Claims
- 1. A liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, which comprises one or more compounds of the formula I ##STR95## in which R is H or an alkyl or alkenyl radical having 1 to 15 carbon atoms which are unsubstituted, monosubstituted by CN or CF.sub.3 or substituted one or more times by halogen, one or more CH.sub.2 groups optionally being replaced, in each case independently of one another by --O--, --S--, ##STR96## --CO--, --CO--O--, --O--CO-- or --O--CO--O--, such that 0 atoms are not linked directly to one another,
- A.sup.1 and A.sup.2 are each, independently of one another, a
- (a) trans-1,4-cyclohexylene radical, which is optionally substituted by one or two fluorine atoms and in which one or more non-adjacent CH.sub.2 groups are optionally replaced independently by --O-- or --S--,
- (b) 1,4-phenylene radical in which one or two CH groups are optionally replaced by N, or
- (c) radical selected from the group consisting of 1,4-cyclohexenylene, 1,4-bicyclo(2,2,2)-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl, the radicals (a) and (b) optionally being substituted by one or two fluorine atoms,
- Z.sup.1 and Z.sup.2 are each, independently of one another, --CO--O--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or a single bond, and one of the radicals Z.sup.1 and Z.sup.2 is optionally --(CH.sub.2).sub.4 -- or --CH.dbd.CH--CH.sub.2 CH.sub.2 --, provided that at least one of Z.sup.1 and Z.sup.2 is --CH.sub.2 CH.sub.2 -- or a single bond,
- X is halogenated alkyl, alkoxy, alkenyl or alkenyloxy, in each case having 1 to 6 carbon atoms,
- L is F and also H when X is OC.sub.2 F.sub.5, and
- m is 0, 1 or 2,
- excluding compounds wherein X is CF.sub.3, OCF.sub.3 or OCHF.sub.2 when m=0, A.sup.2 is a trans-1,4-cyclohexylene radical and Z.sup.2 is a single bond or when m=1, A.sup.1 and A.sup.2 are trans-1,4-cyclohexylene radicals and Z.sup.1 and Z.sup.2 are single bonds.
- 2. A medium according to claim 1, further comprising one or more compounds selected from the group consisting of the compounds of formulae II, III, IV and V: ##STR97## in which: R.sup.0 : alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having 1 to 7 carbon atoms,
- X.sup.0 : F, Cl, CF.sub.3, OCF.sub.3, OCHF.sub.2, OCH.dbd.CF.sub.2, OCF.dbd.CF.sub.2, OCFH.dbd.CF.sub.2 H or OCF.sub.2 --CF.sub.2 H,
- Y.sup.1 and Y.sup.2 : each, independently of one another, H or F
- r: 0 or 1.
- 3. A medium according to claim 2, further comprising one or more compounds selected from the group consisting of compounds of formulae VI to XII: ##STR98## in which the radicals R.sup.0, X.sup.0, Y.sup.1 and Y.sup.2 are as defined.
- 4. A medium according to claim 2, wherein the proportion of compounds of the formulae I to V together is at least 50% by weight in the total mixture.
- 5. A 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.
- 6. A medium according to claim 2, wherein the proportion of compounds of the formulae II to V is from 20 to 80% by weight in the total mixture.
- 7. A medium according to claim 3, which consists essentially of compounds of the formulae I to XII.
- 8. An electrooptical liquid crystal display which contains a liquid-crystalline medium according to claim 1.
- 9. A medium according to claim 1 which contains one or more compounds of the formula ##STR99## in which R is as defined, n is 1 or 2 and X.sup.1 is H, F or Cl.
- 10. A medium according to claim 1, which contains one or more compounds of the formula ##STR100## in which R is as defined, and r is 0 or 1.
- 11. The liquid-crystalline medium of claim 1, having a nematic phase range of -20.degree. C. to 80.degree. C., a clearing point above 80.degree. C., a dielectric anisotropy of .gtoreq.6 and a TN threshold of below 2.0 V.
- 12. The liquid-crystalline medium of claim 2, which comprises one or more compounds of the formulae II or III wherein X.sup.0 is OCF.sub.3, OCHF.sub.2, F, OCH.dbd.CF.sub.2, OCF.dbd.CF.sub.2, or OCF.sub.2 --CF.sub.2 H.
- 13. The liquid-crystalline medium of claim 1, which contains only up to about 10% by weight of compounds having nitrile groups.
- 14. The liquid-crystalline medium of claim 1, which contains no compounds having nitrile groups.
- 15. The liquid-crystalline medium of claim 1, wherein in formula I, L is F.
- 16. A tetrafluorobiphenyl compound of the formula II ##STR101## in which R is H or an alkyl or alkenyl radical having 1 to 15 carbon atoms which are unsubstituted, monosubstituted by CN or CF.sub.3 or substituted one or more times by halogen, one or more CH.sub.2 groups optionally being replaced, in each case independently of one another, by --O--, --S--, ##STR102## --CO--, --CO--O--, --O--CO-- or --O--CO--O--, and r is 0 or 1.
Priority Claims (3)
Number |
Date |
Country |
Kind |
43 15 410 |
May 1993 |
DEX |
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43 15 553 |
May 1993 |
DEX |
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43 15 555 |
May 1993 |
DEX |
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Parent Case Info
This is a divisional application of U.S. patent application Ser. No. 08/691,413 filed Aug. 19, 1996 now U.S. Pat. No. 5,718,840 which is a continuation application of Ser. No. 08/362,574, filed Jan. 9, 1995, now abandoned. which is a continuation application of Ser. No. 08/362,574, filed Jan. 9, 1995, now abandoned.
US Referenced Citations (13)
Foreign Referenced Citations (2)
Number |
Date |
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91 17135 |
Nov 1991 |
EPX |
507094 |
Oct 1992 |
EPX |
Divisions (1)
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Date |
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691413 |
Aug 1996 |
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Continuations (1)
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362574 |
Jan 1995 |
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