WO2023066827A1

WO2023066827A1 - Liquid crystal medium

Info

Publication number: WO2023066827A1
Application number: PCT/EP2022/078760
Authority: WO
Inventors: Harald Hirschmann; Monika Bauer; Kaja Christina Deing
Original assignee: Merck Patent Gmbh
Priority date: 2021-10-18
Filing date: 2022-10-17
Publication date: 2023-04-27
Also published as: TW202330878A

Abstract

The present invention relates to liquid-crystal media having negative dielectric anisotropy comprising a) one or more compounds of formula (I) b) one or more compounds selected from the group of the formulae (IIA), (IIB), (IIC) and (IID), and c) one or more compounds of formula (III) as defined in claim 1, and to the use of the LC media for optical, electro- optical and electronic purposes, in particular useful to enable energy-saving LC displays of the VA, IPS or FFS type.

Description

Liquid crystal medium

The present invention relates to liquid crystal (LC) media having negative dielectric anisotropy and to the use thereof for optical, electro-optical and electronic purposes, for example in LC displays.

One of the liquid-crystal display (LCD) modes used at present is the TN (“twisted nematic”) mode. However, TN LCDs have the disadvantage of a strong viewing-angle dependence of the contrast.

In addition, so-called VA (“vertically aligned”) displays are known which have a broader viewing angle. The LC cell of a VA display contains a layer of an LC medium between two transparent electrodes, where the LC medium usually has a negative dielectric anisotropy. In the switched-off state, the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment. On application of an electrical voltage to the two electrodes, a realignment of the LC molecules parallel to the electrode surfaces takes place.

Also known are so-called IPS (“in-plane switching”) displays, which contain an LC layer between two substrates, where the two electrodes are arranged on only one of the two substrates and preferably have intermeshed, combshaped structures. On application of a voltage to the electrodes, an electric field which has a significant component parallel to the LC layer is thereby generated between them. This causes realignment of the LC molecules in the layer plane.

Furthermore, so-called FFS (“fringe-field switching”) displays have been reported (see, inter alia, S.H. Jung et al., Jpn. J. Appl. Phys., Volume 43, No. 3, 2004, 1028), which contain two electrodes on the same substrate, one of which 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.

FFS displays can be operated as active-matrix or passive-matrix displays. In the case of active-matrix displays, individual pixels are usually addressed by integrated, non-linear active elements, such as, for example, transistors (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.

Furthermore, FFS displays have been disclosed (see S.H. Lee et al., Appl. Phys. Lett. 73(20), 1998, 2882-2883 and S.H. Lee et al., Liquid Crystals 39(9), 2012, 1141-1148), which have similar electrode design and layer thickness as FFS displays, but comprise a layer of an LC medium with negative dielectric anisotropy instead of an LC medium with positive dielectric anisotropy. The LC medium with negative dielectric anisotropy shows a more favourable director orientation that has less tilt and more twist orientation compared to the LC medium with positive dielectric anisotropy, as a result of which these displays have a higher transmission. The displays further comprise an alignment layer, preferably of polyimide provided on at least one of the substrates that is in contact with the LC medium and induces planar alignment of the LC molecules of the LC medium. These displays are also known as "Ultra Brightness FFS (UB-FFS)" mode displays. These displays require an LC medium with high reliability.

In VA displays of the more recent type, uniform alignment of the LC molecules is restricted to a plurality of relatively small domains within the LC cell. Disclinations may exist between these domains, also known as tilt domains. VA displays having tilt domains have, compared with conventional VA displays, a greater viewing-angle independence of the contrast and the grey shades. In addition, displays of this type are simpler to produce since additional treatment of the electrode surface for uniform alignment of the molecules in the switched-on state, such as, for example, by rubbing, is no longer necessary. Instead, the preferential direction of the tilt or pretilt angle is controlled by a special design of the electrodes. ln so-called MVA (“multidomain vertical alignment”) displays, this is usually achieved by the electrodes having protrusions which cause a local pretilt. As a consequence, the LC molecules are aligned parallel to the electrode surfaces in different directions in different, defined regions of the cell on application of a voltage. "Controlled" switching is thereby achieved, and the formation of interfering disclination lines is prevented. Although this arrangement improves the viewing angle of the display, it results, however, in a reduction in its transparency to light. A further development of MVA uses protrusions on only one electrode side, while the opposite electrode has slits, which improves the transparency to light. The slitted electrodes generate an inhomogeneous electric field in the LC cell on application of a voltage, meaning that controlled switching is still achieved. For further improvement of the transparency to light, the separations between the slits and protrusions can be increased, but this in turn results in a lengthening of the response times. In so-called PVA ("patterned VA") displays, protrusions are rendered completely superfluous in that both electrodes are structured by means of slits on the opposite sides, which results in increased contrast and improved transparency to light, but is technologically difficult and makes the display more sensitive to mechanical influences (“tapping”, etc.). For many applications, such as, for example, monitors and especially TV screens, however, a shortening of the response times and an improvement in the contrast and luminance (transmission) of the display are demanded.

A further development are displays of the so-called PS ("polymer sustained") or PSA ("polymer sustained alignment") type, for which the term "polymer stabilised" is also occasionally used. In these, a small amount (for example 0.3% by weight, typically < 1 % by weight) of one or more polymerisable, compound(s), preferably polymerisable monomeric compound(s), is added to the LC medium and, after filling the LC medium into the display, is polymerised or crosslinked in situ, usually by UV photopolymerisation, optionally while a voltage is applied to the electrodes of the display. The polymerisation is carried out at a temperature where the LC medium exhibits a liquid crystal phase, usually at room temperature. The addition of polymerisable mesogenic or liquid-crystalline compounds, also known as reactive mesogens or “RMs”, to the LC mixture has proven particularly suitable. ln the meantime, the PS(A) principle is being used in various conventional LC display modes. Thus, for example, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS- UB-FFS and PS-TN displays are known. The polymerisation of the RMs preferably takes place with an applied voltage in the case of PS-VA and PS- OCB displays, and with or without, preferably without, an applied voltage in the case of PS-IPS displays. As can be demonstrated in test cells, the PS(A) method results in a pretilt in the cell. In the case of PS-VA displays, the pretilt has a positive effect on response times. For PS-VA displays, a standard MVA or PVA pixel and electrode layout can be used. In addition, however, it is also possible, for example, to manage with only one structured electrode side and no protrusions, which significantly simplifies production and at the same time results in very good contrast and in very good transparency to light.

PS-VA displays are described, for example, in EP 1 170626 A2, US 6,861 ,107, US 7,169,449, US 2004/0191428 A1 , US 2006/0066793 A1 and US 2006/0103804 A1. PS-OCB displays are described, for example, in T.-J- Chen et al., Jpn. J. Appl. Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C- Chien, Jpn. J. Appl. Phys. 43, 2004, 7643-7647. PS-IPS displays are described, for example, in US 6,177,972 and Appl. Phys. Lett. 1999, 75(21 ), 3264. PS-TN displays are described, for example, in Optics Express 2004, 12(7), 1221.

Below the layer formed by the phase-separated and polymerised RMs which induce the above mentioned pretilt angle, the PSA display typically contains an alignment layer on one or both of the substrates forming the display cell, that provides the initial alignment of the LC molecules before the polymer stabilisation step. The alignment layer is usually applied on the electrodes (where such electrodes are present) such that it is in contact with the LC medium and induces initial alignment of the LC molecules. The alignment layer may comprise or consist of, for example, a polyimide, which may also be rubbed, or may be prepared by a photoalignment method.

Like the conventional LC displays described above, PSA displays can be operated as active-matrix or passive-matrix displays. In the case of activematrix displays, individual pixels are usually addressed by integrated, nonlinear active elements, such as, for example, transistors (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.

In particular for monitor and especially TV applications, optimisation of the response times, but also of the contrast and luminance (thus also transmission) of the LC display continues to be demanded. The PSA method can provide significant advantages here. In particular in the case of PS-VA, PS-IPS and PS-FFS displays, a shortening of the response times, which correlate with a measurable pretilt in test cells, can be achieved without significant adverse effects on other parameters.

Another problem observed in prior art is that the use of conventional LC media in LC displays, including but not limited to displays of the PSA type, often leads to the occurrence of mura in the display, especially when the LC medium is filled in the display cell manufactured using the one drop filling (ODF) method. This phenomenon is also known as "ODF mura". It is therefore desirable to provide LC media which lead to reduced ODF mura.

Another problem observed in prior art is that LC media for use in displays, including but not limited to displays of the PSA type, do often exhibit high viscosities and, as a consequence, high switching times. In order to reduce the viscosity and switching time of the LC medium, it has been suggested in prior art to add LC compounds with an alkenyl group. However, it was observed that LC media containing alkenyl compounds often show a decrease of the reliability and stability, and a decrease of the VHR especially after exposure to UV radiation. Especially for use in PSA displays this is a considerable disadvantage, because the photo-polymerisation of the RMs in the PSA display is usually carried out by exposure to UV radiation, which may cause a VHR drop in the LC medium.

Especially in view of mobile devices there is great demand for displays with high transmission, which enable the use of less intensive backlight, and, hence, leads to longer battery lifetime. Alternatively, of course, displays with higher brightness can be achieved having improved contrast especially under ambient light. ln addition there is a great demand for displays, and LC media for use in such displays, which enable a high specific resistance at the same time as a large working-temperature range, short response times, even at low temperatures, and a low threshold voltage, a low pretilt angle, a multiplicity of grey shades, high contrast and a broad viewing angle, have high reliability and high values for the VHR after UV exposure, and, in case of the polymerisable compounds, have low melting points and a high solubility in the LC host mixtures. In PSA displays for mobile applications, it is especially desired to have available LC media that show low threshold voltage and high birefringence.

The invention is based on the object of providing novel suitable LC media optionally comprising reactive mesogens (RM), for use in displays, which do not have the disadvantages indicated above or do so to a reduced extent.

In particular, the invention is based on the object of LC media which enable displays with high transmittance and at the same time very high specific resistance values, high VHR values, high reliability, low threshold voltages, short response times, high birefringence, reduce or prevent the occurrence of "image sticking" and "ODF mura" in the display, and in case of media comprising RMs enable fast polymerisation as rapidly and completely as possible and show a high solubility of RM in the LC media which used as host mixtures in PSA displays.

These objects have been achieved in accordance with the present invention by materials and processes as described in the present application. In particular, it has been found, surprisingly, that the use of liquid crystalline hosts as described hereinafter allows achieving the advantageous effects as mentioned above.

The invention relates to a liquid crystal medium comprising a) one or more compounds of formula I

in which

R¹ denotes n-butyl or n-pentyl; b) one or more compounds selected from the group of the formulae HA, IIB,

in which

R^2A, R^2B, R^2C and R^2D each, independently of one another, denote H, an alkyl radical having 1 to 7 C atoms or an alkenyl radical having 2 to 7 C atoms, each of which is unsubstituted, or at least monosubstituted by halogen, where one or more CH2 groups in these radicals may be

such a way that 0 atoms are not linked directly to one another; L¹ and L² each, independently of one another, denote F, Cl, CF3 or CHF2; Y denotes H, F, Cl, CF₃, CHF₂ or CH₃;

Z², Z^2B and Z^2D each, independently of one another, denote a single bond, -CH2CH2-, -CH=CH- -CF2CF2-, -CF=CF- -CF2O-, -OCF2-, -CH2O- -OCH2-, -COO-, -OCO- p denotes 0, 1 or 2 q denotes 0 or 1 and v denotes 1 , 2, 3, 4, 5, or 6 and c) one or more compounds of formula III

R³¹ and R³² each, independently of one another, denote H, an alkyl or alkoxy radical having 1 to 7 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one

-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,

A³ on each occurrence, independently of one another, denotes a 1 ,4- phenylene radical, in which one or two CH groups may be replaced by N, or a 1 ,4-cyclohexylene or 1 ,4-cyclohexenylene radical, in which one or two non-adjacent CH2 groups may be replaced by -0- or -S-, where the radicals may be mono- or polysubstituted by halogen atoms, n denotes 0, 1 or 2,

Z³ on each occurrence independently of one another denotes -CF2O- , -OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -CH=CH- -C=C- or a single bond, L³¹ and L³² each, independently of one another, denote F, Cl, CF3 or CHF₂, and

W denotes 0 or S, and d) optionally a reactive mesogen.

The invention furthermore relates to an LC display comprising the LC medium described above and below.

The invention furthermore relates to a process for preparing an LC medium as described above and below, comprising the steps of mixing one or more compounds of the formulae I and III and one or more compounds selected from the formulae IIA, I IB, IIC and HD and optionally with a reactive mesogen and with further LC compounds and/or additives.

The invention furthermore relates to the use of LC media according to the invention in PSA displays, in particular to the use in PSA displays containing an LC medium, for the production of a tilt angle in the LC medium by in-situ polymerisation of polymerisable compounds in the PSA display, preferably in an electric or magnetic field. Preferred polymerisable compounds, also referred to as reactive mesogens (RM), are described for example in paragraph [0094], [0155] and on page 111 -129 of EP 3 839 008 A1 , which is hereby included by reference.

The invention furthermore relates to an LC display comprising an LC medium according to the invention of the IPS, FFS, UB-FFS, UBplus, VA or PS-VA type.

The invention furthermore relates to the use of LC media according to the invention in polymer stabilised SA-VA displays, and to a polymer stabilised SA-VA display comprising the LC medium according to the invention.

The invention furthermore relates to an LC display of the VA or PSA type comprising two substrates, at least one which is transparent to light, an electrode provided on each substrate or two electrodes provided on only one of the substrates, and located between the substrates a layer of an LC medium that comprises one or more polymerisable compounds and an LC component as described above and below, wherein the polymerisable compounds are polymerised between the substrates of the display.

The invention furthermore relates to a process for manufacturing an LC display as described above and below, comprising the steps of filling or otherwise providing an LC medium, which optionally comprises one or more polymerisable compounds as described above and below, between the substrates of the display, and optionally polymerising the polymerisable compounds.

Preferred embodiments are subject-matter of the dependent clams and can also be taken from the description.

The PSA displays according to the invention have two electrodes, preferably in the form of transparent layers, which are applied to one or both of the substrates. In some displays, for example in PS-VA displays, one electrode is applied to each of the two substrates.

In a preferred embodiment the polymerisable component is polymerised in the LC display while a voltage is applied to the electrodes of the display.

The polymerisable compounds of the polymerisable component are preferably polymerised by photopolymerisation, very preferably by UV photopolymerisation.

It was surprisingly found that the use of the liquid crystal medium according to the invention enables displays with improved transmission while maintaining excellent performance regarding process relevant parameters, i.e.in the case of PSA displays a quick and complete UV-photopolymerisation reaction in particular at longer UV wavelengths in the range from 300-380nm and especially above 320nm, even without the addition of photo initiator, a fast generation of a large and stable pretilt angle, reduced image sticking and ODF mura in the display, a high reliability and a high VHR value and generally fast response times, a low threshold voltage and a high birefringence, as well as high reliability when exposed to the environment when used outdoors.

In particular, the medium according to the invention is distinguished by an excellent low-temperature stability (LTS).

The LC media according to the invention show the following advantageous properties when used in VA or FFS displays:

- improved transmission of the display,

- a high clearing temperature,

- a high voltage-holding-ratio,

- fast switching,

- sufficient stability against heat and/or UV in particular when used outdoors -excellent LTS.

The LC media according to the invention show the following advantageous properties when used in PSA displays:

- improved transmission of the display

- a high clearing temperature,

- a suitable tilt generation which is inside a certain process window,

- fast polymerization leading to minimal residues of RM after the UV-process,

- a high voltage-holding-ratio after the UV-process,

- good tilt stability,

- sufficient stability against heat and/or UV in particular when used outdoors,

- fast switching.

In particular, the liquid crystal medium according to the invention shows a favourably low ratio of rotational viscosity to the splay elastic constant yi / Ki. This contributes to improved switching behaviour especially at low driving voltages which is useful to enable energy-saving displays.

Preferred compounds of the formulae HA, IIB, IIC and HD are indicated

in which the parameter 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, preferably an oxygen atom. 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 preferred compounds of the formula HD are selected from the following sub-formulae:

C_VH2V+I IID-10-15

OC_VH_2V+1 IID-10-16

wherein v denotes 1 , 2, 3, 4, 5 or 6. In a preferred embodiment, the medium comprises one or more compounds of formula IID-10a

in which the occurring groups and parameters have the meanings given above under formula HD, and

R² denotes

, in which r is 0, 1 , 2, 3, 4, 5 or 6 and s is 1 , 2 or

3.

Preferred compounds of formula IID-10a are the compounds IID-10a-1 to IID-

10a-14.

More preferred media according to the invention comprise one or more compounds of the formulae IIA-2, IIA-8, IIA-10, IIA-16, IIA-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1 , IID-4 and IID-10.

Very preferred media according to the invention comprise one or more compounds of formula IIB-2

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and (0) denotes an oxygen atom or a single bond, in particular the compounds I IB-2-1 and I IB-2-2:

Preferred media according to the invention comprise at least one compound of the formula IIC-1 ,

IIC-1 in which alkyl and alkyl* have the meanings indicated above, preferably in amounts of 0.5 % to 5 % by weight, in particular 1 % to 3 % by weight.

In particular, the medium comprises one or more compounds of the formula IIA-2 selected from the following sub-formulae:

Alternatively, preferably in addition to the compounds of the formulae IIA-2-1 to IIA-2-5, the medium comprises one or more compounds of the formulae

In particular, the medium comprises one or more compounds of the formula

IIA-10 or IIA-52 selected from the following sub-formulae:

Alternatively, preferably in addition to the compounds of the formulae IIA-10- 1 to IIA-10-5, the medium comprises one or more compounds of the formulae

In particular, the medium comprises one or more compounds of the formula

IIB-10 selected from the following sub-formulae:

Alternatively, preferably in addition to the compounds of the formulae IIB-10-

1 to IIB-10-5, the medium comprises one or more compounds of the formulae

The compounds of formula III are preferably selected from the compounds of the formula 111-1 , HI-2 and/or HI-4

in which the occurring groups have the same meanings as given under formula HI above and preferably

R³¹ and R³² each, independently of one another, an alkyl or alkoxy radical having 1 to 15 C atoms or an alkenyl radical having 2 to 15 C atoms, more preferably one or both of them denote an alkoxy radical having 1 to 7 C atoms, and

L³¹ and L³² preferably denote F.

The liquid crystal medium according to the invention preferably comprises one, two or more compounds of formula HI-2. In a preferred embodiment the liquid crystal medium contains at least one compound of formula HI-1 and at least one compound of formula HI-2. In a further preferred embodiment the liquid crystal medium contains at least one compound of formula 111-2 and at least one compound of the formula 111-3.

Preferably, the compounds of the formula 111-1 selected from the group of compounds of formulae 111-1 -1 to 111-1 -10, preferably of formula 111-1 -6,

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, alkoxy and alkoxy* each, independently of one another, denote a straightchain alkoxy radical having 1 -6 C atoms, and L³¹ and L³² each, independently of one another, denote F or Cl, preferably both F.

Preferably, the compounds of the formula HI-2 are selected from the group of compounds of formulae HI-2-1 to 111-2-10, preferably of formula HI-2 -6,

Optionally the medium comprises one or more compounds of the formula

IIIA-1 and/or IIIA-2

in which L³¹ and L³² have the same meanings as given under formula III, (0) denotes O or a single bond,

R^IIIA denotes alkyl or alkenyl having up to 7 C atoms or a group Cy- C_mH2m+1 , m and n are, identically or differently, 0, 1 , 2, 3, 4, 5 or 6, preferably 1 , 2 or 3, very preferably 1 ,

Cy denotes a cycloaliphatic group having 3, 4 or 5 ring atoms, which is optionally substituted with alkyl or alkenyl each having up to 3 C atoms, or with halogen or CN, and preferably denotes cyclopropyl, cyclobutyl, cyclopentyl or cyclopentenyl.

The compounds of formula IIIA-1 and/or IIIA-2 are contained in the medium either alternatively or in addition to the compounds of formula III, preferably additionally.

Very preferred compounds of the formulae IIIA-1 and IIIA-2 are the following: alkoxy IIIA-1 -1

alkoxy IIIA-1 -2

alkoxy IIIA-1 -3

in which alkoxy denotes a straight-chain alkoxy radical having 1 -6 C atoms or alternatively -(CH2)_nF in which n is 2, 3, 4, or 5, preferably C2H4F.

In a preferred embodiment of the present invention, the medium comprises one or more compounds of formula HI-3

in which

R³¹ , R³² identically or differently, denote 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-,

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

The compounds of formula HI-3 are preferably selected from the group of compounds of the formulae HI-3-1 to HI-3-10:

in which R³² denotes alkyl having 1 to 7 C-atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl or alternatively -(CH2)_nF in which n is 2,3,4, or 5, preferably C2H4F.

In a preferred embodiment of the present invention, the medium comprises one or more compounds of the formulae 111-4 to 111-6, preferably of formula 111-

in which the parameters have the meanings given above, R³¹ preferably denotes straight-chain alkyl having 1 to 7 C atoms and R³² preferably denotes alkoxy having 1 to 7 C atoms.

In a preferred embodiment the media according to the invention comprise one or more compounds of the formula III selected from the group of compounds of formulae 111-7 to 111-9, preferably of formula 111-8,

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

in which

R⁴¹ denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably an n-alkyl radical, particularly preferably having 2, 3, 4 or 5 C atoms, and

R⁴² denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkoxy radical having 1 to 6 C atoms, both preferably having 2 to 5 C atoms, an unsubstituted alkenyl radical having 2 to 7 C atoms, preferably having 2, 3 or 4 C atoms, more preferably a vinyl radical or a 1 -propenyl radical and in particular a vinyl radical, where the compounds of formula I are excluded from formula IV and its subformulae.

The compounds of the formula IV are preferably selected from the group of the compounds of the formulae IV-1 to IV-4,

in which alkyl and alkyl’, independently of one another, denote alkyl having 1 to 7 C atoms, preferably having 2 to 5 C atoms, alkenyl denotes an alkenyl radical having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably 2 C atoms, alkenyl’ denotes an alkenyl radical having 2 to 5 C atoms, preferably having 2 to 4 C atoms, particularly preferably having 2 to 3 C atoms, and alkoxy denotes alkoxy having 1 to 5 C atoms, preferably having 2 to 4 C atoms.

Preferably, the medium comprises one or more compounds selected from the compounds of the formulae IV-1-1 to IV-1-4

Very preferably, the medium according to the invention comprises the compound of formula IV-1-1.

Very preferably, the medium according to the invention comprises one or more compounds of the formulae IV-2-1 and/or IV-2-2

IV-1-2

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula IV-3,

in which very preferably alkyl denotes an alkyl radical having 1 to 7 C atoms, in particular n-ethyl or n-propyl, very particularly n-propyl, and alkenyl denotes

j_{n w}hjch m is 0, 1 or 2, preferably 0, and n is 0, 1 or 2, preferably 0 or 1 , in particular selected from the compounds of the formulae IV-3-1 to IV-3-6, very particularly preferably of the formula IV-3-2:

In a preferred embodiment, the medium comprises, in particular in addition to the compounds of the formulae IV-3-1 to IV-3-6, one or more compounds of the formulae IV-3-7 to IV-3-9

Preferably, the concentration of the compounds of the formulae IV-3-7 to IV- 3-9 in the medium according to the invention is less than 5% or less than 4% or less than 3%, very preferably 0% to 1 %, in particular 0%.

Very preferably, the medium according to the invention comprises one or more compounds of the formula IV-3 and one or more compounds of the formula I V-1 , where the total concentration of the compounds of the formula I V-1 is in the range of from 1 % to 30%.

Very preferably, the medium according to the invention comprises a compound of formula IV-4, in particular selected from the compounds of the formulae IV-4-1 to IV-4-3, in particular of the formula IV-4-3

In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula I selected from the compounds of the formulae 1-1 to I-4 in combination with one or more compounds selected from the group of compounds of the formulae IA-1 to IA-18:

in which alkyl denotes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, or n-pentyl.

The liquid-crystalline medium according to the invention preferably comprises one or more compounds of the formula IVa,

in which

R⁴¹ and R⁴² each, independently of one another, denote a straight-chain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkenyloxy radical having up to 12 C atoms, and

alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 to 6 C atoms.

The medium according to the invention preferably comprises at least one compound of the formula IVa-1 and/or formula IVa-2, very preferably of formula IVa-2, in particular the compounds IVa-2 in which alkyl denotes n- propyl and alkyl* denotes methyl.

The proportion of compounds of the formula IVa in the mixture as a whole is preferably less than 5 % by weight, very preferably less than 2% by weight.

Preferably, the medium comprises one or more compounds of formula IVb-1

IVb-3

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

The proportion of the compounds of the formulae IV-1 to IV-3 in the mixture as a whole is preferably less than 3 % by weight, in particular less than 2 % by weight.

Of the compounds of the formulae IVb-1 to IVb-3, the compounds of the formula IVb-2 are particularly preferred.

Very particularly preferred biphenyls are

in which alkyl* denotes an alkyl radical having 1 to 6 C atoms and preferably denotes n-propyl or n-butyl. The medium according to the invention particularly preferably comprises one or more compounds of the formulae IVb-1 -1 and/or IVb-2-3.

In the compounds of the formula IVb-1 -1 alkyl denotes preferably propyl, butyl and pentyl and most preferably propyl. In a preferred embodiment, the medium according to the invention comprises one or more compounds of formula V

in which

R⁵¹ , R⁵² denote alkyl having 1 to 7 C atoms, alkoxy having 1 to 7 C atoms, or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms,

Z⁵¹ , Z⁵² each, independently of one another, denote -CH2-CH2-, -CH2-O- , -CH=CH-, -C=C-, -COO- or a single bond, and n is 1 or 2.

The compounds of formula V are preferably selected from the compounds of the formulae V-1 to V-17:

in which R⁵¹ and R⁵² have the meanings indicated for formula V above.

R⁵¹ and R⁵² preferably each, independently of one another, denote straightchain alkyl having 1 to 7 C atoms or alkenyl having 2 to 7 C atoms.

Preferred media comprise one or more compounds of the formulae V-1 , V-3, V-4, V-6, V-7, V-10, V-11 , V-12, V-14, V-15, V-16 and/or V-17, very preferably V-16, in particular the compounds of formula V-16 in which R⁵¹ denotes n-propyl and R⁵² denotes ethyl.

In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of formula VI

in which R⁶ and R⁶² have the meanings of R^2A as defined in claim 1 and R⁶² alternatively denotes F, Cl, CF3 or OCF3, preferably F, and L⁶¹ , L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ independently denote H or F, where at least one of L⁶¹, L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ denotes F.

The compounds of formula VI are preferably selected from the formulae VI-1 to VI-21 , in particular from the formula VI-4:

in which R⁶ denotes a straight-chain alkyl or alkoxy radical having 1 to 6 C atoms, (0) denotes -0- or a single bond, and m is 0, 1 , 2, 3, 4, 5 or 6 and n is 0, 1 , 2, 3 or 4.

R⁶ preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy or pentoxy.

Particular preference is given to compounds of the formulae VI-1 , VI-2, VI-4, VI-20 and VI-21.

Very preferably, the medium according to the invention comprises the compound of formula IV-4, in particular the compounds of the formula IV-4-1 :

in which R⁶ and m have the meanings defined above and preferably R⁶ denotes methyl, ethyl, n-propyl, n-butyl, or n-pentyl, and m is 2, 3 or 4. In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of formula VIA

in which R⁶ and R⁶² have the meanings of R^2A as defined in claim 1 and R⁶² alternatively denotes F, Cl, CF3 or OCF3, preferably F, and L⁶¹ , L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ independently denote H or F, where at least one of L⁶¹, L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ denotes F and

Z⁶¹ and Z⁶² independently denote a single bond, -CH2-CH2-, -CH2-O-

, -CH=CH-, -C=C-, -COO- or -CF2-O- but Z⁶¹ + Z⁶².

Very preferably, the medium according to the invention comprises the compound of formula VIA-1 and/or formula X

in which R⁶ and m have the meanings defined above and preferably R⁶ denotes methyl, ethyl, n-propyl, n-butyl, or n-pentyl, and m is 2, 3 or 4. In a particular preferred embodiment R⁶ denotes n-propyl and m denotes 2.

In a preferred embodiment of the present invention the medium additionally comprises one or more compounds of the formulae VI 1-1 to VII-9

in which

R⁷ denotes a straight-chain alkyl or alkoxy radical having 1 to 6 C atoms, or a straight chain alkenyl radical having 2 to 6 C atoms, and w is an integer from 1 to 6.

Particular preference is given to mixtures comprising at least one compound of the formula VII-9.

Further preferred embodiments are listed below: a) Liquid-crystalline medium comprising at least one compound of the for-

In a preferred embodiment the liquid crystal mixtures according to the present invention contain at least one compound of formula Z-8. b) Preferred liquid-crystalline media according to the invention comprise one or more substances which contain a tetrahydronaphthyl or naphthyl unit, such as, for example, the compounds of the formulae N-1 to N-5,

in which R^{1 N} and R^2N each, independently of one another, have the meanings indicated for R^2A, preferably denote straight-chain alkyl, straight-chain alkoxy or straight-chain alkenyl, and

Z¹ and Z² each, independently of one another, denote -C2H4-, -CH=CH-, -(CH₂)₄-, -(CH₂)₃O- -O(CH₂)₃-, -CH=CHCH₂CH₂-, -CH₂CH₂CH=CH-, -CH₂O-, -OCH₂-, -COO-, -OCO-, -C₂F₄-, -CF=CF-, -CF=CH-, -CH=CF-, -CF₂O-, -OCF₂-, -CH₂- or a single bond. c) Preferred mixtures comprise one or more compounds selected from the group of the difluorodibenzochroman compounds of the formula BC, chromans of the formula CR, and fluorinated phenanthrenes of the formulae PH-1 and PH-2,

in which R^B1, R^B2, R^CR1, R^CR2, R¹, R² each, independently of one another, have the meaning of R^2A. c is 0, 1 or 2. R¹ and R² preferably, independently of one another, denote alkyl or alkoxy having 1 to 6 C atoms.

Particularly preferred compounds of the formulae BC and CR are the compounds BC-1 to BC-7 and CR-1 to CR-5,

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

Very particular preference is given to mixtures comprising one, two or three compounds of the formula BC-2, BF-1 and/or BF-2. d) Preferred mixtures comprise one or more indane compounds of the formula In,

in which

R¹¹, R¹², and R¹³ each, independently of one another, denote a straightchain alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6 C atoms, R¹² and R¹³ alternatively denote halogen, preferably F,

i denotes 0, 1 or 2.

Preferred compounds of the formula In are the compounds of the formulae ln-1 to In-16 indicated below:

Particular preference is given to the compounds of the formulae ln-1 , In- 2, ln-3 and ln-4. e) Preferred mixtures additionally comprise one or more compounds of the formulae L-1 to L-12,

in which

R, R¹ and R² each, independently of one another, have the meanings indicated for R^2A in formula HA above, and alkyl denotes an alkyl radical having 1 to 6 C atoms. The parameter s denotes 1 or 2.

The compounds of the formulae L-1 to L-11 are preferably employed in concentrations of 5 to 15 % by weight, in particular 5 to 12 % by weight and very particularly preferably 8 to 10 % by weight. f) Preferred mixtures additionally comprise one or more compounds of formula IIA-Y

in which R¹¹ and R¹² have one of the meanings given for R^2A in formula HA above, and L¹ and L², identically or differently, denote F or Cl and L³ denotes H or CH₃.

Preferred compounds of the formula IIA-Y are selected from the group consisting of the following sub-formulae

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms; alkoxy denotes a straightchain alkoxy radical having 1-6 C atoms; alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, and 0 denotes an oxygen atom or a single bond, alkenyl and alkenyl* preferably denote 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-. Particularly preferred compounds of the formula IIA-Y are selected from the group consisting of following sub-formulae:

in which alkoxy and alkoxy* have the meanings defined above and preferably denote methoxy, ethoxy, n- propyloxy, n-butyloxy or n-pentyloxy. g) The medium additionally comprises one or more compounds selected from the compounds of formulae P-1 to P-4:

in which

R^p denotes a straight-chain alkyl or alkoxy radical having 1-6 C atoms or an alkenyl radical having 2-6 C atoms, preferably alkyl X^p straight-chain alkyl having 1-6 C atoms, F, Cl, CF3, OCF2H, OCF3, OCHFCF3, OCF2CHFCF3, OCH=CF₂, preferably F, OCF₃ or CF₃, CH₃

L^P1, L^P2 and L^P3 each independently of one another denote H or F.

Preferred compounds of the formulae P1 to P4 are listed in the following:

wherein R^p has the meanings given above. Preferably R^p denotes alkyl or alkenyl, in particular ethyl, propyl, butyl, pentyl, 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- and alkyl denotes a straight-chain alkyl group having 1 -6 carbon atoms. h) In a preferred embodiment the mixtures according to Claim 1 contain at least one compound selected from the group of compounds of formula IIA-

18, IIA-42, IIA-49, IIA-51 , IIA-52, IID-4, IID-10, HI-3, HI-4, IIIA-1-3, IVb-1 , IV-b-

2, VIA-1 , X, V-11 , V-17, Z-8 and IIA-Y.

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

in which

Ar denotes an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms, preferably 6 to 30 C atoms;

Sp denotes a spacer group;

R^s denotes H, alkyl having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms;

Z^s denotes -O-, -C(O)O-, -(CH2)z- or -(CH2)zO-, or a single bond;

R^H denotes H, 0; CH3, OH or OR^S, preferably H or O ;

R^S1 , R^S2, R^S3 and R^S4, identically or differently, denote alkyl having 1 to 6 C atoms, preferably having 1 to 3 C atoms, very preferably CH3;

G denotes H or R^s or a group Z^S-HA; z is an integer from 1 to 6; and q is 3 or 4.

In formula H, aryl preferably denotes an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms, comprising one, two, three or four aromatic rings including condensed rings that may be linked directly or via an alkylene linking group having 1 to 12 C atoms, in which one or more H atoms are optionally replaced with alkyl or alkoxy having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms, or with CN, CF3 or halogen, and in which one or more CH2 groups may each, independently of one another, be replaced by -O-, -S-, -NH-, -N(Ci-C₄-alkyl)-, -CO-, -CO-O-,

-O-CO-, -O-CO-O-, -CH=CH- or -C=C- in such a way that 0 or S atoms are not linked directly to one another.

Preferred aryl groups are benzene, naphthalene, anthracene, biphenyl, m- terphenyl, p-terphenyl, and (phenylalkyl)benzene in which alkyl is straight chain alkyl having 1 to 12 C atoms.

The compounds of formula H are described in EP3354710 A1 and EP3354709 A1 .

The compounds of formula H are preferably selected from the compounds of the formulae H-1 , H-2 and H-3:

in which R^H has the meanings given above and preferably denote H or O, and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7, and Sp denotes a spacer group, preferably alkylene having 1 to 12 C atoms in which one or more non-adjacent -CH2- groups may be replaced with -O-.

Preferred compounds of formula H-1 are selected from the compounds of the formula H-1 -1 :

in which R^H has the meanings given above and preferably denotes H or O, and n is an integer from 0 to 12, preferably 5, 6, 7, 8 or 9, very preferably 7.

Preferred compounds of formula H-2 are selected from the compounds of the formula H-2-1 :

in which R^H has the meanings given above and preferably denotes H or O, and n2, on each occurrence identically or differently, preferably identically, is an integer from 1 to 12, preferably 2, 3, 4, 5, or 6, very preferably 3, and R^s on each occurrence identically or differently, preferably identically, denotes alkyl having 1 to 6 C atoms, preferably n-butyl.

Preferred compounds of formula H-3 are selected from the compounds of the formula H-3-1 :

Preferably, the medium according to the invention comprises a compound selected from the group of compounds of the formulae ST-1 to ST-18:

R^ST denotes H, an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH2 groups in these radicals may each be replaced, independently of one another by -C=C-, -CF2O-, -OCF2-

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

Z^ST each, independently of one another, denote -CO-O-, -O-CO-, -CF2O-

, -OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -(CH₂)4-, -CH=CH-, -CH2O-

, -C2F4-,

-CH2CF2-, -CF2CH2-, -CF=CF- -CH=CF- -CF=CH- -CH=CH- -C DC- or a single bond,

L¹ and L² each, independently of one another, denote F, Cl, CH3, CF3 or CHF₂, p denotes 0, 1 or 2, q denotes 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10.

Of the compounds of the formula ST, special preference is given to the compounds of the formulae ST-1 and ST-3 and in particular:

in which n = 1 , 2, 3, 4, 5, 6 or 7, preferably n = 3

In the compounds of the formulae ST-3a and ST-3b, n preferably denotes 3.

In the compounds of the formula ST-2a, n preferably denotes 7.

Very particularly preferred mixtures according to the invention comprise one or more stabilizers from the group of the compounds of the formulae ST-2a-

ST-12

The compounds of the formulae ST-1 to ST-19 are preferably each present in the liquid-crystal mixtures according to the invention in amounts of 0.005 - 0.5%, 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-1 to ST-18, the concentration correspondingly increases to 0.01 - 1 % in the case of two compounds, based on the mixtures.

However, the total proportion of the compounds of the formulae ST-1 to ST- 18, based on the mixture according to the invention, should not exceed 2%.

The medium according to the invention preferably has negative dielectric anisotropy. In a preferred embodiment, the medium additionally comprises one or more compounds

The term "reliability" as used herein means the quality of the performance of the display during time and with different stress loads, such as light load, temperature, humidity, voltage, and comprises display effects such as image sticking (area and line image sticking), mura, yogore etc. which are known to the skilled person in the field of LC displays. As a standard parameter for categorising the reliability usually the voltage holding ration (VHR) value is used, which is a measure for maintaining a constant electrical voltage in a test display. Among other factors, a high VHR is a prerequisite for a high reliability of the LC medium.

Unless indicated otherwise, the term "PSA" is used hereinafter when referring to displays of the polymer sustained alignment type in general, and the term "PS" is used when referring to specific display modes, like PS-VA, PS-TN and the like.

Also, unless indicated otherwise, the term "RM" is used hereinafter when referring to a polymerisable mesogenic or liquid-crystalline compound.

As used herein, the terms "active layer" and "switchable layer" mean a layer in an electrooptical display, for example an LC display, that comprises one or more molecules having structural and optical anisotropy, like for example LC molecules, which change their orientation upon an external stimulus like an electric or magnetic field, resulting in a change of the transmission of the layer for polarized or unpolarized light.

As used herein, the terms "tilt" and "tilt angle" will be understood to mean a tilted alignment of the LC molecules of an LC medium relative to the surfaces of the cell in an LC display (here preferably a PSA display). The tilt angle here denotes the average angle (< 90°) between the longitudinal molecular axes of the LC molecules (LC director) and the surface of the plane-parallel outer plates which form the LC cell. A low value for the tilt angle (i.e. a large deviation from the 90° angle) corresponds to a large tilt here. A suitable method for measurement of the tilt angle is given in the examples. Unless indicated otherwise, tilt angle values disclosed above and below relate to this measurement method.

As used herein, the terms "reactive mesogen" and "RM" will be understood to mean a compound containing a mesogenic or liquid crystalline skeleton, and one or more functional groups attached thereto which are suitable for polymerisation and are also referred to as "polymerisable group" or "P".

Unless stated otherwise, the term "polymerisable compound" as used herein will be understood to mean a polymerisable monomeric compound.

As used herein, the term "low-molecular-weight compound" will be understood to mean to a compound that is monomeric and/or is not prepared by a polymerisation reaction, as opposed to a "polymeric compound" or a "polymer". As used herein, the term "unpolymerisable compound" will be understood to mean a compound that does not contain a functional group that is suitable for polymerisation under the conditions usually applied for the polymerisation of the RMs.

The term "mesogenic group" as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerisation. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic or LC compounds is given in Pure Appl. Chem. 2001 , 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

As used herein, the terms “optically active” and “chiral” are synonyms for materials that are able to induce a helical pitch in a nematic host material, also referred to as “chiral dopants”.

The term "spacer group", hereinafter also referred to as "Sp", as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001 , 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368. As used herein, the terms "spacer group" or "spacer" mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerisable group(s) in a polymerisable mesogenic compound.

Throughout the patent application, 1 ,4-cyclohexylene rings and 1 ,4-phenyl- ene rings are depicted as follows:

The cyclohexylene rings are trans-1 ,4-cyclohexylene rings.

Above and below,

denotes a trans-1 ,4-cyclohexylene ring.

In a group the single bond shown between the two ring atoms can be attached to

any free position of the benzene ring.

Above and below "organic group" denotes a carbon or hydrocarbon group.

"Carbon group" denotes a mono- or polyvalent organic group containing at least one carbon atom, where this either contains no further atoms (such as, for example, -C=C-) or optionally contains one or more further atoms, such as, for example, N, 0, S, B, P, Si, Se, As, Te or Ge (for example carbonyl, etc.). The term "hydrocarbon group" denotes a carbon group which additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, B, P, Si, Se, As, Te or Ge.

"Halogen" denotes F, Cl, Br or I, preferably F or Cl.

-CO-, -C(= 0)- and -C(O)- denote a carbonyl group, i.e.

.

A carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. A carbon or hydrocarbon radical having more than 3 C atoms can be straightchain, branched and/or cyclic and may also contain spiro links or condensed rings.

The terms "alkyl", "aryl", "heteroaryl", etc., also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc.

The term "aryl" denotes an aromatic carbon group or a group derived therefrom. The term "heteroaryl" denotes "aryl" as defined above, containing one or more heteroatoms, preferably selected from N, 0, S, Se, Te, Si and Ge.

Herein, alkyl is straight-chain or branched and has 1 to 15 C atoms, is preferably straight-chain and has, unless indicated otherwise, 1 , 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methyl, ethyl, n-propyl, n-butyl, n- pentyl, n-hexyl or n-heptyl.

Herein, branched alkyl is alkyl having a secondary and/or tertiary, preferably secondary, carbon atom and is preferably isopropyl, s-butyl, isobutyl, isopentyl, 2-methylhexyl or 2-ethylhexyl, 2-methylpropyl, 2-pentyl, 3-pentyl, 2- methylbutyl, 3-methylbutyl.

Herein, a cyclic alkyl group is taken to mean a cycloaliphatic radical or an alkyl group in which a methylene group is replaced with a cycloaliphatic group (i.e. a cycloalkylalkyl or alkylcycloalkylalkyl), which may be saturated or partially unsaturated, and preferably denotes cyclopropyl, methylcyclopropyl, cyclobutyl, methylcyclobutyl, cyclopentyl, methylcyclopentyl, cyclopent-1 - enyl, cyclopropylmethyl, cyclopropylethyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylmethyl, cyclopentylethyl, cyclopent-1 -enylmethyl.

Herein, an alkoxy radical is straight-chain or branched and contains 1 to 15 C atoms. It is preferably straight-chain and has, unless indicated otherwise, 1 , 2, 3, 4, 5, 6 or 7 C atoms and is accordingly preferably methoxy, ethoxy, n- propoxy, n-butoxy, n-pentoxy, n-hexoxy or n-heptoxy.

Herein, an alkenyl radical is preferably an alkenyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C-C double bond. It is preferably straight-chain and has 2 to 7 C atoms. Accordingly, it is preferably 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. If the two C atoms of the C-C double bond are substituted, the alkenyl radical can be in the form of E and/or Z isomer (trans/cis). In general, the respective E isomers are preferred. Of the alkenyl radicals, prop-2 -enyl, but- 2- and -3-enyl, and pent-3- and -4-enyl are particularly preferred. Herein, alkynyl is taken to mean an alkynyl radical having 2 to 15 C atoms, which is straight-chain or branched and contains at least one C-C triple bond. 1 - and 2-propynyl and 1 -, 2- and 3-butynyl are preferred.

Preferred carbon and hydrocarbon groups are optionally substituted, straightchain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25, C atoms, wherein one or more C atoms may also be replaced by hetero atoms, preferably selected from N, O, S, Se, Te, Si and Ge.

Further preferred carbon and hydrocarbon groups are C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C20 allyl, C4-C20 alkyldienyl, C4-C20 polyenyl, C6- C20 cycloalkyl, C4-C15 cycloalkenyl, C6-C30 aryl, C6-C30 alkylaryl, C6-C30 arylalkyl, C6-C30 alkylaryloxy, C6-C30 arylalkyloxy, C2-C30 heteroaryl, C2-C30 heteroaryloxy.

Particular preference is given to C1-C12 alkyl, C2-C12 alkenyl, C2-C12 alkynyl, C6-C25 aryl and C2-C25 heteroaryl.

Further preferred carbon and hydrocarbon groups are straight-chain, branched or cyclic alkyl having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono- or polysubstituted by F, Cl, Br, I or CN and in which one or more non-adjacent CH2 groups may each be replaced, independently of one another, by -C(R^X)=C(R^X)-, -C=- -N(R^X)-, -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.

R^x preferably denotes H, F, Cl, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- and in which one or more H atoms may be replaced by F or Cl, or denotes an optionally substituted aryl or aryloxy group with 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group with 2 to 30 C atoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoromethyl, perfluoro- n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluorohexyl, etc.

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

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

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

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.

Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from 0, N, S and Se.

Particular preference is given to mono-, bi- or tricyclic aryl groups having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6- or 7-membered aryl and heteroaryl groups, in which, in addition, one or more CH groups may be replaced by N, S or 0 in such a way that 0 atoms and/or S atoms are not linked directly to one another.

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1 , 1 ':3', 1 "]terphenyl-2'-yl, naphthyl, anthracene, binaphthyl, phenanthrene, 9,10-dihydro-phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc.

Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1 ,2,3-triazole, 1 ,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1 ,2-thiazole, 1 ,3-thiazole, 1 ,2,3- oxadiazole, 1 ,2,4-oxadiazole, 1 ,2,5-oxadiazole, 1 ,3,4-oxadiazole, 1 ,2,3- thiadiazole, 1 ,2,4-thiadiazole, 1 ,2,5-thiadiazole, 1 ,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1 ,3,5- triazine, 1 ,2,4-triazine, 1 ,2,3-triazine, 1 ,2,4,5-tetrazine, 1 ,2,3,4-tetrazine, 1 ,2,3,5-tetrazine, or condensed groups, such as indole, isoindole, indolizine, indazole, benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8- quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiophene, benzothiadiazo- thiophene, or combinations of these groups.

The aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

The (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, 0, N, S and Se.

The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e. contain only one ring (such as, for example, cyclohexane), or polycyclic, i.e. contain a plurality of rings (such as, for example, decahydronaphthalene or bicyclooctane). Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 5 to 25 ring atoms, which optionally contain fused rings and are optionally substituted. Preference is furthermore given to 5-, 6-, 7- or 8-membered carbocyclic groups, in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH2 groups may be replaced by -0- and/or -S-.

Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1 ,3-dioxane, 1 ,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as tetrahydronaphthalene, decahydronaphthalene, indane, bicyclo[1 .1 .1 ]- pentane-1 ,3-diyl, bicyclo[2.2.2]octane-1 ,4-diyl, spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl.

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

Preferred substituents, hereinafter also referred to as "L", are, for example, F, Cl, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R^X)₂, -C(=0)Y¹, -C(=O)R^X, -N(R^X)₂, straight-chain or branched alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having 1 to 25 C atoms, in which one or more H atoms may optionally be replaced by F or Cl, optionally substituted silyl having 1 to 20 Si atoms, or optionally substituted aryl having 6 to 25, preferably 6 to 15, C atoms, wherein R^x denotes H, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH2-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that 0- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl, P- or P-Sp-, and

Y¹ denotes halogen.

"Substituted silyl or aryl" preferably means substituted by halogen, -CN, R°, -OR⁰, -CO-R⁰, -CO-O-R⁰, -O-CO-R⁰ or -O-CO-O-R⁰, wherein R° denotes H or alkyl with 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, Cl, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF₃, OCF₃, OCHF2, OC2F5, furthermore phenyl.

For the production of PSA displays, the polymerisable compounds contained in the LC medium are polymerised or crosslinked (if one compound contains two or more polymerisable groups) by in-situ polymerisation in the LC 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 LC medium according to the invention may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, polymerisation initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.

The LC media according to the invention preferably comprise one, two or three chiral dopants, very preferably one chiral dopant.

Particular preference is given to LC media comprising one, two or three polymerisable compounds, also referred to as reactive mesogens (RM).

Preference is furthermore given to LC media that have a chiral nematic LC phase.

Preferably the proportion of polymerisable compounds (RM) in the LC medium is from >0 to < 5%, very preferably from >0 to < 1 %, most preferably from 0.01 to 0.5%.

Preferred embodiments, taken alone or in combination with one another, are listed below. The medium according to the invention preferably comprises

- the compound of formula I in a concentration in the range of from 0.5% to 15%, preferably of 1 % to 10% very preferably from 2% to 7%;

- one, two, three or more compounds of the formula III, preferably of the formula 111-1 and/or HI-2, more preferably of the formula HI-2, in a total concentration in the range of from 2% to 15%, more preferably from 3% to 12%, very preferably from 4% to 10% and in particular from 5% to 8%;

- one or more compounds of the formula HA in a total concentration in the range of from 10% to 40%, more preferably from 15% to 35% and very preferably from 18% to 28% or from 20% to 25%;

- one or more compounds of the formula HA-2 in a total concentration in the range of from 1 % to 12%, more preferably from 2% to 8% and very preferably from 3% to 6%;

- one or more compounds of the formula HA-10 in a total concentration in the range of from 10% to 30%, more preferably from 12% to 25% and very preferably from 15% to 20%; - one or more compounds of the formula I IB , preferably of the formula IIB-2 and/or IIB-10, in a total concentration in the range of from 10% to 30%, more preferably from 12% to 25% and very preferably from 14% to 19%;

- one or more compounds of the formula IIB-2 in a total concentration in the range of from 1 % to 12%, more preferably from 2% to 8% and very preferably from 3% to 6%;

- one or more compounds of the formula IIB-10 in a total concentration in the range of from 5% to 25%, more preferably from 8% to 18% and very preferably from 10% to 15%;

- one or more compounds of formula HA and one or more compounds of formula IIB, preferably selected from the formulae HA, -2, HA-10, IIB-2 and IIB-10, preferably in a total concentration in the range of from 25% to 55%, more preferably from 32% to 50%, and very preferably from 35% to 42%;

- one or more compounds of the formula HA-2 and one or more compounds of the formula IIB-2 in a total concentration in the range of from 3% to 20%, more preferably from 4% to 15% and very preferably from 6% to 11 %;

-one or more compounds of the formula HI and one or more compounds selected from the formulae HA, IIB, HC and HD in a total concentration in the range of from 25% to 65%, more preferably from 35% to 55%, and very preferably from 40% to 50%;

- one or more compounds of the formula IV-1 , preferably the compound IV-1 - 1 , in a total concentration in the range of from 5% to 40%, more preferably from 10% to 30%, and very preferably from 15% to 23%;

- one or more compounds of the formula IV-3, preferably of the formula IV-3- 2 and/or IV-3-5 in a total concentration in the range of from 5% to 25%, more preferably from 10% to 20%, and very preferably from 12% to 16%;

- one or more compounds of the formula I and the compound of the formula IV-3-2 in a total concentration in the range of from 3% to 20%, more preferably of 6% to 15%, and very preferably of 8% to 12%;

- one or more compounds of the formula I and the compound of the formula IV-3-2 and the compounds of the formula IV-1 -1 in a total concentration in the range of from 15% to 45%, more preferably from 22% to 40%, very preferably from 26% to 34%, and in particular from 28% to 32%;

- the compound of the formula IV-3-6, in a total concentration in the range of from 0% to 5%, preferably 0%; - one or more compounds of the formula I and one or more compounds selected from the formulae IV and IVa in a total concentration in the range of from 20% to 50%, more preferably from 28% to 45%, and very preferably from 33% to 40%;

- one or more compounds of the formula I and one or more compounds selected from the formulae IV and IVa and one or more compounds of formula V in a total concentration in the range of from 35% to 60%, more preferably from 38% to 52%, and very preferably from 40% to 48%;

- one or more compounds of the formula IVa and/or IVb in a total concentration in the range of from 5% to 18%, more preferably from 7% to 15%, very preferably from 8% to 13%;

- one or more compounds of the formula V, preferably of the formula V-16, in a total concentration in the range of from 1 % to 12%, more preferably from 2% to 10%, still more preferably from 3% to 10% and very preferably from 4% to 8%.

Particularly preferred mixture concepts are indicated below: (the acronyms used are explained in Tables A-D. n and m here each, independently of one another, denote 1-6).

The mixtures according to the invention preferably comprise

- PYP-n-m, in particular PYP-2-3 and/or PYP-2-4, preferably in concentrations > 5%, in particular 8-30%, based on the mixture as a whole, and/or

- CPY-n-Om, in particular CPY-2-02, CPY-3-02 and/or CPY-5-02, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole, and/or

- B-nO-Om and/or B(S)-nO-Om, preferably in concentrations of 1-15, and/or

- CY-n-Om, preferably CY-3-02, CY-3-04, CY-5-02 and/or CY-5-04, preferably in concentrations > 5%, in particular 15-50%, based on the mixture as a whole, and/or

- CCY-n-Om, preferably CCY-4-02, CCY-3-02, CCY-3-03, CCY-3-O1 and/or CCY-5-02, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole, and/or

- CLY-n-Om, preferably CLY-2-04, CLY-3-02 and/or CLY-3-03, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole, and/or

- LY-n-Om, preferably LY-3-02, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole, and/or

- CCOY-n-Om, preferably CCOY-3-O2, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole, and/or

- CLOY-n-Om, preferably CLOY-3-O2, preferably in concentrations > 5%, in particular 10-30%, based on the mixture as a whole,

- CK-n-F, preferably CK-3-F, CK-4-F and/or CK-5-F, preferably > 5%, in particular 5-25%, based on the mixture as a whole and/or

- at least two compounds of the formula PY-n-Om, preferably PY-1-O2 and PY-3-02.

Preference is furthermore given to mixtures according to the invention which comprise the following mixture concepts:

(n and m each, independently of one another, denote 1-6.)

- CPY-n-Om and CY-n-Om, preferably in concentrations of 10-80%, based on the mixture as a whole, and/or

- CPY-n-Om and CK-n-F, preferably in concentrations of 10-70%, based on the mixture as a whole, and/or

- CPY-n-Om and PY-n-Om, preferably CPY-2-02 and/or CPY-3-02 and PY- 3-02, preferably in concentrations of 10 - 40%, based on the mixture as a whole, and/or

- CPY-n-Om and CLY-n-Om, preferably in concentrations of 10-80%, based on the mixture as a whole, and/or

- CC-3-V1 , preferably in amounts of 3 - 15% and/or

- PGIY-n-Om, preferably in amounts of 3 - 15%, and/or

- CC-n-2V1 , preferably in amounts of 3 - 20%.

It is advantageous for the liquid-crystalline medium according to the invention to preferably have a nematic phase from < -20°C to > 70°C, particularly preferably from < -30°C to > 71 °C, very particularly preferably from < -40°C to > 72°C.

In a preferred embodiment, the medium according to the invention has a clearing temperature of 70°C or more, more preferably of 72°C or more, and in particular of 73°C more.

Herein, the expression "to have a nematic phase" at a given temperature means that no smectic phase and no crystallisation is observed at low temperatures and on the other hand that clearing (phase transition to the isotropic phase) does not occur on heating of a nematic phase at a given temperature. The investigation at low temperatures is carried out in a flow viscometer at the corresponding temperature and checked by storage in test cells having a layer thickness corresponding to the electro-optical use for at least 100 hours. If the storage stability at a temperature of -20°C in a corresponding test cell is 1000 h or more, the medium is referred to as stable at this temperature. At temperatures of -30°C and -40°C, the corresponding times are 500 h and 250 h respectively. At high temperatures, the clearing point is measured by conventional methods in capillaries.

The liquid-crystal mixture preferably has a nematic phase range of at least 60 K and a flow viscosity V20 of at most 30 mm² • s’¹ at 20°C.

The mixture is nematic at a temperature of -20°C or less, preferably at -30°C or less, very preferably at -40°C or less.

The medium according to the invention has a birefringence in the range of from 0.085 to 0.120, preferably from 0.095 to 0.115, in particular from 0.100 to 0.110. ln a preferred embodiment, the medium has a birefringence in the range of from 0.1005 to 0.1080, preferably from 0.1020 to 0.1075, in particular from 0.1035 to 0.1060.

In a preferred embodiment, the medium according to the invention has a dielectric anisotropy As of -2.4 to -5.0, preferably of -2.6 to -4.5, in particular -2.7 to -4.0.

In a very preferred embodiment, the liquid-crystal mixture according to the invention has a dielectric anisotropy As of -2.9 to -3.3.

The rotational viscosity yi at 20°C is preferably in the range of from 70 to 200 mPas, more preferably from 90 to 150 mPa s.

The rotational viscosity yi at 20°C is preferably 100 mPas or less.

The medium according to the invention has an elastic constant Ki in the range of from 12 to 16 pN.

In a preferred embodiment, the medium according to the invention has a ratio of the rotational viscosity to the splay elastic constant yi I Ki of 7.2 mPa-s pN’ ¹ or less.

In a preferred embodiment, the medium according to the invention has a ratio of the rotational viscosity to the splay elastic constant yi I Ki in the range of from 6.6 mPa-s pN’¹ to 7.4 mPa-s pN’¹ , more preferably from 6.9 mPa-s pN’¹ to 7.2 mPa s pN’¹.

The liquid-crystal media according to the invention have relatively low values for the threshold voltage (Vo). They are preferably in the range from 1 .7 V to 3.0 V, particularly preferably < 2.6 V and very particularly preferably < 2.4 V.

For the present invention, the term "threshold voltage" relates to the capacitive threshold (Vo), also called the Freedericks threshold, unless explicitly indicated otherwise. ln addition, the liquid-crystal media according to the invention have high values for the voltage holding ratio in liquid-crystal cells.

In general, liquid-crystal media having a low addressing voltage or threshold voltage exhibit a lower voltage holding ratio than those having a higher addressing voltage or threshold voltage and vice versa.

For the present invention, the term "dielectrically positive compounds" denotes compounds having a As > 1 .5, the term "dielectrically neutral compounds" denotes those having -1 .5 < As < 1 .5 and the term "dielectrically negative compounds” denotes those having As < -1 .5. The dielectric anisotropy of the compounds is determined here by dissolving 10 % of the compounds in a liquid-crystalline host and determining the capacitance of the resultant mixture in at least one test cell in each case having a layer thickness of 20 pm with homeotropic and with homogeneous surface alignment at 1 kHz. The measurement voltage is typically 0.5 V to 1 .0 V, but is always lower than the capacitive threshold of the respective liquid-crystal mixture investigated.

All temperature values indicated for the present invention are in °C.

The mixtures according to the invention are suitable for all VA-TFT applications, such as, for example, VAN, MVA, (S)-PVA, ASV, PSA (polymer sustained VA) and PS-VA (polymer stabilized VA). They are furthermore suitable for IPS (in-jolane switching) and FFS (fringe field switching) applications having negative As.

It goes without saying for the person skilled in the art that the VA, IPS or FFS mixture according to the invention may also comprise compounds in which, for example, H, N, O, Cl and F have been replaced by the corresponding isotopes.

The compounds according to the present invention can be synthesized by or in analogy to known methods described in the literature (for example in the standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), under reaction conditions which are known and suitable for said reactions. Use may also be made here of variants which are known per se, but are not mentioned here. In particular, they can be prepared as described in or in analogy to the following reaction schemes. Further methods for preparing the inventive compounds can be taken from the examples.

Other mesogenic compounds which are not explicitly mentioned above can optionally and advantageously also be used in the media in accordance with the present invention. Such compounds are known to the person skilled in the art.

For the present invention and in the following examples, the structures of the liquid-crystal compounds are indicated by means of acronyms, with the transformation into chemical formulae taking place in accordance with Tables A to C below. All radicals C_mH2m+i, C_nH2n+i, and C1H21+1 or C_mH2m-i, C_nH2n-i and C1H21-1 are straight-chain alkyl radicals or alkylene radicals, in each case having n, m and I C atoms respectively. Preferably n, m and I are independently of each other 1 , 2, 3, 4, 5, 6, or 7. Table A shows the codes for the ring elements of the nuclei of the compound, Table B lists the bridging units, and Table C lists the meanings of the symbols for the left- and righthand end groups of the molecules. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

Table A: Ring elements

Table B: Bridging units

E -CH2-CH2-

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

Apart from the compounds of formula I, HA, IIB, IIC and/or HD, IVa, IVb and V, the mixtures according to the invention optionally comprise one or more compounds of the compounds listed in Table D.

The following abbreviations are used:

(n, m, k and I are, independently of one another, each an integer, preferably 1 to 9 preferably 1 to 7, k and I possibly may be also 0 and preferably are 0 to 4, more preferably 0 or 2 and most preferably 2, n preferably is 1 , 2, 3, 4 or 5, in the combination “-nO-” it preferably is 1 , 2, 3 or 4, preferably 2 or 4, m preferably is 1 , 2, 3, 4 or 5, in the combination “-Om” it preferably is 1 , 2, 3 or

4, more preferably 2 or 4. The combination “-IVm” preferably is “2V1”.)

B(S)-(c5)nO-Om

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

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

Table F

Table F shows example compounds which can preferably be used as reactive mesogenic compounds in the LC media in accordance with the present invention. If the mixtures according to the invention comprise one or more reactive compounds, they are preferably employed in amounts of 0.01-5% by weight. It may also be necessary to add an initiator or a mixture of two or more initiators for the polymerisation. The initiator or initiator mixture is preferably added in amounts of 0.001-2% by weight, based on the mixture. A suitable initiator is, for example, Irgacure (BASF) or Irganox (BASF).

RM-121

ln 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-1 to RM-102. Media of this type are suitable, in particular, for PS-FFS and PS-IPS applications. Of the reactive mesogens shown in Table D, compounds RM-1 , RM-2, RM-3, RM-4, RM-5, RM-9, RM-17, RM-42, RM-48, RM-68, RM-87, RM-91 , RM-98, RM-99 and RM-101 are particularly preferred.

The reactive mesogens or the polymerisable compounds of the formula M and of the formulae RM-1 to RM-102 are furthermore suitable as stabilisers. In this case, the polymerisable compounds are not polymerised, but instead are added to the liquid-crystalline medium in concentrations > 1 %.

Examples

The present invention is illustrated in detail by the following non-restrictive working examples.

The following abbreviations and symbols are used:

Vo threshold voltage, capacitive [V] at 20°C, n_e extraordinary refractive index at 20°C and 589 nm, n₀ ordinary refractive index at 20°C and 589 nm,

An optical anisotropy at 20°C and 589 nm, s± dielectric permittivity perpendicular to the director at 20°C and 1 kHz, sll dielectric permittivity parallel to the director at 20°C and 1 kHz,

As dielectric anisotropy at 20°C and 1 kHz, cl.p., T(N, I) clearing point [°C], yi rotational viscosity at 20°C [mPa-s], Ki elastic constant, "splay" deformation at 20°C [pN],

K₂ elastic constant, "twist" deformation at 20°C [pN],

K3 elastic constant, "bend" deformation at 20°C [pN],

Unless explicitly noted otherwise, all concentrations in the present application are quoted in per cent by weight and relate to the corresponding mixture as a whole, comprising all solid or liquid-crystalline components, without solvents.

Unless explicitly noted otherwise, all temperature values indicated in the present application, such as, for example, for 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), are quoted in degrees Celsius (°C). M.p. denotes melting point, cl.p. = clearing point. Furthermore, C = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols represent the transition temperatures.

All physical properties are and have been 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, and An is determined at 589 nm and As at 1 kHz, unless explicitly indicated otherwise in each case.

The term "threshold voltage" for the present invention relates to the capacitive threshold (Vo), also known as the Freedericks threshold, unless explicitly indicated otherwise. In the examples, the optical threshold may also, as generally usual, be quoted for 10% relative contrast (V10).

Unless stated otherwise, methods of preparing test cells and measuring their electrooptical and other properties are carried out by the methods as described hereinafter or in analogy thereto.

The display used for measurement of the capacitive threshold voltage consists of two plane-parallel glass outer plates with a distance of 25 pm, each of which has on the inside an electrode layer and an unrubbed polyimide alignment layer on top, which effect homeotropic alignment of the liquid-crystal molecules. llnless indicated otherwise, the VHR is determined at 20°C (VHR20) and after 5 minutes in an oven at 100°C (VHR100) in a commercially available instrument Model LCM-1 (00004) from TOYO Corporation, Japan. The voltage used has a frequency of in a range from 1 Hz to 60 Hz, unless indicated more precisely.

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 2.0 h, unless explicitly indicated, without additional heating. The irradiation power in the wavelength range from 300 nm to 800 nm is 765 W / m² V. A UV "cut-off" filter having an edge wavelength of 310 nm 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.

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 1 g of the material, are stored at one or more given temperatures, typically of - 10°C, -20°C, -30°C and/or -40°C 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 time is noted. The time until the last inspection, at which no change has been observed, is noted as the respective LTS.

The ion density from which the resistivity is calculated is measured using the commercially available LC Material Characteristics Measurement System Model 6254 from Toyo Corporation, Japan, using VHR test cells with AL16301 Polyimide (JSR Corp., Japan) having a 3.2pm cell gap. The measurement is performed after 5 min of storage in an oven at 60 °C or 100 The Clearing point is measured using the Mettler Thermosystem FP900. The optical anisotropy (An) is measured using an Abbe Refractometer H005 (Natrium-spectral lamp Na10 at 589nm, 20 °C). The dielectric anisotropy (As) is measured using an LCR-Meter E4980A/Agilent (G005) at 20°C (s-parallel- cells with JALS 2096-R1 ). The turn on voltage (Vo) is measured using an LCR-Meter E4980A/Agilent (G005) at 20°C (s-parallel-cells with JALS 2096- R1 ). The rotational viscosity (yi) is measured using a TOYO LCM-2 (0002) at 20°C (gamma 1 negative cells with JALS-2096-R1 ). The elastic constant (Ki , splay) is measured using an LCR-Meter E4980A/Agilent (G005) at 20°C (s parallel-cells with JALS 2096-R1 ). K3: The elastic constant (K3, bend) is measured using an LCR-Meter E4980A/Agilent (G005) at 20°C (s-parallel- cells with JALS 2096-R1 ).

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.

Mixture Examples

The nematic LC host mixtures M1 to M9 have the composition and physical properties given in the following tables:

Mixture M1

CP P-3-2 6.0 % T(N,I) [°C]: 74.5

CC-3-V1 8.0 % An (589 nm, 20°C): 0.1035

CC-3-V2 6.0 % n_e (20°C, 589.3 nm):

CCH-13 18.5 % n₀ (20°C, 589.3 nm):

CCH-24 3.0 % As (1 kHz, 20°C): -3.0

CCY-3-01 8.0 % sii (1 kHz, 20°C): 3.4

CCY-3-02 10.0 % s± (1 kHz, 20°C): 6.5

CPY-2-02 2.0 % Ki [pN], (20°C): 14.0

CPY-3-02 10.0 % K3 [pN], (20°C): 15.6

CY-3-02 4.5 % n [mPa-s], (20°C): 98 PCH-301 11.0 % Vo [V], (20°C): 2.39

PY-1-02 4.5 % LTS [h] (bulk, -20°C) 1000

PGIY-2-04 2.0 %

B(S)2O-O5 3.5 %

B(S)2O-O4 3.0 %

L 100.0 %

Mixture M2

BCH-32 6.0 % T₍N,I) [°C]: 74

CC-3-V1 8.0 % An (589 nm, 20°C): 0.1041

CC-3-V2 6.0 % n_e (20°C, 589.3 nm):

CCH-13 18.5 % n₀ (20°C, 589.3 nm):

CCH-24 4.0 % As (1 kHz, 20°C): -3.0

CCY-3-01 8.0 % SII (1 kHz, 20°C): 3.4

CCY-3-02 9.0 % s± (1 kHz, 20°C): 6.4

CPY-2-02 2.0 % Ki [pN], (20°C): 13.8

CPY-3-02 10.0 % K3 [pN], (20°C): 15.1

CY-3-02 4.5 % yi [mPa-s], (20°C): 97

PCH-301 10.0 % Vo [V], (20°C): 2.37

PY-1-02 4.5 % LTS [h] (bulk, -20°C) 1000

PGIY-2-04 3.0 %

B(S)2O-O5 3.5 %

B(S)2O-O4 3.0 %

L 100.0 %

Mixture M3

BCH-32 6.0 % T₍N,I) [°C]: 74

CC-3-V1 8.0 % An (589 nm, 20°C): 0.1042

CC-3-V2 6.0 % n_e (20°C, 589.3 nm):

CCH-13 18.5 % n₀ (20°C, 589.3 nm):

CCH-24 3.0 % As (1 kHz, 20°C): -3.1

CCY-3-01 8.0 % SII (1 kHz, 20°C): 3.5

CCY-3-02 9.0 % s± (1 kHz, 20°C): 6.6

CPY-2-02 3.0 % Ki [pN], (20°C): 13.8 CPY-3-02 10.0 % K3 [pN], (20°C): 15.1

CY-3-02 4.5 % yi [mPa-s], (20°C): 98

CP-3-01 10.0 % Vo [V], (20°C): 2.33

PY-1-02 3.5 % LTS [h] (bulk, -20°C) 1000

PGIY-2-04 3.0 %

B(S)2O-O5 3.5 %

B(S)2O-O4 3.0 %

Y-4O-O4 1.0 %

L 100.0 %

Mixture M4 contains the compound B(S)-2O-O1 (c5)

Mixture M4

BCH-32 6.0 % T(N,I) [°C]: 73.5

CC-3-V1 8.0 % An (589 nm, 20°C): 0.1041

CC-3-V2 6.0 % n_e (20°C, 589.3 nm):

CCH-13 18.5 % n₀ (20°C, 589.3 nm):

CCH-24 3.0 % As (1 kHz, 20°C): -3.1

CCY-3-O1 8.0 % SII (1 kHz, 20°C):

CCY-3-02 9.0 % s± (1 kHz, 20°C):

CPY-2-02 3.0 % Ki [pN], (20°C): 13.9

CPY-3-02 10.0 % K3 [pN], (20°C): 15.1

CY-3-02 4.5 % yi [mPa-s], (20°C): 101

PCH-301 10.0 % Vo [V], (20°C): 2.33

PY-1-O2 3.5 % LTS [h] (bulk, -20°C) 1000

PGIY-2-04 3.0 %

B(S)-2O-O1 (c5) 3.5 %

B(S)2O-O4 3.0 %

Y-4O-O4 1.0 %

S 100.0 % Mixture M5 contains the following compound CPY-(c3)2-O2:

Mixture M5

BCH-32 6.0 % T(N,I) [°C]: 72.5

CC-3-V1 8.0 % An (589 nm, 20°C): 0.1036

CC-3-V2 6.0 % As (1 kHz, 20°C): -2.9

CCH-13 18.5 % yi [mPa-s], (20°C): 101

CCH-24 4.0 %

CCY-3-01 8.0 %

CCY-3-02 9.0 %

CPY-2-02 4.0 %

CPY-(c3)2-O2 8.0 %

CY-3-02 4.5 %

PCH-301 10.0 %

PY-1-02 4.5 %

PGIY-2-04 3.0 %

B(S)2O-O5 3.5 %

B(S)2O-O4 3.0 %

S 100.0 %

Mixture M6

Mixture M6 consists of 98.87 % of mixture M1 , 0.03 % of the compound ST-

3a-1 and 0.10% of the compound H-1-1

Mixture M7

Mixture M7 consists of 98.965 % of mixture M1 , 0.03 % of the compound ST- 3a-1 and 0.005% of the compound H-1-1

Mixture M8

BCH-32 7.0 % T₍N,I) [°C]: 73.5

CC-3-V1 7.0 % An [589 nm, 20°C]: 0.1040

CC-3-V2 7.0 % sii [1 kHz, 20°C]: 3.5

CCH-13 20.0 % s± [1 kHz, 20°C]: 6.6 CCH-24 0.5 % As [1 kHz, 20°C]: -3.2

CCY-3-1 6.0% Ki [pN,20°C]: 14.1

CCY-3-02 10.5% K3[pN,20°C]: 15.8

CPY-2-02 6.0 % Vo [V, 20°C]: 2.36

CPY-3-02 11.5% yi [mPa s, 20°C]: 104

CY-3-02 11.5% LTS bulk [h, -20°C]: 1000

PCH-3-01 4.0 % LTS bulk [h, -30°C]: 696

PY-1-02 5.5%

PGIY-2-04 1.0%

B(S)-2O-O5 2.5 %

S 100.0%

Mixture M9

CPP-3-2 1.0% T₍N,I)[°C]: 75

CC-3-V1 7.0% An [589 nm, 20°C]: 0.1044

CC-3-V2 7.0 % s|| [1 kHz, 20°C]: 3.4

CC-1-3 22.0% s± [1 kHz, 20°C]: 6.6

CC-2-4 2.0 % As [1 kHz, 20°C]: -3.2

CCY-3-1 10.5% Ki [pN,20°C]: 14.7

CCY-3-02 10.0% K3[pN,20°C]: 15.9

CPY-2-02 9.5 % Vo [V, 20°C]: 2.37

CPY-3-02 12.0% yi [mPa s, 20°C]: 103

CP-3-01 5.0% LTS bulk [h, -20°C]: 1000

PY-1-02 8.5%

PY-2-02 2.0 %

B(S)-2O-O5 3.5 %

S 100.0%

Mixture M10

B(S)-2O-O4 5.0 % T₍N,I) [°C]: 74

B(S)-2O-O5 5.0 % An [589 nm, 20°C]: 0.1120

B(S)-2O-O6 0.5 % 8|| [1 kHz, 20°C]: 3.6

CCY-3-02 11.0% s± [1 kHz, 20°C]: 6.7

CPY-2-02 12.0% As [1 kHz, 20°C]: -3.1 CPY-3-02 2.0% Ki [pN,20°C]: 15.4

PYP-2-3 2.5% K3[pN,20°C]: 14.9

CC-3-V1 8.0 % Vo [V, 20°C]: 2.32

CC-4-V1 20.0 %

CCH-25 2.0 %

CCH-301 18.0%

PP-1-2V1 8.0%

PY-1-O2 6.0%

S 100.0%

Mixture Example P3

Mixture example P3 consists of 99.595% of Mixture M3, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

Mixture M11

PCH-302 16.0% T₍N,I) [°C]: 75.5

CCH-34 11.0% An [589 nm, 20°C]: 0.1125

CCH-25 5.0 % 8|| [1 kHz, 20°C]: 3.7

COY-3-O2 11.0% s± [1 kHz, 20°C]: 7.5

CCOY-2-O2 5.0 % As [1 kHz, 20°C]: -3.8

CCOY-3-O2 5.0 % yi [mPa s, 20°C]: 137

CCOY-4-O2 4.0 % Ki [pN,20°C]: 15.7

PP-1-5 8.0% K3[pN,20°C]: 16.5

BCH-32 5.0 % V₀[V, 20°C]: 2.17

BCH-52 3.0 % LTS bulk [h, -20°C]: 1000

CCP-3-1 6.0 % LTS bulk [h, -30°C]: 1000

CPY-3-02 10.0%

B(S)-2O-O5 4.0 %

B(S)-2O-O4 3.0 %

CY-3-02 4.0 %

100.0%

Mixture M12

PCH-302 17.0% T₍N,I) [°C]: 75.5

CCH-34 11.0% An [589 nm, 20°C]: 0.1126 CCH-25 7.0% 4.1

COY-3-O2 4.0% 8.1

CCOY-2-O2 4.0 % -4.0

CCOY-3-O2 3.0% 146 CCOY-4-O2 6.5% 15.6

PP-1-5 5.0% 15.6

BCH-32 3.0 %

2.08

CPY-2-02 7.0% LTS bulk [h, -20°C]: 1000

CPY-3-02 12.0% LTS bulk [h, -30°C]: 1000 B(S)-2O-O4 3.0%

B(S)-2O-O5 4.0 %

CLP-3-T 3.0 %

CY-3-02 10.5%

S 100.0%

Mixture M13 B(S)-2O-O4 2.0 % T₍N,I) [°C]: 74.5

B(S)-2O-O5 2.0% An [589 nm, 20°C]: 0.1026 CC-3-V1 8.0 % s|| [1 kHz, 20°C]: 3.3

CC-4-V1 20.0 % s± [1 kHz, 20°C]: 6.3

CCH-24 3.5 % As [1 kHz, 20°C]: -3.0

CCH-25 2.5 % yi [mPa s, 20°C]: 98

CCH-301 0.5% Ki [pN,20°C]: 15.3 CCH-34 4.5% K3 [pN, 20°C]: 16.0

CCH-35 1.0% V₀[V, 20°C]: 2.46

CCY-3-02 10.0% LTS bulk [h, -20°C]: 1000

CPY-2-02 7.5 %

CPY-3-02 9.5 % CY-3-02 15.5%

CY-3-04 2.0 %

PCH-302 4.0 %

PP-1-2V1 7.5% s 100.0% Mixture M14

BCH-32 6.0 % T₍N,I) [°C]: 74

CC-3-V1 8.0% An [589 nm, 20°C]: 0.1042

CC-3-V2 6.0 % s|| [1 kHz, 20°C]: 3.5 CCH-13 18.5% s± [1 kHz, 20°C]: 6.6

CCH-24 3.0% As [1 kHz, 20°C]: -3.1

CCY-3-01 8.0 % yi [mPa s, 20°C]: 98

CCY-3-02 9.0% Ki [pN,20°C]: 13.8

CPY-2-02 3.0% K3[pN,20°C]: 15.1 CPY-3-02 10.0% Vo[V, 20°C]: 2.33

CY-3-02 4.5% LTS bulk [h, -20°C]: 1000

PCH-301 10.0%

PY-1-02 3.5%

PGIY-2-04 3.0 % B(S)-2O-O5 3.5%

B(S)-2O-O4 3.0 %

Y-4O-O4 1.0%

S 100.0%

Mixture M15

BCH-32 6.0 % T₍N,I) [°C]: 74.5

CC-3-V1 8.0% An [589 nm, 20°C]: 0.1040

CC-3-V2 6.0 % s|| [1 kHz, 20°C]: 3.5 CCH-13 18.5% s± [1 kHz, 20°C]: 6.6

CCH-24 3.0% As [1 kHz, 20°C]: -3.1

CCY-3-01 8.0 % yi [mPa s, 20°C]: 98

CCY-3-02 9.0% Ki [pN,20°C]: 13.9

CPY-2-02 3.0% K3[pN,20°C]: 15.3 CPY-3-02 10.5% Vo [V, 20°C]: 2.34

CY-3-02 4.0% LTS bulk [h, -20°C]: 1000

PCH-301 10.5%

PY-1-02 3.5%

PGIY-2-04 2.5 % B(S)-2O-O5 3.5 %

B(S)-2O-O4 3.0 % Y-4O-O4 1.0%

S 100.0%

Mixture M16

CC-3-V1 7.5 % T₍N,I) [°C]: 73.5

CC-4-V1 20.5 % An [589 nm, 20°C]: 0.0989

CCH-24 9.0 % s|| [1 kHz, 20°C]: 3.6

CCP-3-1 10.5% s± [1 kHz, 20°C]: 6.9

CCY-3-01 7.0 % As [1 kHz, 20°C]: -3.3

CCY-3-02 11.5 % yi [mPa s, 20°C]: 94

CY-3-02 12.0% Ki [pN,20°C]: 14.9

B(S)-2O-O5 4.0% K3[pN,20°C]: 15.3

B(S)-2O-O4 3.0 % Vo [V, 20°C]: 2.27

PP-1-3 3.5% LTS bulk [h, -20°C]: 1000

PY-1-02 8.0% LTS bulk [h, -30°C]: >672

PY-2-02 3.5 %

S 100.0%

Mixture M17

CCP-V-1 12.0% T(N,I) [°C]: 74

CCP-V2-1 6.0 % An [589 nm, 20°C]: 0.1039

CCY-4-02 12.0% 8|| [1 kHz, 20°C]: 3.6

CPY-2-02 9.5 % s± [1 kHz, 20°C]: 6.5

B(S)-2O-O4 0.5 % As [1 kHz, 20°C]: -2.9

CC-3-V1 11.0% yi [mPa s, 20°C]: 98

CC-4-V1 3.0 % Ki [pN,20°C]: 13.2

CCH-24 4.0 % K3[pN,20°C]: 14.9

CCH-35 6.5 % Vo [V, 20°C]: 2.39

CY-3-02 10.0% LTS bulk [h, -20°C]: 1000

PCH-301 9.0 %

PY-1-02 10.0%

PY-2-02 6.5 %

100.0%

In order to improve the reliability, the mixtures according to Examples M11 to M36 may additionally be stabilised with one, two or three stabilisers selected from the group of compounds a) to h) mentioned below, where the stabiliser is in each case added in amounts of 0.01 - 0.04%, based on the total mixture.

Polymerisable Mixture Examples

Mixture Example P1

Mixture example P1 consists of 99.595% of Mixture M1 , 0.40% of the compound RM-1

Mixture Example P2 Mixture example P2 consists of 99.595% of Mixture M2, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

Mixture Example P3

Mixture Example P4

Mixture example P4 consists of 99.595% of Mixture M4, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

Mixture Example P5

Mixture example P5 consists of 99.595% of Mixture M5, 0.40% of the compound RM-1 and 0.005% of the compound ST-3a-1.

Mixture Example P6

Mixture example P6 consists of 99.595% of Mixture M1 , 0.40% of the compound RM-19 and 0.005% of the compound ST-3a-1.

Mixture Example P7

Mixture example P7 consists of 99.595% of Mixture M2, 0.40% of the compound RM-19 and 0.005% of the compound ST-3b-1

ST-3b-1

Mixture Example P8

Mixture example P8 consists of 99.595% of Mixture M3, 0.40% of the compound RM-35

Mixture Example P9

Mixture example P9 consists of 99.595% of Mixture M4, 0.40% of the compound RM-156

RM-156

and 0.005% of the compound ST-3a-1 .

Mixture Example P10

Mixture example P10 consists of 99.595% of Mixture M5, 0.40% of the compound RM-157

RM-157

and 0.005% of the compound ST-3b-1 .

Claims

Patent Claims A liquid crystal medium comprising a) one or more compounds of formula I

in which

R¹ denotes n-butyl or n-pentyl; b) one or more compounds selected from the group of the formulae HA,

in which

R^2A, R^2B, R^2C and R^2D each, independently of one another, denote H, an alkyl radical having 1 to 7 C atoms or an alkenyl radical having 2 to 7 C atoms, each of which is unsubstituted, or at least monosubstituted by halogen, where one or more CH2 groups in these radicals may be replaced

in such a way that 0 atoms are not linked directly to one another;

L¹ and L² each, independently of one another, denote F, Cl, CF3 or CHF2;

Y denotes H, F, Cl, CF₃, CHF₂ or CH₃;

Z², Z^2B and Z^2D each, independently of one another, denote a single bond, -CH2CH2-, , -CF2O-, -OCF2-, -CH2O-, -OCH2-, -COO- -OCO-; p denotes 0, 1 or 2; q denotes 0 or 1 and v denotes 1 , 2, 3, 4, 5, or 6; and c) one or more compounds of formula III

R³¹ and R³², each, independently of one another, denote H, an alkyl or alkoxy radical having 1 to 7 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one

-C=C-, -CF2O-, -OCF2-, -CH=CH- by -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,

A³ on each occurrence, independently of one another, denotes a 1 ,4- phenylene radical, in which one or two CH groups may be replaced by N, or a 1 ,4-cyclohexylene or 1 ,4-cyclohexenylene radical, in which one or two non-adjacent CH2 groups may be replaced by -0- or -S-, where the radicals may be mono- or polysubstituted by halogen atoms,

Z³ on each occurrence independently of one another denotes -CF2O- , - OCF2-, -CH2O-, -OCH2-, -CH2-, -CH2CH2-, -CH=CH- -C°C- or a single bond, - 166 -

L³¹ and L³², each, independently of one another, denote F, Cl, CF3 or CHF₂,

W denotes O or S, and n denotes 0, 1 or 2.

2. The liquid crystal medium according to claim 1 , wherein the medium comprises one or more compounds of formula IIB-2

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and (0) denotes an oxygen atom or a single bond.

3. The liquid crystal medium according to claim 2, wherein the medium comprises one or more compounds of formula IIB-2, in which alkyl denotes methyl or propyl and alkyl* denotes ethyl.

4. The liquid crystal medium according to one or more of claims 1 to 3, wherein the medium comprises one or more compounds of formula IV-3,

in which alkyl denotes an alkyl radical having 1 to 7 C atoms, and alkenyl denotes

5. The liquid crystal medium according to one or more of claims 1 to 4, wherein the medium comprises one or more compounds of the formula IV-

in which alkyl and alkyl’, identically or differently, denote alkyl having 1 to 7 C atoms, in a total amount in the range of from 1 % to 30%, where the compounds of formula I are excluded. - 167 - The liquid crystal medium according to claim 5, in which alkyl in formula IV-1 denotes methyl and alkyl’ denotes n-propyl. The liquid crystal medium according to one or more of claims 1 to 6, wherein the medium comprises one or more compounds of the formula

in which

R⁴¹ and R⁴² each, independently of one another, denote a straightchain alkyl, alkoxy, alkenyl, alkoxyalkyl or alkoxy radical having up to 12 C atoms, and

Z⁴ denotes a single bond, -CH2CH2-, -CH=CH- -CF2O-, -OCF2-, -CH2O-, - OCH2-,

-COO-, -OCO-, -C2F4-, -C4H8- or -CF=CF- The liquid crystal medium according to one or more of claims 1 to 7, wherein the medium comprises one or more compounds of the formula V

in which

Z⁵¹, Z⁵² each, independently of one another, denote -CH2-CH2-, -CH2-O- -CH=CH-, -C=C-, -COO- or a single bond, and n is 1 or 2.

9. The liquid crystal medium according to one or more of claims 1 to 8, wherein the medium comprises one or more compounds of formula VI

in which R⁶ and R⁶² have the meanings of R^2A defined in claim 1 and R⁶² alternatively denotes F, Cl, CF3 or OCF3 and

L⁶¹ , L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ independently denote H or F, where at least one of L⁶¹, L⁶², L⁶³, L⁶⁴, L⁶⁵, and L⁶⁶ denotes F.

10. The liquid crystal medium according to one or more of claims 1 to 9, wherein the medium comprises one or more compounds of formula P1 to P4

R^p denotes a straight-chain alkyl or alkoxy radical having 1-6 C atoms or an alkenyl radical having 2-6 C atoms

X^p straight-chain alkyl having 1-6 C atoms, F, Cl, CF3, OCF2H, OCF3,

OCHFCF3, OCF2CHFCF3 or OCH=CF₂

L^P1, L^P2 and L^P3 each independently of one another denote H or F. . The liquid crystal medium according to one or more of claims 1 to 10, wherein the medium comprises one or more compounds selected from the following group of compounds of the formula

wherein the parameters are as defined in Claims 1 , 8 and 9 and alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms, (O)alkyl* or (O)-alkyl denotes alkyl* or O-alkyl* m denotes 0, 1 , 2, 3, 4, 5 or 6

R has the meanings of R^2A in formula HA

R¹¹ and R¹² each, independently of one another, have one of the meanings given for R^2A in formula HA

L¹ and L², each, independently of one another, denote F or Cl

L³ denotes H or CH3

(0) denotes 0 or a single bond

R^IIIA denotes alkyl or alkenyl having up to 7 C atoms or a group Cy-C_mH₂m+i m and n are, identically or differently, 0, 1 , 2, 3, 4, 5 or 6,

Cy denotes a cycloaliphatic group having 3, 4 or 5 ring atoms, which is optionally substituted with alkyl or alkenyl each having up to 3 C atoms, or with halogen or CN.

. The liquid crystal medium according to one or more of claims 1 to 11 , wherein the medium comprises one or more compounds of the formula H H

in which

Ar denotes an aromatic or heteroaromatic hydrocarbon group having 4 to 40 C atoms;

Sp denotes a spacer group;

R^s denotes H, alkyl having 1 to 12 C atoms or alkenyl having 2 to 12 C atoms; single bond;

R^S1 , R^S2, R^S3 and R^S4, identically or differently, denote alkyl having 1 to 6 C atoms;

G denotes H or R^s or a group Z^S-HA; z is an integer from 1 to 6; and q is 3 or 4. . The liquid crystal medium according to one or more of claims 1 to 12, wherein the medium comprises one or more additives selected from the group of dyes, dopants and reactive mesogens. . A liquid crystal display comprising the liquid crystal medium according to one or more of claims 1 to 13. . The display according to claim 14, wherein the display is a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS display. . Use of the liquid crystal medium according to one or more of claims 1 to

13 in a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS display.

. Use of the liquid crystal medium according to one or more of claims 1 to 13 for energy-saving LC displays. . A process of preparing a liquid crystal medium according to any one of claims 1 to 13, comprising the steps of mixing one or more compounds of the formulae I and III and preferably with one or more compounds selected from the formulae HA, I IB, IIC and HD, and optionally with one or more reactive mesogens, and optionally with further LC compounds and/or additives.