LIQUID-CRYSTALLINE MEDIUM AND HIGH-FREQUENCY COMPONENTS COMPRISING SAME

Abstract

The present invention relates to liquid-crystalline media comprising one or more pleochroic compounds, and one or more compounds selected from the group of compounds of formulae I, II and III,

##STR00001##

in which the groups have the meanings as set forth 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-crystalline medium, comprising one or more pleochroic compounds, one or more compounds selected from the group of compounds of formulae I, II and III ##STR00222## in which R.sup.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, n denotes 0 or 1, and ##STR00223## independently of one another, denote ##STR00224## alternatively denotes ##STR00225## in which R.sup.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, Z.sup.21 denotes trans-CHCH, trans-CFCF or CC, and ##STR00226## independently of one another, denote ##STR00227## in which R.sup.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, one of Z.sup.31 and Z.sup.32 denotes trans-CHCH, trans-CFCF or CC, and the other one denotes trans-CHCH, trans-CFCF or a single bond, and ##STR00228## independently of one another, denote ##STR00229## alternatively denotes ##STR00230## and optionally one or more polymerisable mesogenic compounds.

2. The liquid-crystalline medium according to claim 1, which comprises one or more pleochroic dyes selected from the group of azo dyes and thiadiazol dyes.

3. The liquid-crystalline medium according to claim 1, which comprises one or more 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 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, CHCF, (CH.sub.2).sub.3O, O(CH.sub.2).sub.3, CC, O, CH.sub.2, (CH.sub.2).sub.3, CF.sub.2, preferably CF.sub.2O, Z.sup.1, Z.sup.4 denote, independently of one another, 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, CHCF, (CH.sub.2).sub.3O, O(CH.sub.2).sub.3, CC, O, CH.sub.2, (CH.sub.2).sub.3, CF.sub.2, wherein Z.sup.1 and Q or respectively 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, in addition, may be replaced by heteroatoms, preferably 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, ##STR00231## wherein, in addition, one or more H atoms in these 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, or 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, 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 denote Cl or CN, and one of the groups y.sup.1 and Y.sup.2 alternatively denotes OCF.sub.3, preferably H, F, Cl, CN or CF.sub.3, and which optionally further comprises a polymerisation initiator.

4. The liquid-crystalline medium according to claim 1, which comprises one or more compounds of formula I as set forth in claim 1.

5. The liquid-crystalline medium according to claim 1, which comprises one or more compounds of formula II as set forth in claim 1.

6. The liquid-crystalline medium according to claim 1, which comprises one or more compounds of formulae III as set forth in claim 1.

7. The liquid-crystalline medium according to claim 1, which comprises one or more compounds selected from the group of compounds of formulae I-1, I-2, II-1 to II-3 and III-1 to III-6 ##STR00232## ##STR00233## wherein R.sup.1, R.sup.2, R.sup.3, A.sup.11, A.sup.12, A.sup.13, A.sup.21, A.sup.22, A.sup.31, A.sup.32, A.sup.33, Z.sup.31 and Z.sup.32 each have the respective meanings as set forth in claim 1.

8. The liquid-crystalline medium according to claim 1, which further comprises one or more chiral compounds.

9. A composite system, comprising a liquid-crystalline medium which comprises one or more pleochroic compounds and one or more compounds selected from the group of compounds of formulae I, II and III as set forth in claim 1, and a polymer obtained or obtainable from the polymerisation of the polymerisable compound(s) according to claim 1.

10. A component for high-frequency technology, which comprises the liquid-crystalline medium according to claim 1.

11. The component according to claim 10, which is a component suitable for operation in the microwave range, preferably is a phase shifter or a LC based antenna element operable in the microwave range.

12. A method which comprises including a liquid-crystalline medium according to claim 1 in a component for high-frequency technology.

13. A process for the preparation of a liquid-crystalline medium, wherein one or more polymerisable compounds are mixed with one or more pleochroic compounds and one or more compounds selected from the group of the compounds of the formulae I, II and III as set forth in claim 1, and optionally with one or more further compounds and/or with one or more additives.

14. A method for improving the tunability of a liquid-crystalline medium comprising one or more compounds selected from the group of compounds of formulae I, II and III as set forth in claim 1, said method comprising including one or more pleochroic compounds in said liquid-crystalline medium.

15. A microwave antenna array, comprising one or more components according to claim 10.

Description

EXAMPLES

Example 1

Base Mixture

[0331] A liquid-crystal mixture B-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.

TABLE-US-00008 Composition Com- pound Conc./ No. Abbreviation mass-% Physical Properties 1 PU-3-S 18.0 T(N, I)/ C. = 93 2 PVG-4-S 13.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 13.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 27.7 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 5.0 6 PGU-3-S 20.0 .sub.1 (20 C.)/mPa .Math. s = 225 7 PPTU-4-S 10.0 tan .sub. r, (20 C., 19 GHz) = 0.0148 8 PPTU-5-S 10.0 tan .sub. r,|| (20 C., 19 GHz) = 0.0082 100.0 (20 C., 19 GHz) = 0.326 (20 C., 19 GHz) = 22.0 Remark: t.b.d.: to be determined.
k.sub.11=15.0 pN; k.sub.33=15.4 V; V.sub.00=0.86 V

[0332] 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, and suitable response times.

Examples 1.1 to 1.3

[0333] The mixture B-1 is divided into three parts. To each one of these three parts a certain concentration of the dichroic dye TAZO-1, as shown in table E above, is added to obtain the mixtures M-1.1, M-1.2 and M-1.3.

[0334] To these three parts alternatively 1.0%, 3.0% and 5.0%, respectively, of TAZO-1 are added.

TABLE-US-00009 TABLE 1 Compositions of investigated mixtures Material B-1 TAZO-1 Example Mixture Composition Number Concentration/mass-% B-1 100.0 0.0 M-1.1 99.0 1.0 M-1.2 97.0 3.0 M-1.3 95.0 5.0

[0335] The three resultant mixtures M-1.1 to M-1.3 each are filled into test cells with antiparallel rubbed glass substrates covered by PI AI3046. 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.

Example 2

[0336] To the mixture B-1 is added the dichroic dye AZO-1, as shown in table E above, in a concentration of 3.0%.

[0337] The resultant mixture M-2 is investigated with respect to its performance in microwave applications.

Example 3

[0338] To the mixture B-1 is added the dichroic dye AZO-2, as shown in table E above, in a concentration of 3.0%.

[0339] The resultant mixture M-3 is investigated with respect to its performance in microwave applications.

Example 4

[0340] To the mixture B-1 is added the dichroic dye AZO-3, as shown in table E above, in a concentration of 3.0%.

[0341] The resultant mixture M-4 is investigated with respect to its performance in microwave applications.

Example 5

[0342] To the mixture B-1 is added the dichroic dye THIO-1 (Merck KGaA, Darmstadt, Germany), as shown in table E above, in a concentration of 3.0%.

[0343] The resultant mixture M-5 is investigated with respect to its performance in microwave applications.

[0344] The following table shows a comparison for the microwave characteristics for mixtures B-1 and M-1.2, M-2, M-3, M-4 and M-5, wherein the latter mixtures each contain 3% of the respective dye as described above.

TABLE-US-00010 TABLE 2 Comparison of the microwave characteristics measure at 19 GHz (20 C., tan .sub. r, (20 C., Mixture 19 GHz) (20 C., 19 GHz) 19 GHz) B-1 0.326 0.0148 22.0 M-1.2 0.335 0.0138 24.3 M-2 0.331 0.0149 22.2 M-3 0.331 0.0150 22.1 M-4 0.325 0.0149 21.8 M-5 0.327 0.0145 22.6

[0345] Surprisingly, it is found that the provision of the respective dichroic dyes can provide benefits in terms of increased tunability. At the same time the dielectric loss is kept at least at a comparable level or is even improved, such that the figure of merit is at least comparable or even significantly improved. An increasing amount of dichroic dye can further improve the advantageous effects.

[0346] For comparison and as reference, 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.

[0347] The following mixtures are also suitable for applications in the microwave range, in particular for phase shifters or LC based antenna elements in the MW region.

Example 6

Base Mixture

[0348] A liquid-crystal mixture B-6 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.

TABLE-US-00011 Composition Com- pound Conc./ No. Abbreviation mass-% Physical Properties 1 PVG-3-S 6.0 T(N, I)/ C. = 112 2 PVG-4-S 16.0 n.sub.o(20 C., 589.3 nm) = 1.5454 3 PVG-5-S 6.0 n(20 C., 589.3 nm) = t.b.d. 4 PTG-3-S 10.0 .sub.||(20 C., 1 kHz) = 25.7 5 PTG-5-S 14.0 .sub.(20 C., 1 kHz) = 4.4 6 PTU-3-S 8.0 .sub.1 (20 C.)/mPa .Math. s = 270 7 PPTU-4-S 8.0 tan .sub. r, (20 C., 19 GHz) = 0.0143 8 PPTU-5-S 16.0 tan .sub. r,|| (20 C., 19 GHz) = 0.0038 100.0 (20 C., 19 GHz) = 0.252 (20 C., 19 GHz) = 17.6 Remark: t.b.d.: to be determined.

[0349] The mixture B-6 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0350] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 7

Base Mixture

[0351] A liquid-crystal mixture B-7 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.

TABLE-US-00012 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 PU-3-S 16.0 T(N, I)/ C. = 100 2 PVG-4-S 13.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 13.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 7.0 .sub.||(20 C., 1 kHz) = 28.2 5 PTU-5-S 7.0 .sub.(20 C., 1 kHz) = 5.0 6 PGU-3-S 24.0 .sub.1 (20 C.)/mPa .Math. s = 245 7 PPTU-4-S 10.0 tan .sub. r, (20 C., 19 GHz) = t.b.d. 8 PPTU-5-S 10.0 tan .sub. r,|| (20 C., 19 GHz) = t.b.d. 100.0 (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.
k.sub.11=15.8 pN; k.sub.33=15.1 V; V.sub.10=0.87 V

[0352] The mixture B-7 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0353] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 8

[0354] A liquid-crystal mixture B-8 having the composition and properties as indicated in the following table is prepared.

TABLE-US-00013 Composition Com- pound Conc./ No. Abbreviation mass-% Physical Properties 1 GGP-3-S 8.0 T(N, I)/ C. = 98 2 PGG-3-S 12.0 n.sub.e (20 C., 589.3 nm) = t.b.d. 3 PGU-3-S 12.0 n (20 C., 589.3 nm) = t.b.d. 4 PVG-3-S 6.0 .sub.|| (20 C., 1 kHz) = 26.7 5 PVG-4-S 18.0 .sub. (20 C., 1 kHz) = 5.1 6 PTG-3-S 10.0 k.sub.11 (20 C.)/pN 17.7 7 PTG-5-S 18.0 k.sub.33 (20 C.)pN 15.7 8 PTU-3-S 10.0 V.sub.0 (20 C.)/V 0.96 9 PPTU-4-S 6.0 .sub.1 (20 C.)/mPa .Math. s = 698 100.0 tan.sub.r,max(20 C., 19 GHz) = 0.0189 (20 C., 19 GHz) = 0.336 (20 C., 19 GHz) = 17.9 Remark: t.b.d.: to be determined.

[0355] The mixture B-8 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0356] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Examples 9 to 13

Base Mixtures

[0357] To the liquid crystalline medium B-8 of Example 8 alternatively a certain concentration of a further single compound, one each, is added and the resultant base mixtures (B-9 to B-13) are investigated for their general physical properties and for their performance in the microwave regime.

TABLE-US-00014 Composition Example Mixture Compound c(Comp.) c(M-4) No. No. Abbreviation /% 8 B-8 None 0.0 100.0 9 B-9 PTPI(c3)TU-4-F 5.0 95.0 10 B-10 PTPI(2)WU-6-F 10.0 90.0 11 B-11 PTPI(2)GU-4-F 10.0 90.0 12 B-12 PTG(c3)TU-4-F 5.0 95.0 13 B-13 PTN(1,4)TP-3-F 5.0 95.0

TABLE-US-00015 Physical Properties I, General I (20 C. except T(N.I) ) Example Mixture T(N, I)/ No. No. C. n .sub.|| 8 B-8 98 t.b.d. 26.7 21.5 9 B-9 98 t.b.d. 26.1 20.9 10 B-10 90 t.b.d. 26.0 21.0 11 B-11 102 t.b.d. 27.0 21.9 12 B-12 93.9 t.b.d. 27.0 21.8 13 B-13 99.5 t.b.d. 25.9 20.9 Remark: t.b.d.: to be determined.

TABLE-US-00016 Physical Properties II, General II (20 C.) Example Mixture No. No. y.sub.1 k.sub.11/pN k.sub.33/pN V.sub.0/V 8 B-8 241 17.7 15.7 0.96 9 B-9 254 15.1 14.6 0.90 10 B-10 272 15.8 15.8 0.91 11 B-11 319 16.0 16.9 0.90 12 B-12 257 15.8 15.0 0.90 13 B-13 273 18.2 15.9 0.99

TABLE-US-00017 Physical Properties III, Microwave I (20 C., 19 GHz) Example Mixture No. No. .sub.r, .sub.r,|| tan .sub. r,|| tan .sub. r, 8 B-8 3.74 2.49 0.0189 0.0091 9 B-9 3.68 2.48 0.0177 0.0088 10 B-10 3.67 2.49 0.0174 0.0084 11 B-11 3.68 2.48 0.0170 0.0082 12 B-12 3.70 2.49 0.0180 0.0088 13 B-13 3.73 2.49 0.0175 0.0085

TABLE-US-00018 Physical Properties IV, Microwave II (20 C., 19 GHz) Example Mixture No. No. tan .sub. r, .sub. r 8 B-8 0.0189 0.336 17.8 9 B-9 0.0177 0.326 18.4 10 B-10 0.0174 0.323 18.6 11 B-11 0.0170 0.327 19.3 12 B-12 0.0180 0.327 18.1 13 B-13 0.0175 0.332 19.0

[0358] The mixtures B-9 to B-13 are respectively divided into seven parts. Respectively, to three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively, AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0359] The resultant mixtures comprising the respective dichroic compounds in the respective concentrations show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 14

[0360] Base Mixture A liquid-crystal mixture B-14 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.

TABLE-US-00019 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 126.5 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 CGU-2-S 10.0 .sub.||(20 C., 1 kHz) = 27.1 5 CGU-3-S 10.0 .sub.(20 C., 1 kHz) = 4.5 6 CGU-4-S 10.0 .sub.1 (20 C.)/mPa .Math. s = 299 7 CGU-5-S 10.0 k.sub.1 (20 C.)/pN = 14.8 8 PGU-3-S 16.0 k.sub.3/k.sub.1 (20 C.) = 1.43 9 PPTU-4-S 7.0 V.sub.0 (20 C.)/V = 0.86 10 PPTU-5-S 7.0 .sub.r, (20 C., 19 GHz) = 2.36 100.0 .sub.r,|| (20 C., 19 GHz) = 3.44 .sub.r,|| (20 C., 19 GHz) = 0.0116 tan .sub. r,|| (20 C., 19 GHz) = 0.0064 (20 C., 19 GHz) = 0.315 (20 C., 19 GHz) = 27.2 Remark: t.b.d.: to be determined.

[0361] The mixture B-14 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0362] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 15

Base Mixture

[0363] A liquid-crystal mixture B-15 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.

TABLE-US-00020 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 123 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 CGU-2-S 20.0 .sub.||(20 C., 1 kHz) = 26.9 5 CGU-4-S 20.0 .sub.(20 C., 1 kHz) = 4.7 6 PGU-3-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 287 7 PPTU-4-S 7.0 k.sub.1 (20 C.)/pN = 14.0 8 PPTU-5-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.39 100.0 V.sub.0 (20 C.)/V = 0.84 .sub.r, (20 C., 19 GHz) = 2.36 .sub.r,|| (20 C., 19 GHz) = 3.42 tan .sub. r, (20 C., 19 GHz) = 0.0116 tan .sub. r,|| (20 C., 19 GHz) = 0.0066 (20 C., 19 GHz) = 0.310 (20 C., 19 GHz) = 26.7 Remark: t.b.d.: to be determined.

[0364] The mixture B-15 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0365] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 16

[0366] A liquid-crystal Base Mixture B-16 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.

TABLE-US-00021 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 14.0 T(N, I)/ C. = t.b.d. 2 PTU-3-S 14.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 CGU-2-S 20.0 n(20 C., 589.3 nm) = t.b.d. 4 CGU-4-S 20.0 .sub.||(20 C., 1 kHz) = t.b.d. 5 PGU-3-S 18.0 .sub.(20 C., 1 kHz) = t.b.d. 6 PPTU-4-S 7.0 .sub.1 (20 C.)/mPa .Math. s = t.b.d. 7 PPTU-5-S 7.0 k.sub.1 (20 C.)/pN = t.b.d. 100.0 k.sub.3/k.sub.1 (20 C.) = t.b.d. V.sub.0 (20 C.)/V = t.b.d. .sub.r, (20 C., 19 GHz) = t.b.d. .sub.r,|| (20 C., 19 GHz) = t.b.d. tan .sub. r, (20 C., 19 GHz) = t.b.d. tan .sub. r,|| (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.

[0367] The mixture B-16 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0368] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 17

Base Mixture

[0369] A liquid-crystal mixture B-17 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.

TABLE-US-00022 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 8.0 T(N, I)/ C. = 121.5 2 PVG-4-S 8.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 8.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 26.2 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 4.6 6 CGU-3-S 10.0 .sub.1 (20 C.)/mPa .Math. s = 298 7 CGU-4-S 10.0 k.sub.1 (20 C.)/pN = 16.0 8 CGU-5-S 10.0 k.sub.3/k.sub.1 (20 C.) = 1.31 9 PGU-3-S 16.0 V.sub.0 (20 C.)/V = 0.91 9 PPTU-4-S 7.0 .sub.r, (20 C., 19 GHz) = 2.36 11 PPTU-5-S 7.0 .sub.r,|| (20 C., 19 GHz) = 3.48 100.0 tan .sub. r, (20 C., 19 GHz) = 0.0121 tan .sub. r,|| (20 C., 19 GHz) 0.0067 (20 C., 19 GHz) = 0.321 (20 C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

[0370] The mixture B-17 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0371] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 18

Base Mixture

[0372] A liquid-crystal mixture B-18 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.

TABLE-US-00023 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 8.0 T(N, I)/ C. = 124 2 PVG-4-S 8.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 8.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 26.2 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 4.6 6 CGU-4-S 15.0 .sub.1 (20 C.)/mPa .Math. s = 311 7 CGU-5-S 15.0 k.sub.1 (20 C.)/pN = 16.2 8 PGU-3-S 16.0 k.sub.3/k.sub.1 (20 C.) = 1.28 9 PPTU-4-S 7.0 V.sub.0 (20 C.)/V = 0.91 10 PPTU-5-S 7.0 .sub.r, (20 C., 19 GHz) = 2.37 100.0 .sub.r,|| (20 C., 19 GHz) = 3.48 tan .sub. r, (20 C., 19 GHz) = 0.0120 tan .sub. r,|| (20 C., 19 GHz) = 0.0066 (20 C., 19 GHz) = 0.318 (20 C., 19 GHz) = 26.2 Remark: t.b.d.: to be determined.

[0373] The mixture B-18 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0374] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 19

Base Mixture

[0375] A liquid-crystal mixture B-19 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.

TABLE-US-00024 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 126.5 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 CGU-2-S 14.0 .sub.||(20 C., 1 kHz) = 27.4 5 CGU-3-S 13.0 .sub.(20 C., 1 kHz) = 4.6 6 CGU-4-S 13.0 .sub.1 (20 C.)/mPa .Math. s = 297 7 PGU-3-S 16.0 k.sub.1 (20 C.)/ = 14.5 8 PPTU-4-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.45 9 PPTU-5-S 7.0 V.sub.0 (20 C.)/V = 0.84 100.0 .sub.r, (20 C., 19 GHz) = 2.36 .sub.r,|| (20 C., 19 GHz) = 3.44 tan .sub. r, (20 C., 19 GHz) = 0.0115 tan .sub. r,|| (20 C., 19 GHz) = 0.0065 (20 C., 19 GHz) = 0.313 (20 C., 19 GHz) = 27.2 Remark: t.b.d.: to be determined.

[0376] The mixture B-19 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0377] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 20

Base Mixture

[0378] A liquid-crystal mixture B-20 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.

TABLE-US-00025 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PVG-4-S 16.0 T(N, I)/ C. = 115.5 2 PVG-5-S 16.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-3-S 14.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-5-S 10.0 .sub.||(20 C., 1 kHz) = 27.0 5 PTG-5-S 14.0 .sub.(20 C., 1 kHz) = 4.5 6 PGU-3-S 14.0 .sub.1 (20 C.)/mPa .Math. s = 304 7 PPTU-4-S 15.0 k.sub.1 (20 C.)/pN/ = t.b.d. 8 PPTU-5-S 15.0 k.sub.3/k.sub.1 (20 C.) = t.b.d. 100.0 V.sub.0 (20 C.)/V = 1.07 .sub.r, (20 C., 19 GHz) = t.b.d. .sub.r,|| (20 C., 19 GHz) = t.b.d. tan .sub. r, (20 C., 19 GHz) = t.b.d. tan .sub. r,|| (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.

[0379] The mixture B-20 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0380] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 21

Base Mixture

[0381] A liquid-crystal mixture B-21 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.

TABLE-US-00026 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 20.0 T(N, I)/ C. = 116.5 2 PVG-4-S 16.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 16.0 n(20 C., 589.3 nm) = t.b.d. 4 PGU-3-S 16.0 .sub.||(20 C., 1 kHz) = 27.7 5 PPTU-4-S 16.0 .sub.(20 C., 1 kHz) = 4.6 6 PPTU-5-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 292 100.0 k.sub.1 (20 C.)/pN = t.b.d. k.sub.3/k.sub.1 (20 C.) = t.b.d. V.sub.0 (20 C.)/V = 1.05 .sub.r, (20 C., 19 GHz) = t.b.d. .sub.r,|| (20 C., 19 GHz) = t.b.d. tan .sub. r, (20 C., 19 GHz) = t.b.d. tan .sub. r,|| (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.

[0382] The mixture B-21 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0383] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 22

Base Mixture

[0384] A liquid-crystal mixture B-22 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.

TABLE-US-00027 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 16.0 T(N, I)/ C. = 95 2 PVG-4-S 14.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 14.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 27.4 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 5.0 6 PGU-3-S 14.0 .sub.1 (20 C.)/mPa .Math. s = 234 7 PPTU-4-S 10.0 k.sub.1 (20 C.)/pN = 15.6 8 PPTU-5-S 10.0 k.sub.3/k.sub.1 (20 C.) = 1.00 100.0 V.sub.0 (20 C.)/V = 0.88 .sub.r, (20 C., 19 GHz) = 2.56 .sub.r,|| (20 C., 19 GHz) = 3.68 tan .sub. r, (20 C., 19 GHz) = 0.0075 tan .sub. r,|| (20 C., 19 GHz) = 0.0136 (20 C., 19 GHz) = 0.306 (20 C., 19 GHz) = 22.5 Remark: t.b.d.: to be determined.

[0385] The mixture B-22 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0386] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 23

[0387] A liquid-crystal mixture B-23 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.

TABLE-US-00028 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 20.0 T(N, I)/ C. = 96 2 PVG-4-S 15.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 15.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 10.0 .sub.||(20 C., 1 kHz) = 27.8 5 PGU-3-S 14.0 .sub.(20 C., 1 kHz) = 5.0 6 PPTU-4-S 10.0 .sub.1 (20 C.)/mPa .Math. s = 230 7 PPTU-5-S 10.0 k.sub.1 (20 C.)/pN = 15.6 100.0 k.sub.3/k.sub.1 (20 C.) = 1.00 V.sub.0 (20 C.)/V = 0.88 .sub.r, (20 C., 19 GHz) = 2.48 .sub.r,|| (20 C., 19 GHz) = 3.67 tan .sub. r, (20 C., 19 GHz) = 0.0083 tan .sub. r,|| (20 C., 19 GHz) = 0.0152 (20 C., 19 GHz) = 0.324 (20 C., 19 GHz) = 21.0 Remark: t.b.d.: to be determined.

[0388] The mixture B-23 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0389] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 24

Base Mixture

[0390] A liquid-crystal mixture B-24 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.

TABLE-US-00029 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 125 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 CPU-2-S 20.0 .sub.||(20 C., 1 kHz) = 27.2 5 CPU-5-S 20.0 .sub.(20 C., 1 kHz) = 4.6 6 PGU-3-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 310 7 PPTU-4-S 7.0 k.sub.1 (20 C.)/pN = 14.1 8 PPTU-5-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.44 100.0 V.sub.0 (20 C.)/V = 0.85 .sub.r, (20 C., 19 GHz) = t.b.d. .sub.r,|| (20 C., 19 GHz) = t.b.d. tan .sub. r, (20 C., 19 GHz) = t.b.d. tan .sub. r,|| (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.

[0391] The mixture B-24 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0392] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 25

Base Mixture

[0393] A liquid-crystal mixture B-25 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.

TABLE-US-00030 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 124 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 CPU-2-S 20.0 .sub.||(20 C., 1 kHz) = 27.8 5 CPU-3-S 20.0 .sub.(20 C., 1 kHz) = 4.6 6 PGU-3-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 301 7 PPTU-4-S 7.0 k.sub.1 (20 C.)/pN = 14.1 8 PPTU-5-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.44 100.0 V.sub.0 (20 C.)/V = 0.85 .sub.r, (20 C., 19 GHz) = t.b.d. .sub.r,|| (20 C., 19 GHz) = t.b.d. tan .sub. r, (20 C., 19 GHz) = t.b.d. tan .sub. r,|| (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. (20 C., 19 GHz) = t.b.d. Remark: t.b.d.: to be determined.

[0394] The mixture B-25 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0395] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 26

[0396] A liquid-crystal Base Mixture B-26 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.

TABLE-US-00031 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 10.0 T(N, I)/ C. = 127 2 PTU-3-S 10.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PTU-5-S 10.0 n(20 C., 589.3 nm) = t.b.d. 4 PGU-3-S 16.0 .sub.||(20 C., 1 kHz) = 27.1 5 PPTU-4-S 7.0 .sub.(20 C., 1 kHz) = 4.5 6 PPTU-5-S 7.0 .sub.1 (20 C.)/mPa .Math. s = 299 7 CPU-2-S 10.0 k.sub.1 (20 C.)/pN = 14.8 8 CPU-3-S 10.0 k.sub.3/k.sub.1 (20 C.) = 1.43 9 CPU-4-S 10.0 V.sub.0 (20 C.)/V = 0.86 10 CPU-5-S 10.0 .sub.r, (20 C., 19 GHz) = 2.35 100.0 .sub.r,|| (20 C., 19 GHz) = 3.44 tan .sub. r, (20 C., 19 GHz) = 0.0116 tan .sub. r,|| (20 C., 19 GHz) = 0.064 (20 C., 19 GHz) = 0.315 (20 C., 19 GHz) = 27.2 Remark: t.b.d.: to be determined.

[0397] The mixture B-26 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0398] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 27

Base Mixture

[0399] A liquid-crystal mixture B-27 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.

TABLE-US-00032 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 8.0 T(N, I)/ C. = 122 2 PVG-4-S 8.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 8.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 26.2 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 4.6 6 PGU-3-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 298 7 PPTU-4-S 7.0 k.sub.1 (20 C.)/pN = 16.0 8 PPTU-5-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.31 9 CPU-3-S 10.0 V.sub.0 (20 C.)/V = 0.91 10 CPU-4-S 10.0 .sub.r, (20 C., 19 GHz) = 2.36 11 CPU-5-S 10.0 .sub.r,|| (20 C., 19 GHz) = 3.48 100.0 tan .sub. r, (20 C., 19 GHz) = 0.0121 tan .sub. r,|| (20 C., 19 GHz) = 0.0067 (20 C., 19 GHz) = 0.321 (20 C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

[0400] The mixture B-27 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0401] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

Example 28

Base Mixture

[0402] A liquid-crystal mixture B-28 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.

TABLE-US-00033 Composition Com- pound Conc./ No Abbreviation mass-% Physical Properties 1 PU-3-S 8.0 T(N, I)/ C. = 124 2 PVG-4-S 8.0 n.sub.o(20 C., 589.3 nm) = t.b.d. 3 PVG-5-S 8.0 n(20 C., 589.3 nm) = t.b.d. 4 PTU-3-S 8.0 .sub.||(20 C., 1 kHz) = 26.2 5 PTU-5-S 8.0 .sub.(20 C., 1 kHz) = 4.6 6 PGU-3-S 16.0 .sub.1 (20 C.)/mPa .Math. s = 311 7 PPTU-4-S 7.0 k.sub.1 (20 C.)/pN = 16.2 8 PPTU-5-S 7.0 k.sub.3/k.sub.1 (20 C.) = 1.28 9 CPU-4-S 15.0 V.sub.0 (20 C.)/V = 0.91 10 CPU-5-S 15.0 .sub.r, (20 C., 19 GHz) = 2.37 100.0 .sub.r,|| (20 C., 19 GHz) = 3.48 tan .sub. r, (20 C., 19 GHz) = 0.0120 tan .sub. r,|| (20 C., 19 GHz) = 0.0066 (20 C., 19 GHz) = 0.318 (20 C., 19 GHz) = 26.5 Remark: t.b.d.: to be determined.

[0403] The mixture B-28 is divided into seven parts. To three of these seven parts is added respectively the dichroic dye TAZO-1, as shown in table E above, in a concentration of 1.0%, 3.0% and 5.0%. To the other four parts is added respectively AZO-1, AZO-2, AZO-3 or THIO-1, as shown in table E above, respectively in a concentration of 3.0%.

[0404] The resultant mixtures show similarly improved properties as Examples 1.1-1.3 and Examples 2-5, in particular with regard to tunability and figure of merit.

[0405] 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.

[0406] In addition to providing one or more pleochroic compounds, to the above mixtures one or more chiral compounds can be added in order to achieve an improved performance for most applications.