Liquid-crystalline medium

Abstract

A liquid-crystalline medium which is suitable for use in a guest-host system. An LC device, preferably a device for the regulation of the passage of energy, containing the liquid-crystalline medium.

Claims

1. A window which regulates the passage of energy which comprises an electrically switchable LC device of the guest-host type, containing a liquid-crystalline medium in a switching layer, wherein the liquid-crystalline medium comprises: at least one compound of a formula (I-1): ##STR00138## where R.sup.11 is selected from H, F, CN, or an alkyl or alkoxy group having 1 to 10 C atoms, where one or more H atoms in alkyl or alkoxy groups are optionally replaced by F, Cl or CN; at least one compound of a formula (II-1): ##STR00139## where A.sup.22 is selected from ##STR00140## and A.sup.23 is selected from ##STR00141## at least one compound of a formula (III): ##STR00142## and at least three different dichroic dyes, where R.sup.21, R.sup.22, R.sup.31, R.sup.32 are on each occurrence, identically or differently, H, F, Cl, CN, NCS, R.sup.1OCO, R.sup.1COO, an alkyl, alkoxy or thioalkoxy group having 1 to 10 C atoms, or an alkenyl, alkenyloxy or thioalkenyloxy group having 2 to 10 C atoms, where one or more H atoms in the above-mentioned groups may be replaced by F, Cl or CN, and where one or more CH.sub.2 groups in the above-mentioned groups may be replaced by O, S, OCO or COO, R.sup.1 is on each occurrence, identically or differently, an alkyl group having 1 to 10 C atoms, in which one or more hydrogen atoms may be replaced by F or Cl, and in which one or more CH.sub.2 groups may be replaced by O or S, Z.sup.31 is selected on each occurrence, identically or differently, from COO, OCO, CF.sub.2CF.sub.2, CF.sub.2O, OCF.sub.2, CH.sub.2CH.sub.2, CHCH, CFCF, CFCH, CHCF, CC, OCH.sub.2, CH.sub.2O and a single bond, A.sup.31, A.sup.32 are selected on each occurrence, identically or differently, from ##STR00143## ##STR00144## X is selected on each occurrence, identically or differently, from F, Cl, CN or an alkyl, alkoxy or alkylthio group having 1 to 10 C atoms, where one or more hydrogen atoms in the above-mentioned groups may be replaced by F or Cl, and where one or more CH.sub.2 groups in the above-mentioned groups may be replaced by O or S, and n is 3, 4 or 5; and where the compound of the formula (II-1) carries at least two fluorine substituents; where the medium contains 30-50% by weight of the at least one compound of the formula (II-1) and 15-45% by weight of compounds of the formula (III); and where the medium has a clearing point greater than 100 C.

2. A window according to claim 1, wherein the liquid crystalline medium therein comprises 10-60% by weight of compounds of the formula (I-1).

3. A window according to claim 1, where, in the liquid crystalline medium, the ratio of the proportions of compounds of the formula (I-1) to compounds of the formula (II-1) is between 1:0.9 and 1:5.

4. A window according to claim 1, wherein the liquid crystalline medium has a dielectric anisotropy greater than 3.

5. A window according to claim 1, where, in the liquid crystalline medium, the group A.sup.23 is ##STR00145## wherein both groups X are F.

6. A window according to claim 1, where, in the liquid crystalline medium, the value n in the compound of the formula (III) is equal to 3.

7. A window according to claim 1, where, in the liquid crystalline medium, the at least three dichroic dyes comprise at least one dichroic dye which absorbs blue light, at least one dichroic dye which absorbs green to yellow light, and at least one dichroic dye which absorbs red light.

8. A window according to claim 1, where, in the liquid crystalline medium, at least one dichroic dye has a degree of anisotropy R of greater than 0.4.

9. A window according to claim 1, where, in the liquid crystalline medium, at least one dichroic dye is a fluorescent dye.

10. A window according to claim 1, where, in the liquid crystalline medium, the dichroic dyes are selected from azo compounds, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, perylenes, terrylenes, quaterrylenes, higher rylenes and pyrromethenes.

11. Process for the preparation of the window according to claim 1, comprising first mixing the compounds of the formulae (I-1), (II-1) and (III) and optionally further components, without the dichroic dyes, and subsequently adding and dissolving the dichroic dyes.

Description

WORKING EXAMPLES

(1) The following examples illustrate the present invention and are not to be interpreted as restrictive.

(2) In the present application, structures of liquid-crystalline compounds are reproduced by abbreviations (acronyms). These abbreviations are explicitly presented and explained in WO 2012/052100 (pp. 63-89), so that refer-ence is made to the said published application for an explanation of the abbreviations in the present application.

(3) The following liquid-crystalline media (mixtures Example 1 to Example 11 according to the invention and comparative mixtures V-1 to V-3) are pre-pared by mixing the components indicated. The parameters clearing point, n, n.sub.e, n.sub.o, the solubility of various dyes, the stability of the solutions and the degree of anisotropy of the dye in the liquid-crystalline medium in question are determined for the mixtures and indicated below.

(4) All physical properties are determined in accordance with Merck Liquid Crystals, Physical Properties of Liquid Crystals, Status Nov. 1997, Merck KGaA, Germany, and apply for a temperature of 20 C. The value of n is determined at 589 nm, and the value of is determined at 1 kHz, unless explicitly stated otherwise in each case. n.sub.e and n.sub.o are in each case the refractive indices of the extraordinary and ordinary light beam under the conditions indicated above.

(5) The degree of anisotropy R is determined from the value for the extinction coefficient E(p) (extinction coefficient of the mixture in the case of parallel alignment of the molecules to the polarisation direction of the light) and the value for the extinction coefficient of the mixture E(s) (extinction coefficient of the mixture in the case of perpendicular alignment of the molecules to the polarisation direction of the light), in each case at the wavelength of the maximum of the absorption band of the dye in question. If the dye has a plurality of absorption bands, the longest-wave absorption band is selected. The alignment of the molecules of the mixture is achieved by an alignment layer, as known to the person skilled in the art in the area of LC display technology. In order to eliminate influences by liquid-crystalline medium, other absorptions and/or reflections, each measurement is carried out against an identical mixture comprising no dye, and the value obtained is subtracted.

(6) The measurement is carried out using linear-polarised light whose vibration direction is either parallel to the alignment direction (determination of E(p)) or perpendicular to the alignment direction (determination of E(s)). This can be achieved by a linear polariser, where the polariser is rotated with respect to the device in order to achieve the two different vibration direc-tions. The measurement of E(p) and E(s) is thus carried out via the rotation of the vibration direction of the incident polarised light. Alternatively, the sample can also be rotated against a spatially fixed polarisation direction of the incident polarised light.

(7) The degree of anisotropy R is calculated from the resultant values for E(s) and E(p) in accordance with the formula
R=[E(p)E(s)]/[E(p)+2*E(s)],
as indicated, inter alia, in Polarized Light in Optics and Spectroscopy, D. S. Kliger et al., Academic Press, 1990. A detailed description of the method for the determination of the degree of anisotropy of liquid-crystalline media comprising a dichroic dye is also given in B. Bahadur, Liquid CrystalsApplications and Uses, Vol. 3, 1992, World Scientific Publishing, Section 11.4.2.

(8) In order to determine the low-temperature stability of the liquid-crystalline media according to the invention, dye D-1 (cf. following table of dyes) is dissolved in the medium in question in an amount of 0.25% by weight. The medium is subsequently stored at a temperature of 20 C., 30 C. and 40 C. (in each case one of three identical samples at each of the three temperatures mentioned) and checked visually for the occurrence of crystals or similar changes. The time up to which no change is observed in any of the three samples is quoted as the low-temperature stability (in days).

(9) Mixtures Example 1 to Example 11 according to the invention are:

(10) TABLE-US-00004 TABLE 1 Example 1 Example 2 Clearing point 114.5 C. 113 C. n 0.1342 0.1393 n.sub.e 1.6293 1.6345 n.sub.o 1.4951 1.4952 Low-temperature stability 41 63 (in days) Composition Compound % Compound % CPG-3-F 5 CPG-3-F 5 CPG-5-F 5 CPG-5-F 5 CPU-3-F 15 CPU-3-F 12 CPU-5-F 15 CPU-5-F 12 CP-3-N 16 CP-3-N 16 CP-5-N 16 CP-5-N 16 CCGU-3-F 7 CCGU-3-F 7 CGPC-3-3 4 CPGU-3--OT 4 CGPC-5-3 4 CCZPC-3-3 4 CGPC-5-5 4 CCZPC-3-4 4 CCZPC-3-3 3 CCZPC-3-5 3 CCZPC-3-4 3 CPZG-3-N 4 CCZPC-3-5 3 CPZG-4-N 4 CPZG-5-N 4

(11) TABLE-US-00005 TABLE 2 Example 3 Example 4 Clearing point 110.5 C. 110.0 C. Low-temperature stability 37 45 (in days) Composition Compound % Compound % CPU-3-F 20 CPU-3-F 20 CPU-5-F 20 CPU-5-F 20 CP-3-N 16 CCU-3-F 5 CP-5-N 16 CP-3-N 16 CCGU-3-F 7 CP-5-N 15 CGPC-3-3 4 CGPC-3-3 4 CGPC-5-3 4 CGPC-5-3 4 CGPC-5-5 4 CGPC-5-5 4 CCZPC-3-3 3 CCZPC-3-3 4 CCZPC-3-4 3 CCZPC-3-4 3 CCZPC-3-5 3 CCZPC-3-5 3 CPPC-3-3 2

(12) TABLE-US-00006 TABLE 3 Example 5 Example 6 Clearing point 109.0 C. 112.0 C. Low-temperature stability 40 39 (in days) Composition Compound % Compound % CPU-3-F 8 CPU-2-F 6 CPU-5-F 20 CPU-3-F 8 CCU-3-F 8 CPU-5-F 15 CCG-V-F 11 CPU-7-F 17 CP-3-N 16 CP-3-N 14 CP-5-N 15 CP-5-N 15 CGPC-3-3 4 CGPC-3-3 4 CGPC-5-3 4 CGPC-5-3 4 CGPC-5-5 4 CGPC-5-5 4 CCZPC-3-3 4 CCZPC-3-3 4 CCZPC-3-4 3 CCZPC-3-4 4 CCZPC-3-5 3 CCZPC-3-5 4 CPPC-3-3 1

(13) TABLE-US-00007 TABLE 4 Example 7 Example 8 Clearing point 116.0 C. 112.0 C. Low-temperature stability 55 36 (in days) Composition Compound % Compound % CPU-5-F 15 CPU-3-F 15 CPU-7-F 17 CPU-5-F 15 CP-3-N 18 CP-3-N 13 CP-5-N 15 CP-5-N 12 CP-1V-N 7 CP-1V-N 5 CGPC-3-3 4 CG-3-N 5 CGPC-5-3 4 CU-3-N 5 CGPC-5-5 4 CGPC-3-3 4 CCZPC-3-3 3 CGPC-5-3 4 CCZPC-3-4 3 CGPC-5-5 4 CCZPC-3-5 2 CCZPC-3-3 3 CPPC-3-3 2 CCZPC-3-4 3 CPGP-4-3 3 CCZPC-3-5 2 CPGP-5-2 3 CPPC-3-3 4 CPGP-4-3 3 CPGP-5-2 3

(14) TABLE-US-00008 TABLE 5 Example 9 Example 10 Clearing point 111.0 C. 110.0 C. Low-temperature stability 45 57 (in days) Composition Compound % Compound % CPU-3-F 10 CPU-3-F 10 CPU-5-F 13 CPU-5-F 13 CPG-3-F 5 CPG-3-F 5 CPG-5-F 7 CPG-5-F 7 CP-3-N 13 CP-3-N 15 CP-5-N 12 CP-1V-N 9 CP-1V-N 9 CP-V2-N 10 CG-3-N 5 CG-1V-N 5 CGPC-3-3 4 CGPC-3-3 4 CGPC-5-3 4 CGPC-5-3 4 CGPC-5-5 4 CGPC-5-5 4 CCZPC-3-3 4 CCZPC-3-3 4 CPPC-3-3 4 CPPC-3-3 4 CPPC-3-3 4 CPPC-3-3 4 CPGP-4-3 3 CPGP-4-3 3 CPGP-5-2 3 CPGP-5-2 3

(15) TABLE-US-00009 TABLE 6 Example 11 Clearing point 113.0 C. Low-temperature stability 67 (in days) Composition Compound % CPU-3-F 12 CPU-5-F 15 CPG-3-F 3 CPG-5-F 5 CP-3-N 15 CP-5-N 10 CP-1V-N 6 CGPC-3-3 4 CGPC-5-3 3 CGPC-5-5 3 CPPC-3-3 4 CPZIC-3-4 8 CCZP-3-3 5 CPZP-3-3 5 CCZGI-3-3 2

(16) Comparative mixtures V-1, V-2 and V-3 are:

(17) TABLE-US-00010 TABLE 7 Comparative Comparative Example V1 Example V2 Clearing point 77.5 C. 110 C. n 0.1255 0.1234 n.sub.e 1.6230 1.6150 n.sub.o 1.4975 1.4916 Low-temperature stability 13 3 (in days) Composition Compound % Compound % PZG-2-N 0.94 CP-3-N 18 PZG-3-N 0.94 CP-4-N 12 PZG-5-N 2.18 CP-5-N 21 CP-3-O1 7.49 CP-3-O1 13 CC-3-4 3.12 CPPC-3-3 3 CPP-3-2 2.50 CPPC-5-3 3 CCZGI-3-3 2.50 CPPC-5-5 3 CCZGI-3-5 2.50 CGPC-3-3 3 CCZPC-3-5 0.94 CGPC-5-3 3 CPZG-3-N 1.25 CGPC-5-5 3 CGPC-3-3 1.25 CCZGI-3-3 4 PZG-4-N 2.18 CCZGI-3-5 5 CCZPC-3-4 1.25 CCZPC-3-3 3 CGPC-5-3 0.94 CCZPC-3-4 3 CCZPC-3-3 1.25 CCZPC-3-5 3 CPU-3-F 34.40 CPU-5-F 34.40

(18) TABLE-US-00011 TABLE 8 Comparative Example V3 Clearing point 115.5 C. Low-temperature stability 6 (in days) Composition Compound % CPG-2-F 3 CPG-3-F 4 CPG-5-F 4 CPU-3-F 4 CPU-5-F 4 CCU-2-F 4 CCU-3-F 4 CCU-5-F 4 CCGU-3-F 5 CP-3-O1 12 CP-3-O2 18 CGPC-3-3 3 CGPC-5-3 3 CGPC-5-5 3 CCZPC-3-3 3 CCZPC-3-4 3 CCZPC-3-5 3 CCP-2-OT 4 CCP-3-OT 4 CCP-4-OT 4 CCP-5-OT 4

(19) The above examples show that the mixtures according to the invention have a high clearing point and good solubility of dichroic dye D-1. Furthermore, the mixtures according to the invention have very good stability of the solution of the dye at low temperatures (cf. description of the conditions above, duration 37 to 63 days).

(20) Results for comparative mixtures which have a mixture concept disclosed in the prior art are discussed below: V-1 and V-3 are mixtures in accordance with the prior art which comprise polyfluorinated tricyclic compounds, but no cyanophenyl compounds. By contrast, V-2 is a mixture in accordance with the prior art which comprises cyanophenyl compounds, but no fluorinated tricyclic compounds.

(21) Comparative mixtures V-1 to V-3 have poorer values for the stability of the solution of the dichroic dye in the mixture (3 or 6 or 13 days respectively) than the mixtures according to the invention. Although mixture V-1 has a less poor value for the solution stability than V-2 and V-3, it has, however, the disadvantage of a very low clearing point (77.5 C.).

(22) Furthermore, the solubility of various dyes and their degree of anisotropy are determined for Mixture Example 1 according to the invention. The results are listed in the following table.

(23) The dyes in the mixture according to the invention have good values for the solubility and the degree of anisotropy.

(24) Solubility of dichroic dyes in Mixture Example 1:

(25) TABLE-US-00012 TABLE 9 Degree of Solubility in Dye anisotropy R % by weight D-1 0.5 0.25 D-2 0.77 0.5 D-3 0.64 0.5 D-4 0.6 0.15 D-5 0.68 0.50 D-6 0.76 0.70 D-7 0.54 0.25 D-8 0.76 0.5 D-9 0.81 0.30 D-10 0.83 0.25 D-11 0.82 0.25 D-12 0.59 0.13

(26) The compounds used are:

(27) TABLE-US-00013 TABLE 10 D-1 D-2 D-3 D-4 0 D-5 D-6 D-7 D-8 D-9 D-10 D-11 D-12