point above 90°

C., has a birefringence of ≦

0.07.

35. Medium according to claim 18, wherein the medium has a TN threshold below 1.9 V.

36. Medium according to claim 18, wherein the medium has a TN threshold below 1.7 V.