Patent Description:
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 electro-optical modes used are, for example, the twisted nematic (TN), super twisted nematic (STN), optically compensated bend (OCB) and electrically controlled birefringence (ECB) modes together with their various modifications, as well as others. All these modes utilise an electric field which is generated substantially perpendicular to the substrates and the liquid-crystal layer.

Besides these modes, there are also electro-optical modes that utilise an electric field which is substantially parallel to the substrates or the liquid-crystal layer. For example, <CIT> discloses 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-plane switching IPS) display. The principles of operating such a display are descried, for example, by <NPL>).

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.

<CIT>, for example, discloses various possibilities for the design of the electrodes and for addressing an IPS display. <CIT> likewise describes various embodiments of such IPS displays.

Liquid-crystalline materials for IPS displays of this type are described, for example, in <CIT>.

Furthermore, so-called "fringe-field switching" (FFS) displays have been reported (see, inter alia, <NPL>), 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 modern 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 liquid-crystalline media having a dielectric anisotropy of only about <NUM> 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 in prior art, for example, from <CIT>, <CIT>), <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. 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 necessary here.

FFS and IPS displays can be operated as active-matrix displays (AMD) or passive-matrix displays (PMD). In the case of active-matrix displays individual pixels are usually addressed by integrated, non-linear active elements such as, for example, thin-film transistors (TFTs), while in the case of passive-matrix displays individual pixels are usually addressed by the multiplex method as known from the prior art.

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.

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.

The provision of further liquid-crystalline media and the use thereof in a display having high transmission, a good black state and a high contrast ratio is a central challenge for modern FFS and IPS applications. In addition, modern applications also require good low-temperature stability and fast addressing times.

In particular it is desirable to have media with low birefringence that have low birefringence and at the same time have sufficient stability at low temperatures. Such media are useful for mobile use, for example in automotive applications where exposure to harsh environmental conditions such as very low temperatures may occur.

This was achieved by providing liquid-crystalline media as described and claimed hereinafter.

It was observed that a high brightness in displays like those of the HB-FFS mode can be achieved by using liquid-crystalline media having positive dielectric anisotropy and also having an increased dielectric constant ε⊥ perpendicular to the longitudinal axes of the liquid-crystalline molecules. This can be achieved by adding a limited amount of liquid-crystalline compounds with negative dielectric anisotropy, which have high ε⊥ properties, to the liquid-crystalline medium whilst maintaining a positive dielectric anisotropy of the entire medium. However, the addition of compounds with high ε⊥ have some drawbacks. For example this can lead to higher values of the rotational viscosity γ<NUM>, and consequently to higher values of the ratio γ<NUM> /K<NUM> of the rotational viscosity γ<NUM> and the elastic constant K<NUM> for twist deformation, which leads to higher response times. Since K<NUM> is approximately proportional to the elastic constant K<NUM> for splay deformation (the value of K<NUM> is typically about half the value of K<NUM>), this can easily be determined by measuring γ<NUM> and K<NUM>.

Another disadvantage is that the reliability (VHR) of HB-FFS mixtures can be worse compared to conventional FFS mixtures.

The invention has the object of providing liquid-crystalline media, preferably for FFS and IPS displays, in particular for HB-FFS 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 preferably have high specific resistance, low threshold voltage, high dielectric anisotropy, a good low temperature stability (LTS), fast response times and low rotational viscosities, and enable high brightness.

It is another object of the present invention to provide improved liquid-crystal media suitable for the use in HB-FFS displays that have improved reliability while keeping high transmittance compared to media from the prior art.

To solve the problem, the present invention provides a liquid-crystalline medium according to claim <NUM>.

Advantageous embodiments of the invention are subject of the dependent claims or can also be taken from the description.

The present invention relates to a liquid-crystal medium, as in claim <NUM> and defined below, with positive dielectric anisotropy, comprising.

The combination of compounds of formula I with compounds of formulae II-1a, II-1c to II-<NUM>, II-<NUM>, II-<NUM> and/or III, and additionally with a compound of the formulae LY-<NUM>, LY-<NUM> and LY-<NUM> enables liquid-crystalline media which show a moderately positive dielectric anisotropy and at the same time an increased dielectric constant ε⊥ perpendicular to the longitudinal axes of the liquid-crystalline molecules, while maintaining a low rotational viscosity and a low value of the ratios of γ<NUM> /K<NUM> and γ<NUM> /K<NUM>. This enables liquid-crystalline displays, especially of the HB-FFS, FFS and IPS mode, with high brightness and transmission and fast response times.

In particular, the low-temperature stability (LTS) of the medium according to the invention is remarkably high. The medium is sufficiently stable at temperatures as low as -<NUM> which is why the medium is particularly suitable for mobile applications, for example in automotive applications.

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 suitably 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 likewise suitable for use in liquid-crystal displays of the FFS, HB-FFS and IPS mode, based on dielectrically positive liquid crystals, and polymer stabilised variants thereof, for large size TV applications.

The invention further relates to the use of a liquid-crystalline medium as described above and below for electro-optical purposes, in particular for the use in liquid-crystal displays, shutter glasses, LC windows, 3D applications, preferably in 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 and positive PS-VA displays, very preferably in FFS, HB-FFS, IPS, PS-HB-FFS and PS-IPS displays.

The invention further relates to an electro-optical liquid-crystal display containing a liquid-crystalline medium as described above and below, in particular 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, preferably a FFS, HB-FFS, IPS, PS-HB-FFS or PS-IPS display.

In the present application, 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 straight-chain or branched or cyclic alkyl. It is preferably straight-chain, has <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> 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, branched alkyl is preferably isopropyl, s-butyl, isobutyl, isopentyl, <NUM>-methylbutyl, <NUM>-methylhexyl or <NUM>-ethylhexyl.

As used herein, cyclic alkyl is taken to mean straight-chain or branched alkyl or alkenyl having up to <NUM> C atoms, preferably alkyl having <NUM> to <NUM> C atoms, in which a group CH<NUM> is replaced with a carbocyclic ring having <NUM> to <NUM> C atoms, very preferably selected from the group consisting of cyclopropylalkyl, cyclobutylalkyl, cyclopentylalkyl and cyclopentenylalkyl, wherein alkyl is straight chain alkyl having <NUM> to <NUM> C atoms.

Herein, oxaalkyl preferably denotes straight-chain <NUM>-oxapropyl (= methoxymethyl), <NUM>-(= ethoxymethyl) or <NUM>-oxabutyl (= <NUM>-methoxyethyl), <NUM>-, <NUM>- or <NUM>-oxapentyl, <NUM>-, <NUM>-, <NUM>- or <NUM>-oxahexyl, <NUM>-, <NUM>-, <NUM>-, <NUM>- or <NUM>-oxaheptyl, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>- or <NUM>-oxaoctyl, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>- or <NUM>-oxanonyl, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>-, <NUM>- or <NUM>-oxadecyl.

Herein, alkenyl, i.e. an alkyl radical in which one CH<NUM> group has been replaced by -CH=CH- , may be straight-chain or branched. It is preferably straight-chain and has <NUM> to <NUM> C atoms. Accordingly, it denotes, in particular, vinyl, prop-<NUM>- or -<NUM>-enyl, but-<NUM>-, -<NUM>- or -<NUM>-enyl, pent-<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-enyl, hex-<NUM>-, -<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-enyl, hept-<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-enyl, oct-<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-enyl, non-<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-enyl, dec-<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>-, -<NUM>- or -<NUM>-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 ω-position.

Herein, a mono- or polyfluorinated alkyl or alkoxy radical having <NUM>, <NUM> or <NUM> C atoms or a mono- or polyfluorinated alkenyl radical having <NUM> or <NUM> C atoms is particularly preferably F, Cl, CF<NUM>, CHF<NUM>, OCF<NUM>, OCHF<NUM>, OCFHCF<NUM>, OCFHCHF<NUM>, OCFHCHF<NUM>, OCF<NUM>CH<NUM>, OCF<NUM>CHF<NUM>, OCF<NUM>CHF<NUM>, OCF<NUM>CF<NUM>CHF<NUM>, OCF<NUM>CF<NUM>CHF<NUM>, OCFHCF<NUM>CF<NUM>, OCFHCF<NUM>CHF<NUM>, OCF<NUM>CF<NUM>CF<NUM>, OCF<NUM>CF<NUM>CClF<NUM>, OCClFCF<NUM>CF<NUM>, OCH=CF<NUM> or CH=CF<NUM>, very particularly preferably F or OCF<NUM>, furthermore CF<NUM>, OCF=CF<NUM>, OCHF<NUM> or OCH=CF<NUM>.

The compounds of formula I are preferably selected from the group of compounds of the formulae I-<NUM> to I-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

The compounds according to the invention are selected from the group of compounds of the formulae II-1a, II-1c to II-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which the occurring groups have the respective meanings given above.

In a preferred embodiment of the present invention the medium comprises one or more compounds selected from the group of compounds of the formulae II-1a to II-<NUM> wherein L<NUM> and L<NUM>, and/or L<NUM> and L<NUM> are both F, respectively.

In another preferred embodiment the medium comprises compounds selected from the group of compounds of formulae II-1a to II-<NUM>, wherein L<NUM>, L<NUM>, L<NUM> and L<NUM> all are F.

Especially preferred compounds of formula II-<NUM> are
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

Preferably the compounds of formula II-<NUM> are selected from the group of compounds of formulae II-2a to II-2c
<CHM>
<CHM>
<CHM>
in which the occurring groups have the respective meanings given above and preferably L<NUM> and L<NUM> are both F.

Preferably the compounds of formula II-<NUM> are selected from the group of compounds of formulae II-3a to II-3e
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which the occurring groups have the respective meanings given above and preferably.

Especially preferred compounds of formula II-<NUM> are
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

In addition to the preferred compounds of formula II above the medium optionally comprises one or more compounds of formula II selected from the compounds of the formulae IIA1 to IIA7:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> and X<NUM> have the meanings given in formula II or one of the preferred meanings given above and below.

Preferred compounds are those of formula IIA1, IIA2 and IIA3, very preferred those of formula IIA1 and IIA2.

In the compounds of formulae IIA1 to IIA7, R<NUM> preferably denotes alkyl having <NUM> to <NUM> C atoms, very preferably ethyl or n-propyl, and X<NUM> preferably denotes For OCF<NUM>, very preferably F.

In another preferred embodiment of the present invention the medium comprises one or more compounds of formula III preferably selected from the group of formulae III-<NUM> and III-<NUM>, preferably of formula III-<NUM>:
<CHM>
<CHM>
in which the occurring groups and parameters have the respective meanings given under formula III above.

Preferably the compounds of formula III-<NUM> are selected from the group of compounds of formulae Ill-1a and III-1b
<CHM>
<CHM>
in which the occurring groups have the respective meanings given above and L<NUM> and L<NUM>, independently of each other, denote H or F.

The compounds of formula III-1a are preferably selected from the group of compounds of formulae III-1a-<NUM> to III-1a-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

Preferably the compounds of formula III-<NUM> are selected from the group of compounds of formulae Ill-2a to III-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which the occurring groups have the respective meanings given above and L<NUM> and L<NUM>, independently of one another, denote H or F.

Preferably, the compounds of formula II-2a are selected from the group of compounds of formulae Ill-2a-<NUM> to III-2a-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-2b are preferably selected from the group of compounds of formulae III-2b-<NUM> and III-2b-<NUM>, preferably III-2b-<NUM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula II-2c, are preferably selected from the group of compounds of formulae III-2c-<NUM> to III-2c-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formulae III-2d and III-2e are preferably selected from the group of compounds of formulae III-2d-<NUM> and III-2e-<NUM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-2f are preferably selected from the group of compounds of formulae III-2f-<NUM> to III-2f-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-<NUM> are preferably selected from the group of compounds of formulae III-<NUM>-<NUM> to III-<NUM>-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-<NUM> are preferably selected from the group of compounds of formulae Ill-<NUM>-<NUM> to III-<NUM>-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-2i are preferably selected from the group of compounds of formulae III-2i-<NUM> to III-2i-<NUM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-2j are preferably selected from the group of compounds of formulae III-2j-<NUM> to III-2j-<NUM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-<NUM> are preferably selected from the group of compounds of formulae III-<NUM>-<NUM> to III-<NUM>-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-2I are preferably selected from the group of compounds of formulae III-2I-<NUM> to III-2I-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> has the meaning given above.

The compounds of formula III-<NUM> are preferably selected from the compounds of formula III-<NUM>-<NUM>
<CHM>.

Alternatively or in addition to the compounds of the formulae III-<NUM> and/or III-<NUM> the media according to the present invention optionally comprise one or more compounds of formula III-<NUM>,
<CHM>.

In addition to the preferred compounds of formula III above the medium optionally comprises one or more compounds selected from the group consisting of the formulae IIIA-<NUM> to IIIA-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> and X<NUM> have the meanings given in formula III or one of the preferred meanings given above and below. Preferred compounds are those of formula IIIA1, IIIA4, IIIA6, IIIA16, IIIA19 and IIIA20.

In the compounds of formulae IIIA1 to IIIA21 R<NUM> preferably denotes alkyl having <NUM> to <NUM> C atoms, very preferably ethyl or propyl, X<NUM> preferably denotes F or OCF<NUM>, very preferably F.

The compounds of the invention are selected from the group consisting of the formulae LY-<NUM>, LY-<NUM> and LY-<NUM>, very preferably from the formula LY-<NUM>:
<CHM>
<CHM>
<CHM>
in which RY1 has the meanings given for R<NUM> under formula I, (O) denotes O or a single bond, and v is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>.

Particularly preferred compounds of the formula LY-<NUM> are selected from the following group:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Additionally, the medium comprises the compound LYA-<NUM>, LYA-<NUM> and/or LYA-<NUM>
<CHM>
<CHM>
<CHM>
In which n is an integer from <NUM> to <NUM>.

Preferably, the medium according to the invention comprises one or more compounds of the formula IV
<CHM>
in which.

The compounds of the formula IV are preferably selected from the group of the compounds of the formulae IV-<NUM> to IV-<NUM>, very preferably of the formula IV-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
in which.

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV selected from the compounds of the formulae IV-<NUM> to IV-<NUM> in combination with one or more compounds selected from the group of compounds of the formulae IVA-<NUM> to IVA-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which alkyl denotes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or n-pentyl.

Preferably, the medium comprises one or more compounds of formula IV-<NUM>, preferably selected from the compounds of the formulae IV-<NUM>-<NUM> to IV-<NUM>-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Preferably, the medium according to the invention comprises one or more compounds of the formulae IV-<NUM>-<NUM> and/or IV-<NUM>-<NUM>
<CHM>
<CHM>.

Preferably, the medium according to the invention comprises a compound of formula IV-<NUM>, very preferably selected from the compounds of the formulae IV-<NUM>-<NUM> to IV-<NUM>-<NUM>, in particular the compound of formula IV-<NUM>-<NUM> and/or IV-<NUM>-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Preferably, the medium according to the invention comprises a compound of formula IV-<NUM>, in particular selected from the compounds of the formulae IV-<NUM>-<NUM> and IV-<NUM>-<NUM>:
<CHM>
<CHM>.

Preferably, the medium according to the invention comprises one or more compounds of the formula IVa and/or IVb
<CHM>
<CHM>
in which.

Preferred compounds of the formula IVa are selected from the compounds of the formulae IVa-<NUM> to IVa-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
in which.

The medium according to the invention preferably comprises at least one compound of the formula IVa-<NUM>.

Preferred compounds of the formula IVb are selected from the compounds of the formulae IVb-<NUM> to IVb-<NUM>:
<CHM>
<CHM>
<CHM>
in which.

Of the compounds of the formulae IVb-<NUM> to IVb-<NUM>, the compounds of the formula IVb-<NUM> are particularly preferred.

Particularly preferred compounds of the formulae IVb are selected from the following compounds:
<CHM>
<CHM>
<CHM>
<CHM>.

The medium according to the invention particularly preferably comprises the compound IVb-<NUM>-<NUM>.

Preferably, the medium according to the invention comprises one or more compounds of the formula V
<CHM>
in which.

The compounds of formula V are preferably selected from the compounds of the formulae V-<NUM> to V-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> and R<NUM> have the meanings indicated above for formula V. R<NUM> and R<NUM> preferably each, independently of one another, denote straight-chain alkyl having <NUM> to <NUM> C atoms or alkenyl having <NUM> to <NUM> C atoms.

Preferred media comprise one or more compounds of the formulae V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM>, V-<NUM> and/or V-<NUM>. Very preferably, the medium comprises one or more compounds of the formulae V-<NUM>, V-<NUM>, V-<NUM> and/or V-<NUM>, in particular V-<NUM> and V-<NUM> and V-<NUM>.

In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VI-<NUM> to VI-<NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which.

In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VII-<NUM> to VII-<NUM>,
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which.

Particular preference is given to compounds of the formulae VII-<NUM>, VII-<NUM>, VII-<NUM>, VII-<NUM> and VII-<NUM>. In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having <NUM> to <NUM> C atoms. In the compounds of the formula VII-<NUM>, R preferably denotes alkyl or alkenyl, in particular alkyl. In the compound of the formula VII-<NUM>, R preferably denotes alkyl.

Preferably, the medium according to the invention comprises one or more compounds with negative dielectric anisotropy in addition to the compound of formula LY, selected from the group consisting of the formulae YA, YB, YC and YD, B, BA-<NUM> and BA-<NUM> below:
<CHM>
<CHM>
<CHM>
<CHM>
in which.

where the compounds of formula LY are excluded from formula YD.

Preferred compounds of the formulae YA, YB, YC and YD are indicated below:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which the parameter a denotes <NUM> or <NUM>, alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having <NUM>-<NUM> C atoms, and alkenyl denotes a straight-chain alkenyl radical having <NUM>-<NUM> C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH<NUM>=CH-, CH<NUM>=CHCH<NUM>CH<NUM>-, CH<NUM>-CH=CH-, CH<NUM>-CH<NUM>-CH=CH-, CH<NUM>-(CH<NUM>)<NUM>-CH=CH-, CH<NUM>-(CH<NUM>)<NUM>-CH=CH- or CH<NUM>-CH=CH-(CH<NUM>)<NUM>-.

Particularly preferred mixtures according to the invention comprise one or more compounds of the formulae YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YA-<NUM>, YB-<NUM>, YB-<NUM>, YB-<NUM>, YC-<NUM>, YD-<NUM> and YD-<NUM>.

The proportion of compounds of the formulae YA and/or YB in the mixture as a whole is preferably at least <NUM> % by weight.

Preferred media according to the invention comprise at least one compound of the formula YC-<NUM>,
<CHM>
in which alkyl and alkyl* have the meanings indicated above, preferably in amounts of < <NUM> % by weight, in particular > <NUM> % by weight.

In particular, the medium comprises one or more compounds of the formula YA-<NUM> selected from the following sub-formulae:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Alternatively, preferably in addition to the compounds of the formulae YA-<NUM>-<NUM> to YA-<NUM>-<NUM>, the medium comprises one or more compounds of the formulae YA-2a-<NUM> to YA-2a-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Alternatively, preferably in addition to the compounds of the formulae YA-<NUM>-<NUM> to YA-<NUM>-<NUM>, the medium comprises one or more compounds of the formulae YA-10a-<NUM> to YA-10a-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

In particular, the medium comprises one or more compounds of the formula YB-<NUM> selected from the following sub-formulae:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

Alternatively, preferably in addition to the compounds of the formulae YB-<NUM>-<NUM> to YB-<NUM>-<NUM>, the medium comprises one or more compounds of the formulae YB-10a-<NUM> to YB-10a-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

The medium according to the invention optionally comprises one or more compounds of formula B
<CHM>
in which.

The compounds of formula B are preferably selected from the compounds of the formula B-<NUM> and/or B-<NUM>
<CHM>
<CHM>
in which the occurring groups have the same meanings as given under formula B above and preferably.

Preferably, the compounds of the formula B-<NUM> selected from the group of compounds of formulae B-<NUM>-<NUM> to B-<NUM>-<NUM>, preferably of formula B-<NUM>-<NUM>,
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which
alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having <NUM>-<NUM> C atoms, alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having <NUM>-<NUM> C atoms, alkoxy and alkoxy* each, independently of one another, denote a straight-chain alkoxy radical having <NUM>-<NUM> C atoms, and L<NUM> and L<NUM> each, independently of one another, denote F or Cl, preferably both F.

Preferably, the compounds of the formula B-<NUM> are selected from the group of compounds of formulae B-<NUM>-<NUM> to B-<NUM>-<NUM>, preferably of formula B-<NUM>-<NUM>,
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which
alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having <NUM>-<NUM> C atoms, alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having <NUM>-<NUM> C atoms, alkoxy and alkoxy* each, independently of one another, denote a straight-chain alkoxy radical having <NUM>-<NUM> C atoms, and L<NUM> and L<NUM> each, independently of one another, denote F or Cl, preferably both F.

Optionally the medium comprises one or more compounds of the formula BA-<NUM> and/or BA-<NUM>
<CHM>
<CHM>
in which L<NUM> and L<NUM> have the same meanings as given under formula B, (O) denotes O or a single bond,.

The compounds of formula BA-<NUM> and/or BA-<NUM> are contained in the medium either alternatively or in addition to the compounds of formula B, preferably additionally.

Very preferred compounds of the formulae BA-<NUM> and BA-<NUM> are the following:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which alkoxy denotes a straight-chain alkoxy radical having <NUM>-<NUM> C atoms or alternatively -(CH<NUM>)nF in which n is <NUM>,<NUM>,<NUM>, or <NUM>, preferably C<NUM>H<NUM>F.

In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula B-<NUM>
<CHM>
in which.

The compounds of formula B-<NUM> are preferably selected from the group of compounds of the formulae B-<NUM>-<NUM> to B-<NUM>-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which R<NUM> denotes alkyl having <NUM> to <NUM> C-atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl or alternatively -(CH<NUM>)nF in which n is <NUM>,<NUM>,<NUM>, or <NUM>, preferably C<NUM>H<NUM>F.

In a preferred embodiment of the present invention, the medium comprises one or more compounds of the formulae B-<NUM> to B-<NUM>, preferably of formula B-<NUM>,
<CHM>
<CHM>
<CHM>
in which the occurring groups have the meanings given above, R<NUM> preferably denotes straight-chain alkyl and R<NUM> preferably denotes alkoxy, each having <NUM> to <NUM> C atoms.

In a preferred embodiment the media comprise one or more compounds of the formula I selected from the group of compounds of formulae B-<NUM> to B-<NUM>, preferably of formula B-<NUM>,
<CHM>
<CHM>
<CHM>
in which the parameters have the meanings given above, R<NUM> preferably denotes straight-chain alkyl and R<NUM> preferably denotes alkoxy each having <NUM> to <NUM> C atoms.

Further preferred embodiments are listed below:.

Preferred compounds of the formula YA-Y are selected from the group consisting of the following sub-formulae
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which, Alkyl and Alkyl* each, independently of one another, denote a straight-chain alkyl radical having <NUM>-<NUM> C atoms, Alkoxy denotes a straight-chain alkoxy radical having <NUM>-<NUM> C atoms, Alkenyl and Alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having <NUM>-<NUM> C atoms, and O denotes an oxygen atom or a single bond. Alkenyl and Alkenyl* preferably denote CH<NUM>=CH-, CH<NUM>=CHCH<NUM>CH<NUM>-, CH<NUM>-CH=CH-, CH<NUM>-CH<NUM>-CH=CH-, CH<NUM>-(CH<NUM>)<NUM>-CH=CH-, CH<NUM>-(CH<NUM>)<NUM>-CH=CH- or CH<NUM>-CH=CH-(CH<NUM>)<NUM>-.

Particularly preferred compounds of the formula YA-Y are selected from the group consisting of following sub-formulae:
<CHM>
<CHM>
in which Alkoxy and Alkoxy* have the meanings defined above and preferably denote methoxy, ethoxy, n-propyloxy, n-butyloxy or n-pentyloxy.

Preferably, the media according to the invention, comprise a stabilizer selected from the group of compounds of the formulae ST-<NUM> to ST-<NUM>. <CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which.

Of the compounds of the formula ST, special preference is given to the compounds of the formulae
<CHM>
<CHM>
in which n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, preferably n = <NUM> or <NUM>
<CHM>
in which n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, preferably n = <NUM>
<CHM>
in which n = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, preferably n = <NUM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

In the compounds of the formulae ST-3a and ST-3b, n preferably denotes <NUM>. In the compounds of the formula ST-2a, n preferably denotes <NUM>.

Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of the compounds of the formulae ST-2a-<NUM>, ST-3a-<NUM>, ST-3b-<NUM>, ST-<NUM>-<NUM>, ST-<NUM>-<NUM> and ST-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

The compounds of the formulae ST-<NUM> to ST-<NUM> are preferably each present in the liquid-crystal mixtures according to the invention in amounts of <NUM> - <NUM>%, based on the mixture.

If the mixtures according to the invention comprise two or more compounds from the group of the compounds of the formulae ST-<NUM> to ST-<NUM>, the concentration correspondingly increases to <NUM> - <NUM>% in the case of two compounds, based on the mixtures.

However, the total proportion of the compounds of the formulae ST-<NUM> to ST-<NUM>, based on the mixture according to the invention, should not exceed <NUM>%.

In another preferred embodiment of the present invention the liquid-crystalline medium additionally comprises one or more polymerisable compounds. The polymerisable compounds are preferably selected from formula M.

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

wherein at least one of the radicals Ra and Rb denotes or contains a group P or P-Sp-,.

Particularly preferred compounds of the formula I are those in which B<NUM> and B<NUM> each, independently of one another, denote <NUM>,<NUM>-phenylene, <NUM>,<NUM>-phenylene, naphthalene-<NUM>,<NUM>-diyl, naphthalene-<NUM>,<NUM>-diyl, phenanthrene-<NUM>,<NUM>-diyl, <NUM>,<NUM>-dihydro-phenanthrene-<NUM>,<NUM>-diyl, anthracene-<NUM>,<NUM>-diyl, fluorene-<NUM>,<NUM>-diyl, coumarin, flavone, where, in addition, one or more CH groups in these groups may be replaced by N, cyclohexane-<NUM>,<NUM>-diyl, in which, in addition, one or more non-adjacent CH<NUM> groups may be replaced by O and/or S, <NUM>,<NUM>-cyclohexenylene, bicycle[<NUM>. <NUM>]pentane-<NUM>,<NUM>-diyl, bicyclo[<NUM>. <NUM>]octane-<NUM>,<NUM>-diyl, spiro[<NUM>]heptane-<NUM>,<NUM>-diyl, piperidine-<NUM>,<NUM>-diyl, decahydronaphthalene-<NUM>,<NUM>-diyl, <NUM>,<NUM>,<NUM>,<NUM>-tetrahydronaphthalene-<NUM>,<NUM>-diyl, indane-<NUM>,<NUM>-diyl or octahydro-<NUM>,<NUM>-methanoindane-<NUM>,<NUM>-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 B<NUM> and B<NUM>
each, independently of one another, denote <NUM>,<NUM>-phenylene, <NUM>,<NUM>-phenylene, naphthalene-<NUM>,<NUM>-diyl or naphthalene-<NUM>,<NUM>-diyl,.

Very preferred compounds of formula M are selected from the following formulae:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning:.

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
<CHM>
in which L has one of the meanings indicated above and r denotes <NUM>, <NUM>, <NUM>, <NUM> or <NUM>,.

Preferred compounds of formulae M1 to M31 are those in which P<NUM>, P<NUM> and P<NUM> 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 Sp<NUM>, Sp<NUM> and Sp<NUM> are a single bond.

Further preferred compounds of formulae M1 to M31 are those in which one of Sp<NUM>, Sp<NUM> and Sp<NUM> is a single bond and another one of Sp<NUM>, Sp<NUM> and Sp<NUM> is different from a single bond.

Further preferred compounds of formulae M1 to M31 are those in which those groups Sp<NUM>, Sp<NUM> and Sp<NUM> that are different from a single bond denote -(CH<NUM>)s1-X"-, wherein s1 is an integer from <NUM> to <NUM>, preferably <NUM>, <NUM>, <NUM> or <NUM>, 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 E below.

Preferably the proportion of polymerisable compounds in the liquid-crystalline medium, preferably selected from formula M and Table E, is from <NUM> to <NUM>%, very preferably from <NUM> to <NUM>%, most preferably from <NUM> to <NUM>%.

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 E, 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 CH<NUM>=CW<NUM>-CO-O-, CH<NUM>=CW<NUM>-CO-,
<CHM>
<CHM>
CH<NUM>=CW<NUM>-(O)k3-, CW<NUM>=CH-CO-(O)k3-, CW<NUM>=CH-CO-NH-, CH<NUM>=CW<NUM>-CO-NH-, CH<NUM>-CH=CH-O-, (CH<NUM>=CH)<NUM>CH-OCO-, (CH<NUM>=CH-CH<NUM>)<NUM>CH-OCO-, (CH<NUM>=CH)<NUM>CH-O-, (CH<NUM>=CH-CH<NUM>)<NUM>N-, (CH<NUM>=CH-CH<NUM>)<NUM>N-CO-, HO-CW<NUM>W<NUM>-, HS-CW<NUM>W<NUM>-, HW<NUM>N-, HO-CW<NUM>W<NUM>-NH-, CH<NUM>=CW<NUM>-CO-NH-, CH<NUM>=CH-(COO)k1-Phe-(O)k2-, CH<NUM>=CH-(CO)k1-Phe-(O)k2-, Phe-CH=CH-, HOOC-, OCN- and W<NUM>W<NUM>W<NUM>Si-, in which W<NUM> denotes H, F, CI, CN, CF<NUM>, phenyl or alkyl having <NUM> to <NUM> C atoms, in particular H, F, Cl or CH<NUM>, W<NUM> and W<NUM> each, independently of one another, denote H or alkyl having <NUM> to <NUM> C atoms, in particular H, methyl, ethyl or n-propyl, W<NUM>, W<NUM> and W<NUM> each, independently of one another, denote CI, oxaalkyl or oxacarbonylalkyl having <NUM> to <NUM> C atoms, W<NUM> and W<NUM> each, independently of one another, denote H, Cl or alkyl having <NUM> to <NUM> C atoms, Phe denotes <NUM>,<NUM>-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k<NUM>, k<NUM> and k<NUM> each, independently of one another, denote <NUM> or <NUM>, k<NUM> preferably denotes <NUM>, and k<NUM> denotes an integer from <NUM> to <NUM>.

Very preferred groups P are selected from the group consisting of CH<NUM>=CW<NUM>-CO-O-, CH<NUM>=CW<NUM>-CO-,
<CHM>
<CHM>
CH<NUM>=CW<NUM>-O-, CH<NUM>=CW<NUM>-, CW<NUM>=CH-CO-(O)k3-, CW<NUM>=CH-CO-NH-, CH<NUM>=CW<NUM>-CO-NH-, (CH<NUM>=CH)<NUM>CH-OCO-, (CH<NUM>=CH-CH<NUM>)<NUM>CH-OCO-, (CH<NUM>=CH)<NUM>CH-O-, (CH<NUM>=CH-CH<NUM>)<NUM>N-, (CH<NUM>=CH-CH<NUM>)<NUM>N-CO-, CH<NUM>=CW<NUM>-CO-NH-, CH<NUM>=CH-(COO)k1-Phe-(O)k2-, CH<NUM>=CH-(CO)k1-Phe-(O)k2-, Phe-CH=CH- and W<NUM>W<NUM>W<NUM>Si-, in which W<NUM> denotes H, F, Cl, CN, CF<NUM>, phenyl or alkyl having <NUM> to <NUM> C atoms, in particular H, F, Cl or CH<NUM>, W<NUM> and W<NUM> each, independently of one another, denote H or alkyl having <NUM> to <NUM> C atoms, in particular H, methyl, ethyl or n-propyl, W<NUM>, W<NUM> and W<NUM> each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having <NUM> to <NUM> C atoms, W<NUM> and W<NUM> each, independently of one another, denote H, Cl or alkyl having <NUM> to <NUM> C atoms, Phe denotes <NUM>,<NUM>-phenylene, k<NUM>, k<NUM> and k<NUM> each, independently of one another, denote <NUM> or <NUM>, k<NUM> preferably denotes <NUM>, and k<NUM> denotes an integer from <NUM> to <NUM>.

Very particularly preferred groups P are selected from the group consisting of CH<NUM>=CW<NUM>-CO-O-, in particular CH<NUM>=CH-CO-O-, CH<NUM>=C(CH<NUM>)-CO-O- and CH<NUM>=CF-COO-, furthermore CH<NUM>=CH-O-, (CH<NUM>=CH)<NUM>CH-O-CO-, (CH<NUM>=CH)<NUM>CH-O-,
<CHM>.

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"-, wherein.

Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH<NUM>)p1-, - (CH<NUM>CH<NUM>O)q1-CH<NUM>CH<NUM>-, -CH<NUM>CH<NUM>-S-CH<NUM>CH<NUM>-, -CH<NUM>CH<NUM>-NH-CH<NUM>CH<NUM>- or -(SiR<NUM>R<NUM>-O)p1-, in which p1 is an integer from <NUM> to <NUM>, q1 is an integer from <NUM> to <NUM>, and R<NUM> and R<NUM> have the meanings indicated above.

Particularly preferred groups Sp and -Sp"-X"- are -(CH<NUM>)p1-, -(CH<NUM>)p1-O-, -(CH<NUM>)p1-O-CO-, -(CH<NUM>)p1-CO-O-, -(CH<NUM>)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-methyliminoethylene, <NUM>-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 <CIT>.

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.

In further preferred embodiments, the medium according to the invention comprises the following compounds, where the acronyms are explained in Table D below:.

The liquid-crystalline media according to the invention enable a significant broadening of the available parameter space. The achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and high optical anisotropy are far superior to previous materials from the prior art.

The liquid-crystalline media according to the invention, while retaining the nematic phase down to -<NUM> and preferably down to -<NUM>, particularly preferably down to -<NUM>, and the clearing point ≥ <NUM>, preferably ≥ <NUM>, at the same time allow rotational viscosities γ<NUM> of ≤ <NUM> mPa·s, particularly preferably ≤ <NUM> mPa·s, to be achieved, enabling excellent MLC displays having fast response times to be achieved. The rotational viscosities are determined at <NUM>.

The dielectric anisotropy Δε of the liquid-crystalline media according to the invention at <NUM> and <NUM> is preferably ≥ +<NUM>, preferably in the range of from +<NUM> to +<NUM>, more preferably from <NUM> to <NUM>, very preferably from <NUM> to <NUM> and particularly preferably from <NUM> to <NUM>.

The birefringence Δn of the liquid-crystalline media according to the invention at <NUM> is preferably from <NUM> to <NUM>, very preferably from <NUM> to <NUM>, in particular from <NUM> to <NUM>.

In an embodiment, the birefringence Δn of the liquid-crystalline media according to the invention at <NUM> is preferably from <NUM> to <NUM>.

The rotational viscosity γ<NUM> of the liquid-crystalline media according to the invention is preferably ≤ <NUM> mPa s, more preferably ≤ <NUM> mPa s, very preferably ≤ <NUM> mPa s.

The ratio γ<NUM>/K<NUM> (in which γ<NUM> is the rotational viscosity γ<NUM> and K<NUM> is the elastic constant for splay deformation) of the liquid-crystalline media according to the invention is preferably ≤ <NUM> mPa·s/pN.

The nematic phase range of the liquid-crystalline media according to the invention preferably has a width of at least <NUM>°, more preferably of at least <NUM>, in particular at least <NUM>°. This range preferably extends at least from -<NUM>° to +<NUM>.

Herein, 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 CnH2n+<NUM>, CmH<NUM>+<NUM> and CIH2I+<NUM>, and CnH2n-<NUM>, CmH<NUM>-<NUM> and CIH2I-<NUM> denote straight-chain alkyl or alkylene, respectively, in each case having n, m or I C atoms, wherein n and m, independently are <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> and I is <NUM>, <NUM> or <NUM>. Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B and Table C show the linking groups and 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.

In a preferred embodiment of the present invention, the media comprise one or more compounds selected from the group of the compounds of Table D.

Table E shows chiral dopants which are preferably employed in the mixtures according to the invention.

Preferably, the media according to the invention comprise one or more compounds selected from the group of the compounds from Table E.

In a preferred embodiment, the mixtures according to the invention comprise one or more polymerisable compounds, preferably selected from the polymerisable compounds of the formulae RM-<NUM> to RM-<NUM>. Of these, compounds RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM>, RM-<NUM> and RM-<NUM> to RM-<NUM> are particularly preferred.

The following examples are intended to explain the invention without limiting it. In the examples, m. denotes the melting point and T(N,I) denotes the clearing point of a liquid-crystalline substance in degrees Celsius; Furthermore: C denotes crystalline solid state, S denotes smectic phase (the index denotes the phase type), N denotes nematic state, Ch denotes cholesteric phase, I denotes isotropic phase, Tg denotes glass-transition temperature. The number between two symbols indicates the conversion temperature in degrees Celsius.

The host mixture used for determination of the optical anisotropy Δn of single compounds is the commercial mixture ZLI-<NUM> (Merck KGaA). The dielectric anisotropy Δε is determined using commercial mixture ZLI-<NUM>. The physical data of the compound to be investigated are obtained from the change in the dielectric constants of the host mixture after addition of the compound to be investigated and extrapolation to <NUM> % of the compound employed. In general, <NUM> % of the compound to be investigated are dissolved in the host mixture, depending on the solubility.

Unless indicated otherwise, parts or per cent data denote parts by weight or per cent by weight.

Unless explicitly noted otherwise, all values indicated in the present application for temperatures, such as, for example, the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I) or cl. , are indicated in degrees Celsius (°C).

The term "threshold voltage" for the present invention relates to the capacitive threshold (V<NUM>), also called the Freedericksz threshold, unless explicitly indicated otherwise. In the examples, as is generally usual, the optical threshold can also be indicated for <NUM> % relative contrast (V<NUM>).

The display used for measurement of the capacitive threshold voltage consists of two plane-parallel glass outer plates at a separation of <NUM>, which each have on the insides an electrode layer and an unrubbed polyimide alignment layer on top, which cause a homeotropic edge alignment of the liquid-crystal molecules.

The display or test cell used for measurement of the tilt angle consists of two plane-parallel glass outer plates at a separation of <NUM>, which each have on the insides an electrode layer and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to one another and cause a homeotropic edge alignment of the liquid-crystal molecules.

The polymerisable compounds are polymerised in the display or test cell by irradiation with UV light of defined intensity for a prespecified time, with a voltage simultaneously being applied to the display (usually <NUM> V to <NUM> V alternating current, <NUM>). In the examples, unless indicated otherwise, a metal halide lamp and an intensity of <NUM> mW/cm<NUM> is used for polymerisation. The intensity is measured using a standard meter (Hoenle UV-meter high end with UV sensor).

The tilt angle is determined using the Mueller Matrix Polarimeter "AxoScan" from Axometrics. A low value (i.e. a large deviation from the <NUM>° angle) corresponds to a large tilt here.

Unless stated otherwise, the term "tilt angle" means the angle between the LC director and the substrate, and "LC director" means in a layer of LC molecules with uniform orientation the preferred orientation direction of the optical main axis of the LC molecules, which corresponds, in case of calamitic, uniaxially positive birefringent LC molecules, to their molecular long axis.

Unless indicated otherwise, the VHR is determined at <NUM> (VHR<NUM>) and after
<NUM> minutes in an oven at <NUM> (VHR<NUM>) in a commercially available instrument Model LCM-<NUM> (O0004) from TOYO Corporation, Japan. The voltage used has a frequency of in a range from <NUM> to <NUM>, unless indicated more precisely.

The accuracy of the VHR measurement values depends on the respective value of the VHR. The accuracy decreases with decreasing values. The deviations generally observed in the case of values in the various magnitude ranges are compiled in their order of magnitude in the following table.

The stability to UV irradiation is investigated in a "Suntest CPS+", a commercial instrument from Heraeus, Germany, using a Xenon lamp NXE1500B. The sealed test cells are irradiated for <NUM>, unless explicitly indicated, without additional heating. The irradiation power in the wavelength range from <NUM> to <NUM> is <NUM> W / m<NUM> V. A UV "cut-off" filter having an edge wavelength of <NUM> is used in order to simulate the so-called window glass mode. In each series of experiments, at least four test cells are investigated for each condition, and the respective results are indicated as averages of the corresponding individual measurements.

The decrease in the voltage holding ratio (ΔVHR) usually caused by the exposure, for example by UV irradiation or by LCD backlighting, is determined in accordance with the following equation (<NUM>): <MAT>.

In order to investigate the low-temperature stability, also known as "LTS", i.e. the stability of the LC mixture in the bulk against spontaneous crystallisation of individual components at low temperatures or the occurrence of smectic phases, as the case may be, several sealed bottles, each containing about <NUM> of the material, are stored at one or more given temperatures, typically of -<NUM>, -<NUM>, -<NUM> and/or -<NUM> and it is inspected at regular intervals visually, whether a phase transition is observed or not. As soon as the first one of the samples at a given temperature shows a change the test is discontinued and the time until the last inspection, at which no change has been observed, is noted as the respective LTS. The test is run for <NUM>. If after <NUM> no change has occurred, the result is "LTS ><NUM>".

The ion density from which the resistivity is calculated is measured using the commercially available LC Material Characteristics Measurement System Model <NUM> from Toyo Corporation, Japan, using VHR test cells with AL16301 Polyimide (JSR Corp. , Japan) having a <NUM> cell gap. The measurement is performed after <NUM> of storage in an oven at <NUM> or <NUM>.

The so-called "HTP" denotes the helical twisting power of an optically active or chiral substance in an LC medium (in µm). Unless indicated otherwise, the HTP is measured in the commercially available nematic LC host mixture MLD-<NUM> (Merck KGaA) at a temperature of <NUM>.

The Clearing point is measured using the Mettler Thermosystem FP900. The optical anisotropy (Δn) is measured using an Abbe-Refraktometer H005 (Natrium-spectral lamp Na10 at <NUM>, <NUM>). The dielectric anisotropy (Δε) is measured using an LCR-Meter E4980A/Agilent (G005) at <NUM> (ε-parallel-cells with JALS <NUM>-R1). The turn on voltage (V<NUM>) is measured using an LCR-Meter E4980A/Agilent (G005) at <NUM> (ε-parallel-cells with JALS <NUM>-R1). The rotational viscosity (γ<NUM>) is measured using a TOYO LCM-<NUM> (<NUM>) at <NUM> (gamma <NUM> negative cells with JALS-<NUM>-R <NUM> ). The elastic constant (K<NUM>, splay) is measured using an LCR-Meter E4980A/Agilent (G005) at <NUM> (ε parallel-cells with JALS <NUM>-R1). K<NUM>: The elastic constant (K<NUM>, bend) is measured using an LCR-Meter E4980A/Agilent (G005) at <NUM> (ε-parallel-cells with JALS <NUM>-R1).

Unless explicitly noted otherwise, all concentrations in the present application are indicated in per cent by weight and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents. All physical properties are determined in accordance with "<NPL>, and apply for a temperature of <NUM>, unless explicitly indicated otherwise.

The following mixture examples having negative dielectric anisotropy are suitable, in particular, for liquid-crystal displays which have at least one planar alignment layer, such as, for example, IPS and FFS displays, in particular UB-FFS ( = ultra-bright FFS), and for VA displays.

The nematic mixtures C-<NUM> to C-<NUM>, M-<NUM> to M-<NUM> are prepared as follows:.

The compound of formula I contributes to an improvement of the LTS at -<NUM>: Mixture Example M-<NUM> differs from Comparative Mixture C-<NUM> in that it comprises <NUM>% of the compound CDU-<NUM>-F which results in improved LTS at -<NUM>. Surprisingly, an increase of the amount of compounds of the formula I (CDU-<NUM>-F and CDU-<NUM>-F) to <NUM>%, <NUM>% or <NUM>% in the mixture examples M-<NUM>, M-<NUM> or M-<NUM>, respectively, result in an LTS of more than <NUM> at -<NUM>.

It is essential for the medium to contain both a compound of formula I and of formula LY: Replacement of the compound CLY-<NUM>-O2 in the mixture with a similar compound results in worse LTS. Comparative Examples C-<NUM> is very similar to mixtures M-<NUM>, M-<NUM> and M-<NUM> but contains the compound CCY-<NUM>-O2 instead of a compound of formula Y such as for example CLY-<NUM>-O2. The LTS is reduced from <NUM> to <NUM>.

Comparative Example C-<NUM> is very similar to mixtures M-<NUM>, M-<NUM> and M-<NUM> but contains the compound CPY-<NUM>-O2 instead of a compound of formula Y such as for example CLY-<NUM>-O2. The LTS is reduced from <NUM> to <NUM>.

Mixture M-<NUM> consists of <NUM>% of mixture M-<NUM>, <NUM>% of the compound ST-<NUM> and <NUM>% of the compound ST-3b-<NUM>
<CHM>
<CHM>.

Mixture M-<NUM> consists of mixture M-<NUM> including 250ppm of the compound ST-3a-<NUM>
<CHM>.

Mixture M-<NUM> consists of mixture M-<NUM> including 500ppm of the compound ST-<NUM>-<NUM>
<CHM>.

Mixture Example M-<NUM> contains the following compound CDU-(c3)-F:
<CHM>.

Mixture Example M-<NUM> contains the following compound CDU-(F3)-F:
<CHM>.

Mixture M-<NUM> contains the following compound CLY-(c3)<NUM>-O2:
<CHM>.

Mixture M10 contains the compound B(S)-2O-O1(c5)
<CHM>.

Mixture example P1 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM>
<CHM>
and <NUM>% of the compound ST-3a-<NUM>
<CHM>.

Mixture example P2 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3a-<NUM>.

Mixture example P3 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3a-<NUM>.

Mixture example P4 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3a-<NUM>.

Mixture example P5 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3a-<NUM>.

Mixture example P6 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3a-<NUM>.

Mixture example P7 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM> and <NUM>% of the compound ST-3b-<NUM>
<CHM>.

Mixture example P8 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM>
<CHM>
and <NUM>% of the compound ST-3a-<NUM>
<CHM>.

Mixture example P9 consists of <NUM>% of Mixture M-<NUM>, <NUM>% of the compound RM-<NUM>
<CHM>
and <NUM>% of the compound ST-3a-<NUM>.

Claim 1:
A liquid-crystal medium with positive dielectric anisotropy, comprising
- one or more compounds of formula I
<CHM>
in which
R<NUM> denotes H, an alkyl or alkoxy radical having <NUM> to <NUM> C atoms, in which one or more CH<NUM> groups in these radicals are optionally replaced by
<CHM>
<CHM>
-CH=CH-, -C≡C-, -O-, -CO-O- or -O-CO- in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen, and
Y<NUM> denotes H or CH<NUM>;
- one or more compounds selected from the group of compounds of the formulae II-1a, II-1c to II-<NUM>, <NUM>-<NUM>, II-<NUM> and III
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
in which
R<NUM> and R<NUM> have the meanings given for R<NUM> under formula I,
<CHM>
<CHM>
independently of one another denote
<CHM>
<CHM>
<CHM>
<CHM>
L<NUM>, L<NUM>, L<NUM>, L<NUM>
L<NUM> and L<NUM> independently of each other, denote H or F,
Y<NUM> and Y<NUM> identically or differently, denote H or CH<NUM>,
X<NUM> and X<NUM> independently of each other, denote halogen, halogenated alkyl or halogenated alkoxy with <NUM> to <NUM> C-atoms or halogenated alkenyl or halogenated alkenyloxy with <NUM> or <NUM> C-atoms,
Z<NUM> denotes -CH<NUM>CH<NUM>-, -CF<NUM>CF<NUM>-, -COO-, trans- -CH=CH-, trans-CF=CF-, -CH<NUM>O- or a single bond, and
I, m, n and o are, independently of each other, <NUM> or <NUM>,
where the compounds of formula I are excluded from formula III;
- and one or more compounds selected from the group of compounds of the formulae LY-<NUM>, LY-<NUM> and LY-<NUM>
<CHM>
<CHM>
<CHM>
in which
RY1 has the meanings given for R<NUM> under formula I, (O) denotes O or a single bond, and
v is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>.