LIQUID CRYSTAL MATERIAL

Abstract

The present application relates to a liquid-crystalline material which comprises at least one dye compound and at least one compound of a formula (IA) or (IB). The liquid-crystalline material is suitable for use in optical switching devices, in particular in devices for the homogeneous regulation of the passage of light through an area.

Claims

1. Liquid-crystalline material having a clearing point of higher than 95 C. and having a positive dielectric anisotropy , comprising one or more dye compounds F and one or more compounds of a formula (IA) or (IB) ##STR00114## where the following applies to the groups and indices occurring: A.sup.11 is selected on each occurrence, identically or differently, from ##STR00115## ##STR00116## X is selected on each occurrence, identically or differently, from F, Cl, CN, alkyl groups having 1 to 10 C atoms, alkoxy groups having 1 to 10 C atoms and thioalkoxy groups having 1 to 10 C atoms, where one or more hydrogen atoms in the alkyl, alkoxy and thioalkoxy groups may be replaced by F or Cl, and where one or more CH.sub.2 groups in the alkyl, alkoxy and thioalkoxy groups may be replaced by O or S; A.sup.12 is on each occurrence, identically or differently, a group of a formula (A12A) or (A12B) ##STR00117## where the bond denoted by * denotes the bond to the group Z.sup.11; Z.sup.11 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 single bonds; E is selected from alkylene groups having 3 to 12 C atoms, where one or more H atoms in the alkylene groups may be replaced by F, Cl, Si(R.sup.1).sub.2OSi(R.sup.1).sub.2OSi(R.sup.1).sub.3, Si(R.sup.1).sub.3 or CN, and where one or more CH.sub.2 groups in the alkylene groups may be replaced by CR.sup.1CR.sup.1, CC, Si(R.sup.1).sub.2, Si(R.sup.1).sub.2O, O, S, OCO or COO; R.sup.11 is selected from H, F, Cl, CN, NCS, R.sup.1OCO, R.sup.1COO, alkyl groups having 1 to 10 C atoms, alkoxy groups having 1 to 10 C atoms, thioalkoxy groups having 1 to 10 C atoms, alkenyl groups having 2 to 10 C atoms, alkenyloxy groups having 2 to 10 C atoms and thioalkenyloxy groups having 2 to 10 C atoms, where one or more H atoms in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by F, Cl, Si(R.sup.1).sub.2OSi(R.sup.1).sub.2OSi(R.sup.1).sub.3, Si(R.sup.1).sub.3 or CN, and where one or more CH.sub.2 groups in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by Si(R.sup.1).sub.2, Si(R.sup.1).sub.2O, O, S, OCO, COO or a unit A.sup.11; R.sup.1 is selected on each occurrence, identically or differently, from alkyl groups having 1 to 10 C atoms, in which one or more hydrogen atoms may be replaced by F, Cl, Si(R.sup.1).sub.2OSi(R.sup.1).sub.2OSi(R.sup.1).sub.3, Si(R.sup.1).sub.3 or CN, and in which one or more CH.sub.2 groups may be replaced by Si(R.sup.1).sub.2, Si(R.sup.1).sub.2O, O or S; R.sup.12 is selected on each occurrence, identically or differently, from H, F, Cl, CN, NCS, CF.sub.3, CF.sub.2CF.sub.3, CHF.sub.2, CH.sub.2F, CHCF.sub.2, CHCFH, CHCH(CN), OCF.sub.3, OC(CF.sub.3).sub.3, OCF.sub.2CF.sub.3, OCHF.sub.2, OCH.sub.2F, OCHCF.sub.2, OCHCFH, OCF.sub.2CFCF.sub.2, OSF.sub.5, SF.sub.5, SCF.sub.3, SCF.sub.2CF.sub.3, SCHF.sub.2, SCH.sub.2F, SCHCF.sub.2, SCHCFH, R.sup.1OCO, R.sup.1COO, alkyl groups having 1 to 10 C atoms, alkoxy groups having 1 to 10 C atoms, thioalkoxy groups having 1 to 10 C atoms, alkenyl groups having 2 to 10 C atoms, alkenyloxy groups having 2 to 10 C atoms and thioalkenyloxy groups having 2 to 10 C atoms, where one or more H atoms in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by F, Cl or CN, and where one or more CH.sub.2 groups in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by O, S, OCO or COO; where at least one radical R.sup.12 in the group A.sup.12 is selected from F, Cl, CN, NCS, CF.sub.3, CF.sub.2CF.sub.3, CHF.sub.2, CH.sub.2F, CHCF.sub.2, CHCFH, CHCH(CN), OCF.sub.3, OC(CF.sub.3).sub.3, OCF.sub.2CF.sub.3, OCHF.sub.2, OCH.sub.2F, OCHCF.sub.2, OCHCFH, OCF.sub.2CFCF.sub.2, OSF.sub.5, SF.sub.5, SCF.sub.3, SCF.sub.2CF.sub.3, SCHF.sub.2, SCH.sub.2F, SCHCF.sub.2 and SCHCFH; and n is on each occurrence, identically or differently, 1, 2, 3 or 4.

2. Liquid-crystalline material according to claim 1, characterised in that the index n is on each occurrence, identically or differently, 2 or 3.

3. Liquid-crystalline material according to claim 1, characterised in that the compound of the formula (IA) conforms to a formula (IA-1), (IA-2), (IA-3) or (IA-4) ##STR00118## where the following applies to the groups occurring: R.sup.111, R.sup.121, R.sup.131, R.sup.141 are defined like R.sup.11 for the compound of formula (IA); Z.sup.121, Z.sup.141 are selected from COO, OCO, CF.sub.2CF.sub.2, CF.sub.2O, OCF.sub.2, CH.sub.2CH.sub.2, OCH.sub.2 and CH.sub.2O; A.sup.111, A.sup.121, A.sup.131, A.sup.141 are identical or different on each occurrence and are defined like A.sup.11 for the compound of formula (IA); A.sup.112, A.sup.122, A.sup.132, A.sup.142 are selected from ##STR00119## R.sup.112 is selected on each occurrence, identically or differently, from F, CF.sub.3, CF.sub.2CF.sub.3, CHF.sub.2, CH.sub.2F, OCF.sub.3, OCF.sub.2CF.sub.3, OCHF.sub.2, OCH.sub.2F, SF.sub.5 and OSF.sub.5.

4. Liquid-crystalline material according to claim 3, characterised in that A.sup.112, A.sup.122, A.sup.132, A.sup.142 are selected from ##STR00120##

5. Liquid-crystalline material according to claim 1, characterised in that the compound of the formula (IA) or (IB) is present therein in a total proportion of 70% by weight to 90% by weight.

6. Liquid-crystalline material according to claim 1, characterised in that it comprises one or more tricyclic compounds in which all three rings are aromatic in a total proportion of at least 1% by weight.

7. Liquid-crystalline material according to claim 1, characterised in that it comprises one or more compounds of a formula (II) ##STR00121## where the following applies to the groups and indices occurring: A.sup.21 is selected on each occurrence, identically or differently, from ##STR00122## Z.sup.21 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 and single bonds; R.sup.21, R.sup.22 are selected on each occurrence, identically or differently, from alkyl groups having 1 to 10 C atoms and alkenyl groups having 1 to 10 C atoms; k is equal to 1, 2, 3 or 4.

8. Liquid-crystalline material according to claim 1, characterised in that it comprises compounds containing one or more cyano groups in a proportion of at most 10% by weight.

9. Liquid-crystalline material according to claim 1, characterised in that it comprises at least two different dye compounds F, which each cover different regions of the light spectrum, giving overall the impression of a black colour of the material.

10. Liquid-crystalline material according to claim 1, characterised in that it comprises two or more different dye compounds F, and these are either all positively dichroic or all negatively dichroic.

11. Liquid-crystalline material according to claim 1, characterised in that the dye compounds F are selected from azo compounds, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, benzothiadiazoles, pyrromethenes and diketopyrrolopyrroles.

12. Liquid-crystalline material according to claim 1, characterised in that the dye compounds F conform to a formula (F) ##STR00123## where the following applies to the groups occurring: Ch is any desired chromophoric group; A.sup.F is selected on each occurrence, identically or differently, from ##STR00124## ##STR00125## ##STR00126## X is selected on each occurrence, identically or differently, from F, Cl, CN, alkyl groups having 1 to 10 C atoms, alkoxy groups having 1 to 10 C atoms and thioalkoxy groups having 1 to 10 C atoms, where one or more hydrogen atoms in the alkyl, alkoxy and thioalkoxy groups may be replaced by F or Cl, and where one or more CH.sub.2 groups in the alkyl, alkoxy and thioalkoxy groups may be replaced by O or S; R.sup.F is identical or different on each occurrence and is selected from H, F, Cl, CN, NCS, R.sup.1OCO, R.sup.1COO, alkyl groups having 1 to 10 C atoms, alkoxy groups having 1 to 10 C atoms, thioalkoxy groups having 1 to 10 C atoms, alkenyl groups having 2 to 10 C atoms, alkenyloxy groups having 2 to 10 C atoms and thioalkenyloxy groups having 2 to 10 C atoms, where one or more H atoms in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by F, Cl or CN, and where one or more CH.sub.2 groups in the alkyl, alkoxy, thioalkoxy, alkenyl and alkenyloxy groups may be replaced by O, S, OCO or COO; R.sup.1 is selected on each occurrence, identically or differently, from alkyl groups 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.F 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 single bonds; and i is on each occurrence, identically or differently, 1, 2 or 3.

13. Liquid-crystalline material according to claims 12, characterised in that the group Ch conforms to one of the following formulae (Ch-1) and (Ch-2): ##STR00127## where the groups are bonded to the remainder of the compound of the formula (F) in each case via the bonds labelled with *, where the groups may be substituted at each of the free positions by radicals R.sup.F; where Y is selected on each occurrence, identically or differently, from O and NR.sup.F; and where R.sup.F is defined as for the compound of formula (F).

14. Liquid-crystalline material according to claim 1, characterised in that its dielectric anisotropy is greater than 3.

15. An optical switching device, comprising a liquid-crystalline material according to claim 1.

16. Device for the homogeneous regulation of the passage of light through an area, comprising a liquid-crystalline material according to claim 1.

17. Device according to claim 16, characterised in that the liquid-crystalline material is present in a switching layer.

18. Device according to claim 16, characterised in that it is suitable for the regulation of the passage of light in the form of daylight from the environment into a room.

19. Device according to claim 16, characterised in that it is electrically switchable.

20. Device according to claim 16, characterised in that it does not comprise a polariser.

21. Window containing a device according to claim 16.

Description

WORKING EXAMPLES

A) General Process

[0137] The degree of anisotropy R is determined from the value for the extinction coefficient E(p) (extinction coefficient of the mixture on parallel alignment of the molecules to the direction of polarisation of the light) and the value for the extinction coefficient of the mixture E(s) (extinction coefficient of the mixture on perpendicular alignment of the molecules to the direction of polarisation 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 strongest absorption band in the VIS or NIR region is selected. The alignment of the molecules of the mixture is achieved by means of an alignment layer, as is known to the person skilled in the art in the area of LC display technology. In order to eliminate the influences caused by liquid-crystalline medium, other absorptions and/or reflections, a measurement is in each case carried out against an identical mixture comprising no dye and the value obtained is subtracted.

[0138] The measurement is carried out using linear-polarised light, whose direction of vibration 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 means of a linear polariser, where the polariser is rotated against the device in order to achieve the two different directions of vibration. The measurement of E(p) and E(s) is thus carried out via the rotation of the direction of vibration of the incident polarised light.

[0139] The degree of anisotropy R is calculated from the values obtained 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.

[0140] The chemical structures of the individual constituents of the mixtures are reproduced by means of abbreviations (acronyms). These abbreviations are explicitly presented and explained in WO 2012/052100 (pp. 63-89), and reference is therefore made to the said application for an explanation.

[0141] The clearing point in C., the optical anisotropy n and the dielectric anisotropy are indicated for the mixtures. The physical properties are determined in accordance with Merck Liquid Crystals, Physical Properties of Liquid Crystals, Status November 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.

B) Composition of the Host Mixtures (Liquid-Crystalline Material without Dye)

[0142]

TABLE-US-00003 H-1 H-2 Clearing point 109.5 C. 124 C. Dielectric anisotropy 9.0 12.4 Optical anisotropy n 0.0986 0.1695 Composition Compound % Compound % CCGU-3-F 6 CPU-3-F 11 CCQU-3-F 12 CPU-5-F 11 CCQU-5-F 10 CGU-2-F 7 CCU-3-F 10 CGU-3-F 8 CGPC-3-3 6 PGU-2-F 9 CP-3-O1 10 PGU-3-F 9 CCZU-3-F 15 PGU-5-F 7 CCZU-5-F 1.5 CCGU-3-F 8 PGUQU-3-F 2.5 CCP-V-1 6 CPGU-3-OT 4 CPPC-3-3 3 CPG-3-F 4 CGPC-3-3 5 CPP-3-2 5 CGPC-5-3 5 CC-3-4 4 CGPC-5-5 5 CC-3-5 5 PGIGI-3-F 6 CC-3-O1 5 H-3 H-4 Clearing point 108.5 C. 114.3 C. Dielectric anisotropy 13.4 11.2 Optical anisotropy n 0.1082 0.0861 Composition Compound % Compound % CC-3-O1 8 CC-3-V1 10 CCP-3-1 4 PGUQU-3-F 4 CCP-3-3 7 CCGU-3-F 5.5 CP-3-O1 8 CCG-3-OT 9 CCP-3-OT 9 CPU-3-F 11 CCP-5-OT 5 CPU-5-F 4 CPU-3-F 10 CCQU-3-F 10 CCQU-3-F 20 CCQU-5-F 7.5 CCGU-3-F 2.5 CCZU-2-F 4 PUQU-3-F 3 CCZU-3-F 12 APUQU-2-F 5 CCZU-5-F 4 APUQU-3-F 8 CCEU-3-F 12 PGUQU-3-F 5 CCEU-5-F 7 CPGU-3-OT 3.5 CPGP-4-3 2 H-5 (comp.) Clearing point 114.5 C. Optical anisotropy n 0.1342 Composition Compound % CPG-3-F 5 CPG-5-F 5 CPU-3-F 15 CPU-5-F 15 CP-3-N 16 CP-5-N 16 CCGU-3-F 7 CGPC-3-3 4 CGPC-5-3 4 CGPC-5-5 4 CCZPC-3-3 3 CCZPC-3-4 3 CCZPC-3-5 3

C) Determination of the Solubility of Dye Compounds

[0143] The solubility is determined from supersaturated solutions with regular taking of samples, filtration and spectroscopic determination of the concentration. The sampling is carried out at regular intervals in order to follow the long-term behaviour. The investigation is carried out over 12 weeks. The samples are stored at +20 C. The maximum dye concentration up to which no crystallisation takes place under the conditions indicated is indicated as solubility.

[0144] The following dyes are used here:

##STR00113##

[0145] In liquid-crystalline mixture H-1, solubility experiments are carried out with dyes D-1 to D-5.

[0146] The following solubilities are obtained here:

TABLE-US-00004 Dye compound Solubility (% by weight) D-1 1.1 D-2 1.5 D-3 0.6 D-4 1.6 D-5 2.7

[0147] In liquid-crystalline mixture H-2, solubility experiments are carried out with dyes D-1 to D-5.

[0148] The following solubilities are obtained here:

TABLE-US-00005 Dye compound Solubility (% by weight) D-2 1.5 D-4 1.5

[0149] In liquid-crystalline mixture H-3, solubility experiments are carried out with dyes D-1 to D-5.

[0150] The following solubilities are obtained here:

TABLE-US-00006 Dye compound Solubility (% by weight) D-2 1.5 D-4 1.5

[0151] In liquid-crystalline mixture H-4, solubility experiments are carried out with dyes D-1 to D-5.

[0152] The following solubilities are obtained here:

TABLE-US-00007 Dye compound Solubility (% by weight) D-2 1.5 D-4 1.6

[0153] The results show that good solubility of the dyes, where the solubility remains stable over a long period, is achieved with the mixtures according to the invention. This applies, in particular, to benzothiadiazole dyes, diketopyrrolopyrrole dyes and azo dyes.

D) Determination of the Voltage Holding Ratio (VHR) of the Dye Mixtures

[0154] For mixtures H-1 to H-4 (according to the invention) and comparative mixture H-5, the voltage holding ratio (VHR) is measured in each case for the individual mixture and for the combination with dye D-2. On the one hand the initial value for the VHR and on the other hand the value for the VHR after light exposure are determined here (sun test for 1 week). The light exposure consists in exposing the sample to intense light (exclusion of UV light by 400 nm cut-off filter) in a Suntest CPS+ from MTS-Atlas. The value VHR correspondingly represents the difference between the value for the VHR after light exposure and the initial value for the VHR.

[0155] For determination of the VHR, the material is subjected to a voltage pulse, and its electrical properties are determined. The procedure here is as described in Merck Liquid Crystals, Physical Properties of Liquid Crystals, Section VIII, Status November 1997, Merck KGaA, Germany, and in H. Seiberle et al., SID 1992, 92, pp. 25 ff.

[0156] The value VHR represents a measure of the constancy of the electrical resistance of the material over time, and is therefore of importance for the performance of the optical switching device comprising the LC material. The value is, in particular, of importance for the performance and visual impression of smart windows comprising the LC material.

TABLE-US-00008 VHR(100 C.) VHR VHR(100 C.) VHR(100 C.) mixture + VHR (100 C.) mixture, VHR mixture + 0.25% of D-2, (100 C.) mixture, after sun test (100 C.) 0.25% of D-2, after sun test mixture + Mixture initial value for 1 week mixture initial value for 1 week 0.25% of D-2 H-1 98.4 98.3 0.1 98.1 76.7 21.4 H-2 95.8 95.7 0.1 96.7 64.9 31.8 H-3 97.9 98.0 0.1 96.9 77.0 19.9 H-4 98.3 97.5 0.8 98.7 66.8 31.9 H-5 92.6 91.6 1.0 89.4 36.3 53.1 (comp.)

[0157] The results show that very good results for the value VHR are surprisingly obtained with mixtures H-1 to H-4 according to the invention.

[0158] VHR denotes the drop in the VHR after the mixture has been subjected to the light exposure described above for one week (sun test for 1 week).

[0159] The very good results are achieved, in particular, in the case of the combination with benzothiadiazole and diketopyrrolopyrrole dyes (D-2 is a benzothiadiazole dye).

[0160] Comparative mixture H-5 exhibits significantly worse results for the value VHR, in particular in the case of the combination with dyes.