WO2022084168A1

WO2022084168A1 - 4,6-difluorodibenzothiophene derivatives and liquid-crystal medium containing these

Info

Publication number: WO2022084168A1
Application number: PCT/EP2021/078562
Authority: WO
Inventors: Sven Christian Laut; Matthias Bremer; Atsutaka Manabe; Harald Hirschmann
Original assignee: Merck Patent Gmbh
Priority date: 2020-10-19
Filing date: 2021-10-15
Publication date: 2022-04-28
Also published as: EP4229046A1; CN116368132A; TW202222791A

Abstract

The present invention relates to 4,6-difluorodibenzothiophene derivatives of formulae I-1 and I-2, to a process for the preparation thereof, to liquid-crystalline (LC) media comprising these derivatives and to electro-optical devices and in particular displays containing these liquid-crystalline media.

Description

4,6-DIFLUORODIBENZOTHIOPHENE DERIVATIVES AND LIQUID-CRYSTAL MEDIUM CONTAINING THESE

The present invention relates to 4,6-difluorodibenzothiophene derivatives, to a process for the preparation thereof, to liquid-crystalline (LC) media comprising these derivatives, and to electro-optical devices and in particular displays containing these liquid-crystalline media.

Liquid crystals have found widespread use since the first commercially usable liquid-crystalline compounds were found. Liquid-crystal displays (LCDs) are used in many areas for the display of information. LCDs are used both for direct-view displays and for projection-type displays.

The spatial arrangement of the molecules in a liquid crystal has the effect that many of its properties are direction-dependent. Of particular importance for use in liquid-crystal displays are the optical, dielectric and elasto-mechanical anisotropies. Depending on whether the molecules are oriented with their longitudinal axes perpendicular or parallel to the two plates of a capacitor, the latter has a different capacitance. In other words, the dielectric constant s of the liquid-crystalline medium has different values for the two orientations.

Substances whose dielectric constant is larger when the longitudinal axes of the molecules are oriented perpendicular to the capacitor plates than when they are oriented parallel are known as being dielectrically positive. Substances whose dielectric constant is smaller when the longitudinal axes of the molecules are oriented perpendicular to the capacitor plates than when they are oriented parallel are known as being dielectrically negative.

Both the polarisability of the molecules and the permanent dipole moment play a role for the dielectric anisotropy. On application of a voltage to the display, the longitudinal axis of the molecules orients itself in such a way that the larger of the dielectric constants becomes effective. The strength of the interaction with the electric field depends on the difference between the two constants. In the case of small differences, higher switching voltages are necessary than in the case of large differences. The introduction of suitable polar groups, such as, for example, nitrile groups or fluorine, into the liquid-crystal molecules enables a broad range of working voltages to be achieved.

In the case of the liquid-crystalline molecules used in some conventional liquid-crystal displays, the dipole moment oriented along the longitudinal axis of the molecules is larger than the dipole moment oriented perpendicular to the longitudinal axis of the molecules. In the TN (“twisted nematic”) cells, a liquid-crystalline layer with a thickness of only from about 5 to 10 pm is arranged between two flat glass plates, onto each of which an electrically conductive, transparent layer of tin oxide or indium tin oxide has been vapour-deposited as electrode. A likewise transparent alignment layer, usually consisting of a plastic, for example polyimides, is located between these films and the liquid-crystalline layer. This alignment layer serves to bring the longitudinal axes of the adjacent crystalline molecules into a preferential direction through surface forces in such a way that, in the voltage-free state, they lie uniformly on the inside of the display surface with the same alignment in a flat manner or with the same small tilt angle. Two polarisation films which only enable linear-polarised light to enter and escape are adhesively bonded to the outside of the display in a certain arrangement.

By means of liquid crystals in which the larger dipole moment is oriented parallel to the longitudinal axis of the molecule, very high-performance displays have already been developed. In most cases, mixtures of from 5 to 20 components are used in order to achieve a sufficiently broad temperature range of the mesophase and short response times and low threshold voltages. However, difficulties are still caused by the strong viewing-angle dependence in liquid-crystal displays as used, for example, for laptops. The best imaging quality can be achieved if the surface of the display is perpendicular to the viewing direction of the observer. If the display is tilted relative to the observation direction, the imaging quality drops drastically under certain circumstances.

For greater comfort, attempts have been made to make the angle through which the display can be tilted from the viewing direction of an observer as large as possible. Attempts have been made to improve the viewing-angle dependence using liquid-crystalline compounds whose dipole moment perpendicular to the longitudinal axis of the molecules is larger than that parallel to the longitudinal axis of the molecule. In the field-free state, these molecules are oriented perpendicular to the glass surface of the display. In this way, it has been possible to achieve an improvement in the viewingangle dependence. Displays of this type are known as VA-TFT (“vertically aligned") displays.

There are also electro-optical display modes that utilise an electric field which is substantially parallel to the substrates or the liquid-crystal layer. For example, WO 91/10936 describes a liquid-crystal display in which the electric signals are generated in such a way that the electric fields have a significant component parallel to the liquid-crystal layer, and which has since then become known as in-jolane switching (IPS) display. The principles of operating such a display are described, for example, by R.A. Soref in Journal of Applied Physics, Vol. 45, No. 12, pp. 5466-5468 (1974).

IPS displays contain an LC layer between two substrates with planar orientation, where the two electrodes are arranged on only one of the two substrates and preferably have interdigitated, comb-shaped structures. On application of a voltage to the electrodes an electric field with a significant component parallel to the LC layer is generated between them. This causes realignment of the LC molecules in the layer plane. Furthermore, so-called “fringe-field switching” (FFS) displays have been reported, see, inter alia, S.H. Jung et al., Jpn. J. Appl. Phys., Vol. 43, No. 3, 1028, 2004, which contain two electrodes on the same substrate, one of which is structured in a comb-shaped manner and the other is unstructured. A strong, so-called "fringe field" is thereby generated, i.e. a strong electric field close to the edge of the electrodes, and, throughout the cell, an electric field which has both a strong vertical component and also a strong horizontal component. FFS displays have a low viewing-angle dependence of the contrast. FFS displays usually contain an LC medium with positive dielectric anisotropy and an alignment layer, usually of polyimide, which provides planar alignment to the molecules of the LC medium.

Liquid-crystal displays of the IPS and FFS electro-optical mode are in particular suitable for use in modem desktop monitors, TV sets and multimedia applications. The liquid-crystalline media according to the present invention are preferably used in displays of this type. In general, dielectrically positive liquid-crystalline media having rather lower values of the dielectric anisotropy are used in FFS displays, but in some cases liquidcrystalline media having a dielectric anisotropy of only about 3 or even less are also used in IPS displays.

A further improvement has been achieved by the so-called HB-FFS mode. One of the unique features of the HB-FFS mode in contrast to the traditional FFS technology is that it enables higher transmittance which allows operation of the panel with less energy consumption.

Liquid-crystal compositions which are suitable for LCDs and especially for FFS and IPS displays are known from, for example, JP 07-181 439 (A), EP 0 667 555, EP 0 673 986, DE 195 09 410, DE 195 28 106, DE 19528 107, WO 96/23 851 and WO 96/28 521. However, these compositions have certain disadvantages. Amongst other deficiencies, most of them result in disadvantageously long addressing times, have inadequate values of the resistivity and/or require excessively high operating voltages. Both an improvement in the operating properties and also in the shelf life are desirable.

Typical applications of in-plane switching (IPS) and fringe-field switching (FFS) technologies are monitors, notebooks, televisions, mobile telephones, tablet PCs, etc.

Both the IPS and the FFS technology have certain advantages over other LCD technologies, such as, for example, the vertical alignment (VA) technology, e.g. a broad viewing angle dependency of the contrast.

WO 02/055463 A1 and EP 2 937 342 A1 describe fluorinated aromatic compounds and their use in liquid crystal mixtures and the use of the mixtures in liquid crystal displays.

There is still a need in the art for further liquid-crystalline materials and in particular compounds which may improve the properties of liquid-crystalline mixtures and enable further optimisation of liquid crystal displays.

An object of the present invention is therefore to provide compounds, in particular mesogenic compounds, which have favourable properties for use in liquid-crystalline mixtures and which can give benefits in these mixtures which are suitably advantageous to further optimise the liquid crystal materials and displays. It is also an object to provide a facile process to prepare these compounds.

It is a further object of the present invention to provide liquid-crystalline media, in particular for FFS, HB-FFS and IPS displays, but also for TN, positive VA or STN displays, and in particular for active-matrix displays like those addressed by TFTs, which do not exhibit the disadvantages indicated above or only do so to a lesser extent and which preferably have high specific resistance, low threshold voltage, suitable dielectric anisotropy, a good low temperature stability (LTS), fast response times and low rotational viscosities, enable high brightness and high transmittance, and which in addition exhibit favourable reliability and stability.

It is a further object of the present invention to provide displays with a high contrast ratio and a good black state, a high transmittance in one optical state, fast addressing times and a favourable stability, in particular at low temperatures and at high temperatures. Further objects of the present invention are immediately evident to the person skilled in the art from the following detailed description.

The objects are solved by the subject-matter defined in the independent claims, while preferred embodiments are set forth in the respective dependent claims and are further described below.

The present invention in particular provides the following items including main aspects, preferred embodiments and particular features, which respectively alone and in combination contribute to solving the above object and eventually provide additional advantages.

A first aspect of the present invention provides a compound selected from the group of compounds of formulae 1-1 and I-2

in which

R¹¹ denotes H, an alkyl or alkoxy radical having 1 to 15 C atoms, in which one or more CH₂ groups in these radicals are optionally replaced, independently of one another, by

-C=C- -CF₂O-, -OCF₂-, -CH=CH-

-O-, -CO-O- or -O-CO- in such a way that 0 atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, and

R¹² denotes a branched alkyl or alkoxy radical having 1 to 15 C atoms.

It has surprisingly been found that the compounds according to the invention can exhibit favourable solubility in liquid-crystalline media and in addition can favourably contribute to the stability and reliability of the media Based on the advantageous physical and chemical properties of the compounds, these compounds are in particular useful to set and adjust or tune the electro-optical properties of liquid-crystalline media, which in turn can be useful to further optimise LC displays. For example, while having a negative dielectric anisotropy, these compounds can be included in liquidcrystalline media having overall a positive dielectric anisotropy. This provision can be useful to increase the dielectric constant s± perpendicular to the longitudinal axes of the liquid-crystalline molecules and be beneficial e.g. in terms of increasing the transmission in certain display modes as further described below.

Another aspect of the invention relates to a liquid-crystal medium which comprises one or more compounds selected from the group of compounds of formulae 1-1 and I-2 as set forth herein.

In a preferred embodiment the liquid-crystal medium has a positive dielectric anisotropy, in particular a dielectric anisotropy of +0.5 or more.

It has favourably been recognized that a high brightness in displays like those of the HB-FFS mode can be obtained by using liquid-crystalline media having positive dielectric anisotropy and also having an increased dielectric constant s± perpendicular to the longitudinal axes of the liquidcrystalline molecules. This provision can advantageously be achieved by adding a limited amount of the one or more liquid-crystalline compounds according to the invention, which have a negative dielectric anisotropy and which have high s± properties, to the liquid-crystalline medium whilst maintaining a positive dielectric anisotropy of the entire medium.

However, in principle the addition of compounds with high s± may have some drawbacks. For example, this addition can lead to higher values of the rotational viscosity yi, and consequently to higher values of the ratio yi /K22 of the rotational viscosity yi and the elastic constant K22 for twist deformation, which leads to higher response times. Since K22 is approximately proportional to the elastic constant Ku for splay deformation, where the value of K22 is typically about half the value of Ku, this can suitably be determined by measuring yi and Ku. It has also been recognized that the reliability, in particular the voltage holding ratio (VHR), of such mixtures, especially HB-FFS mixtures, may be affected compared to conventional FFS mixtures.

Surprisingly, the media comprising the compound(s) according to the invention advantageously show a relatively high value of s± and at the same time enable a decrease of the rotational viscosity and the ratios of yi /K22 and yi /Ku, and enable fast response times in displays using liquidcrystalline media as described and claimed herein. In addition, the displays that make use of the media according to the invention favourably exhibit a particularly high contrast and suitable reliability.

Thus liquid-crystalline media which show a moderately positive dielectric anisotropy and at the same time an increased dielectric constant s± perpendicular to the longitudinal axes of the liquid-crystalline molecules may be provided, which favourably can maintain a low rotational viscosity and a low value of the ratio yi /Ku. This enables the provision of liquidcrystal displays, especially of the HB-FFS, FFS and IPS modes, with high brightness and transmittance and short response times.

The liquid-crystalline media according to the invention are suitable for mobile applications and TFT applications, such as, for example, mobile telephones and PDAs. Furthermore, the liquid-crystalline media according to the invention are particularly suitable for use in FFS, HB-FFS and IPS displays based on dielectrically positive liquid crystals.

The liquid-crystal media according to the present invention are especially suitable for use in liquid-crystal displays of the FFS, HB-FFS and IPS modes, based on dielectrically positive liquid crystals, and polymer stabilised variants thereof, in particular for large size TV applications. A further aspect of the invention relates to electro-optical devices containing the liquid-crystal medium according to the invention and in particular to a liquid-crystal display.

In a preferred embodiment the electro-optical device is a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, PS-HB-FFS, SA-HB-FFS, polymer stabilised SA-HB-FFS, positive VA or positive PS-VA display.

In another aspect of the present invention there is provided a facile and efficient process for the preparation of the compound selected from the group of compounds of the formulae 1-1 and I-2 as set forth herein. In particular, the process comprises the step of subjecting a branched haloalkane to a chemical reaction. The branched haloalkane preferably is a branched bromoalkane.

Without limiting the present invention thereby, in the following the invention is illustrated by the detailed description of the aspects, embodiments and particular features, and particular embodiments are described in more detail.

Herein, halogen denotes F, Cl, Br or I, preferably F or Cl, and more preferably F.

In the present invention, all atoms also include their isotopes. In particular, one or more hydrogen atoms (H) may be replaced by deuterium (D), which is particularly preferred in some embodiments; a high degree of deuteration enables or simplifies analytical determination of compounds, in particular in the case of low concentrations.

Herein, an alkyl radical and/or an alkoxy radical is taken to mean straightchain or branched alkyl or respectively alkoxy. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy.

Herein, oxaalkyl preferably denotes straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or

4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-,

5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

Herein, alkenyl, i.e. an alkyl radical in which one CH₂ group has been replaced by -CH=CH- , may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. Accordingly, it denotes, in particular, vinyl, prop-1- or -2-enyl, but-1 -, -2- or -3-enyl, pent-1 -, -2-, -3- or -4-enyl, hex-1 -, -2-, -3-, -4- or -5-enyl, hept-1 -, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1 -, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1 -, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

Herein, an alkyl or alkenyl radical which is at least monosubstituted by halogen, is preferably straight-chain, and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resultant radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the o-position.

Herein, a mono- or polyfluorinated alkyl or alkoxy radical having 1 , 2 or 3 C atoms or a mono- or polyfluorinated alkenyl radical having 2 or 3 C atoms is particularly preferably F, Cl, CF₃, CHF₂, O CF₃, OCHF₂, OCFHCF₃, OCFHCHF₂, OCFHCHF₂, OCF₂CH₃, OCF₂CHF₂, OCF₂CHF₂, OCF₂CF₂CHF₂, OCF₂CF₂CHF₂, OCFHCF₂CF₃, OCFHCF₂CHF₂, OCF₂CF₂CF₃, OCF₂CF₂CCIF2, OCCIFCF₂CF₃, OCH=CF₂ or CH=CF₂, very particularly preferably F or OCF₃, furthermore CF₃, OCF=CF₂, OCHF₂ or OCH=CF₂.

Herein, 1 ,4-cyclohexylene rings are depicted as follows:

wherein the cyclohexylene rings are trans-1 ,4-cyclohexylene rings.

Herein, 1 ,4-phenylene rings are depicted as follows:

The compound according to the invention is selected from the group of compounds of formulae 1-1 and I-2 as set forth herein.

In accordance with the invention it is also possible to provide a composition or mixture which comprises, preferably consists of, two or more compounds selected from the group of compounds of formulae 1-1 and I-2.

In a preferred embodiment the compound according to the invention is selected from the compounds of formula 1-1 .

In another preferred embodiment the compound according to the invention is selected from the compounds of formula I-2.

According to the invention R¹² in formulae 1-1 and I-2 denotes a branched alkyl or alkoxy radical having 1 to 15 C atoms.

The branched alkyl moiety of these groups may be selected from secondary and/or tertiary alkyl, preferably from secondary alkyl. In an embodiment the groups R¹¹ and R¹² in formula 1-1 and/or formula I-2 denote, independently of each other, branched alkyl or alkoxy radicals having 1 to 15 C atoms, preferably branched alkoxy radicals having 1 to 15 C atoms.

In a further preferred embodiment the group R¹¹ in formula 1-1 and/or formula I-2 denotes an unbranched, i.e. straight-chain alkyl or alkoxy radical having 1 to 9 C atoms, preferably a straight-chain alkoxy radical having 1 to 9 C atoms. It is particularly preferred that R¹¹ denotes a straight-chain alkoxy radical having 1 to 7 C atoms.

In a preferred embodiment the group R¹² in formula 1-1 and/or formula I-2 denotes a branched alkyl or alkoxy radical having 1 to 12 C atoms, preferably a branched alkoxy radical having 1 to 12 C atoms.

Branched alkoxy groups for R¹² in formula 1-1 and/or formula I-2 are preferably selected from isopropoxy, isobutoxy, isopentoxy, isohexyloxy, isoheptyloxy, isooctyloxy, isononyloxy, 1 -methyl propoxy, 2-methylbutoxy, 3- methylpentoxy, 4-methylhexyloxy, 2-ethylbutoxy, 3-ethylpentoxy, 2,4- dimethylpentoxy and 3,4-dimethylhexyloxy, more preferably from isobutoxy, isopentoxy, isohexyloxy, isoheptyloxy, 2-methylbutoxy and 2,4- dimethylpentoxy, and particularly preferably from isobutoxy and isopentoxy.

In an alternative embodiment R¹² groups in formula 1-1 and/or formula I-2 are branched alkyl groups which are preferably selected from isopropyl, isobutyl, isopentyl, isohexyl, isoheptyl, isooctyl, isononyl, 1 -methylpropyl, 2- methylbutyl, 3-methylpentyl, 4-methylhexyl, 2-ethylbutyl, 3-ethyl-pentyl, 2,4- dimethylpentyl, 3,4-dimethylhexyl, more preferably from isobutyl, isopentyl and isohexyl.

In a particularly preferred embodiment the compound according to the present invention is selected from the group of compounds of formulae l-A to l-N

The compounds of the formulae 1-1 and I-2 can be synthesised by methods known per se, as are described in the literature, e.g. in the standard works such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart, and specifically under reaction conditions which are known and suitable for the specified reactions. In this connection, it is also possible to utilise variants known per se that are not mentioned here in more detail.

The starting materials may optionally also be formed in situ such that they are not isolated from the reaction mixture but are immediately reacted further to give the compounds of formula 1-1 and/or formula I-2.

The syntheses of compounds of the formulae 1-1 and I-2 according to the invention are described by way of example in the Examples. The starting substances can be obtained by generally accessible literature procedures or commercially.

Preferred synthetic pathways towards compounds according to the invention are shown in the scheme below and are further illustrated by means of the Working Examples. The syntheses can be adapted to the particular desired compounds of the formulae 1-1 and I-2 by choice of suitable starting materials. Preferred compounds of formulae 1-1 and I-2 are preferably synthesized as shown in Scheme 1 .

Scheme 1

wherein R’ is a branched alkyl and R has the meanings as given for formulae 1-1 and I-2 above.

The described process steps and the subsequent work-up of the reaction mixture can in principle be carried out as a batch reaction or in a continuous reaction mode. The continuous reaction mode involves e.g. the reaction in a continuous stirred-tank reactor, a stirred-tank cascade, a loop or crossflow reactor, a flow tube or in a microreactor. The work-up of the reaction mixtures is optionally carried out, as required, by filtration through solid phases, chromatography, separation between immiscible phases, e.g. extraction, adsorption onto solid supports, disti Native removal of solvents and/or azeotropic mixtures, selective distillation, sublimation, crystallisation, co-crystallisation or by nanofiltration through membranes. In a preferred embodiment the present invention relates to a process for the preparation of compounds of the formulae 1-1 and I-2, in particular in accordance with the syntheses shown above.

In a further aspect of the present invention the compound selected from the group of compounds of formulae 1-1 and I-2 as set forth herein is used in a liquid-crystalline medium.

In an embodiment the liquid-crystal medium comprises two or more compounds selected from the group of the compounds of the formulae 1-1 and I-2.

In particular, the liquid-crystalline medium is a liquid-crystalline mixture which besides the one or more compounds according to the invention comprises one or more mesogenic compounds which are different from the former compounds.

In an embodiment the liquid-crystal medium according to the invention includes at least one compound of formula 1-1.

In another embodiment the liquid-crystal medium according to the invention includes at least one compound of formula I-2.

In further embodiment the liquid-crystal medium according to the invention includes at least one compound of formula 1-1 and in addition at least one compound of formula I-2.

Preferably, the one or more compounds selected from the group of compounds of formulae 1-1 and I-2 and in particular the further preferred compounds thereof are contained in the liquid-crystal medium in a total amount of 20% by weight or less, more preferably 15% by weight or less and even more preferably 10% by weight or less. It is preferred that the total amount of the one or more compounds selected from the group of compounds of formulae 1-1 and I-2 and in particular the further preferred compounds thereof contained in the liquid-crystal medium is in the range of from 2.5% by weight to 20% by weight, more preferably from 5% by weight to 15% by weight and in particular from 7% by weight to 10% by weight.

It is preferred that the liquid-crystal medium has a positive dielectric anisotropy As.

Above and below, As denotes the dielectric anisotropy, wherein As = s|| -s±. The dielectric anisotropy As is preferably determined at 20°C and 1 kHz.

In particular, the liquid-crystal medium preferably has a dielectric anisotropy As of +0.5 or more, more preferably of +1 .5 or more, and even more preferably of +2.5 or more. It is particularly preferred that the liquid-crystal medium exhibits a dielectric anisotropy As in the range of from +1 .5 to +12.0, more preferably from +3.0 to +10.0, even more preferably from +4.0 to +8.0 and in particular from +4.5 to +6.0.

In a preferred embodiment the liquid-crystal medium further comprises one or more compounds selected from the group of compounds of formulae 11-1 and II-2

in which

R² denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, in which optionally one or more CH₂ groups, independently of one another, may be replaced by

are independently of each other

|_21 |_22

L²³ and L²⁴ independently of each other, denote H or F,

L²⁵ denotes H or CH₃, and

X² denotes halogen, preferably F, halogenated alkyl or alkoxy with 1 to 3 C atoms or halogenated alkenyl or alkenyloxy with 2 or 3 C atoms.

The medium preferably comprises the one or more compounds of formulae 11-1 and/or 11-2 in a total amount of 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, still more preferably 20% by weight or more and in particular 22.5% by weight or more.

In formulae 11-1 and II-2 L²¹ and L²² or L²³ and L²⁴ are preferably both F.

In another preferred embodiment in formulae 11-1 and II-2 all of L²¹, L²², L²³ and L²⁴ denote F.

The compounds of formula 11-1 are preferably selected from compounds of formula 11-1 -a

in which the the occurring groups have the meanings given in for formula II- 1 , and wherein preferably X² is F.

It is particularly preferred that the medium comprises one or more compounds of formula 11-1 -a-1

11-1 -a-1 ,

in which R² has the meaning as set forth for formula 11-1 .

The one or more compounds of formula 11-1 -a-1 are preferably contained in the liquid-crystal medium in a total amount of 5% by weight or more, more preferably 10% by weight or more and in particular in a range of from 15% by weight to 20% by weight.

In a further embodiment the liquid-crystal medium comprises one or more compounds selected from the compounds of formulae 11-1 -b to 11-1 -h

wherein R² has the meaning as given in formula 11-1 .

The compounds of formula II-2 are preferably selected from the group of compounds of formulae ll-2-a, ll-2-b, ll-2-c and ll-2-d

in which the parameters have the respective meanings given for formula II- 2 above, and wherein preferably X² is F.

In a preferred embodiment of the present invention the medium comprises compounds selected from the group of compounds of formulae ll-2-a to ll-2-d, wherein L²¹ and L²² or L²³ and L²⁴ are both F.

In another preferred embodiment the medium comprises compounds selected from the group of compounds of formulae ll-2-a to ll-2-d, wherein L²¹ [_22 |_23 _anc| |_24 _a|| _are p

It is particularly preferred that the medium comprises one or more compounds selected from the of compounds of formula ll-2-d.

Especially preferred compounds of formula II-2 are compounds of formulae ll-2-i, ll-2-ii, ll-2-iii and ll-2-iv

wherein R² has the meaning given for formula II-2 above.

In a preferred embodiment the medium contains at least one compound of formula ll-2-i, preferably in a total amount of 2.5% by weight or more, more preferably 3.5% by weight or more and in particular 4.5% by weight or more.

In a further embodiment the liquid-crystal medium comprises one or more compounds selected from the compounds of formulae II-2-A to II-2-L

wherein R² has the meaning given for formula 11-2 above.

In an embodiment the liquid-crystal medium comprises one or more compounds selected from the group of compounds of formulae 111-1 to HI-32

wherein R³ has the meaning as given for R² in formula 11-2 above.

In an embodiment the liquid-crystal medium preferably comprises at least one compound of formula 111-1 , preferably in an amount of at least 2% by weight, more preferably at least 5% by weight.

Preferably, the medium according to the invention comprises one or more compounds of formula IV

in which

R⁴¹ and R⁴² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, preferably R⁴¹ is alkyl with 1 to 7 C atoms and R⁴² is alkyl with 1 to 7 C atoms or alkoxy with 1 to 7 C atoms or R⁴¹ is alkenyl with 2 to 7 C atoms and R⁴² is alkyl with 1 to 7 C atoms,

, on each occurrence, identically or differently, denote

Z⁴¹, Z⁴² on each occurrence, identically or differently, denote -CH₂CH₂-, -COO-, trans- -CH=CH-, trans--CF=CF-, -CH₂O-, -CF₂O-, -C≡C- or a single bond, preferably a single bond, and p is 0, 1 or 2, preferably 0 or 1, more preferably 0. Preferably the liquid-crystal media according to the present invention comprise one or more compounds of formula IV selected from the group of compounds of formulae IV-1 to IV-5

in which R⁴¹ and R⁴² have the respective meanings given under formula IV above and in formulae IV-1 , IV-4 and IV-5 R⁴¹ preferably is alkyl or alkenyl, preferably alkenyl and R⁴² preferably is alkyl or alkenyl, preferably alkyl; in formula IV-2 R⁴¹ and R⁴² preferably are alkyl and in formula IV-3 R⁴¹ preferably is alkyl or alkenyl, preferably alkyl and R⁴² preferably is alkyl or alkoxy, preferably alkoxy. Particularly preferably, the medium according to the invention comprises one or more compounds of formula IV-1 and one or more compounds of formula IV-4.

Optionally it is preferred that the medium further comprises one or more compounds of formula IV selected from the group of compounds of formulae IV-6 to IV-13

in which

R⁴¹ and R⁴² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, and

L⁴ denotes H or F.

In a preferred embodiment the medium comprises one or more compounds of formula IV-1

in which

R⁴¹ and R⁴² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms.

Preferably, the liquid-crystal medium comprises the one or more compounds of formula I V-1 in a total amount of at least 10% by weight, more preferably at least 20% by weight, even more preferably at least 30% by weight and in particular at least 34% by weight.

In a preferred embodiment the liquid-crystal medium comprises one or more compounds of formula IV-13, in which L⁴ is F.

In an embodiment the media may comprise one or more compounds of formula V

in which

R⁵ is alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with

1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, and preferably is alkyl with 1 to 7 C atoms or alkenyl with 2 to 7 C atoms,

L⁵¹ and L⁵², independently of each other, denote H or F, preferably L⁵¹ denotes F,

X⁵ denotes halogen, halogenated alkyl or alkoxy with 1 to 3

C-atoms or halogenated alkenyl or alkenyloxy with 2 or 3 C-atoms, preferably F, Cl, -OCF₃ or -CF₃, most preferably F, Cl or -OCF₃,

Z⁵ denotes -CH₂CH₂-, -CF₂CF₂-, -COO-, trans- -CH=CH- trans- -CF=CF- or -CH₂O, preferably -CH₂CH₂-, -COO- or trans- -CH=CH- and most preferably -COO- or -CH₂CH₂-, and q is O or l . Preferably the media according to the present invention comprise one or more compounds of formula V selected from the group of compounds of formulae V-1 and V-2

in which the parameters have the respective meanings given for formula V above, and the parameters L⁵³ and L⁵⁴ are, independently of each other, H or F, and preferably Z⁵ is -CH₂-CH₂-.

Preferably the compounds of formula V-1 are selected from the group of compounds of formulae V-1 a and V-1 b

in which the R⁵ has the meaning given for formula V above.

Preferably the compounds of formula V-2 are selected from the group of compounds of formulae V-2a to V-2d

in which the R⁵ has the meaning given for formula V above.

Preferably the liquid-crystalline media according to the present invention additionally comprise one or more compounds of formula VI

in which

R⁶¹ and R⁶² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms, preferably R⁶¹ is alkyl and R⁶² is alkyl or alkenyl, each having up to 7 C atoms,

Z⁶¹ and Z⁶² on each occurrence, identically or differently, denote -CH₂CH₂-, -COO-, trans- -CH=CH- trans- -CF=CF-, -CH₂O-, -CF₂O- or a single bond, preferably at least one of them is a single bond, and is 0, 1 or 2, preferably 0 or 1 .

Preferably the compounds of formula VI are selected from the group of compounds of formulae VI-1 to VI-4

in which R⁶¹ and R⁶² have the respective meanings given for formula VI above, and R⁶¹ preferably is alkyl having 1 to 7 C atoms and in formula VI-1 R⁶² preferably is alkenyl having up to 7 C atoms, more preferably -(CH₂)₂-CH=CH-CH₃, and in formula VI-2 R⁶² preferably is alkenyl having up to 7 C atoms, more preferably -(CH₂)₂-CH=CH₂, and in formulae VI-3 and VI-4 R⁶² preferably is alkyl having 1 to 7 C atoms. Preferably, the liquid-crystal medium comprises one or more compounds of formula VI-1 , preferably in a total amount of at least 2.5% by weight, more preferably at least 4% by weight, and in particular at least 7.5% by weight.

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula Y

in which the individual radicals have the following meaning:

R¹, R² independently of each other, denote a straight-chain, branched or cyclic alkyl or alkoxy radical that is unsubstituted or halogenated and has 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 -C=C-, -CF₂O-, -CH=CH-,

-O-, -CO-O- or -O-CO- in such a way that 0 atoms are not linked directly to one another,

Z^x, Z^y independently of each other, denote

-CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CO-O-, -O-CO-, -C2F4-, -CF=CF- -CH=CH-CH₂O- or a single bond, preferably a single bond,

L¹, L², L³ and L⁴ independently of each other, denote H, F or Cl, preferably H or F, more preferably F, and x, y independently of each other, denote 0, 1 or 2, with x+y ≤ 3.

Preferably, the compounds of formula Y contain at least one substituent L^1-4 that is F or Cl, preferably F, more preferably at least two substituents L^1-4 that are F.

In the compounds of formula Y and its subformulae, R¹ and R² preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms, furthermore alkenyl having 2 to 6 C atoms, in particular vinyl, 1 E-propenyl, 1 E-butenyl, 3-butenyl, 1 E-pentenyl, 3E-pentenyl or 4-pentenyl.

In the compounds of formula Y and its subformulae, preferably both radicals L¹ and L² denote F. In another preferred embodiment of the present invention, in the compounds of formula Y and its subformulae one of the radicals L¹ and L² denotes F and the other denotes Cl. In a preferred embodiment of the present invention the medium contains one or more compounds of formula Y that are selected from the following subformulae

in which R¹, R², Z^x, Z^y, L¹ and L² have one of the meanings given in formula

Y or one of the preferred meanings as given above and below, a denotes 1 or 2, b denotes 0, 1 or 2, preferably 1 or 2,

L³, L⁴ independently of each other, denote F or Cl, preferably F.

Preferably, in the compounds of formula Y1 and Y2 both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes Cl, or both L³ and L⁴ denote F or one of L³ and L⁴ denotes F and the other denotes Cl.

Preferably, the medium comprises one or more compounds of the formula Y1 selected from the group consisting of the following subformulae

in which 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 (0) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂-CH=CH-, CH₃- (CH₂)₂-CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH-(CH₂)₂-.

Very preferably the medium contains one or more compounds of formula

Y1 selected from formulae Y1-2 and Y1-10.

Preferably, the medium comprises one or more compounds of the formula Y2 selected from the group consisting of the following subformulae:

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, and (0) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂-CH=CH-, CH₃-(CH₂)₂-CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH-(CH₂)₂-.

Very preferably the medium contains one or more compounds of formula Y2 selected from formulae Y2-2 and Y2-10, in particular one or more compounds of formula Y2-10.

The proportion of the compounds of formula Y1 or its subformulae in the medium is preferably from 1 to 10% by weight.

The proportion of the compounds of formula Y2 or its subformulae, in particular formula Y2-10, in the medium is preferably from 1 % by weight to 15% by weight, more preferably from 2% by weight to 10% by weight.

The total proportion of the compounds of formulae Y1 and Y2 or their subformulae in the medium is preferably from 0 to 20%, very preferably from 1 to 15%, most preferably from 1 to 10% by weight.

In a particular embodiment the medium contains 1 , 2 or 3 compounds of formulae Y1 and Y2 or their subformulae, very preferably selected from formulae Y1 -2, Y1 -10, Y2-2 and Y2-10.

Preferably, the medium comprises one or more compounds of formula Y selected from the following subformula

in which R¹, R², L¹, L², X, x and Z^x have the meanings given in formula Y, in which at least one of the rings X is cyclohexenylene. If x is 2, preferably, one ring X is cyclohexylene-1 ,4-diyl and the other ring X is cyclohexylene-1 ,4-diyl or cyclohexane-1 ,4-diyl.

Preferably, in formula LY x is 1 or 2, and

Preferably, both radicals L¹ and L² denote F. In an alternative embodiment one of the radicals L¹ and L² denotes F and the other denotes Cl.

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 for formula LY above, (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 CH₃, C₂H₅, n-C₃H₇, n-C₄H₉, n-C₅H₁₁, CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂- CH=CH-, CH₃-(CH₂)₂-CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH- (CH₂)₂-. Preferably, the medium contains 1, 2 or 3 compounds of formula LY. The proportion of the compounds of formula LY or its subformulae in the medium is preferably from 0 to 15% by weight. It is particularly preferred that the medium contains one or more compounds of formula LY4, wherein the proportion of the compounds of formula LY4 in the medium preferably is from 1 % by weight to 15% by weight, more preferably from 2% by weight to 10% by weight.

In an embodiment the medium comprises one or more compounds selected from the group of compounds of formulae Y4-1 to Y4-24

in which R denotes a straight-chain alkyl or alkoxy radical having 1 to 7 C atoms, R* denotes a straight-chain alkenyl radical having 2 to 7 C atoms, (0) denotes an oxygen atom or a single bond, and m denotes an integer from 1 to 6. R* preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃- CH=CH-, CH₃-CH₂-CH=CH-, CH₃-(CH₂)₂-CH=CH- or CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH-(CH₂)₂-. R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.

Preferably, the total proportion of the compounds of formulae 1-1 , I-2 and Y, and in particular their respective sub-formuale, in the medium is from 2% by weight to 30% by weight, more preferably from 5% by weight to 26% by weight, and even more preferably from 8% by weight to 20% by weight.

In another embodiment the liquid-crystal medium further comprises one or more compounds selected from the group of compounds of formulae B-1 , B-2 and B-3

in which

R¹¹ and R¹² identically or differently, denote H or a straight-chain alkyl or alkoxy radical having 1 to 15 C atoms, in which one or more CH₂ groups in these radicals are optionally replaced, independently of one another, by -C=C-,

in such a way that 0 atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, preferably a straight-chain alkoxy radical having 1 to 7 C atoms.

The compounds of formula B-1 are preferably selected from the group of compounds of the formulae B-1 -a to B-1 -e

in which R¹¹ and R¹², identically or differently, denote alkyl having 1 to 7 C atoms, preferably ethyl, n-propyl, n-butyl or n-pentyl.

The compounds of formula B-2 are preferably selected from the group of compounds of the formulae B-2-a to B-2-e

in which R¹¹ and R¹², identically or differently, denote alkyl having 1 to 12 C atoms, preferably alkyl having 1 to 7 C atoms.

The compounds of formula B-3 are preferably selected from the group of compounds of the formulae B-3-a to B-3-j

in which R¹² denotes alkyl having 1 to 7 C atoms, preferably ethyl, n-propyl or n-butyl.

In a preferred embodiment the one or more compounds selected from the group of compounds of formulae B-1 , B-2 and B-3 are selected from the group of compounds B-A to B-J

The one or more compounds selected from the group of compounds of formulae B-1 , B-2 and B-3 are preferably comprised in the liquid-crystal medium in a total amount of from 0 to 15% by weight, more preferably 10% by weight or less and even more preferably 5% by weight or less.

The liquid-crystal media according to the invention preferably retain the nematic phase down to -20°C, more preferably down to -30°C, and even more preferably down to -40°C. Preferably, the liquid-crystal media according to the invention have a clearing point of > 75°C, more preferably

> 80°C, and in particular > 85°C. In addition, the liquid-crystal media preferably exhibit rotational viscosities yi of ≤ 110 mPa-s, particularly preferably ≤ 100 mPa-s, where the rotational viscosities are determined at 20°C. Thus LC displays having fast response times may be favourably provided.

The liquid-crystal medium preferably has an optical anisotropy An of 0.06 or more, more preferably 0.08 or more, still more preferably 0.10 or more and even more preferably 0.12 or more.

Above and below, An denotes the optical anisotropy, wherein An = n_e - n₀, and wherein preferably the optical anisotropy An is determined at 20°C and at a wavelength of 589.3 nm. The liquid-crystal medium preferably has an optical anisotropy in the range of from 0.07 to 0.15 and in particular from 0.10 to 0.12.

The rotational viscosity yi of the liquid-crystal media preferably is ≤ 80 mPa s, more preferably ≤ 70 mPa s, and even more preferably ≤ 60 mPa s.

The ratio yi/Kn, in which yi is the rotational viscosity and Ku is the elastic constant for splay deformation, of the liquid-crystal media preferably is ≤ 4.5 mPa-s/pN, more preferably ≤ 4.2 mPa-s/pN, most preferably ≤ 4.0 mPa-s/pN.

The nematic phase range of the liquid-crystal media according to the invention preferably has a width of at least 90°C, more preferably of at least 100°C, in particular of at least 110°C. This range particularly preferably extends at least from -25°C to +80°C.

It has surprisingly been found that the presently provided liquid-crystal medium can favourably contribute to obtaining an advantageous electro- optical device performance, e.g. in terms of the achievable contrast and the high bright state transmittance, while exhibiting functionality and reliability also at high temperatures and at low temperatures.

Above and below, the definitions of the abbreviations, also referred to as acronyms, of preferred compounds are given in table A to C below.

In further preferred embodiments, the medium according to the invention comprises

- one or more compounds selected from the group of compounds of formulae 1-1 and I-2, preferably of formula 1-1 , in a total concentration in the range of from 2.5% by weight to 20% by weight, more preferably from 5% by weight to 15% by weight and in particular from 7% by weight to 10% by weight, and/or

- one or more compounds of formulae 11-1 and/or II-2 in a total amount of 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, still more preferably 20% by weight or more and in particular 22.5% by weight or more, and/or

- one or more compounds of formula 11-1 -a-1 , preferably in a total amount of 5% by weight or more, more preferably 10% by weight or more and in particular in a range of from 15% by weight to 20% by weight, and/or - at least one compound of formula ll-2-i, preferably in a total amount of 2.5% by weight or more, more preferably 3.5% by weight or more and in particular 4.5% by weight or more, and/or

- one or more compounds of formula I V-1 , preferably selected from CC-n-V and CC-n-Vm, more preferably from CC-n-V, and in particular CC-3-V, CC-3-V1 and/or CC-3-2V1 , preferably in a total amount of at least 10% by weight, more preferably at least 20% by weight, even more preferably at least 30% by weight and in particular at least 34% by weight, and/or

- one or more compounds of formula VI-1 , preferably PP-n-2Vm and in particular PP-1 -2V1 , preferably in a total amount of at least 2.5% by weight, more preferably at least 4% by weight, and in particular at least 7.5% by weight, and/or

- one or more compounds of formula Y2-10, preferably in a total amount of from 1 % by weight to 15% by weight, more preferably from 2% by weight to 10% by weight, and/or

- one or more compounds of formula LY4, preferably in a total amount of from 1 % by weight to 15% by weight, more preferably from 2% by weight to 10% by weight. The term "alkyl" or "alkyl*" herein encompasses straight-chain and branched alkyl groups, preferably having 1-6 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl and hexyl. Groups having 2-5 carbon atoms are generally preferred. Branched alkyl groups may be selected from secondary and/or tertiary alkyl, preferably from secondary alkyl. The term "alkenyl" or “alkenyl*” encompasses straight-chain and branched alkenyl groups, preferably having 2-6 carbon atoms, in particular the straight-chain groups. Preferred alkenyl groups are C₂-C₇-1E-alkenyl, C₄-C₆-3E-alkenyl, in particular C₂-C₆-1E-alkenyl. Examples of particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl and 5-hexenyl. Groups having up to 5 carbon atoms are generally preferred, in particular CH₂=CH, CH₃CH=CH. The term "fluoroalkyl" preferably encompasses straight-chain groups having a terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluoro- butyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other posi- tions of the fluorine are not excluded. The term "oxaalkyl" or "alkoxy" preferably encompasses straight-chain radi- cals of the formula C_nH₂n+1-O-(CH₂)m, in which n and m each, independently of one another, denote 1 to 6. m may also denote 0. Preferably, n = 1 and m = 1-6 or m = 0 and n = 1-3. The individual compounds of the above-mentioned formulae and the sub- formulae thereof which can be used in addition to the compounds of formulae I-1 and I-2 in the liquid-crystalline media according to the invention are either known or can be prepared analogously to the known compounds. In another preferred embodiment of the present invention the liquid-crystal medium additionally comprises one or more polymerisable compounds. The polymerisable compounds are preferably selected from formula M R^a-B¹-(Z^b-B²)_m-R^b M in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: R^a and R^b P, P-Sp-, H, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, - SCN, SF₅ or 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 -C(R⁰)=C(R⁰⁰)-, -C ^C-, -N(R⁰⁰)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in 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, Cl, Br, I, CN, P or P-Sp-, where, if B¹ and/or B² contain a saturated C atom, R^a and/or R^b may also denote a radical which is spiro-linked to this saturated C atom, wherein at least one of the radicals R^a and R^b denotes or contains a group P or P-Sp-, P a polymerisable group, Sp a spacer group or a single bond, B¹ and B² an aromatic, heteroaromatic, alicyclic or heterocyclic group, preferably having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

Z^b -O-, -S-, -CO-, -CO-O-, -OCO-, -O-CO-O-, -OCH₂-, -CH₂O-,

-SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -(CH₂)m-, -CF₂CH₂-, -CH₂CF₂-, -(CF₂)m-, -CH=CH-, -CF=CF-, -C=C- -CH=CH-COO-, -OCO-CH=CH-, CR°R⁰⁰ or a single bond,

R° and R⁰⁰ each, independently of one another, denote H or alkyl having 1 to 12 C atoms, m denotes 0, 1 , 2, 3 or 4, n1 denotes 1 , 2, 3 or 4,

L P, P-Sp-, OH, CH₂OH, F, Cl, Br, I, -CN, -NO₂, -NCO, -NCS,

-OCN, -SCN, -C(=O)N(R^X)₂, -C(=O)Y¹, -C(=O)R^X, -N(R^X)₂, optionally 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, Cl, P or P-Sp-,

P and Sp have the meanings indicated above,

Y¹ denotes halogen,

R^x denotes P, P-Sp-, 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-, -CO-O-, -O-CO-, -O-CO-O- in such a way that 0 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, Cl, P or P-Sp-, 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.

Particularly preferred compounds of the formula M are those in which B¹ and B² each, independently of one another, denote 1 ,4-phenylene, 1 ,3- phenylene, naphthalene-1 ,4-diyl, naphthalene-2,6-diyl, phenanthrene-2,7- diyl, 9,10-dihydro-phenanthrene-2,7-diyl, anthracene-2,7-diyl, fluorene-2,7- diyl, coumarine, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-1 ,4-diyl, in which, in addition, one or more non-adjacent CH₂ groups may be replaced by 0 and/or S, 1 ,4-cyclohexenylene, bicycle[1.1.1]pentane-1 ,3-diyl, bicyclo[2.2.2]octane-1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, piperid ine-1 ,4-diyl, decahydronaphthalene-2,6-diyl, 1 ,2,3,4-tetrahydronaphthalene-2,6-diyl, indane-2,5-diyl or octahydro-4,7-methanoindane-2,5-diyl, where all these groups may be unsubstituted or mono- or polysubstituted by L as defined above.

Particularly preferred compounds of the formula M are those in which B¹ and B² each, independently of one another, denote 1 ,4-phenylene, 1 ,3- phenylene, naphthalene-1 ,4-diyl or naphthalene-2,6-diyl.

Very preferred compounds of formula M are selected from the following formulae:

in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:

P¹, P², P³ a polymerisable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy,

Sp¹, Sp², Sp³ a single bond or a spacer group where, in addition, one or more of the radicals P¹-Sp¹-, P¹-Sp²- and P³-Sp³- may denote R^aa, with the proviso that at least one of the radicals P¹-Sp¹-, P²-Sp² and P³-Sp³- present is different from R^aa, preferably -(CH₂)_PI-, -(CH₂)_PI-O-, -(CH₂)_PI-CO-O- or - (CH₂)_PI-O-CO-O-, in which p1 is an integer from 1 to 12,

R^aa H, F, Cl, CN or 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 -C(R°)=C(R⁰⁰)-, -C=C-, -N(R°)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that 0 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, Cl, CN or P¹-Sp¹-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms),

R°, R°° H or alkyl having 1 to 12 C atoms,

Rv and R^z H, F, CH₃ or CF₃, X¹, X², X³ -CO-O-, -O-CO- or a single bond,

Z^M1 -O-, -CO-, -C(R^yR^z)- or -CF₂CF₂-,

_ZM2 _ZM3 -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂- or -(CH₂)_n-, where n is 2, 3 or 4,

L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms,

L', L" H, F or Cl, r 0, 1 , 2, 3 or 4, s 0, 1 , 2 or 3, t 0, 1 or 2, x 0 or 1.

Especially preferred are compounds of formulae M2 and M13.

Further preferred are trireactive compounds M15 to M31 , in particular M17, M18, M19, M22, M23, M24, M25, M30 and M31 .

In the compounds of formulae M1 to M31 the group

in which L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO2, CH₃, C₂H₅, C(CH₃)₃, CH(CH₃)_2, CH₂CH(CH₃)C₂H₅, OCH_3I OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF_3I OCHF₂, OC2F5 or P-Sp-, very preferably F, Cl, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, more preferably F, Cl, CH₃, OCH₃, COCH₃ or OCF₃ , especially F or CH₃.

Preferred compounds of formulae M1 to M31 are those in which P¹, P² and P³ denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group.

Further preferred compounds of formulae M1 to M31 are those in which Sp¹, Sp² and Sp³ are a single bond.

Further preferred compounds of formulae M1 to M31 are those in which one of Sp¹, Sp² and Sp³ is a single bond and another one of Sp¹, Sp² and Sp³ is different from a single bond.

Further preferred compounds of formulae M1 to M31 are those in which those groups Sp¹, Sp² and Sp³ that are different from a single bond denote -(CH₂)si-X"-, in which s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is X" is the linkage to the benzene ring and is -O-, -O-CO-, -CO-O- -O-CO-O- or a single bond. Particular preference is given to liquid-crystalline media comprising one, two or three polymerisable compounds of formula M, preferably selected from formulae M1 to M31.

Further preferably the liquid-crystalline media according to the present invention comprise one or more polymerisable compounds selected from Table G below.

Preferably the proportion of polymerisable compounds in the liquidcrystalline medium, preferably selected from formula M and Table G, is from 0.01 to 5%, very preferably from 0.05 to 1 %, most preferably from 0.1 to 0.5%.

It was observed that the addition of one or more polymerisable compounds to the liquid-crystalline medium, like those selected from formula M and Table G, leads to advantageous properties like fast response times. Such a liquid-crystalline medium is especially suitable for use in PSA displays where it shows low image sticking, a quick and complete polymerisation, the quick generation of a low pretilt angle which is stable after UV exposure, a high reliability, high VHR value after UV exposure, and a high birefringence. By appropriate selection of the polymerisable compounds it is possible to increase the absorption of the liquid-crystalline medium at longer UV wavelengths, so that it is possible to use such longer UV wavelengths for polymerisation, which is advantageous for the display manufacturing process.

The polymerisable group P is a group which is suitable for a polymerisation reaction, such as, for example, free-radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain. Particular preference is given to groups for chain polymerisation, in particular those containing a C=C double bond or -C=C- triple bond, and groups which are suitable for polymerisation with ring opening, such as, for example, oxetane or epoxide groups. Preferred groups P are selected from the group consisting of CH₂=CW¹-

, CH₂=CW²-(O)k3-, CW¹=CH-CO-(O)k3-, CW¹=CH-CO-NH-, CH₂=CW¹-CO-NH-, CH₃-CH=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, HO-CW²W³-, HS-CW²W³-, HW²N-, HO-CW²W³-NH-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)k1-Phe-(O)k2-, CH₂=CH-(CO)_k1-Phe-(O)_k2-, Phe-CH=CH-, HOOC-, OCN- and W⁴W⁵W⁶Si-, in which W¹ denotes H, F, Cl, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH3, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k1, k2 and k3 each, independently of one another, denote 0 or 1, k3 preferably denotes 1, and k₄ denotes an integer from 1 to 10. Very preferred groups P are selected from the group consisting of CH₂=CW¹-

CH₂=CW²-O-, CH₂=CW²-, CW¹=CH-CO-(O)k3-, CW¹=CH-CO-NH-, CH₂=CW¹-CO-NH-, (CH₂=CH)₂CH- OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)_k1-Phe-(O)_k2-, CH₂=CH-(CO)k1-Phe-(O)k2-, Phe-CH=CH- and W⁴W⁵W⁶Si-, in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n- propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, k1, k2 and k3 each, independently of one another, denote 0 or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10. Very particularly preferred groups P are selected from the group consisting of CH₂=CW¹-CO-O-, in particular CH₂=CH-CO-O-, CH₂=C(CH₃)-CO-O- and CH₂=CF-CO-O-, furthermore CH₂=CH-O-, (CH₂=CH)₂CH-O-CO-, (CH₂=CH)₂CH-O-,

Further preferred polymerisable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate. If Sp is different from a single bond, it is preferably of the formula Sp"-X", so that the respective radical P-Sp- conforms to the formula P-Sp"-X"-, in which Sp" denotes alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and in which, in addition, one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by -O-, -S-, -NH-, -N(R⁰)-, -Si(R⁰R⁰⁰)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R⁰⁰)-CO-O-, -O-CO-N(R⁰)-, -N(R⁰)-CO-N(R⁰⁰)-, -CH=CH- or -C ^C- in such a way that O and/or S atoms are not linked directly to one another, X" denotes -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R⁰)-, -N(R⁰)-CO-, -N(R⁰)-CO-N(R⁰⁰)-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰-, -CY²=CY³-, -C ^C-, -CH=CH-CO-O-, -O-CO-CH=CH- or a single bond, R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl having 1 to 20 C atoms, and Y² and Y³ each, independently of one another, denote H, F, Cl or CN. X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR⁰-, -NR⁰- CO-, -NR⁰-CO-NR⁰⁰- or a single bond. Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH₂)p1-, - (CH₂CH₂O)_q1-CH₂CH₂-, -CH₂CH₂-S-CH₂CH₂-, -CH₂CH₂-NH-CH₂CH₂- or - (SiR⁰R⁰⁰-O)_p1-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R⁰ and R⁰⁰ have the meanings indicated above. Particularly preferred groups Sp and -Sp”-X”- are -(CH₂)_p1-, -(CH₂)_p1-O-, -(CH₂)_p1-O-CO-, -(CH₂)_p1-CO-O-, -(CH₂)_p1-O-CO-O-, in which p1 and q1 have the meanings indicated above. Particularly preferred groups Sp" are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methylimino- ethylene, 1-methylalkylene, ethenylene, propenylene and butenylene. For the production of PSA displays, the polymerisable compounds contained in the liquid-crystalline medium are polymerised or crosslinked (if one compound contains two or more polymerisable groups) by in-situ polymerisation in the liquid-crystalline medium between the substrates of the LC display, optionally while a voltage is applied to the electrodes. The structure of the PSA displays according to the invention corresponds to the usual geometry for PSA displays, as described in the prior art cited at the outset. Geometries without protrusions are preferred, in particular those in which, in addition, the electrode on the colour filter side is unstructured and only the electrode on the TFT side has slots. Particularly suitable and preferred electrode structures for PS-VA displays are described, for example, in US 2006/0066793 A1. The combination of compounds of the preferred embodiments mentioned above with the polymerised compounds described above causes low threshold voltages, low rotational viscosities and very good low-temperature stabilities in the liquid-crystalline media according to the invention at the same time as constantly high clearing points and high VHR values. The use of liquid-crystalline media containing polymerisable compounds allows the rapid establishment of a particularly low pretilt angle in PSA displays. In particular, the liquid-crystalline media exhibit significantly shortened response times, in particular also the grey-shade response times, in PSA displays compared with the media from the prior art.

Preference is generally given to liquid-crystalline media which have a nematic liquid-crystalline phase, and preferably have no chiral liquid crystal phase.

The invention also relates to the use of a liquid-crystalline medium according to the present invention as described above and below for electro-optical purposes, in particular for the use is in shutter glasses, for 3D applications, in TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB- FFS, PS-FFS, positive VA and positive PS-VA displays, and to electro- optical displays, in particular of the aforementioned types, containing a liquid-crystalline medium according to the present invention as described above and below, in particular a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS- IPS, FFS, HB-FFS, PS-FFS, positive VA (vertically aligned) or positive PS- VA display.

The invention also relates to electro-optical displays, such as, for example, STN or MLC displays, having two plane-parallel outer plates, which, together with a frame, form a cell, integrated non-linear elements for switching individual pixels on the outer plates, and a nematic liquid-crystal mixture having positive dielectric anisotropy and high specific resistance located in the cell, wherein the a nematic liquid-crystal mixture is a liquid-crystalline medium according to the present invention as described above and below.

The liquid-crystalline media according to the invention enable a significant broadening of the available parameter latitude. The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and suitable optical anisotropy are superior to previous materials from the prior art. Comparative measurements of the voltage holding ratio (VHR) are shown e.g. in S. Matsumoto et al., Liquid Crystals 5, 1320 (1989); K. Niwa et al., Proc. SID Conference, San Francisco, June 1984, p. 304 (1984); G. Weber et al., Liquid Crystals 5, 1381 (1989).

The construction of the MLC display according to the invention from polaris- ers, electrode base plates and surface-treated electrodes corresponds to the usual design for displays of this type. The term usual design is broadly drawn here and also encompasses all derivatives and modifications of the MLC display, in particular including matrix display elements based on poly-Si TFTs or MIM.

The liquid-crystalline media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing the compound(s) as set forth in claim 1 with further mesogenic compounds and/or additives. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing.

The liquid-crystalline media may also comprise further additives known to the person skilled in the art and described in the literature, such as, for example, polymerisation initiators, inhibitors, surface-active substances, stabilizers, antioxidants, e.g. BHT, TEMPOL, microparticles, free-radical scavengers, nanoparticles, etc. For example, 0-15% of pleochroic dyes or chiral dopants can be added. Suitable stabilizers and dopants are mentioned below in Tables E and F.

In an embodiment the liquid-crystalline media contain one or more chiral dopants, preferably in a concentration from 0.01 to 1% by weight, very preferably from 0.05 to 0.5% by weight. The chiral dopants are preferably selected from the group consisting of compounds from Table E below, very preferably from the group consisting of R- or S-1011 , R- or S-2011 , R- or S- 3011 , R- or S-4011 , and R- or S-5011 .

In another embodiment the liquid-crystalline media contain a racemate of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the previous paragraph.

In another embodiment the LC medium according to the present invention contains a self-aligning (SA) additive, preferably in a concentration of 0.1 to 2.5% by weight. An LC medium according to this embodiment is especially suitable for use in polymer stabilised SA-FFS or SA-HB-FFS displays.

In a preferred embodiment the SA-FFS or SA-HB-FFS display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment the SA-FFS or SA-HB-FFS display contains a polyimide alignment layer.

Preferred SA additives for use in this embodiment are selected from compounds comprising a mesogenic group and a straight-chain or branched alkyl side chain that is terminated with one or more polar anchor groups selected from hydroxy, carboxy, amino or thiol groups.

Further preferred SA additives contain one or more polymerisable groups which are attached, optionally via spacer groups, to the mesogenic group. These polymerisable SA additives can be polymerised in the LC medium under similar conditions as applied for the RMs in the PSA process.

Suitable SA additives to induce homeotropic alignment, especially for use in SA-VA mode displays, are described for example in US 2013/0182202 A1 , US 2014/0838581 A1 , US 2015/0166890 A1 and US 2015/0252265 A1 . In another preferred embodiment an LC medium or a polymer stabilised SA- FFS or SA-HB-FFS display according to the present invention contains one or more self-aligning additives selected from Table H below.

Furthermore, it is possible to add to the liquid-crystalline media, for example, 0 to 15% by weight of pleochroic dyes, furthermore nanoparticles, conductive salts, preferably ethyldimethyldodecylammonium 4- hexoxybenzoate, tetrabutylammonium tetraphenylborate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38281 , 24 50 088, 26 37 430 and 28 53 728.

The displays according to the present invention are preferably addressed by an active matrix, preferably by a matrix of TFT. However, the liquid crystals according to the invention can also advantageously be used in displays having other known addressing means.

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, unless explicitly indicated otherwise.

Above and below, unless explicitly stated otherwise, all concentrations are given in weight percent, i.e. per cent data denote per cent by weight. All temperatures are indicated in degrees Celsius.

In the present invention and especially in the following examples, the structures of the mesogenic compounds are indicated by means of abbreviations, also referred to as acronyms. In these acronyms, the chemical formulae are abbreviated as follows using Tables A to C below. All groups C_nH_2n+1, C_mH_2m+1 and C1H21+1 or C_nH_2n.-i, C_mH_2m.-i and C1H21-1 denote straight-chain alkyl or alkenyl, preferably 1 E-alkenyl, having n, m and I C atoms respectively, where n, m and I, independently of one another, denote an integer from 1 to 9, preferably 1 to 7, or from 2 to 9, preferably 2 to 7, respectively. C_OH_2O+I denotes straight-chain alkyl having 1 to 7, preferably 1 to 4, C atoms, or branched alkyl having 1 to 7, preferably 1 to 4, C atoms.

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. Table D shows illustrative structures of compounds with their respective abbreviations.

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 The illustrative structures show compounds which are particularly preferably employed.

in which k, I, m and n are, independently of one another, each an integer, preferably from 1 to 9, more preferably from 1 to 7.

Table E

Table E indicates possible chiral dopants which are optionally added to the liquid-crystal media according to the invention. The liquid-crystal media preferably comprise 0-10% by weight, in particular 0.01-5% by weight and particularly preferably 0.01-3% by weight of chiral dopants.

Table F

Stabilizers which may preferably be added to the liquid-crystal media in amounts of 0.005-3% by weight are shown below.

n = 1 , 2, 3, 4, 5, 6 or 7

q = 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10

Table G

Table G shows illustrative reactive mesogenic compounds (RMs) which can be used in the liquid-crystal media in accordance with the present invention.

RM-145

In a preferred embodiment, the liquid-crystalline media according to the invention comprise one or more polymerisable compounds, preferably selected from the polymerisable compounds of the formulae RM-1 to RM-143. Of these, compounds RM-1 , RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41 , RM-48, RM-52, RM-54, RM-57, RM-64, RM-74, RM-76, RM-88, RM-102, RM-103, RM-109, RM-117, RM-120, RM-121 and RM-122 are particularly preferred.

Table H

Table H shows self-alignment additives for vertical alignment which can be used in LC media for SA-VA and SA-FFS displays according to the present invention, optionally together with the polymerisable compounds, more preferably with the polymerisable compounds of formula M.

In a preferred embodiment, the LC media and SA-FFS and SA-HB-FFS displays according to the present invention comprise one or more SA additives selected from formulae SA-1 to SA-34, preferably from formulae SA-14 to SA-34, more preferably from formulae SA-20 to SA-28, most preferably of formula SA-20, in particular in combination with one or more RMs of formula M.

The following Examples are merely illustrative of the present invention and they should not be considered as limiting the scope of the invention in any way. The Examples and modifications or other equivalents thereof will become apparent to those skilled in the art in the light of the present disclosure.

However, the physical properties and compositions shown in the following illustrate which properties can be achieved and in which ranges they can be modified. Especially the combination of the various properties, which can be preferably achieved, is thus well defined.

Working Examples

Unless indicated otherwise, parts or per cent data denote parts by weight or per cent by weight based on the mixture as a whole.

The symbols and abbreviations have the following meanings: V₀ Freedericksz threshold voltage, capacitive [V] at 20°C, V10 voltage [V] for 10% transmission, ne extraordinary refractive index measured at 20°C and 589 nm, no ordinary refractive index measured at 20°C and 589 nm, ^n optical anisotropy measured at 20°C and 589 nm, ^ ^ dielectric susceptibility (or "dielectric constant") perpendicular to the longitudinal axes of the molecules at 20°C and 1 kHz, ^ ^ ^ dielectric susceptibility (or "dielectric constant") parallel to the longitudinal axes of the molecules at 20°C and 1 kHz, ^ ^ dielectric anisotropy at 20°C and 1 kHz, cl.p. or T(N,I) clearing point [°C], ^ flow viscosity measured at 20°C [mm²·s^-1], ^1 rotational viscosity measured at 20°C [mPa ^s], K₁₁ elastic constant, "splay" deformation at 20°C [pN], K₂₂ elastic constant, "twist" deformation at 20°C [pN], K33 elastic constant, "bend" deformation at 20°C [pN], LTS low-temperature stability of the phase, determined in bulk, and VHR voltage holding ratio. The term "threshold voltage" for the present invention relates to the capacitive threshold (V₀), unless explicitly indicated otherwise. In the Examples, as is generally usual, the optical threshold can also be indicated, for example for 10% relative contrast (V10). Synthesis Examples The compounds are synthesized as follows from starting materials 1 and 2 shown in DE 102015004271 A1:

Synthesis Example 1

50.45 g (180 mmol) of compound 1 is dissolved in 350 ml dichloromethane and cooled to 10°C. Boron tribromide (49.60 g (198 mmol)) is added dropwise below 15°C. After the addition is complete, the solution is allowed to warm to room temperature. After the workup the material is crystallized from acetone to yield 4,6-difluoro-3,7-dihydroxydibenzo[b,d]thiophene 3.

15 g (59 mmol) of compound 3, 20.42 g (124 mmol) of 1-bromo-4- methylpentane, 18.90 g (137 mmol) of potassium carbonate are combined with 100 ml of ethyl methyl ketone and heated under reflux overnight. After the workup the material is crystallized from acetone to compound 4. Synthesis Example 2

8.13 g (29 mmol) of compound 1, 5 g (30 mmol) of 1 -bromo-4- methylpentane, 4.6 g (33 mmol) of potassium carbonate are reacted as described analogous to Synthesis Example 1 above to yield compound 5.

Synthesis Example 3

47.57 g (180 mmol) of compound 2 and 49.60 g (198 mmol) of boron tribromide are reacted in 350 ml of dichloromethane as described for compound 3 above to yield compound 6.

10 g (42 mmol) of compound 6, 7.03 g (47 mmol) of (S)-(+)-1-bromo-2- methylbutane and 6.73 g (49 mmol) of potassium carbonate are combined with 40 ml of ethyl methyl ketone and heated under reflux overnight. Compound 7 is recrystallized from acetone.

6.1 g (19.9 mmol) of compound 7 is dissolved in 140 ml of tetrahydrofuran and cooled to -75°C. 19.13 ml (30.46 mmol) of butyllithium in n-hexane (15%) is added dropwise. After the addition is complete, the mixture is warmed to -50°C for 2 hours and then cooled again to -75°C. 3.55 ml (31 .3 mmol) of trimethylborate is added dropwise and the solution is warmed to room temperature. A mixture of glacial acetic acid and water (7 ml, 1 : 1 ) is added. Hydrogen peroxide (4.6 ml, 54 mmol) as a 35% solution in water is added dropwise and the mixture is kept below 45°C by cooling with an ice bath. After the workup the compound 8 is crystallized from toluene.

1.2 g (4 mmol) of compound 8, 0.65 g (4 mmol) of 1-bromo-3-methylbutane and 0.6 g (4 mmol) of potassium carbonate are combined with 3.5 ml of ethyl methyl ketone and heated to reflux overnight. After the workup compound 9 is obtained by crystallization from isopropanol/acetone.

Synthesis Example 4

6 g (21 mmol) of compound 1, 2.5 g (22 mmol) of 2,4-dimethyl-pentane-1-ol and 6.74 g (25.7 mmol) of triphenylphosphine are dissolved in 100 ml of tetrahydrofuran. 5.34 ml (27.2 mmol) of diisopropylazodicarboxylate are added dropwise at room temperature without cooling and the mixture is stirred overnight. After the workup the crude product is recrystallized from isopropanol/acetone to obtain compound 10.

Mixtures Examples and Comparative Mixture Example

The following nematic mixtures are prepared, wherein the Mixtures comprise preferred compounds of formulae 1-1 and I-2 as described herein.

The following compounds l-A, l-B, l-E, l-M, 11-1 -g, II-2-B and II-2-C respectively correspond to the compounds of formulae l-A, l-B, l-E, l-M, 11-1 -g, II-2-B and II-2-C as specified and shown in the description above.

Comparative Mixture CM-1

APUQU-2-F 5.0% clearing point [°C]: 78.5

CC-3-V 31.5% An [589 nm, 20°C]: 0.1001

CC-3-V1 6.5% n_e [589 nm, 20°C]: 1.5877

CCP-3-3 6.0% n₀ [589 nm, 20°C]: 1.4876

CCP-V-1 12.0% As [1 kHz, 20°C]: 6.0

CCP-V2-1 12.0% so [1 kHz, 20°C]: 9.0

CPGP-5-2 2.0% si [1 kHz, 20°C]: 3.0

PP-1-2V1 5.0% n [mPa s, 20°C]: 64

PUQU-3-F 20.0% Ki [pN, 20°C]: 13.3

S 100.0% K₃ [pN, 20°C]: 15.5

LTS bulk [h, -20°C]: 48

Mixture M-1

CCP-V2-1 11.0% CPGP-5-2 1.5% PP-1-2V1 4.5% compound II-1-g 18.0% compound I-A 10.0% ^ 100.0% Mixture M-6 compound II-2-C 4.5% CC-3-V 28.0% CC-3-V1 6.0% CCP-3-3 5.5% CCP-V-1 11.0% CCP-V2-1 11.0% CPGP-5-2 1.5% PP-1-2V1 4.5% PUQU-3-F 18.0% compound I-B 10.0% ^ 100.0% Mixtures M-7, M-8 and M-9 Mixtures M-7, M-8 and M-9 are respectively prepared by mixing 99.7% of mixtures M-1, M-2 and respectively M-3 as described above with 0.3% of the compound of formula

Compared to Comparative Mixture CM-1 , mixtures M-1 to M-9 give advantageously improved transmittance in displays.

Claims

Patent Claims A compound selected from the group of compounds of formulae 1-1 and I-2

in which

-C=C- -CF₂O-, -OCF₂-, -CH=CH-

-O-, -CO-O- or -O-CO- in

such a way that 0 atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, and

R¹² denotes a branched alkyl or alkoxy radical having 1 to 15 C atoms. The compound according to claim 1 , wherein R¹¹ and R¹², independently of each other, denote branched alkyl or alkoxy radicals having 1 to 15 C atoms, preferably branched alkoxy radicals having 1 to 15 C atoms. The compound according to claim 1 , wherein R¹¹ denotes a straightchain alkyl or alkoxy radical having 1 to 9 C atoms, preferably a straight-chain alkoxy radical having 1 to 9 C atoms. The compound according to one or more of claims 1 to 3, wherein R¹² denotes a branched alkoxy radical having 1 to 12 C atoms. The compound according to one or more of claims 1 to 4, wherein the compound is selected from the group of compounds of formulae l-A to l-N

A liquid-crystal medium, comprising one or more compounds selected from the group of compounds of formulae 1-1 and I-2 as set forth in one or more of claims 1 to 5. The liquid-crystal medium according to claim 6, wherein the medium has a positive dielectric anisotropy. The liquid-crystal medium according to claim 6 or 7, wherein the medium comprises one or more compounds selected from the group of compounds of formulae 11-1 and II-2

in which

re independently of each other

|_21 |_22

L²³ and L²⁴ independently of each other, denote H or F,

L²⁵ denotes H or CH₃, and

X² denotes halogen, halogenated alkyl or alkoxy with 1 to 3

C atoms or halogenated alkenyl or alkenyloxy with 2 or 3 C atoms.

9. The liquid-crystal medium according to one or more of claims 6 to 8, wherein the medium comprises one or more compounds selected from the group of compounds of formulae 11-1 -a, ll-2-a, ll-2-b, ll-2-c and ll-2-d

in which the the occurring groups have the meanings given in claim 8, and wherein preferably X² is F. The liquid-crystal medium according to one or more of claims 6 to 9, wherein the medium comprises one or more compounds of formula IV

IV in which R⁴¹ and R⁴² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms,

on each occurrence, identically or differently, denote

^41 ^42 on each occurrence, identically or differently, denote -CH₂CH₂-, -COO-, trans- -CH=CH-, fra/?s--CF=CF-, -CH₂O-, -CF₂O-, -C=C- or a single bond, preferably a single bond, and p is 0, 1 or 2, preferably is 0. The liquid-crystal medium according to one or more of claims 6 to 10, wherein the medium comprises one or more compounds of formula IV-1

IV-1

in which

R⁴¹ and R⁴² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms. The liquid-crystal medium according to one or more of claims 6 to 11 , wherein the medium comprises one or more compounds of formula VI-1

in which

R⁶¹ and R⁶² independently of each other, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms. The liquid-crystal medium according to one or more of claims 6 to 12, wherein the medium comprises one or more compounds of formula Y

in which

Z^x, Z^y independently of each other, denote -CH₂CH₂-, -CH=CH- -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH- CH₂O-, or a single bond, preferably a single bond, L¹, L², L³, L⁴ independently of each other, denote H, F or Cl, preferably F, and x, y independently of each other, denote 0, 1 or 2, with x+y ≤ 3. The liquid-crystal medium according to one or more of claims 6 to 13, wherein the medium comprises one or more compounds selected from the group of compounds of formulae Y1 , Y2 and LY

in which

R¹, R², Z^x, Z^y, L¹, L², L³, L⁴ have the meanings given in claim 13 for formula Y, a, b and x identically or differently, are 1 or 2,

in which L³ and L⁴ , identically or differently, denote F or

Cl, and

The liquid-crystal medium according to one or more of claims 6 to 14, comprising one or more compounds selected from the group of compounds of formulae B-1 , B-2 and B-3

in which

in such a way that 0 atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, preferably a straight-chain alkoxy radical having 1 to 7 C atoms. An electro-optical device containing a liquid-crystal medium according to one or more of claims 6 to 15. The electro-optical device according to claim 16, wherein the device is a liquid-crystal display, preferably a TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, PS-HB-FFS, SA-HB-FFS, polymer stabilised SA-HB-FFS, positive VA or positive PS-VA display. A process for the preparation of a compound according to one or more of claims 1 to 5, wherein the process comprises the step of subjecting a branched haloalkane to a chemical reaction.