Liquid-crystalline medium
Liquid-crystalline media having one or more compounds of formula C and high-frequency components containing these media, especially microwave components for high-frequency devices, such as devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas (e.g. phased array antennas).
1. A liquid crystal medium, comprising at least one compound of formula C
in which
R C denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 12 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 12 C atoms, in which alkyl, alkoxy, alkenyl, alkenyloxy or alkoxy-alkyl one or more CH 2 -groups may be replaced by
L C1 , L C2 identically or differently, denote H, Cl or F,
R C1 , R C2 , R C3 ,
R C4 , R C5 , and R C6 identically or differently, denote H, F, Cl, or alkyl having 1 to 6 C atoms, or cyclopropyl, cyclobutyl or cyclopentyl;
and
one or more compounds of I or II,
and at least one compound of formula III-1
in which
R 1 denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which alkyl, alkoxy, alkenyl, alkenyloxy or alkoxy-alkyl one or more CH 2 -groups may be replaced by
n is 0, 1 or 2,
on each occurrence, independently of one another, denote
in which R L , on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms,
and wherein
alternatively denotes
R 2 denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which one or more CH 2 -groups may be replaced by
Z 21 denotes trans-CH═CH—, trans-CF═CF— or —C≡C—, and
independently of one another, denote
in which
R L , on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms;
R 3 denotes H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17 C atoms, or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, in which one or more CH 2 -groups may be replaced by
one of Z 31 and Z 32 , denotes trans-CH═CH—, trans-CF═CF— or —C≡C— and the other one, independently thereof, denotes —C≡C—, trans-CH═CH—, trans-CF═CF— or a single bond, and
independently of one another, denote
in which R L , on each occurrence identically or differently, denotes H or alkyl having 1 to 6 C atoms,
and wherein
alternatively denotes
the liquid crystal medium also comprising 10 to 32% by weight of one or more compounds of formula T
in which
R T denotes halogen, CN, NCS, R F , R F —O— or R F —S—, wherein
R F denotes fluorinated alkyl or fluorinated alkenyl having 2 to 12 C atoms,
on each occurrence, independently of one another, denote
L 1 and L 2 identically or differently, denote Cl, F, alkyl having 1 to 6 C atoms or cyclopropyl, cyclobutyl or cyclopentyl, and
t is 0, 1 or 2
wherein the one or more compounds of formula C and one or more compounds of formula III-1 are present in the medium in an amount of 35 to 50%.
2. The liquid-crystal medium according to claim 1 , wherein the medium has a clearing temperature of 90° C. or more.
3. The liquid-crystal medium according to claim 1 , wherein the medium has a birefringence at 20° C. and 598.3 nm of 0.300 or more.
4. The liquid-crystal medium according to claim 1 , wherein the medium comprises a compound of formula I where n is 0, in a total concentration of 10% or less.
5. The liquid-crystal medium according to claim 1 , wherein the compounds of formula T are of the formulae T-1 or T-2 or mixtures thereof
n is 1, 2, 3, 4, 5, 6, or 7,
are as defined in claim 1 .
6. The liquid-crystal medium according to claim 5 , wherein the medium comprises one or more compounds of the formula T-1 in which n is 1.
7. The liquid-crystal medium according to claim 1 , wherein the compound of formula I is of formula I-1 to I-5
in which
L 1 , L 2 and L 3 on each occurrence, identically or differently, denote H or F,
are as defined in claim 1 .
8. The liquid-crystal medium according to claim 1 , wherein the compound of formula II is of formulae II-1 to II-3
wherein R 2 ,
and are as defined in claim 1 .
9. The liquid-crystal medium according to claim 8 , wherein the medium comprises one or more compounds of formula II-1 in a total concentration of 25% or less.
10. The liquid-crystal medium according to claim 1 , wherein the medium additionally comprises one or more chiral compounds.
11. The liquid-crystal medium according to claim 10 , wherein the one or more chiral compounds are chiral dopants of the formulae A-I, A-II, A-III or A-Ch:
in which
R a11 , R a12
and R b12 , independently of one another, denote alkyl having 1 to 15 C atoms, in which, in addition, one or more non-adjacent CH 2 groups may each be replaced, independently of one another, by —C(R z )═C(R z )—, —C≡C—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN, with the proviso that R a12 is different from R b12
R a21 and R a22 , independently of one another, denote alkyl having 1 to 15 C atoms, in which, in addition, one or more non-adjacent CH 2 groups may each be replaced, independently of one another, by —C(R z )═C(R z )—, —C≡C—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN,
R a31 , R a32
and R b32 , independently of one another, denote C 1-15 straight-chain or C 2-15 branched alkyl, in which, in addition, one or more non-adjacent CH 2 groups may each be replaced, independently of one another, by —C(R z )═C(R z )—, —C≡C—, —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, Br, I or CN, with the proviso that R a32 is different from R b32 ;
R z denotes H, CH 3 , F, Cl, or CN,
R 8 has one of the meanings of Ra11,
Z 8 denotes —C(O)O—, CH 2 O, CF 2 O or a single bond,
A 11 is independently defined as A′ 2 below, or alternatively denotes
A 12 denotes
in which r is 0, 1, 2, 3, or 4;
L 12 , on each occurrence, independently of one another, denotes halogen, CN, C 1-12 -alkyl, C 2-12 -alkenyl, C 1-12 -alkoxy or C 2-12 -alkenyloxy and in which one or more H atoms are optionally replaced with halogen;
A 21 denotes
A 22 independently has the meanings given for A 12
A 31 independently has the meanings given for A 11 ,
alternatively denotes
A 32 independently has the meanings given for A 12
n2 on each occurrence, identically or differently, is 0, 1 or 2, and
n3 is 1, 2 or 3.
12. A high-frequency technology component comprising in said component the liquid crystal medium according to claim 1 .
13. The component according to claim 12 , wherein the component is suitable for operation in the microwave range.
14. The component according to claim 12 , wherein the component is a liquid-crystal based antenna element, a phase shifter, a tunable filter, a tunable metamaterial structure, a matching network or a varactor.
15. A microwave antenna array, comprising one or more components according to claim 12 .
16. A liquid crystal lens or a liquid crystal wavefront corrector, comprising a liquid-crystal medium according to claim 1 .
17. A process for the preparation of a liquid-crystal medium according to claim 1 , comprising mixing one or more compounds of formula C with one or more compounds of formula T and III-1 and optionally with one or more compounds of formula I and/or II and optionally additional mesogenic compounds; and optionally adding a chiral compound.