Liquid-crystalline medium

Abstract

A liquid-crystalline media comprising one or more compounds of formula S ##STR00001## where the parameters have the meaning defined in claim 1,
and one or more compounds of the formula I and one or more compounds of the formula II
or one or more compounds of the formula I and one or more compounds of the formula III
or one or more compounds of the formula II and one or more compounds of the formula III
or one or more compounds of the formula I and one or more compounds of the formula II and one or more compounds of the formula III: ##STR00002##
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 microwave antenna array comprising a component for high-frequency technology which is a phase shifter, wherein the phase shifter comprises a liquid-crystal medium, which liquid-crystal medium has a birefringence, Δn, of from 0.25 to 0.90 and a dielectric anisotropy, Δε, of 1 or more and which liquid-crystal medium comprises: one or more compounds of formula S-2, in the medium in a concentration of 500 ppm to 5000 ppm, ##STR00153## in which Z.sup.1, Z.sup.2 independently of one another, denote —O—, —(C═O)—, or a single bond, but do not both simultaneously denote —O—, r and s, independently of one another, denote 0 or 1, denotes a divalent straight-chain or branched alkyl having 1 to 20 C atoms, cycloalkyl, cycloalkylalkyl or alkylcycloalkyl, where one or more —CH.sub.2— groups in all these groups are optionally replaced by —O— in such a way that two O atoms in the molecule are not bonded directly to one another, and Alkyl denotes a straight-chain or branched alkyl having 1 to 20 C atoms; and one or more compounds of the formula I and one or more compounds of the formula II-1 to II-4, or one or more compounds of the formula II-1 to II-4 and one or more compounds of the formula III, or one or more compounds of the formula I and one or more compounds of the formula II-1 to II-4 and one or more compounds of the formula III: ##STR00154## 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 ##STR00155## independently of one another, denote ##STR00156## ##STR00157## in which Z.sup.21 and Z.sup.22 denote trans-CH═CH— or trans-CF═CF—, R.sup.21 and R.sup.22, independently of one another, denote H, unfluorinated alkyl or alkoxy having 1 to 7 C atoms or unfluorinated alkenyl having 2 to 7 C atoms, n and m, independently of one another, denote an integer in the range from 0 to 15, z denotes 0, 1, 2, 3 or 4, 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 C atoms, X.sup.22, denotes 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, and ##STR00158## independently of one another, denote ##STR00159## 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-CH═CH—, trans —CF═CF—, —C≡C— or a single bond, and ##STR00160## independently of one another, denote ##STR00161## and optionally one or more further compounds.

2. The microwave antenna array of claim 1, wherein the liquid-crystal medium comprises one or more compounds of the formula I.

3. The microwave antenna array of claim 2, wherein the concentration of the compounds of the formula I in the medium in total is in the range from 15% to 70%.

4. The microwave antenna array of claim 1, wherein the liquid-crystal medium comprises one or more compounds of the formula III.

5. The microwave antenna array of claim 1, wherein the concentration of the compounds of the formulae II-1 to II-4 in the medium in total is in the range from 1% to 60%.

6. The microwave antenna array of claim 2, wherein the liquid-crystal medium comprises one or more compounds selected from the group of the compounds of the formulae I-1 to I-3: ##STR00162##

7. The microwave antenna array of claim 1, wherein the one or more compounds of formula S-2 in the liquid crystal medium include a compound of the formula S2-1: ##STR00163##

8. The microwave antenna array of claim 1, wherein the liquid crystal medium comprises one or more compounds of the formulae II-1 to II-4, wherein: R.sup.21 and R.sup.22, independently of one another, denote H, unfluorinated alkyl or alkoxy having 1 to 7 C atoms or unfluorinated alkenyl having 2 to 7 C atoms, X.sup.22 denotes F, Cl, —CN or —NCS, at least one of ##STR00164## denotes ##STR00165## and the others, independently of one another, denote ##STR00166## R.sup.21 denotes C.sub.nH.sub.2n+1 or CH.sub.2═CH—(CH.sub.2).sub.Z, and R.sup.22 denotes C.sub.mH.sub.2m+1 or O—C.sub.mH.sub.2m+1 or (CH.sub.2).sub.Z—CH═CH.sub.2, n and m, independently of one another, denote an integer in the range from 1 to 7, and z denotes 0 or 2.

9. The microwave antenna array of claim 1, wherein the liquid crystal medium comprises one or more compounds of the formula II-1 to II-4 which are of the following formulae: ##STR00167## in which n denotes an integer in the range from 0 to 7.

10. The microwave antenna array of claim 1, wherein the liquid crystal medium comprises one or more compounds of the formula II-1 or II-2.

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.

(3) Irradiation experiments are performed in glass capillary tubes of 0.4 mm glass thickness. After the liquid crystal is filled into the tube the tube is irradiated with a total dose of gamma ray of 300 krad, which corresponds to 15-30 years of operation in space. The clearing temperatures of the samples are measured before and after irradiation.

Examples 1.1 to 1.4

(4) The following mixture (M-1) is prepared and investigated.

(5) TABLE-US-00008 Mixture M-1 Composition Compound Concentration/ No. Abbreviation % by weight 1 PPTUI-3-2 20.0 2 PPTUI-3-4 36.0 3 GGP-3-CL 10.0 4 GGP-5-CL 20.0 5 CPGP-5-2 7.0 6 CPGP-5-3 7.0 Σ 100.0 Physical properties T(N, I) = 173.0° C. Δn(20° C., 589 nm) = 0.3348 Δε(20°, 1 kHz) = 4.0 γ.sub.1(20° C.) = 727 mPa .Math. s k.sub.11(20° C.) = 23.5 pN k.sub.33(20° C.) = 32.0 pN

(6) Mixture M-1 is divided into ten parts. First, as a reference (ref.), the clearing temperature of the unstabilised mixture is measured before and after irradiation. Next, the remaining parts are use to prepare the stabilised mixtures given in table 1 using the stabilisers of formula S1-1 and S2-1 in the amounts given in table 1. Again, the clearing temperatures are measured before and after irradiation.

(7) TABLE-US-00009 TABLE 1 c(Stab.)/ T.sub.(N, I) Example Mixture Stabiliser ppm before after (Ref.) M-1 none 0 173.0 163.0 1.1 M-1-1 S1-1 100 173.0 165.0 1.2 M-1-2 S1-1 500 173.0 172.0 1.3 M-1-3 S2-1 100 173.0 164.5 1.4 M-1-4 S2-1 500 173.0 172.5

(8) A lower clearing temperature after irradiation means some damage to the liquid crystal.

(9) As can be seen from the results given in table 1, the unstabilised mixture M-1 suffers from a serious drop of the clearing temperature upon irradiation. A small amount of 100 ppm of either compound S1-1 or S2-1 already shows a stabilising effect. The use of 500 ppm of S1-1 or S2-1 results, within the error limits, in complete stabilisation against gamma ray irradiation.