Liquid-crystalline medium

Abstract

The invention relates to liquid-crystalline mixtures comprising at least one compound of the formula I, ##STR00001##
in which
X, L.sup.1, L.sup.2, L.sup.3, L.sup.4 and alkenyl have the meanings indicated in claim 1,
in order to increase the pretilt at the polyimide surface,
and to
liquid-crystalline media comprising one or more compounds of the formula I in electro-optical liquid-crystal displays and in LC lenses.

Claims

1. A liquid-crystalline medium, comprising at least one compound of formula I, ##STR00246## in which X denotes F, a fluorinated alkyl radical having 1-6 C atoms, a fluorinated alkoxy radical having 1-6 C atoms, a fluorinated alkenyl radical having 2-6 C atoms, a fluorinated alkylalkoxy radical having 1-6 C atoms, L.sup.1-4 each, independently of one another, denote H or F, and alkenyl denotes an alkenyl radical having 2-6 C atoms, and at least one compound of formulae II and/or III: ##STR00247## in which A denotes 1,4-phenylene or trans-1,4-cyclohexylene, a denotes 1, R.sup.3 denotes alkenyl having 2 to 9 C atoms, and R.sup.4 denotes a straight-chain alkyl radical having 1 to 12 C atoms or alkenyl radical having 2 to 9 C atoms; provided that the one or more of the following conditions are met: the liquid crystalline medium contains at least one compound of formula I wherein L.sup.1-4 have one of the following meanings L.sup.1=L.sup.2=L.sup.3=L.sup.4=F, L.sup.1=L.sup.2=L.sup.3=L.sup.4=F and L.sup.4=H, or L.sup.1=L.sup.3=F and L.sup.2=L.sup.4=H, and the liquid crystalline medium contains at least one compound of formula I wherein alkenyl is a straight-chain alkenyl having 2 to 5 carbon atoms.

2. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae ##STR00248## in which R.sup.3a and R.sup.4a each, independently of one another, denote H, CH.sub.3, C.sub.2H.sub.5 or C.sub.3H.sub.7, and “alkyl” denotes a straight-chain alkyl group having 1 to 8 C atoms.

3. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae IV to VIII: ##STR00249## in which R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00250## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms, Y.sup.1-6 each, independently of one another, denote H or F, Z.sup.0 denotes —C.sub.2H.sub.4—, —(CH.sub.2).sub.4—, —CH═CH—, —CF═CF—, —C.sub.2F.sub.4—, —CH.sub.2CF.sub.2—, —CF.sub.2CH.sub.2—, —CH.sub.2O—, —OCH.sub.2—, —COO—, —CF.sub.2O— or —OCF.sub.2—, in the formulae V and VI also a single bond, and r denotes 0 or 1.

4. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae Va to Vj: ##STR00251## in which R.sup.0 and X.sup.0 have the meanings indicated below, R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00252## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms.

5. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae VI-1a to VI-1d: ##STR00253## in which R.sup.0 and X.sup.0 have the meanings indicated below, R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00254## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms.

6. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae VI-2a to VI-2f: ##STR00255## in which R.sup.0 and X.sup.0 have the meanings indicated below, R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00256## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms.

7. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formulae X and/or XI: ##STR00257## in which R.sup.0 and X.sup.0 have the meanings indicated below, R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00258## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms, Y.sup.1-4 each, independently of one another, denote H or F, and ##STR00259## each, independently of one another, denote ##STR00260##

8. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the formula XII, ##STR00261## in which R.sup.1 and R.sup.2 each, independently of one another, denote n-alkyl, alkoxy, oxaalkyl, fluoroalkyl, alkenyloxy or alkenyl, each having up to 9 C atoms, and Y.sup.1 denotes H or F.

9. The liquid-crystalline medium according to claim 1, additionally comprising at least one compound of the following formulae: ##STR00262## in which R.sup.0, X.sup.0, Y.sup.1 and Y.sup.2 have the meanings indicated below, R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00263## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms, Y.sup.1 denotes H or F Y.sup.2 denotes H or F.

10. The liquid-crystalline medium according to claim 1, comprising 0.5-10% by weight of compounds of the formula I.

11. The liquid-crystalline medium according to claim 1, additionally comprising one or more UV stabilisers and/or antioxidants.

12. A liquid-crystalline medium according to claim 1 within an electro-optical device.

13. A liquid-crystalline medium according to claim 12 within an active-matrix display, passive-matrix display or a liquid-crystal lens.

14. An electro-optical liquid-crystal display containing a liquid-crystalline medium according to claim 1.

15. A process for the preparation of a liquid-crystalline medium according to claim 1, comprising mixing one or more compounds of the formula I with at least one further mesogenic compound and optionally additives.

16. A compound of formulae I1 to I5: ##STR00264## in which X denotes F, a fluorinated alkyl radical having 1-6 C atoms, a fluorinated alkoxy radical having 1-6 C atoms, a fluorinated alkenyl radical having 2-6 C atoms, a fluorinated alkylalkoxy radical having 1-6 C atoms, L.sup.1-4 each, independently of one another, denote H or F, and alkenyl denotes an alkenyl radical having 2-6 C atoms; provided that the one or more of the following conditions are met: L.sup.1-4 have one of the following meanings L.sup.1=L.sup.2=L.sup.3=L.sup.4=F, L.sup.1=L.sup.2=L.sup.3=L.sup.4=F and L.sup.4=H, or L.sup.1=L.sup.3=F and L.sup.2=L.sup.4=H, and alkenyl is a straight-chain alkenyl having 2 to 5 carbon atoms.

17. The liquid-crystalline mixture according to claim 1, further comprising at least one compound of formula D1, D2 or D3 ##STR00265## in which R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00266## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms and Y.sup.1 and Y.sup.2 each independently are H or F.

18. The liquid-crystalline mixture according to claim 1, further comprising at least one compound of formula XIX to XXVII ##STR00267## in which R.sup.0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH.sub.2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF.sub.2O—, —CH═CH—, ##STR00268## —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, X.sup.0 denotes F, Cl, a mono- or polyfluorinated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyfluorinated alkenyl or alkenyloxy radical having 2 to 6 C atoms and Y.sup.1 and Y.sup.2 each independently are H or F.

19. The liquid crystalline medium according to claim 1, wherein X is F or OCF.sub.3.

20. The liquid crystalline medium according to claim 1, wherein X is F.

21. The liquid crystalline medium according to claim 1, wherein R is H.sub.2C═CHC.sub.2H.sub.4, CH.sub.2CH═CH or CH.sub.2—CH.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows that the alkenyl compounds of the formula I, such as, for example, UQU-1V-F, disproportionately increase the pretilt in Mixture M1 compared with the corresponding alkyl compounds.

EXAMPLE M2

(2) TABLE-US-00010 CC-3-V 32.00% Clearing point [° C.]: 80.5 UQU-1V-F 5.00% S .fwdarw. N [° C.]: −40 PGP-2-2V 2.00% Δn [589 nm, 20° C.]: 0.1297 CCP-V-1 10.00% Δε [1 kHz, 20° C.]: +16.1 PGU-3-F 7.00% V.sub.10 [V]: 1.05 BCH-3F.F.F 10.00% APUQU-3-F 9.00% PGUQU-3-F 5.00% PGUQU-4-F 6.00% PGUQU-5-F 7.00% DPGU-4-F 7.00%

EXAMPLE M3

(3) TABLE-US-00011 CC-3-V 28.50% Clearing point [° C.]: 82.0 UQU-1V-F 10.00% S .fwdarw. N [° C.]: −30 PGP-2-2V 1.00% Δn [589 nm, 20° C.]: 0.1304 CCP-V-1 12.50% Δε [1 kHz, 20° C.]: +15.4 PGU-3-F 6.00% BCH-3F.F.F 8.00% APUQU-3-F 8.00% PGUQU-3-F 5.00% PGUQU-4-F 5.00% PGUQU-5-F 6.00% DPGU-4-F 7.00% CPGP-4-3 3.00%

EXAMPLE M4

(4) TABLE-US-00012 CC-3-V 30.00% Clearing point [° C.]: 81.0 UQU-1V2-F 5.00% S .fwdarw. N [° C.]: −30 PGP-2-2V 1.00% Δn [589 nm, 20° C.]: 0.1300 CCP-V-1 13.00% Δε [1 kHz, 20° C.]: +15.8 PGU-3-F 9.00% V.sub.10 [V]: 1.09 BCH-3F.F.F 8.00% APUQU-3-F 7.00% PGUQU-3-F 5.00% PGUQU-4-F 6.00% PGUQU-5-F 8.00% DPGU-4-F 8.00%