WO2018015320A1

WO2018015320A1 - Liquid crystalline medium

Info

Publication number: WO2018015320A1
Application number: PCT/EP2017/067954
Authority: WO
Inventors: Peer Kirsch; Andreas Ruhl; Michael Junge; Ursula Patwal; Mila Fischer
Original assignee: Merck Patent Gmbh
Priority date: 2016-07-19
Filing date: 2017-07-17
Publication date: 2018-01-25
Also published as: KR102414126B1; TWI752056B; US20190153320A1; JP6972103B2; CN109476997B; US11168257B2; KR20190031514A; EP3487955B1; CN109476997A; JP2019527748A; EP3487955A1; TW201811986A

Abstract

The present invention relates to liquid crystalline media comprising one or more benzothiadiazol derivatives of formula (I), in which R¹¹, R¹², A¹¹, A¹², A²¹, A²², Z¹¹, Z¹², Z²¹, Z²², W, X¹¹, X¹², r and s have the meanings indicated in claim 1, to the use of such liquid crystal media for optical, electro-optical and electronic purposes, in particular in devices for regulating the passage of energy from an outside space into an inside space, for example in windows.

Description

Liquid Crystalline Medium

The present invention relates to a liquid crystalline medium comprising annelated benzothiadiazole derivatives, the use of said medium for optical, electro-optical and electronic purposes, in particular in devices for regulating the passage of energy from an outside space into an inside space, for example in windows. The invention further relates to devices containing the liquid crystalline medium according to the invention. Liquid crystals are used in particular as dielectrics in display devices, since the optical properties of such substances can be influenced by an applied voltage. Electro-optical devices based on liquid crystals are extremely well known to the person skilled in the art and can be based on various effects. Devices of this type are, for example, cells having dynamic scattering, DAP (deformation of aligned phases) cells, TN cells having a twisted nematic structure, STN ("supertwisted nematic") cells, SBE ("superbirefringence effect") cells, OMI ("optical mode interference") cells and guest-host cells.

The last-mentioned devices based on the guest-host effect were described for the first time by Heilmeier and Zanoni (G. H. Heilmeier et al., Appl. Phys. Lett., 1968, 13, 91 f) and have since then found widespread use, principally in LC display elements. In a guest-host system, the LC medium comprises one or more dichroic dyes in addition to the liquid crystal. Owing to the directional dependence of the absorption by the dye molecules, the transparency of the liquid crystal to light can be modulated if the dyes change their alignment together with the liquid crystal.

Besides use in LC displays, devices of this type are known as switching elements for regulating the passage of light or energy, for example from WO 2009/141295 and WO 2010/1 18422; a device for regulating the passage of energy is in the present application taken to mean a device which regulates the passage of energy through an area which is arranged within a structure of relatively lower energy transmissivity. For example, the area of relatively high energy transmissivity can be a glass area or an open area, and the structure of lower energy transmissivity which contains the area of higher energy transmissivity can be a wall.

The device preferably regulates the passage of energy from insolation, either directly or indirectly.

The regulated passage of energy takes place from an outside space, preferably the environment exposed directly to insolation, into an inside space, for example a building or a vehicle, or another unit which is substantially sealed off from the environment.

For the purposes of the present invention, the term energy is taken to mean, in particular, energy by electromagnetic radiation in the UV-A, VIS and NIR region. In particular, it is taken to mean energy by radiation which is not absorbed or is only absorbed to a negligible extent by the materials usually used in windows (for example glass). According to the definitions usually used, the UV-A region is taken to mean a wavelength of 320 to 380 nm, the VIS region is taken to mean a wavelength of 380 nm to 780 nm and the NIR region is taken to mean a wavelength of 780 nm to 2000 nm. Correspondingly, the term light is generally taken to mean electromagnetic radiation having wavelengths between 320 and 2000 nm.

For the purposes of the present invention, a dichroic dye is taken to mean a light-absorbing compound in which the absorption properties are dependent on the alignment of the compound with the direction of polarisation of the light. A dichroic dye compound in accordance with the present invention typically has an elongate shape, i.e. the compound is significantly longer in one spatial direction (longitudinal axis) than in the other two spatial directions. In the area of devices for regulating the passage of energy from an outside space into an inside space, a number of different technical solutions have been proposed in past years.

An advantageous solution is the use of switching layers comprising a Iiquid-crystalline medium in combination with one or more dichroic dyes. By application of a voltage, a change in the spatial alignment of the molecules of the dichroic compound can be achieved in these switching layers, causing a change in the transmission of the switching layer owing to their direction-dependent absorption. A corresponding device is described, for example, in WO 2009/141295.

Alternatively, such a change in transmission can also be achieved without electrical voltage by a temperature-induced transition from an isotropic state of the Iiquid-crystalline medium to a Iiquid-crystalline state, as described, for example, in US 2010/0259698.

The prior art discloses liquid-crystal media for display elements of the guest-host type which comprise cyanobiphenyl derivatives and one or more dichroic dyes (WO 2009/141295 and WO 2010/1 18422). For the same application, US 6033598 and US 5762824 describe LC media which, besides one or more dichroic dyes, comprise one or more compounds each consisting of three ring elements which are substituted by one or more fluorine atoms.

Rylene dyes have been described for use in the above-mentioned devices, for example in WO 2009/141295, WO 2013/004677 and WO2014/090373. However, rylene dyes generally have some disadvantages, in particular they often have low solubility in LC media, result in low low-temperature stability of the liquid-crystal mixture and often exhibit low colour purity, which, in particular, makes use in windows more difficult, where, for archi- tectonic reasons, the aesthetic impression is important and the purest colours possible are desired.

Furthermore known are naphthothiadiazole derivatives for various applications as for example for the use as organic semiconductor, as disclosed in WO 2015/041026, exemplified by the following structure:

wherein, inter alia, R¹ denotes straight chain or branched alkyl and R² and R³ denote H.

A similar compound with an oxadiazolothiadiazolobenzene central ring of the following structure

is described

In the documents cited above, the use of these compounds as dichroitic dye in liquid crystal mixtures is neither disclosed nor suggested.

The invention is based on the object of providing novel dichroic dyes which do not exhibit the above-mentioned disadvantages, or only do so to a small extent, and in addition have at least one, preferably several of the following desired properties: good solubility of the dyes in the liquid-crystalline medium, good light and temperature stability and high anisotropy of the absorption, i.e. a high capacity of the dye to align with the liquid crystal. In addition, the dyes should have strong light absorption in the VIS and/or

NIR region of light. Furthermore, the invention is based on the object of providing compounds which not only have a favourable combination of the application-technical parameters, but also, in addition, are distinguished by particularly high colour purity.

Usually, mixtures of dyes are used in liquid crystal media for the application according to the present invention because of the limited solubility of a single dye material in the liquid crystal medium and especially when it is desired to achieve black, i.e. when the whole range of the VIS and NIR part of the electromagnetic spectrum has to be covered and dyes of different colours are mixed. Therefore, there is generally a strong need for novel dichroic dyes to be able to choose from for the development of tailor-made liquid crystal media.

Surprisingly, it has been found that one or more of the requirements mentioned above are satisfied by compounds of the formula I as described below.

The invention relates to an LC medium comprising

a dye component A) comprising one or more compounds of the formula I and optionally further dichroic dyes,

a liquid-crystalline component B), also referred to below as "LC host mixture", comprising one or more, preferably two or more mesogenic compounds,

in which

W

R^z on each occurrence, identically or differently, denotes H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH₂

directly to one another, and in which, in addition, one or more H atoms may be replaced by F or CI,

A¹¹ , A¹² each, independently of one another, denote an aryl or heteroaryl group, which may be substituted by one or more radicals L, are each, independently of one another, defined like A¹¹ or

denote a cyclic alkyl group having 3 to 10 C atoms, in which one or more non-adjacent CH₂ groups may be replaced by O, on each occurrence, identically or differently, denotes OH,

optionally substituted aryl having 6 to 20 C atoms, or straight- chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which, in addition, one or more H atoms may be replaced by F or CI, an aryl or heteroaryl group, which may be substituted by one or more radicals L, and alternatively two adjacent groups L together also denote a straight-chain or branched alkylene group having 2 to 10 C atoms, in which one, several or all H atoms may be replaced by F and in which one or more - CH₂CH₂- groups can be replaced by -CH=CH-,

independently of one another, denote H, F, CI, CN or alkyl having 1 -12 C atoms, each, independently of one another, denote H or alkyl having 1 -12 C atoms,

Preference is given to LC media in which component B) is an LC compound or an LC mixture which has a nematic liquid-crystal phase.

The invention furthermore relates to the use of LC media comprising one or more dichroic dyes of the formula I as described above and below for optical, electro-optical and electronic purposes, in particular in devices for regulating the passage of energy from an outside space into an inside space.

The invention furthermore relates to devices for regulating the passage of energy from an outside space into an inside space.

The invention further relates to new compounds of formula I shown below.

The invention relates to compounds of formula I defined above, wherein the groups

are different from one another.

The invention further relates to compounds of formula I wherein R¹¹ and R¹², independently of one another, denote a branched alkyl group having 3 to 25 C atoms, in which one or more H atoms can be replaced by F, one or more CH₂ groups can be replaced by O and/or NH and one or more CH groups can be replaced by N.

The invention relates to compounds of formula IB shown below.

Above and below, the following meanings apply:

The term "organic group" denotes a carbon or hydrocarbon group. The term "carbon group" denotes a mono- or polyvalent organic group containing at least one carbon atom, where this either contains no further atoms (such as, for example, -C≡C-) or optionally contains one or more further atoms, such as, for example, N, O, S, P, Si, Se, As, Te or Ge (for example carbonyl, etc.). The term "hydrocarbon group" denotes a carbon group which additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, P, Si, Se, As, Te or Ge.

"Halogen" denotes F, CI, Br or I.

A carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. A carbon or hydrocarbon radical having 3 or more atoms can be straight- chain, branched and/or cyclic and may also contain spiro links or condensed rings. The terms "alkyl", "aryl", "heteroaryl", etc., also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc.

The term "aryl" denotes an aromatic carbon group or a group derived therefrom. The term "heteroaryl" denotes "aryl" as defined above, contain- ing one or more heteroatoms. Preferred carbon and hydrocarbon groups are optionally substituted alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 25, particularly preferably 1 to 18, C atoms, optionally substituted aryl or aryloxy having 6 to 40, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyi, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 6 to 40, preferably 6 to 25, C atoms.

Further preferred carbon and hydrocarbon groups are

Further preferred carbon and hydrocarbon groups are straight-chain, branched or cyclic alkyl radicals having 1 to 40, preferably 1 to 25, C atoms, which are unsubstituted or mono- or polysubstituted by F, CI , Br, I or CN and in which one more non-adjacent CH₂ groups may each be replaced, independently of one another

atoms are not linked directly to one another.

R^z preferably denotes H, halogen, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-

an optionally substituted aryl or aryloxy group having 6 to 40 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms. Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclo- pentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl and perfluorohexyl.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl and cyclooctenyl.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl and octynyl.

Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxy- ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy and n-dodecoxy.

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino and phenylamino. Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se. A ring system of this type may also contain individual non-conjugated units, as is the case, for example, in the fluorene basic structure. Particular preference is given to mono-, bi- or tricyclic aryl groups having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groups having 2 to 25 C atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6- or 7-membered aryl and heteroaryl groups, in which, in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and/or S atoms are not linked directly to one another.

Preferred aryl groups are derived, for example, from the parent structures benzene, biphenyl, terphenyl, [1 ,1 ':3',1 "]terphenyl, naphthalene, anthracene, binaphthyl, phenanthrene, pyrene, dihydropyrene, chrysene, peryl- ene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1 ,2,3-triazole, 1 ,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1 ,2-thiazole, 1 ,3-thiazole, 1 ,2,3-oxadiazole, 1 ,2,4-oxadiazole, 1 ,2,5-oxadiazole, 1 ,3,4-oxadiazole,

1 ,2,3-thiadiazole, 1 ,2,4-thiadiazole, 1 ,2,5-thiadiazole, 1 ,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1 ,3,5-triazine, 1 ,2,4-triazine, 1 ,2,3-triazine, 1 ,2,4,5-tetrazine, 1 ,2,3,4-tetra- zine, 1 ,2,3,5-tetrazine, or condensed groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimid- azole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalin- imidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quino- line, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxa- zine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyri- dine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, dihydro- thieno [3,4-b]-1 ,4-dioxin, isobenzothiophene, dibenzothiophene, benzothia- diazothiophene, or combinations of these groups. The heteroaryl groups may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, O, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e. contain only one ring (such as, for example, cyclohexane), or poly- cyclic, i.e. contain a plurality of rings (such as, for example, decahydro- naphthalene or bicyclooctane). Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 3 to 25 C atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH₂ groups may be replaced by -O- and/or -S-. Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1 ,3-dioxane, 1 ,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1 .1 .1]- pentane-1 ,3-diyl, bicyclo[2.2.2]octane-1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

The aryl, heteroaryl, carbon and hydrocarbon radicals optionally have one or more substituents, which are preferably selected from the group comprising silyl, sulfo, sulfonyl, formyl, amine, imine, nitrile, mercapto, nitro, halogen,

hydroxyl, or combinations of these groups.

Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, in particular bulky groups, such as, for example, t-butyl or optionally substituted aryl groups.

Preferred substituents, also referred to as

-N(R^Z)₂, in which R^z has the meaning indicated above, and Y¹ denotes halogen, optionally substituted silyl or aryl having 6 to 40, preferably 6 to 20, C atoms, and straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which one or more H atoms may optionally be replaced by F or CI.

More preferred substituents L are, for example

OC2F₅, furthermore phenyl.

"Substituted silyl or aryl" preferably means substituted by halogen, -CN,

has the meaning indicated above.

In a preferred embodiment, W in formula I denotes -S- or -O-, preferably -S-.

preferably stand, independently of one another, for a single bond, very particularly preferably for a single

bond.

Z²¹ and Z²² preferably denote, independently of one another, a single bond,

or -CF2O-, particularly preferably

or a single bond, and very particularly preferably a single bond. preferably on each occurrence, identically or differently,

represent an aryl group having 6 to 15 C atoms or a heteroaryl group having 2 to 15 C atoms, which may be substituted by one or more radicals L. are particularly preferably selected on each occurrence,

identically or differently, from groups, optionally substituted by radicals L, derived from the parent substances benzene, fluorene, naphthalene, pyridine, pyrimidine, thiophene, thiadiazole, dihydrothienodioxin, benzo- thiophene, dibenzothiophene, benzodithiophene, cyclopentadithiophene, thienothiophene, indenothiophene, furan, benzofuran, dibenzofuran and quinoline, very particularly preferably benzene, naphthalene, thiadiazole, thienothiophene and thiophene. The groups R¹¹ and R¹² preferably, independently of one another, denote a branched alkyl group having 3 to 25 C atoms, in which one or more H atoms can be replaced by F, one or more CH₂ groups can be replaced by O and/or NH and one or more CH groups can be replaced by N.

The groups R¹¹ and R¹² very particularly preferably, independently of one another, denote a branched alkyl group, preferably with a methyl, ethyl, n- propyl, n-butyl, or n-pentyl group bonded to an ethyl, n-propyl, n-hexyl, n- heptyl, n-octyl, n-nonyl or n-decyl group, for example 2-ethylhexyl,

In another preferred embodiment, the groups R¹¹ and R¹², independently of one another, denote a straight chain or branched alkyl or dialkylamino group having 1 to 25 C atoms per alkyl group.

The groups R^x1 and R^x2 are preferably on each occurrence, identically or differently, H, F or an alkyl group having 1 to 6 C atoms. R^x1 and R^x2 are particularly preferably on each occurrence, identically or differently, H or F, very particularly preferably H.

The indices r and s are preferably, independently of one another, equal to 1 , 2 or 3, particularly preferably equal to 1 or 2, very particularly preferably equal to 1 .

The compounds of formula I are preferably selected from the group of compounds of the sub-formulae IA and IB

wherein the occurring groups have the meaning indicated for formula I above.

The compounds of formula I are preferably chosen from compounds of sub-formula IA.

Preferred embodiments of the formula IA are the following formulae IA-1 , IA-2 and IA-3, particularly preferred are IA-2 and IA-3:

where the groups occurring have the meanings indicated above and Z , Z on each occurrence, identically or differently, preferably denote a single bond, particularly

preferably a single bond.

For the formulae IA-1 , IA-2 and IA-3, it is preferred that at least one A¹¹ or A¹² bonded directly to the benzo-bis(thiadiazole) moiety stands for 1 ,4- phenylene, 1 ,4-naphthylene, 2,6-naphthylene, thiazole-2,5-diyl, thiophene- 2,5-diyl, or thienothiophene-2,5-diyl. The groups may be substituted by one or more radicals L defined above. Particularly preferred substituents L are furthermore

phenyl.

Particularly preferred subformulae of formula IA-3 are the following:

a, independently of one another, denotes 0, 1 , 2, 3 or 4,

b, independently of one another, denotes 0, 1 or 2,

c, independently of one another, denotes 0 or 1 , and

d, independently of one another, denotes 1 , 2, 3, 4, 5 or 6.

Very particularly preferred compounds of the formula I are selected from the group of the following sub-formulae:

where R¹¹ and R¹² independently from one another denote a straight-chain alkyi or alkoxy group having 1 to 15 C atoms or a branched alkyi or alkoxy group having 3 to 25 C atoms, particularly preferably n-pentyl, n-hexyl, n-heptyl, or 2-ethylhexyl, 2-ethylheptyl, 2-ethyloctyl, 2-ethylnonyl,

2- ethyldecyl, 3-ethylhexyl, 3-ethylheptyl, 3-ethyloctyl, 3-ethylnonyl,

3- ethyldecyl, 2-octyldodecyl.

The compounds of the formula I can be prepared analogously to processes known to the person skilled in the art and described in standard works of organic chemistry, such as, for example, Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme Verlag, Stuttgart. For specific processes for the preparation of compounds of the formula I, reference is furthermore made to the known literature and to the working examples.

As compounds of formula IB are new, the present invention further relates to compounds of formula IB. Compounds of formula IB are preferably prepared by the procedure depicted in scheme 1 by hydrogenation of dinitro compounds 1 using a substoichiometric amount of hydrogen of preferably 0.2 to 0.8 equivalents, more preferably of 0.3 to 0.7 equivalents, particularly preferably of 0.4 to 0.6 equivalents.

Scheme 1

The starting material (1 ) is prepared following known literature procedures as published for example in T.L.Tam et al., Organic Lett. 2010, 12(15), 3340-3343, and WO 2015/041026 A1 .

The compound of the formula I is preferably a positively dichroic dye, i.e. a dye which has a positive degree of anisotropy R. The degree of anisotropy

R is determined, from the value for the extinction coefficient of the LC mixture comprising the dye in the case of alignment of the molecules parallel to the direction of polarisation of the light and the value for the extinction coefficient in the case of perpendicular alignment of the molecules to the direction of polarisation of the light. The degree of anisotropy R is particularly preferably greater than 0.4, very particularly preferably greater than 0.6 and most preferably greater than 0.7.

The absorption preferably reaches a maximum when the polarisation direction of the light is parallel to the direction of the longest elongation of the molecule of the formula I, and it reaches a minimum when the polarisation direction of the light is perpendicular to the direction of the longest elongation of the molecule of the formula I.

In principle, a suitable host mixture is any dielectrically negative or positive LC mixture which is suitable for use in conventional VA, TN, IPS or FFS displays.

Suitable LC mixtures are known to the person skilled in the art and are described in the literature. LC media for VA displays having negative dielectric anisotropy are described in for example EP 1 378 557 A1 .

Suitable LC mixtures having positive dielectric anisotropy which are suitable for LCDs and especially for IPS displays are known, for example, from JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09 410, DE 195 28 106, DE 195 28 107, WO 96/23 851 , WO 96/28 521 and WO2012/079676.

Preferred embodiments of the liquid-crystalline medium having negative or positive dielectric anisotropy according to the invention are indicated below.

The LC host mixture is preferably a nematic LC mixture, and preferably does not have a chiral LC phase. ln a preferred embodiment of the present invention the LC medium contains an LC host mixture with negative dielectric anisotropy. Preferred

embodiments of such an LC medium, and the corresponding LC host mixture, are those of sections a)-w) below: a) LC medium which comprises one or more compounds selected from the group of compounds of the formulae CY, PY and AC:

wherein

independently of one another, denote alkyl

having 1 to 12 C atoms, where, in addition, one or two non- adjacent CH₂ groups may be replaced by -O-, -CH=CH-,

such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms,

Z^x and Z^y each, independently of one another, denote

ich the individual radicals have the following meanings:

each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by

such a way that O atoms are not linked directly to one another,

Preferably, both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes CI, or both L³ and L⁴ denote F or one of L³ and L⁴ denotes F and the other denotes CI.

The compounds of the formula CY are preferably selected from the group consisting of the following sub-formulae:



wherein a denotes 1 or 2, alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably

The compounds of the formula PY are preferably selected from the group consisting of the following sub-formulae:





wherein alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂=CH-,

The compounds of the formula AC are preferably selected from the group of compounds of the following sub-formulae:

LC medium which additionally comprises one or more compounds of the following formula:

which the individual radicals have the following meanings

The compounds of the formula ZK are preferably selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably

Especially preferred are compounds of formula ZK1 and ZK3.

Particularly preferred compounds of formula ZK are selected from the following sub-formulae:

wherein the propyl, butyl and pentyl groups are straight-chain groups.

Most preferred are compounds of formula ZK1 a and ZK3a. LC medium which additionally comprises one or more compounds of the following formula:

in which the individual radicals on each occurrence, identically or differently, have the following meanings: each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non- adjacent CH₂ groups may be replaced by -O-, -CH=CH-,

e denotes 1 or 2.

The compounds of the formula DK are preferably selected from the group consisting of the following sub-formulae:

in which the individual radicals have the following meanings:

with at least one ring F being different from cyclohexylene, f denotes 1 or 2,

R¹ and R² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH₂ groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another,

Preferably, both radicals L¹ and L² denote F or one of the radicals L¹ and L² denotes F and the other denotes CI. The compounds of the formula LY are preferably selected from the group consisting of the following sub-formulae:







in which R¹ has the meaning indicated above, alkyl denotes a straight-chain alkyl radical having 1 -6 C atoms, (O) denotes an oxygen atom or a single bond, and v denotes an integer from 1 to 6. R¹ preferably denotes straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, in particular

LC medium which additionally comprises one or more compounds selected from the group consisting of the following formulae:

in which alkyl denotes and

X denotes F,

Particular preference is given to com

pounds of the formula G1 in which X denotes F.

in which R⁵ has one of the meanings indicated above for R¹, alkyl denotes

d denotes 0 or 1 , and z and m each, independently of one another, denote an integer from 1 to 6. R⁵ in these compounds is particularly preferably

is preferably 1 . The LC medium according to the invention preferably comprises one or more compounds of the above-mentioned formulae in amounts of≥ 5% by weight.

LC medium which additionally comprises one or more biphenyl compounds selected from the group consisting of the following formulae:

in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl and alkenyl^* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl^* preferably

The proportion of the biphenyls of the formulae B1 to B3 in the LC mixture is preferably at least 3% by weight, in particular≥ 5% by weight.

The compounds of the formula B2 are particularly preferred. The compounds of the formulae B1 to B3 are preferably selected from the group consisting of the following sub-formulae:

in which alkyl^* denotes an alkyl radical having 1 -6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formulae B1 a and/or B2c.

LC medium which additionally comprises one or more terphenyl compounds of the following formula:

in which R⁵ and R⁶ each, independently of one another, have one of the meanings indicated above, and

each, independently of one another, denote

in which L⁵ denotes F or CI, preferably F, and L⁶ denotes F, CI, OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F.

The compounds of the formula T are preferably selected from the group consisting of the following sub-formulae:







in which R denotes a straight-chain alkyl or alkoxy radical having 1 -7 C atoms, R^* denotes a straight-chain alkenyl radical having 2-7 C atoms, (O) denotes an oxygen atom or a single bond, and m denotes an integer from 1 to 6. R^* preferably denotes CH₂=CH-,

R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, meth- oxy, ethoxy, propoxy, butoxy or pentoxy.

LC medium which additionally comprises one or more compounds of the following formula O:

R⁰¹, R⁰² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH₂ groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another,

The compounds of the formula O are preferably selected from the group consisting of the following sub-formulae:

in which R⁰¹ and R⁰² have the meanings indicated above and preferably each, independently of one another, denote straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms.

Preferred media comprise one or more compounds selected from the formulae 03, 04 and 05.

in which

R⁹ denotes H, CH₃, C2H₅ or n-C3H₇, (F) denotes an optional fluorine substituent, and q denotes 1 , 2 or 3, and R⁷ has one of the meanings indicated for R¹, preferably in amounts of > 3% by weight, in particular > 5% by weight and very particularly preferably 5-30% by weight.

Particularly preferred compounds of the formula Fl are selected from the group consisting of the following sub-formulae:

in which R⁷ preferably denotes straight-chain alkyl, and R⁹ denotes

Particular preference is given to the compounds

of the formulae FI1 , FI2 and FI3. LC medium which additionally comprises one or more compounds selected from the group consisting of the following formulae:

in which R⁸ has the meaning indicated for R¹ , and alkyl denotes a straight-chain alkyl radical having 1 -6 C atoms.

LC medium which additionally comprises one or more compounds which contain a tetrahydronaphthyl or naphthyl unit, such as, for example, the compounds selected from the group consisting of the following formulae:



in which

each, independently of one another, denote alkyl having

1 to 12 C atoms, where, in addition, one or two non- adjacent CH₂ groups may be replaced by

such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms, and R¹⁰ and R¹¹ preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, and

a single bond.

LC medium which additionally comprises one or more difluoro- dibenzochromans and/or chromans of the following formulae:

in which

preferably in amounts of 3 to 20% by weight, in particular in amounts of 3 to 15% by weight.

Particularly preferred compounds of the formulae BC, CR and RC are selected from the group consisting of the following sub-formulae:





in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, (O) denotes an oxygen atom or a single bond, c is 1 or 2, and alkenyl and alkenyl^* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl^* preferably denote

Very particular preference is given to mixtures comprising one, two or three compounds of the formula BC-2. LC medium which additionally comprises one or more fluorinated phenanthrenes and/or dibenzofurans of the following formulae:

in which R¹¹ and R¹² each, independently of one another, have one of the meanings indicated above for R¹¹, b denotes 0 or 1 , L denotes F, and r denotes 1 , 2 or 3.

Particularly preferred compounds of the formulae PH and BF are selected from the group consisting of the following sub-formulae:

in which R and R' each, independently of one another, denote a straight-chain alkyl or alkoxy radical having 1 -7 C atoms.

LC medium which additionally comprises one or more monocyclic compounds of the following formula

wherein

R¹ and R² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent

CH₂ groups may be replaced by -

n such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms,

L¹ and L² each, independently of one another, denote

Preferably, both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes CI,

The compounds of the formula Y are preferably selected from the group consisting of the following sub-formulae:

which, Alkyl and Alkyl^* each, independently of one another, denote straight-chain alkyl radical having 1 -6 C atoms, Alkoxy denotes a straight-chain alkoxy radical having 1 -6 C atoms, Alkenyl and Alkenyl^* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, and O denotes an oxygen atom or a single bond. Alkenyl and Alkenyl^* preferably denote

Particularly preferred compounds of the formula Y are selected from the group consisting of the following sub-formulae:

wherein Alkoxy preferably denotes straight-chain alkoxy with 3, 4, or 5 C atoms. q) LC medium which comprises 1 to 15, preferably 3 to 12, compounds of the formulae CY1 , CY2, PY1 , PY2, AC1 , AC2 and/or AC3. The proportion of these compounds in the mixture as a whole is preferably 20 to 99%, more preferably 30 to 95%, particularly preferably 40 to 90%. The content of these individual compounds is preferably in each case 2 to 20%. r) LC medium which comprises 1 to 10, preferably 1 to 8, compounds of the formula ZK, in particular compounds of the formulae ZK1 , ZK2 and/or ZK6. The proportion of these compounds in the mixture as a whole is preferably 3 to 25%, particularly preferably 5 to 45%. The content of these individual compounds is preferably in each case 2 to 20%. s) LC medium in which the proportion of compounds of the formulae CY, PY and ZK in the mixture as a whole is greater than 70%, preferably greater than 80%. t) LC medium which contains one or more, preferably 1 to 5,

compounds selected of formula PY1 -PY8, very preferably of formula PY2. The proportion of these compounds in the mixture as a whole is preferably 1 to 30%, particularly preferably 2 to 20%. The content of these individual compounds is preferably in each case 1 to 20%. u) LC medium which contains one or more, preferably 1 , 2 or 3,

compounds of formula T2. The content of these compounds in the mixture as a whole is preferably 1 to 20%.

The LC medium according to the invention preferably comprises the terphenyls of the formula T and the preferred sub-formulae thereof in an amount of 0.5-30% by weight, in particular 1 -20% by weight.

Particular preference is given to compounds of the formulae T1 , T2, T3 and T21 . In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having 1 -5 C atoms.

The terphenyls are preferably employed in mixtures according to the invention if the Δη value of the mixture is to be > 0.1 . Preferred mixtures comprise 2-20% by weight of one or more terphenyl compounds of the formula T, preferably selected from the group of compounds T1 to T22. v) LC medium which contains one or more, preferably 1 , 2 or 3,

compounds of formula BF1 and/or BSF1 . The total content of these compounds in the mixture as a whole is preferably 1 to 15%,

preferably 2 to 10% particularly preferably 4 to 8%. v) Preferred media comprise one or more compounds of formula O, preferably selected from the formulae 03, 04 and 05 in a total concentration of 2 to 25%, preferably 3 to 20%, particularly preferably 5 to 15%. w) Preferred media comprise one or more compounds of formula DK, preferably selected from the formulae DK1 , DK4, DK7, DK 9, DK10 and DK1 1 . The total concentration of compounds of formulae DK9, DK10 and DK1 1 is preferably 2 to 25%, more preferably 3 to 20%, particularly preferably 5 to 15%.

In another preferred embodiment of the present invention the LC medium contains an LC host mixture with positive dielectric anisotropy. Preferred embodiments of such an LC medium, and the corresponding LC host mixture, are those of sections aa) - zz) below:

LC-medium, characterised in that it comprises one or more compounds selected from the group of compounds of the formulae II and III

R 20

each, identically or differently, denote a halogenated or un- substituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH₂ groups in these radicals may each be replaced, independently of one another, by

one another,

X 20

each, identically or differently, denote F, CI, CN, SF₅, SCN, NCS, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 C atoms, and

20-24

Y each, identically or differently, denote H or F;

The compounds of the formula II are preferably selected from the following formulae:

 R preferably denotes alkyl having 1 to 6 C atoms. X preferably denotes F. Particular preference is given to compounds of the formulae I la and Mb, in particular compounds of the formulae I la and Mb wherein X denotes F.

The compounds of the formula III are preferably selected from the following formulae:

wherein R and X have the meanings indicated above.

R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F. Particular preference is given to compounds of the formulae Ilia and llle, in particular compounds of the formula Ilia;

LC-medium additionally comprising one or more compounds selected from the following formulae:

wherein

have the meanings indicated above, and

The compounds of the formula IV are preferably selected from the following formulae:

wherein ^u have the meanings indicated above.

R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes

The compounds of the formula V are preferably selected from the following formulae:

R preferably denotes alkyl having 1 to 6 C atoms. X preferably

The compounds of the formula VI are preferably selected from the following formulae:

wherein R and X have the meanings indicated above.

R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F, furthermore

The compounds of the formula VII are preferably selected from the following formulae:

wherein R and X have the meanings indicated above.

R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F, furthermore OCF₃, OCHF₂ and OCH=CF₂.

The medium additionally comprises one or more compounds selected from the formulae ZK1 to ZK10 given above. Especially preferred are compounds of formula ZK1 and ZK3. Particularly preferred compounds of formula ZK are selected from the sub- formulae ZK1 a, ZK1 b, ZK1 c, ZK3a, ZK3b, ZK3c and ZK3d.

The medium additionally comprises one or more compounds selected from the formulae DK1 to DK12 given above. Especially preferred compounds are DK1 , DK4, DK7, DK 9, DK10 and DK1 1 .

The medium additionally comprises one or more compounds selected from the following formulae:

wherein X²⁰ has the meanings indicated above, and

The compounds of the formulae DK-3a and IX are preferably selected from the following formulae:

The medium additionally comprises one or more compounds selected from the formulae B1 , B2 and B3 given above, preferably from the formula B2. The compounds of the formulae B1 to B3 are particularly preferably selected from the formulae B1 a, B2a, B2b and B2c.

The medium additionally comprises one or more compounds selected from the following formula:

wherein L , L denote H or F, and R and R each, identically or differently, denote n-alkyl, alkoxy, oxaalkyi, fluoroalkyi or alkenyl, each having up to 6 C atoms, and preferably each, identically or differently, denote alkyl having 1 to 6 C atoms. The medium comprises one or more compounds of the following formulae:

wherein

have the meanings indicated in formula III, and





wherein R and X have the meaning indicated above and

preferably R²⁰ denotes alkyl having 1 to 6 C atoms and X²⁰ denotes F. The mixture according to the invention particularly preferably comprises at least one compound of the formula Xlla and/or Xlle.

The medium comprises one or more compounds of formula T given above, preferably selected from the group of compounds of the formulae T21 toT23 and T25 to T27. Particular preference is given to the compounds of the formulae T21 to T23. Very particular preference is given to the compounds of the formulae

The medium comprises one or more compounds selected from the group of formulae DK9, DK10 and DK1 1 given above.

wherein R and X each, independently of one another, have one of the meanings indicated above, and γ

each, independently of one another, denote H or F. X²⁰ is preferably .

R²⁰ preferably denotes alkyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyl, each having up to 6 C atoms.

The mixture according to the invention particularly preferably comprises one or more compounds of the formula XVIII-a,

wherein R has the meanings indicated above. R preferably denotes straight-chain alkyl, in particular ethyl, n-propyl, n-butyl and n-pentyl and very particularly preferably n-propyl. The compound(s) of the formula XVIII, in particular of the formula XVIII-a, is (are) preferably employed in the mixtures according to the invention in amounts of 0.5-20% by weight, particularly preferably 1 -15% by weight. mm) The medium additionally comprises one or more compounds of the formula XIX,

wherein

have the meanings indicated in formula I, s denotes 0 or 1 , and

In the formula XIX, X may also denote an alkyl radical having 1 -6 C atoms or an alkoxy radical having 1 -6 C atoms. The alkyl or alkoxy radical is preferably straight-chain.

R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F;

The compounds of the formula XIX are preferably selected from the following formulae:



wherein R²⁰, X²⁰ and Y²⁰ have the meanings indicated above. R²⁰ preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F, and Y²⁰ is preferably F;

R is straight-chain alkyl or alkenyl having 2 to 6 C atoms; nn) The medium comprises one or more compounds of the formulae G1 to G4 given above, preferably selected from G1 and G2 wherein alkyl denotes Ci-6-alkyl, L^x denotes H and X denotes F or CI. In G2, X particularly preferably denotes CI. The medium comprises one or more compounds of the following formulae:

wherein R and X have the meanings indicated above. R preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F. The medium according to the invention particularly preferably comprises one or more compounds of the formula XXII wherein X²⁰ preferably denotes F. The compound(s) of the formulae XX - XXII is (are) preferably employed in the mixtures according to the invention in amounts of 1 -20% by weight, particularly preferably 1 -15% by weight. Particularly preferred mixtures comprise at least one compound of the formula XXII. pp) The medium comprises one or more compounds of the following pyrimidine or pyridine compounds of the formulae

wherein R and X have the meanings indicated above. R preferably denotes alkyl having 1 to 6 C atoms. X²⁰ preferably denotes F. The medium according to the invention particularly preferably comprises one or more compounds of the formula M-1 , wherein X²⁰ preferably denotes F. The compound(s) of the formulae M-1 - M-3 is (are) preferably employed in the mixtures according to the invention in amounts of 1 -20% by weight, particularly preferably 1 -15% by weight.

Further preferred embodiments are indicated below: qq) The medium comprises two or more compounds of the formula XII, in particular of the formula Xlla and/or Xlle; The medium comprises 2-30% by weight, preferably 3-20% by weight, particularly preferably 3-15% by weight, of compounds of the formula XII;

Besides the compounds of the formulae XII, the medium comprises further compounds selected from the group of the compounds of the formulae ll-XVIII;

The proportion of compounds of the formulae ll-XVIII in the mixture as a whole is 40 to 95%, preferably 50 to 90%, particularly preferably 55 to 88% by weight;

The medium preferably comprises 10-40%, more preferably 12-30%, particularly preferably 15 to 25% by weight of compounds of the formulae II and/or III;

The medium comprises 1 -10% by weight, particularly preferably 2-7% by weight, of compounds of the formula XV and/or XVI;

The medium comprises at least one compound of the formula Xlla and/or at least one compound of the formula Xlle and at least one compound of the formula Ilia and/or lla.

Preferred media comprise one or more compounds of formula O, preferably selected from the formulae 03, 04 and 05 in a total concentration of 2 to 25%, preferably 3 to 20%, particularly preferably 5 to 15%.

Preferred media comprise one or more compounds of formula DK, preferably selected from the formulae DK1 , DK4, DK7, DK 9, DK10 and DK1 1 . The total concentration of compounds of formulae DK9, DK10 and DK1 1 is preferably 2 to 25%, more preferably 3 to 20%, particularly preferably 5 to 15%. zz) Preferred media comprise one or more compounds of formulae IV to VI, preferably selected from the group of compounds of formulae IVa,

IVb, IVc, IVd, Va, Vc and Vlb in a concentration of 10 to 80%, preferably 12 to 75% particularly preferably 15 to 70% by weight..

In case the medium has negative dielectric anisotropy (Δε), the value for Δε is preferably in the range from -2.0 to -8.0, more preferably in the range from -3.0 to -6.0, and particularly preferably from -3.5 to 5.0.

In case the medium has positive dielectric anisotropy, the value for Δε is preferably in the range from 3.0 to 60.0, more preferably in the range from 5.0 to 30.0, and particularly preferably from 8.0 to 15.0.

The liquid-crystal media in accordance with the present invention prefera- bly have a clearing point of 80°C or more, more preferably 90°C or more, even more preferably 105°C or more, and particularly preferably 1 10°C or more.

The nematic phase of the media according to the invention preferably extends at least from -10°C or less to 80°C or more, preferably up to 90°C or more, more preferably at least from -20°C or less to 100°C or more and particularly preferably from -30°C or less to 1 10°C or more.

In a preferred embodiment of the present invention the birefringence (Δη) of the liquid crystal media is in the range of 0.040 or more to 0.080 or less, more preferably in the range of 0.045 or more to 0.070 or less and most preferably in the range of 0.050 or more to 0.060 or less. In this

embodiment, the dielectric anisotropy is positive or negative, preferably negative. ln another preferred embodiment of the present invention the Δη of the liquid crystal media is n the range of 0.075 or more to 0.130 or less, more preferably in the range of 0.090 or more to 0.125 or less and most preferably in the range of 0.095 or more to 0.120 or less.

In yet another preferred embodiment of the present invention the Δη of the liquid crystal media is n the range of 0.100 or more to 0.200 or less, more preferably in the range of 0.1 10 or more to 0.180 or less and most preferably in the range of 0.120 or more to 0.160 or less.

The dichroic compound of the formula I is preferably present in the switching layer in a proportion of 0.01 to 10% by weight, particularly preferably 0.05 to 7% by weight and very particularly preferably 0.1 to 7% by weight. The media preferably comprise one, two, three, four or five compounds of the formula I according to the invention.

The LC medium according to the invention is preferably a nematic liquid crystal.

The media according to the invention are prepared in a manner conventional per se. In general, the components are dissolved in one another, preferably at elevated temperature. The mixing is preferably carried out under inert gas, for example under nitrogen or argon. One or more dyes of the formula I and optionally further dichroic dyes are subsequently added, preferably at elevated temperature, particularly preferably at above 40°C and very particularly preferably at above 50°C. In general, the desired amount of the components used in smaller amount is dissolved in the components making up the principal constituent. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, toluene, chloroform or methanol, and to remove the solvent again, for example by distillation, after mixing. The invention furthermore relates to the process for the preparation of the LC media according to the invention.

The invention furthermore relates to the use of an LC medium comprising at least one compound of the formula I in a liquid-crystal display of the guest-host type.

The invention furthermore relates to a liquid-crystal display of the guest- host type containing an LC medium which comprises at least one compound of the formula I.

The invention furthermore relates to the use of a mixture comprising a liquid-crystalline medium and at least one compound of a formula I in a device for regulating the passage of energy from an outside space into an inside space.

The device according to the invention, in addition to one or more compounds of the formula I, and preferably a liquid-crystalline medium, preferably also comprises further dichroic dyes having a different structure to formula I in the switching layer. It particularly preferably comprises one, two, three or four further dyes, very particularly preferably two or three further dyes and most preferably three further dyes having a different structure to formula I.

With respect to the property of dichroism, the preferred properties described for the compound of the formula I are also preferred for the optional further dichroic dyes.

The absorption spectra of the dichroic dyes of the switching layer preferably complement one another in such a way that the impression of a black colour arises for the eye. The two or more dichroic dyes of the liquid- crystalline medium according to the invention preferably cover a large part of the visible spectrum. The precise way in which a mixture of dyes which appears black or grey to the eye can be prepared is known to the person skilled in the art and is described, for example, in Manfred Richter, Ein- fuhrung in die Farbmetrik [Introduction to Colorimetry], 2nd Edition, 1981 , ISBN 3-1 1 -008209-8, Verlag Walter de Gruyter & Co.

The setting of the colour location of a mixture of dyes is described in the area of colorimetry. To this end, the spectra of the individual dyes are calculated taking into account the Lambert-Beer law to give an overall spec- trum and converted into the corresponding colour locations and luminance values under the associated illumination, for example illuminant D65 for daylight, in accordance with the rules of colorimetry. The position of the white point is fixed by the respective illuminant, for example D65, and is quoted in tables (for example reference above). Different colour locations can be set by changing the proportions of the various dyes.

According to a preferred embodiment, the switching layer comprises one or more dichroic dyes which absorb light in the red and NIR region, i.e. at a wavelength of 600 to 2000 nm, preferably in the range from 650 to

1800 nm, particularly preferably in the range from 650 to 1300 nm. In a preferred embodiment, these dichroic dyes are selected from azo compounds, anthraquinones, methine compounds, azomethine compounds, merocyanine compounds, naphthoquinones, tetrazines, perylenes, ter- rylenes, quaterrylenes, higher rylenes, pyrromethenes, azo dyes, nickel dithiolenes, (metal) phthalocyanines, (metal) naphthalocyanines and (metal) porphyrins. Of these, particular preference is given to perylenes and terrylenes.

The further dichroic dyes of the switching layer having a different structure to the formula I are preferably selected from the dye classes indicated in B. Bahadur, Liquid Crystals - Applications and Uses, Vol. 3, 1992, World Scientific Publishing, Section 1 1 .2.1 , and particularly preferably from the explicit compounds given in the table present therein.

The said dyes belong to the classes of dichroic dyes which are known to the person skilled in the art and have been described many times in the literature. Thus, for example, anthraquinone dyes are described in

EP 34832, EP 44893, EP 48583, EP 54217, EP 56492, EP 59036,

GB 2065158, GB 2065695, GB 2081736, GB 2082196, GB 2094822, GB 2094825, JP-A 55-123673, DE 3017877, DE 3040102, DE 31 15147, DE 31 15762, DE 3150803 and DE 3201 120, naphthoquinone dyes are described in DE 3126108 and DE 3202761 , azo dyes in EP 43904,

DE 3123519, WO 82/2054, GB 2079770, JP-A 56-57850, JP-A 56-104984, US 4308161 , US 4308162, US 4340973, T. Uchida, C. Shishido, H. Seki and M. Wada: Mol. Cryst. Lig. Cryst. 39, 39-52 (1977), and H. Seki, C. Shishido, S. Yasui and T. Uchida: Jpn. J. Appl. Phys. 21 , 191 -192 (1982), and perylenes are described in EP 60895, EP 68427 and WO 82/1 191 . Rylene dyes as described, for example, in EP 2166040, US 201 1/0042651 , EP 68427, EP 47027, EP 60895, DE 31 10960 and EP 698649.

According to a preferred embodiment, the switching layer of the device according to the invention comprises, besides compounds of the formula I, exclusively dichroic dyes selected from rylene dyes.

Examples of preferred further dichroic dyes which may be present in the switching layer of the device are shown in Table 1 below:

Table 1



ln a preferred embodiment, the switching layer of the device according to the invention comprises one or more quencher compounds. This is particu- larly preferred if the device according to the invention comprises one or more fluorescent dyes in its switching layer.

Quencher compounds are compounds which quench the fluorescence. The quencher compounds can take on the electronic excitation energy of adja- cent molecules, such as, for example, fluorescent dyes, in the switching layer and undergo a transition into an electronically excited state in the process. The quenched fluorescent dye is thus converted into the electronic ground state and is thus prevented from emitting fluorescence or under- going a subsequent reaction. The quencher compound itself returns to the ground state through radiation-free deactivation or by emission of light and is again available for further quenching.

The quencher compound may have various functions in the switching layer of the device according to the invention. Firstly, the quencher compound may contribute to extending the lifetime of a dye system, by deactivation of electronic excitation energy. Secondly, the quencher compound eliminates additional colour effects which may be aesthetically undesired, for example coloured emission in the inside space emanating from the fluorescent dyes in the switching layer.

In order to achieve effective quenching, the quencher compound should be adapted to the respective dye system, in particular the dye absorbing at the longest wavelength in a dye combination. The way to do this is known to the person skilled in the art.

Preferred quencher compounds are described, for example, in Table 8.1 on page 279 in Joseph R. Lakowicz, Principles of Fluorescence Spectroscopy, 3^rd Edition, 2010, ISBN 10: 0-387-31278-1 , Verlag Springer Science+ Business Media LLC. Further classes of molecule are familiar to the person skilled in the art, for example under the key words dark quencher or black hole quencher. Examples are azo dyes and aminoanthraquinones. The quencher compounds used in the switching layer of the device according to the invention may also be non-fluorescent dyes or dyes which only fluoresce in the NIR.

In a preferred embodiment of the switching layer according to the invention, any quencher compounds present are selected so that fluorescence in the visible part of the spectrum is suppressed.

The device according to the invention is preferably suitable for regulating the passage of energy in the form of sunlight from the environment into an inside space. The passage of energy to be regulated here takes place from the environment (the outside space) into an inside space.

The inside space here can be any desired space that is substantially sealed off from the environment, for example a building, a vehicle or a container.

The invention therefore furthermore relates to the use of the device for regulating the passage of energy from an outside space into an inside space.

However, the device can also be employed for aesthetic room design, for example for light and colour effects. For example, door and wall elements containing the device according to the invention in grey or in colour can be switched to transparent. Furthermore, the device may also comprise white or coloured flat backlighting which is modulated in brightness or yellow flat backlighting which is modulated in colour by means of a blue guest-host display. One or both glass sides of the device according to the invention may be provided with roughened or structured glass for the coupling-out of light and/or for the generation of light effects.

In a further alternative use, the device is employed for regulating the incidence of light on the eyes, for example in protective goggles, visors or sunglasses, where the device keeps the incidence of light on the eyes low in one switching state and reduces the incidence of light less in another switching state.

The device according to the invention is preferably arranged in an opening in a relatively large two-dimensional structure, where the two-dimensional structure itself only allows slight passage of energy, or none at all, and where the opening has relatively high energy transmissivity. The two- dimensional structure is preferably a wall or another boundary of an inside space to the outside. Furthermore, the two-dimensional structure preferably covers an area of at least equal size, particularly preferably an area at least twice as large as the opening in it in which the device according to the invention is disposed.

The device is preferably characterised in that it has an area of at least 0.05 m², preferably at least 0.1 m², particularly preferably at least 0.5 m² and very particularly preferably at least 0.8 m².

The device is preferably accommodated in an opening having relatively high energy transmissivity, as described above, in a building, a container, a vehicle or another substantially closed space. The device can generally be used for any desired inside spaces, particularly if they have only limited exchange of air with the environment and have light-transmitting boundary surfaces through which input of energy from the outside in the form of light energy can take place. The use of the device for inside spaces which are subjected to strong insolation through light-transmitting areas, for example through window areas, is particularly relevant.

The device according to the invention is switchable. Switching here is taken to mean a change in the passage of energy through the device. The device according to the invention is preferably electrically switchable, as described, for example, in WO 2009/141295 and in WO 2014/090373.

However, it may also be thermally switchable, as described, for example, in WO 2010/1 18422. In this case, the switching preferably takes place through a transition from a nematic state to an isotropic state through a change in the temperature of the switching layer comprising the compound of the formula I and a liquid-crystalline medium. In the nematic state, the molecules of the liquid-crystalline medium are in ordered form and thus so is the compound of the formula I, for example aligned parallel to the surface of the device through the action of an alignment layer. In the isotropic state, the molecules are in unordered form, and thus so is the compound of the formula I. The difference between ordered and unordered presence of the dichroic compound of the formula I causes a difference in the light transmissivity of the switching layer of the device according to the invention, in accordance with the principle that dichroic compounds have a higher or lower absorption coefficient depending on the alignment in relation to the plane of vibration of the light.

If the device is electrically switchable, it preferably comprises two or more electrodes, which are installed on both sides of the switching layer. The electrodes preferably consist of ITO or a thin, preferably transparent metal and/or metal-oxide layer, for example silver or FTO (fluorine-doped tin oxide) or an alternative material known to the person skilled in the art for this use. The electrodes are preferably provided with electrical connec- tions. The voltage is preferably provided by a battery, a rechargeable battery or an external power supply.

The switching operation in the case of electrical switching takes place through an alignment of the molecules of the liquid-crystalline medium by the application of voltage.

In a preferred embodiment, the device is converted from a state having high absorption, i.e. low light transmissivity, which is present without voltage, into a state having lower absorption, i.e. higher light transmissivity. The liquid-crystalline medium of the switching layer is preferably nematic in both states. The voltage-free state is preferably characterised in that the molecules of the liquid-crystalline medium, and thus the molecules of the compound of the formula I, are aligned parallel to the plane of the switching layer. This is preferably achieved by a correspondingly selected alignment layer. The state under voltage is preferably characterised in that the molecules of the liquid-crystalline medium, and thus the molecules of the compound of the formula I, are perpendicular to the plane of the switching layer.

In an alternative embodiment to the embodiment mentioned above, the device is converted from a state having low absorption, i.e. high light transmissivity, which is present without voltage, into a state having higher absorption, i.e. lower light transmissivity. The liquid-crystalline medium of the switching layer is preferably nematic in both states. The voltage-free state is preferably characterised in that the molecules of the liquid-crystalline medium of the switching layer, and thus the molecules of the compound of the formula I, are aligned perpendicular to the plane of the switching layer. This is preferably achieved by a correspondingly selected alignment layer. The state under voltage is preferably characterised in that the molecules of the liquid-crystalline medium of the switching layer, and thus the molecules of the compound of the formula I, are parallel to the plane of the switching layer.

According to a preferred embodiment of the invention, the device can be operated without an external power supply by providing the energy required by means of a solar cell or another device for conversion of light and/or heat energy into electrical energy which is connected to the device. The provision of the energy by means of the solar cell can take place directly or indirectly, i.e. via a battery or rechargeable battery or other unit for the storage of energy connected in-between. The solar cell is preferably mounted on the outside of the device or is an internal component of the device, as disclosed, for example, in WO 2009/141295. Particular preference is given here to solar cells which are particularly efficient in the case of diffuse light, and transparent solar cells.

The device according to the invention preferably has the following layer sequence, where further layers may additionally be present. The layers indicated below are preferably directly adjacent to one another in the device:

- substrate layer, preferably comprising glass or polymer

- electrically conductive transparent layer, preferably comprising ITO

- alignment layer

- switching layer comprising one or more compounds of the formula I

- alignment layer

- electrically conductive transparent layer, preferably comprising ITO

- substrate layer, preferably comprising glass or polymer

The preferred embodiments of the individual layers are described below.

The device according to the invention preferably comprises one or more, particularly preferably two, alignment layers. The alignment layers are pref- erably directly adjacent to the two sides of the switching layer comprising the compound of the formula I.

The alignment layers used in the device according to the invention can be any desired layers known to the person skilled in the art for this purpose.

Preference is given to polyimide layers, particularly preferably layers comprising rubbed polyimide. Polyimide rubbed in a certain manner known to the person skilled in the art results in alignment of the molecules of the liquid-crystalline medium in the rubbing direction if the molecules are par- allel to the alignment layer (planar alignment). It is preferred here for the molecules of the liquid-crystalline medium not to be completely planar on the alignment layer, but instead to have a slight pretilt angle. In order to achieve vertical alignment of the compounds of the liquid-crystalline medium to the surface of the alignment layer (homeotropic alignment), polyimide treated in a certain manner is preferably employed as material for the alignment layer (polyimide for very high pretilt angles). Furthermore, polymers obtained by an exposure process to polarised light can be used as alignment layer in order to achieve alignment of the compounds of the liquid-crystalline medium in accordance with an alignment axis (photo- alignment).

The switching layer in the device according to the invention is furthermore preferably arranged between two substrate layers or enclosed thereby. The substrate layers can consist, for example, of glass or a polymer, preferably a light-transmitting polymer.

The device is preferably characterised in that it does not comprise a polymer-based polariser, particularly preferably does not comprise a polariser in the solid material phase and very particularly preferably comprises no polariser at all. However, in accordance with an alternative embodiment, the device may also comprise one or more polarisers. The polarisers in this case are preferably linear polarisers.

If precisely one polariser is present, its absorption direction is preferably perpendicular to the orientation axis of the compounds of the liquid-crystalline medium of the device according to the invention on the side of the switching layer on which the polariser is located.

In the device according to the invention , both absorptive and also reflective polarisers can be employed. Preference is given to the use of polarisers which are in the form of thin optical films. Examples of reflective polarisers which can be used in the device according to the invention are DRPF (diffusive reflective polariser film, 3M), DBEF (dual brightness enhanced film, 3M), DBR (layered-polymer distributed Bragg reflectors, as described in US 7,038,745 and US 6,099,758) and APF films (advanced polariser film, 3M, cf. Technical Digest SID 2006, 45.1 , US 201 1/0043732 and US 7,023,602). It is furthermore possible to employ polarisers based on wire grids (WGPs, wire-grid polarisers) which reflect infrared light.

Examples of absorptive polarisers which can be employed in the devices according to the invention are the Itos XP38 polariser film and the Nitto Denko GU-1220DUN polariser film. An example of a circular polariser which can be used in accordance with the invention is the APNCP37-035- STD polariser (American Polarizers). A further example is the CP42 polariser (ITOS).

The device according to the invention furthermore preferably comprises an optical waveguide system which transports the light to a solar cell or another device for the conversion of light and/or heat energy into electrical energy, preferably as described in WO 2009/141295. The optical waveguide system collects and concentrates light hitting the device. It preferably collects and concentrates light emitted by fluorescent dichroic dyes in the switching layer. The optical waveguide system is in contact with a device for the conversion of light energy into electrical energy, preferably a solar cell, so that the collected light hits the latter in concentrated form. In a preferred embodiment of the invention, the device for the conversion of light energy into electrical energy is mounted at the edge of the device accord- ing to the invention, integrated into the latter and electrically connected to means for the electrical switching of the device.

In a preferred embodiment, the device according to the invention is a con- stituent of a window, particularly preferably a window comprising at least one glass surface, very particularly preferably a window which comprises multipane insulating glass. Window here is taken to mean, in particular, a structure in a building which comprises a frame and at least one glass pane surrounded by this frame. It preferably comprises a heat-insulating frame and two or more glass panes (multipane insulating glass).

According to a preferred embodiment, the device according to the invention is applied directly to a glass surface of a window, particularly preferably in the interspace between two glass panes of multipane insulating glass.

The invention furthermore relates to a window comprising a device according to the invention, preferably having the preferred features indicated above.

Owing to the electronic properties of the compounds according to the invention, they are also suitable, besides the use as dye, as organic semiconductors.

The invention therefore furthermore relates to the use of compounds of the formula I in organic electronic components, such as, for example, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), printed circuits, radio frequency identification elements (RFIDs), lighting elements, photovoltaic devices and optical sensors.

Owing to their coloured nature and good solubility in organic materials, the compounds according to the invention are eminently suitable as dyes. The invention therefore likewise relates to the use of dyes of the formula I for colouring a polymer.

In the present invention and especially in the following examples, the structures of the mesogenic compounds are indicated by means of abbreviations, also called acronyms. In these acronyms, the chemical formulae are abbreviated as follows using Tables A to C below. All groups

denote straight-chain

alkyl or alkenyl, preferably 1 E-alkenyl, each having n, m and I C atoms respectively. Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B shows the linking groups. Table C gives the meanings of the codes for the left-hand or right-hand end groups. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right- hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

Table A: Ring elements



Table C: End groups

Left-hand side Right-hand side

in which n and m each denote integers, and the three dots are placeholders for other abbreviations from this table.

The following table shows illustrative structures together with their respective abbreviations. These are shown in order to illustrate the meaning of the rules for the abbreviations. They furthermore represent compounds which are preferably used.

Table D: Illustrative structures

in which n, m and I preferably, independently of one another, denote 1 to 7.

The following table, Table E, shows illustrative compounds which can be used as additional stabilisers in the mesogenic media according to the present invention.

Table E

Table E shows possible stabilisers which can be added to the LC media according to the invention.

(n here denotes an integer from 1 to 12, preferably 1 , 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups are not shown).





The LC media preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1 % by weight, of stabilisers. Table F below shows illustrative compounds which can preferably be used as chiral dopants in the mesogenic media according to the present invention.

Table F

ln a preferred embodiment of the present invention, the mesogenic media comprise one or more compounds selected from the group of the compounds from Table F.

The mesogenic media according to the present application preferably com- prise two or more, preferably four or more, compounds selected from the group consisting of the compounds from the above tables.

The liquid-crystal media according to the present invention preferably comprise seven or more, preferably eight or more, individual compounds, preferably of three or more, particularly preferably of four or more, different formulae, selected from the group of the compounds from Table D. The proportions of these compounds and other components present in minor amounts are neglected when indicating the proportions of the liquid- crystalline compounds and the dichroic dyes.

It goes without saying to the person skilled in the art that the LC media according to the invention may also comprise compounds in which, for example, H, N, O, CI or F have been replaced by the corresponding isotopes.

All per cent data and amount ratios are per cent by weight. Examples

The present invention is described in detail by the following, non-restrictive example.

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 Δη is determined at 589 nm, and the value of Δε is determined at 1 kHz, unless explicitly indicated otherwise in each case. n_e and n₀ are in each case the refractive indices of the extraordinary and ordinary light beam under the conditions indicated above. 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 strongest 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 or reflections, each measurement is carried out against an identical mixture comprising no dye, and the value obtained is subtracted.

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 directions. The measurement of E(p) and E(s) is thus carried out via the rotation of the vibration direction of the incident polarised light.

The degree of anisotropy R is calculated from the resultant values for E(s) and E(p) in accordance with the formula

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-crystal- line media comprising a dichroic dye is also given in B. Bahadur, Liquid Crystals - Applications and Uses, Vol. 3, 1992, World Scientific Publishing, Section 1 1 .4.2.

Synthesis

A degassed mixture of 2 (2.1 g, 7.7 mmol), 3 (2.0 g, 3.65 mmol), tris(dibenzylidenacetone)dipalladium(0) (37 mg, 0.04 mmol), tris(o- tolyl)phosphine (50 mg, 0.16 mmol), toluene (65 mL) and 2 M aq. Na₂CO₃- solution (40 mL) are refluxed for 18 h under argon. The reaction is extracted with ether, the combined extracts are evaporated and the residue is purified by chromatography (S1O2; toluene/n-fteptane 2:3) and

recrystallised from

Step 2: 4,7-bis[5-[4-(3-ethylheptyl)-2-fluoro-phenyl]-2-thienyl]-5,6-diamino- 2,1 ,3-benzothiadiazole [5]

A solution of 4 (6.3 g, 7.5 mmol) in THF (65 ml_) is hydrogenated on Sponge-Nickel-catalyst (Johnson-Matheson A-7000) under normal pressure at room temp, until one equivalent of hydrogen is consumed. The reaction is filtered, evaporated and the residue is used in the next step without purification.

Step 3: 4,8-bis[5-[4-(3-ethylheptyl)-2-fluoro-phenyl]-2-thienyl]-benzo[1 ,2- c;4,5c']bis[1 ,2,5]thiadiazole

To a solution of 5 (6.3 g, 8.0 mmol) in CH2CI2 (100 ml_), triethylamine (4.5ml_, 32.5 mmol) followed by thionyl chlorid (1 .2 ml_, 16.5 mmol) are added dropwise under ice cooling. The reaction is refluxed for 18 h, quenched with water, extracted with ether and the combined extracts are evaporated. The crude product is purified by chromatography (S1O2; toluene/n-fteptane 1 :1 ) and recrystallised from toluene/n-fteptane 1 :1 to yield 4,8-bis[5-[4-(3-ethylheptyl)-2-fluoro-phenyl]-2-thienyl]-benzo[1 ,2- c;4,5c']bis[1 ,2,5]thiadiazole (BTD-1 ) as dark green crystals, m.p. 246 °C.

Compound 6 is prepared by Suzuki coupling of 4,7-dibromo-5,6-dinitro- 2,1 ,3-benzothiadiazole with 2-[4-[4-(3-ethylheptyl)-2-fluoro-phenyl]phenyl]- 4,4,5,5-tetramethyl-1 ,3,2-dioxaborolane in analogy to procedures known from the literature, for example described in US 2013/0037784.

A solution of 6 (2.1 g, 2.53 mmol) in THF (20 ml_) is hydrogenated on Sponge-Nickel-catalyst (Johnson-Matheson A-7000, 1 g) under normal pressure at room temp, until 0.75 equivalents of hydrogen are consumed. The intermediate product is oxidised by exposure to air, and the solution is filtered, evaporated and the residue is purified by column chromatography to

[1 ,2,5]thiadiazolo[3,4-/]-2,1 ,3-benzoxadiazole (BOD-1 ), m.p. 178°C.

The following compounds are obtained analogously to Example 1 (BTD-1 ):

Use Examples

The dyes prepared are investigated with respect to their physical properties in order to establish their suitability for use in devices for regulating energy transmission.

Preparation of liquid-crystalline dye mixtures

Nematic LC host mixtures N-1 to N-19 are prepared as follows:

Device Examples

For the following device examples, the nematic host mixture N-17 is used and mixtures with the following dyes are prepared:



Comparative example 1

The following comparative mixture C-1 which is known from the state of the art is prepared and investigated.

Chromaticity coordinate of double cell in the off-state:

The values shown in table 1 as well as the corresponding values below are measured according to norm EN410.

Example 1

A mixture M-1 containing 99.9% of nematic host mixture N-17 and 0.1 % of

BTD-1 is prepared and investigated.

The mixture M-1 shows two absorption maxima at 393nm and 822nm. At a wavelength of 822nm the mixture M-1 shows a degree of anisotropy of 0.69. At 393nm the degree of anisotropy is 0.65. This means, that both absorption bands have the same direction of polarisation. The extinction coefficients are shown in table 2.

Example 2

A mixture M-2 is prepared as follows:

From table 3 can be seen that the mixture is switchable, as shown by the differences of transmittance values for the on and off states. Surprisingly, the switching in the NIR region of the electromagnetic spectrum is much higher than in the visible region which can be seen from the bigger difference between on and off state of the solar direct transmittance than of the corresponding values of the light transmittance.

The mixture M-2 is very well suitable for the use in devices for regulating the passage of energy from an outside space into an inside space, for example in windows.

Example 3

As can be seen from the transmittance data in table 4, the mixture M-3 is very well switchable. The mixture M-3 is very well suitable for the use in devices for regulating the passage of energy from an outside space into an inside space, for example in windows.

The comparison of the mixture M-3 with the comparative example C-1 from the state of the art shows that surprisingly, M-3 has an advantageously higher difference between on-state and off-state for the solar direct transmittance. Example 4

As can be seen from the transmittance data in table 5, the mixture M-4 is very well switchable. The mixture M-4 is very well suitable for the use in devices for regulating the passage of energy from an outside space into an inside space, for example in windows. The comparison of the mixture M-4 with the comparative example C-1 from the state of the art shows that surprisingly, M-4 has an advantageously higher difference between on-state and off-state for the solar direct transmittance.

Mixture examples

To the host mixtures given above, the dyes according to the invention are added in the concentration iven in the table below.

The mixtures M-1 to M-19 are very well suitable for the use in devices for regulating the passage of energy from an outside space into an inside space, for example in windows.

Claims

Patent Claims Liquid crystalline medium comprising

a dye component A) comprising one or more compounds of formula I,

and

a liquid-crystalline component B) comprising one or more mesogenic compounds,

wherein in formula I of componen A)

identically or differently, denote H, F, straight-chain or

branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by

y

atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be

on each occurrence, identically or differently, denotes H halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non- adjacent CH₂ groups may be replaced by -O-, -S-, -CO-

such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F or CI, each, independently of one another, denote an aryl or

heteroaryl group, which may be substituted by one or more radicals L, are each, independently of one another, defined like A¹¹

or denote a cyclic alkyl group having 3 to 10 C atoms, in which one or more CH₂ groups may be replaced by O in such a way that no two O atoms are adjacent, on each occurrence, identically or differently, denotes

substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which, in addition, one or more H atoms may be replaced by F or CI, an aryl or heteroaryl group, which may be substituted by one or more radicals L, and alternatively two adjacent groups L together also denote a straight-chain or branched alkylene group having 2 to 10 C atoms, in which one, several or all H atoms may be replaced by F and in which one or more -CH₂CH₂- groups can be replaced by

on each occurrence, identically or differently, denote a

Liquid crystalline medium according to claim 1 , characterised in that one or more compounds of formula I are selected from the compounds of formulae IA and IB

wherein the occurring groups and parameters have the meaning indicated for formula I in claim 1 .

Liquid crystalline medium according to claim 1 or 2, characterised in that it comprises one or more compounds of formula IA selected from the group of compounds of the sub-formulae IA-1 to IA-3

wherein have the meanings indicated in

claim 1 and

4. Liquid crystalline medium according to one or more of claims 1 to 3, characterised in that A¹¹ and A¹² denote, independently of one another, 1 ,4-phenylene, 1 ,

4-naphthylene, 2,6-naphthylene, thiazole- 2,5-diyl, thiophene-2,5-diyl or thienothiophene-2,5-diyl, wherein one or more H atoms may be replaced by a group L as defined in claim 1 .

5. Liquid crystalline medium according to one or more of claims 1 to 4, characterised in that it comprises one or more compounds of formula I wherein Z²¹ and Z²² denote a single bond.

6. Liquid crystalline medium according to one or more of claims 1 to 5, characterised in that it comprises one or more compounds of formula I wherein R¹¹ and R¹² denote a branched alkyl group having 3 to 25 C atoms, in which one or more H atoms can be replaced by F, one or more CH₂ groups can be replaced by O and/or NH and one or more

CH groups can be replaced by N.

7. Liquid crystalline medium according to one or more of claims 1 to 6, characterised in that it has negative dielectric anisotropy and comprises one or more compounds selected from the group of compounds of formulae CY, PY and AC

directly to one another,

8. Liquid crystalline medium according to one or more of claims 1 to 6, characterised in that it has positive dielectric anisotropy and comprises one or more compounds selected from the group of compounds of formulae II to VIII



each, identically or differently, denote a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH₂ groups in these radicals may each be replaced, independently of

atoms are not linked directly to one another, each, identically or differently, denote F, CI, CN, SF₅, SCN, NCS, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 C atoms, and each, identically or differently, denote H or F;

denotes 0 or 1 , and denotes 0 or 1

9. Liquid crystalline medium according to one or more of claims 1 to 8, characterised in that it additionally comprises one or more compounds selected from the group of compounds of formulae DK and O

not linked directly to one another,

Liquid crystalline medium according to claim 9, characterised in that it comprises one or more compounds of formula O, selected from the group of compounds of the sub-formulae O3 to O5

wherein

, identically or differently, denote straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms.

11. Liquid crystalline medium according to claim 9 or 10, characterised in that it comprises one or more compounds of formula DK selected from the group of compounds of the sub-formulae DK1 to DK12:

in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms.

12. Use of liquid crystalline media according to one or more of Claims 1 to 1 1 in electro-optical displays, devices for regulating the passage of energy from an outside space into an inside space, electrical semiconductors, organic field-effect transistors (OFETs), printed circuits, radio frequency identification elements (RFIDs), organic light-emitting diodes (OLEDs), lighting elements, photovoltaic devices, optical sensors, effect pigments, decorative elements or as dye for colouring polymers.

13. Device for regulating the passage of energy from an outside space into an inside space, where the device contains a switching layer comprising a liquid crystalline medium according to one or more of claims 1 to 1 1 .

14 Window containing a device according to Claim 13.

15. Compound of formula I

wherein -W- denotes -O-, and the other groups occurring have the meaning indicated in claim 1 ,

or

wherein the groups

or

characterised in that R¹¹ and R¹², independently of one another, denote a branched alkyl group having 3 to 25 C atoms, in which one or more H atoms can be replaced by F, one or more CH₂ groups can be replaced by O and/or NH and one or more CH groups can be replaced by N, and where the other groups occurring have the meaning indicated in claim 1 .

16. Compound according to claim 15, characterised in that R¹¹ and R¹², independently of one another, are selected from the group of radicals consisting of 2-ethylhexyl, 2-ethylheptyl, 2-ethyloctyl, 2-ethylnonyl,

2- ethyldecyl, 3-ethylhexyl, 3-ethylheptyl, 3-ethyloctyl, 3-ethylnonyl,

3- ethyldecyl and 2-octyldodecyl.