Liquid-crystalline medium and high-frequency components comprising same

Abstract

The present invention relates to liquid-crystalline media comprising one or more pleochroic dyes and one or more compounds selected from the group of compounds of formulae I, II and III, ##STR00001##
in which the parameters have the meaning indicated in Claim 1, and to components comprising these media for high-frequency technology, in particular phase shifters and microwave array antennas.

Claims

1. A liquid-crystal medium comprising: one or more pleochroic compounds one or more compounds selected from the group of compounds of formulae I, II and III ##STR00212## in which L.sup.11 denotes R.sup.11 or X.sup.11, L.sup.12 denotes R.sup.12 or X.sup.12, R.sup.11 and R.sup.12, independently of one another, denote H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 15 C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15 C atoms, X.sup.11 and X.sup.12, independently of one another, denote H, F, Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2 to 7 C atoms, and ##STR00213## independently of one another, denote ##STR00214## in which L.sup.21 denotes R.sup.21 and, in the case where Z.sup.21 and/or Z.sup.22 denote trans-CHCH or trans-CFCF, alternatively denotes X.sup.21, L.sup.22 denotes R.sup.22 and, in the case where Z.sup.21 and/or Z.sup.22 denote trans-CHCH or trans-CFCF, alternatively denotes X.sup.22, R.sup.21 and R.sup.22, independently of one another, denote H, unfluorinated alkyl or unfluorinated alkoxy having 1 to 17, C atoms or unfluorinated alkenyl, unfluorinated alkenyloxy or unfluorinated alkoxyalkyl having 2 to 15, X.sup.21 and X.sup.22, independently of one another, denote F or Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, fluorinated alkenyloxy or fluorinated alkoxyalkyl having 2 to 7 C atoms, one of Z.sup.21 and Z.sup.22 denotes trans-CHCH, trans-CFCF or CC and the other, independently thereof, denotes trans-CHCH, trans-CFCF or a single bond, and ##STR00215## independently of one another, denote ##STR00216## in which L.sup.31 denotes R.sup.31 or X.sup.31, L.sup.32 denotes R.sup.32 or X.sup.32, R.sup.31 and R.sup.32, independently of one another, denote 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, X.sup.31 and X.sup.32, independently of one another, denote H, F, Cl, CN, NCS, SF.sub.5, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms or fluorinated alkenyl, unfluorinated or fluorinated alkenyloxy or unfluorinated or fluorinated alkoxyalkyl having 2 to 7 C atoms, Z.sup.31 to Z.sup.33, independently of one another, denote trans-CHCH, trans CFCF, CC or a single bond, and ##STR00217## independently of one another, denote ##STR00218## optionally one or more chiral compounds, and optionally one or more polymerisable compounds of formula P
P.sup.a(Sp.sup.a).sub.s1-(A.sup.1-Z.sup.1).sub.n1-A.sup.2-Q-A.sup.3-(Z.sup.4-A.sup.4).sub.n2-(Sp.sup.b).sub.s2-P.sup.bP wherein the individual radicals have the following meanings: P.sup.a, P.sup.b each, independently of one another, are a polymerisable group, Sp.sup.a, Sp.sup.b each, independently of one another, denote a spacer group, s1, s2 each, independently of one another, denote 0 or 1, n1, n2 each, independently of one another, denote 0 or 1, Q denotes a single bond, CF.sub.2O, OCF.sub.2, CH.sub.2O, OCH.sub.2, (CO)O, O(CO), (CH.sub.2).sub.4, CH.sub.2CH.sub.2, CF.sub.2CF.sub.2, CF.sub.2CH.sub.2, CH.sub.2CF.sub.2, CHCH, CFCF, CFCH, (CH.sub.2).sub.3O, O(CH.sub.2).sub.3, CHCF, CC, O, CH.sub.2, (CH.sub.2).sub.3, or CF.sub.2, Z.sup.1, Z.sup.4 denote a single bond, CF.sub.2O, OCF.sub.2, CH.sub.2O, OCH.sub.2, (CO)O, O(CO), (CH.sub.2).sub.4, CH.sub.2CH.sub.2, CF.sub.2CF.sub.2, CF.sub.2CH.sub.2, CH.sub.2CF.sub.2, CHCH, CFCF, CFCH, (CH.sub.2).sub.3O, O(CH.sub.2).sub.3, CHCF, CC, O, CH.sub.2, (CH.sub.2).sub.3, CF.sub.2, where Z.sup.1 and Q or Z.sup.4 and Q do not simultaneously denote a group selected from CF.sub.2O and OCF.sub.2, A.sup.1, A.sup.2, A.sup.3, A.sup.4 each, independently of one another, denote a diradical group selected from the following groups: a) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene and 1,4-bicyclohexylene, in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by O and/or S and in which, in addition, one or more H atoms may be replaced by F, b) the group consisting of 1,4-phenylene and 1,3-phenylene, in which, in addition, one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by L, c) the group consisting of tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1,3-diyl, piperidine-1,4-diyl, thiophene-2,5-diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L, d) the group consisting of saturated, partially unsaturated or fully unsaturated, and optionally substituted, polycyclic radicals having 5 to 20 cyclic C atoms, one or more of which may, in addition, be replaced by heteroatoms, where, in addition, one or more H atoms in these polycyclic radicals may be replaced by L, and A.sup.3, alternatively may be a single bond, L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF.sub.5 or straight-chain or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms.

2. A liquid-crystal medium according to claim 1, wherein the one or more pleochroic compounds is an azo dye or a thiadiazol dye.

3. A liquid-crystal medium according to claim 2, wherein said one or more optional chiral compounds has an absolute value of the helical twisting power (HTP) of 10 m or more.

4. A liquid-crystal medium according to claim 1, comprising one or more compounds of the formula I.

5. A liquid-crystal medium according to claim 1, comprising one or more compounds of the formula II.

6. A liquid-crystal medium according to claim 1, comprising one or more compounds of the formula III.

7. A liquid-crystal medium according to claim 1, comprising a polymerizable compound of formula P and a polymerization initiator.

8. A composite system comprising a liquid crystal medium of claim 1, wherein a polymer is obtained from the polymerisation of one or more compounds of formula P and one or more pleochroic compound and one or more compounds of formulae I to III.

9. A component for high-frequency technology, comprising a liquid crystal medium according to claim 1.

10. A component according to claim 9, wherein said component is operable in the microwave frequency range.

11. A component according to claim 9, wherein said component is a phase shifter or a LC based antenna element operable in the microwave frequency region.

12. A method comprising including a liquid-crystal medium according to claim 1 in a component for high-frequency technology.

13. A process for the preparation of a liquid-crystal medium according to claim 1, comprising: mixing one or more polymerisable compounds of formula P with one or more compounds selected from the group of the compounds of the formulae I, II and III, and optionally with one or more further compounds and/or with one or more additives.

14. A microwave antenna array, comprising one or more components according to claim 9.

15. A component for high-frequency technology, comprising a composite system according to claim 8.

16. The liquid crystal medium according to claim 1, wherein A.sup.1, A.sup.2, A.sup.3, A.sup.4 each, independently of one another, denote a diradical group selected from the group consisting of bicyclo[1.1.1]pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, ##STR00219## where, in addition, one or more H atoms in these polycyclic radicals may be replaced by L, and/or one or more double bonds may be replaced by single bonds, and/or one or more CH groups may be replaced by N, and R.sup.03, R.sup.04 each, independently of one another, denote H, F or straight-chain or branched alkyl having 1 to 12 C atoms, in which, in addition, one or more H atoms may be replaced by F, M denotes O, S, CH.sub.2, CHY.sup.1 or CY.sup.1Y.sup.2, and Y.sup.1 and Y.sup.2 each, independently of one another, have one of the meanings indicated above for R.sup.03 or R.sup.04, or denote Cl or CN, are, independently of one another, H, F, or CF.sub.3 and one of the groups Y.sup.1 and Y.sup.2 alternatively denotes OCF.sub.3.

17. The liquid crystal medium according to claim 1, wherein Q is CF.sub.2O.

18. The liquid crystal medium according to claim 1, wherein n1, n2 each, independently of one another, denote 0.

Description

EXAMPLES

(1) The following examples illustrate the present invention without limiting it in any way.

(2) However, it is clear to the person skilled in the art from the physical properties what properties can be achieved and in what ranges they can be modified. In particular, the combination of the various properties which can preferably be achieved is thus well defined for the person skilled in the art.

Examples 1.1 to 1.10 and Comparative Example 1

Comparative Example 1

(3) A liquid-crystal mixture C-1 having the composition and properties as indicated in the following table is prepared and characterized with respect to its general physical properties and its applicability in microwave components at 19 GHz.

(4) TABLE-US-00008 Composition Physical Properties Compound Conc./ No. Abbreviation mass-% T(N, I) = 172.7 C. 1 PPTUI-3-2 20.0 n(20 C., 589.3 nm) = 0.335 2 PPTUI-3-4 36.0 (20 C., 1 kHz) = 4.6 3 GGP-3-CL 10.0 .sub.1 (20 C.) = 746 mPa .Math. s 4 GGP-5-CL 20.0 tan .sub.r, (20 C., 19 GHz) = 0.0138 5 CPGP-5-2 7.0 tan .sub.r,|| (20 C., 19 GHz) = 0.0034 6 CPGP-5-3 7.0 (20 C., 19 GHz) = 0.243 100.0 (20 C., 19 GHz) = 17.6

(5) This mixture is suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the micro wave (MW) region. In comparison to the Examples 1.1 and 1.2 this mixture clearly exhibits inferior response times.

Examples 1.1 to and 1.4

(6) The mixture C-1 is divided into four parts. To each one of these four parts a certain concentration of the dichroic dye AZO-1, as shown in table G above, is added.

(7) To one each of these four parts alternatively 1.5%, 3.0%, 4.5% and 6.0%, respectively, of AZO-1 are added.

(8) TABLE-US-00009 TABLE 1 Compositions of the mixtures investigated Material C-1 AZO-1 Example Mixture Composition Number Concentration/mass-% C-1 100.0 0.0 M-1.1 98.5 1.5 M-1.2 97.0 3.0 M-1.3 95.5 4.5 M-1.4 94.0 6.0

(9) The four resultant mixtures are called M-1.1 to M-1.4. These four mixtures each are filled into test cells with antiparallel rubbed glass substrates covered by PI A13046. The test cells have a cell gap of 50 m. The mixtures are investigated with respect to their general physical properties and to their performance in the microwave regime.

(10) TABLE-US-00010 TABLE 2 Physical Properties (at 20 C.) of the mixtures investigated Mixture C-1 M-1.1 M-1.2 M-1.3 M-1.4 Property Value T(N, I)/ C. 173 t.b.d. t.b.d. t.b.d. t.b.d. n(20 C., 589.3 nm) 0.335 t.b.d. t.b.d. t.b.d. t.b.d. (20 C., 1 kHz) 4.6 t.b.d. t.b.d. t.b.d. t.b.d. .sub.1 (20 C.)/mPa .Math. s 746 t.b.d. t.b.d. t.b.d. t.b.d. V.sub.0/V t.b.d. t.b.d. t.b.d. t.b.d. t.b.d. Remarks: t.b.d.: to be determined V.sub.0 in 50 m test cell, described above.

(11) TABLE-US-00011 TABLE 3 Microwave characteristics and response times (at 20 C.) of the mixtures investigated Mixture C-1 M-1.1 M-1.2 M-1.3 M-1.4 Property Value .sub.r (20 C., 19 GHz) 2.409 2.432 2.423 2.406 2.427 .sub.r|| (20 C., 19 GHz) 3.184 3.239 3.222 3.233 3.266 tan .sub.r, 0.0138 0.0139 0.139 0.139 0.140 (20 C., 19 GHz) tan .sub.r,|| 0.0034 0.0033 0.0035 0.0036 0.0036 (20 C., 19 GHz) (20 C., 19 GHz) 0.243 0.249 0.248 0.256 0.257 (20 C., 19 GHz) 17.6 18.0 17.8 18.5 18.3

(12) These four mixtures, M-1.1 to M-1.4 are very well suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the micro wave (MW) region. Additionally in comparison to the comparative example these mixtures of the Examples 1.1 to 1.4 clearly exhibit superior, i.e. significantly higher values of the tunability, while the loss (tan .sub.,r) is only very slightly increased. The beneficial effect increases with increasing concentration of the dichroic dye. A relatively small concentration of the dichroic dye of only 4.5% does already lead to an increase of the tunability by approximately 15%. Consequently also the figure of merit () is significantly improved.

Examples 1.5 and 1.6

(13) The mixture C-1 used in examples 1.1 to 1.4 is prepared again and now divided into two parts. To each one of these two parts a certain concentration again of a dichroic dye, however now of the dichroic dye DAZO-1 (Merck KGaA, Darmstadt, Germany), as shown in table G above, is added.

(14) To one each of these two parts alternatively 3% and 6.0%, respectively, of AZO-2 are added.

(15) The two resultant mixtures, M-1.5 and M-1.6, are investigated with respect to their performance in microwave applications.

(16) TABLE-US-00012 TABLE 4 Compositions of the mixtures investigated Material C-1 DAZO-1 Example Mixture Composition Number Concentration/mass-% C-1 100.00 0.00 M-1.5 97.0 3.0 M-1.6 94.0 6.0

(17) TABLE-US-00013 TABLE 5 Physical Properties (at 20 C.) of the mixtures investigated Mixture C-1 M-1.5 M-1.6 Property Value T(N, I)/ C. 173 t.b.d. t.b.d. n(20 C., 589.3 nm) 0.335 t.b.d. t.b.d. (20 C., 1 kHz) 4.6 t.b.d. t.b.d. .sub.1 (20 C.)/mPa .Math. s 746 t.b.d. t.b.d. V.sub.0/V t.b.d. t.b.d. t.b.d. Remarks: t.b.d.: to be determined V.sub.0 in 50 m test cell, described above.

(18) TABLE-US-00014 TABLE 6 Microwave characteristics and dielectric losses (at 20 C.) of the mixtures investigated Mixture C-1 M-1.5 M-1.6 Property Value .sub.r (20 C., 19 GHz) 2.409 2.427 2.426 .sub.r|| (20 C., 19 GHz) 3.184 3.208 3.223 tan .sub.r, (20 C., 19 GHz) 0.0138 0.0137 0.0136 tan .sub.r,|| (20 C., 19 GHz) 0.0034 0.0032 0.0032 (20 C., 19 GHz) 0.243 0.244 0.247 (20 C., 19 GHz) 17.6 17.7 18.2

(19) Remarkably, like in examples 1.1 to 1.4 also here, the tunability of the materials and, hence, their figure of merit (), is increased by with increasing concentration of the dichroic dye while the dielectric loss is kept almost constant.

Examples 1.7 and 1.8

(20) The mixture C-1 is prepared once again and again divided into two parts. To each one of these two parts a certain concentration now of the dichroic dye THIO-1 (also Merck KGaA, Darmstadt, Germany), as shown in table G above, having a positive value of the HTP and high value at the same time, is added. To one each of these two parts alternatively 3.0% and 6.0%, respectively of THIO-1 are added.

(21) TABLE-US-00015 TABLE 7 Compositions of the mixtures investigated Material C-1 THIO-1 Example Mixture Composition Number Concentration/mass-% C-1 100.00 0.00 M-1.7 97.0 3.0 M-1.8 94.0 6.0

(22) The two resultant mixtures, called M-1.7 and M-1.8, are investigated with respect to their performance in microwave applications.

(23) TABLE-US-00016 TABLE 8 Physical Properties (at 20 C.) of the mixtures investigated Mixture C-1 M-1.7 M-1.8 Property Value T(N, I)/ C. 173 t.b.d. t.b.d. n(20 C., 589.3 nm) 0.335 t.b.d. t.b.d. (20 C., 1 kHz) 4.6 t.b.d. t.b.d. .sub.1 (20 C.)/mPa .Math. s 746 t.b.d. t.b.d. V.sub.0/V t.b.d. t.b.d. t.b.d. Remarks: t.b.d.: to be determined V.sub.0 in 50 m test cell, described above.

(24) TABLE-US-00017 TABLE 9 Microwave characteristics and dielectric losses (at 20 C.) of the mixtures investigated Mixture C-1 M-1.7 M-1.8 Property Value .sub.r (20 C., 19 GHz) 2.409 2.415 t.b.d. .sub.r|| (20 C., 19 GHz) 3.184 3.197 t.b.d. tan .sub.r, (20 C., 19 GHz) 0.0138 0.0134 t.b.d. tan .sub.r,|| (20 C., 19 GHz) 0.0034 0.0032 t.b.d. (20 C., 19 GHz) 0.243 0.2445 t.b.d. (20 C., 19 GHz) 17.6 18.3 t.b.d. Remarks: t.b.d.: to be determined.

(25) Strikingly, also here, like in examples 1.1 to 1.6, the tunability of the materials is increased by the introduction of the dichroic dye. Here, however, the dielectric loss is even slightly decreased at the same time.

(26) It has to be noticed here, however, that the molecular mass of the dichroic dye AZO-1 is only about half that of the other two dichroic dyes used, i.e. DAZO-1 and THIO-1. Thus, for a given concentration in weight-% the molar concentration of AZO-1 is almost double that of the other two compounds. In case the observed effect would be related to the molarity of the dichroic dye an effect of double the magnitude could be expected in case AZO-1 is used in comparison to the other two dichroic dyes.

Comparative Example 2

(27) For comparison, the well known compound 4-pentyl-4-cyanobiphenyl (also called 5CB or K15, Merck KGaA) gives tan .sub.r=0.026 and =4.3 at 20 C.

(28) TABLE-US-00018 TABLE 10 Comparison of the properties at 19 GHz and 20 C. Example Liquid crystal .sub.r tan .sub. .sub.r, 1.1 M-1.1 0.81 0.0139 18.0 Comparison 5CB 0.026 4.3

Example 2

(29) A liquid-crystal mixture M-2 having the composition and properties as indicated in the following table is prepared.

(30) TABLE-US-00019 Composition Physical properties Compound T(N, I) = 170.1 C. No. Abbreviation 1 GGP-3-CL 10.0 n.sub.e (20 C., 589.3 nm) = 1.5267 2 GGP-5-CL 20.0 n (20 C., 589.3 nm) = 0.2918 3 PPTUI-3-2 20.0 4 PPTUI-3-4 20.0 .sub.|| (20 C., 1 kHz) = 7.8 5 PPTUI-4-4 16.0 (20 C., 1 kHz) = 4.4 6 CPGP-5-2 7.0 7 CPGP-5-3 7.0 .sub.1 (20 C.) = 698 mPa .Math. s 100.0

(31) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 3

(32) A liquid-crystal mixture M-3 having the composition and properties as indicated in the following table is prepared.

(33) TABLE-US-00020 Composition Physical properties Compound T(N, I) = 183.5 C. No. Abbreviation 1 GGP-3-CL 10.0 2 GGP-5-CL 19.0 n (20 C., 589.3 nm) = 0.283 3 PPTUI-3-2 18.0 4 PPTUI-3-4 18.0 .sub.|| (20 C., 1 kHz) = 8.0 5 PPTUI-4-4 10.0 (20 C., 1 kHz) = 3.5 6 PGIGP-3-5 6.00 7 PPGU-3-F 3.00 .sub.1 (20 C.) = 753 mPa .Math. s 8 CPGP-5-2 8.0 9 CPGP-5-3 8.0 100.0

(34) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters.

Example 4

(35) A liquid-crystal mixture M-4 having the composition and properties as indicated in the following table is prepared.

(36) TABLE-US-00021 Composition Physical properties Compound No. Abbreviation 1 GGP-3-CL 10.0 2 GGP-5-CL 17.0 3 PPTUI-3-2 13.0 4 PPTUI-3-4 13.0 5 PPTUI-4-4 10.0 6 PPGU-3-F 3.0 7 PPGU-4-F 3.0 8 PPGU-V2-F 3.0 9 PGIGP-3-5 7.0 10 PGIGP-5-5 7.0 11 CPGP-5-2 7.0 12 CPGP-5-3 7.0 100.0

(37) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 5

(38) A liquid-crystal mixture M-5 having the composition and properties as indicated in the following table is prepared.

(39) TABLE-US-00022 Composition Physical properties Compound T(N, I) = 134.5 C. No. Abbreviation 1 GGP-3-F 10.0 n.sub.e (20 C., 589.3 nm) = 1.8036 2 GGP-5-F 10.0 n (20 C., 589.3 nm) = 0.2774 3 GGP-3-CL 10.0 4 GGP-4-CL 20.0 .sub.|| (20 C., 1 kHz) = 15.2 5 GGP-5-CL 20.0 (20 C., 1 kHz) = 10.2 6 GGP-6-CL 10.0 7 GGPP-5-3 5.0 .sub.1 (20 C.) = 758 mPa .Math. s 8 PGGP-3-5 5.0 9 PGGP-3-6 5.0 10 PGGP-5-3 5.0 100.0

(40) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 6

(41) A liquid-crystal mixture M-6 having the composition and properties as indicated in the following table is prepared.

(42) TABLE-US-00023 Composition Physical properties Compound No. Abbreviation 1 GGP-3-F 5.0 n.sub.e (20 C., 589.3 nm) = 1.7885 2 GGP-3-CL 10.0 n (20 C., 589.3 nm) = 0.2640 3 GGP-4-CL 10.0 4 GGP-5-CL 15.0 .sub.|| (20 C., 1 kHz) = 8.8 5 GGP-5-3 20.0 (20 C., 1 kHz) = 4.7 6 PGP-2-5 10.0 7 PGP-3-7 15.0 .sub.1 (20 C.) = 660 mPa .Math. s 8 PGP-2-2V 10.0 9 PGGP-3-5 5.0 100.0

(43) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 7

(44) A liquid-crystal mixture M-7 having the composition and properties as indicated in the following table is prepared.

(45) TABLE-US-00024 Composition Physical properties Compound T(N, I) = 124.5 C. No. Abbreviation 1 GGP-3-CL 10.0 n.sub.e (20 C., 589.3 nm) = 1.7951 2 GGP-4-CL 20.0 n (20 C., 589.3 nm) = 0.2709 3 GGP-5-CL 20.0 4 GGP-6-CL 10.0 .sub.|| (20 C., 1 kHz) = 11.6 5 GGP-5-3 25.0 (20 C., 1 kHz) = 6.8 6 PGGP-3-5 5.0 7 PGGP-3-6 5.0 .sub.1 (20 C.) = 895 mPa .Math. s 8 PGGP-5-3 5.0 100.0

(46) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 8

(47) A liquid-crystal mixture M-8 having the composition and properties as indicated in the following table is prepared.

(48) TABLE-US-00025 Composition Physical properties Compound T(N, I) = 184.5 C. No. Abbreviation 1 GGP-3-CL 5.0 2 GGP-5-CL 19.0 3 PGU-7-F 2.0 4 PPTUI-3-2 18.0 5 PPTUI-3-4 18.0 6 PPTUI-4-4 10.0 7 PPGU-7-F 2.0 8 PGIGP-3-5 6.0 9 DPGU-3-F 2.0 10 DPGU-3-OT 2.0 11 CPGP-5-2 8.0 12 CPGP-5-3 8.0 100.0

(49) TABLE-US-00026 TABLE 4 Properties of mixture M-8 at 30 GHz T/ C. .sub.r, .sub.r,|| tan .sub.r, tan .sub.r,|| .sub.r 9.47 2.51 2.92 0.0094 0.0035 0.140 15.0 19.67 2.51 2.92 0.0115 0.0041 0.139 12.1 30.07 2.49 2.94 0.0135 0.0046 0.152 11.2 40.52 2.44 2.96 0.0169 0.0046 0.175 10.3 50.17 2.36 2.96 0.0214 0.0050 0.204 9.48 59.99 2.34 2.94 0.0246 0.0056 0.204 8.24 70.41 2.34 2.93 0.0276 0.0061 0.199 7.22 79.74 2.35 2.91 0.0291 0.0067 0.195 6.69 84.52 2.35 2.91 0.0295 0.0071 0.192 6.51 Note: at 20 C., the following is obtained approximately by intrapolation: .sub.r = 2.51, tan .sub.r, = 0.0115, .sub.r = 0.140 and = 14.5.

(50) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 9

(51) A liquid-crystal mixture M-9 having the composition and properties as indicated in the following table is prepared.

(52) TABLE-US-00027 Composition Physical properties Compound T(N, I) = 178 C. No. Abbreviation 1 GGP-5-CL 10.0 2 GGP-6-CL 5.0 3 PGP-3-2V 3.0 4 PGP-2-2V 3.0 5 PPTUI-3-2 15.0 6 PPTUI-3-4 18.0 7 PPTUI-4-4 21.0 8 PPGU-7-F 2.0 9 PPGU-V2-F 2.0 10 PGIGP-3-5 7.0 11 CPTP-3-2 4.0 12 CPGU-3-OT 2.0 13 CPGU-4-OT 2.0 14 DPGU-3-OT 2.0 15 CPGP-5-2 4.0 100.0

(53) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters and for antenna elements.

Example 10

(54) A liquid-crystal mixture M-10 having the composition and properties as indicated in the following table is prepared.

(55) TABLE-US-00028 Composition Physical properties Compound T(N, I) = 159.5 C. No. Abbreviation 1 GGP-5-CL 20.0 .sub.|| (20 C., 1 kHz) = 7.9 2 GGP-5-3 12.0 (20 C., 1 kHz) = 4.3 3 PPTUI-3-2 12.0 4 PPTUI-3-4 16.0 .sub.1 (20 C.) = 686 mPa .Math. s 5 PPTUI-4-4 20.0 6 PGUQU-5-F 5.0 7 PGGP-3-5 5.0 8 PGGP-3-6 4.0 9 APGP-3-3 3.0 10 APGP-3-4 3.0 100.0

(56) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters and for antenna elements.

Example 11

(57) A liquid-crystal mixture M-11 having the composition and properties as indicated in the following table is prepared.

(58) TABLE-US-00029 Composition Physical properties Compound T(N, I) = 169 C. No. Abbreviation 1 GGP-5-3 10.0 2 PPTUI-3-F 8.0 3 PPTUI-4-F 8.0 4 PPTUI-3-2 12.0 5 PPTUI-3-4 16.0 6 PPTUI-4-4 20.0 7 PPTUI-3-A4 5.0 8 PGUQU-5-F 7.0 9 PGGP-3-5 4.0 10 PGGP-3-6 4.0 11 APGP-3-3 3.0 12 APGP-3-4 3.0 100.0

(59) This mixture is very highly suitable for applications in the microwave range, in particular for phase shifters and for antenna elements.

(60) The mixtures of examples 2 to 11 are treated and investigated as described under examples 1.1 to 1.4, 1.5 and 1.6 and 1.7 and 1.8. The resultant mixtures comprising the chiral compound in the respective concentrations show similarly improved properties. They are especially characterized in particular by improved tunability and figure of merit.

(61) Alternatively to the dichroic dyes used in the examples described above fluorescent dichroic dyes may be used. These allow easy detection of any leakage of modulation medium from the respective microwave components.