WO2023066953A1

WO2023066953A1 - Liquid-crystal medium comprising polymerizable compounds

Info

Publication number: WO2023066953A1
Application number: PCT/EP2022/079014
Authority: WO
Inventors: Timo Uebel; Rocco Fortte; Qiong TONG; Chia-Sheng Hsieh; Yinghua Huang; Leo WEEGELS
Original assignee: Merck Patent Gmbh
Priority date: 2021-10-20
Filing date: 2022-10-19
Publication date: 2023-04-27
Also published as: TW202328407A

Abstract

The present invention relates to an LC medium comprising two or more polymerizable compounds, at last one of which has absorption in the long UV wavelength range, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the PSA (polymer sustained alignment) or SA (self-aligning) mode, to an LC display of the PSA or SA mode comprising the LC medium, and to a process of manufacturing the LC display that enables minimization of production cost and energy saving.

Description

Liquid-Crystal Medium Comprising Polymerizable Compounds The present invention relates to an LC medium comprising two or more polymerizable compounds, at least one of which has absorption in the long UV wavelength range, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in LC displays of the PSA (polymer sustained alignment) or SA (self-aligning) mode, to an LC display of the PSA or SA mode comprising the LC medium, and to a process of manufacturing the LC display that enables minimization of production cost and energy saving. The popularity of 8K and gaming monitors leads to an increased need for LC display (LCD) panels having higher refresh rates and thus for LC media having faster response times. Many of these LCD panels are using polymer stabilized (PS) or polymer sustained alignment modes (PSA) modes, like the PS-VA (vertically aligned), PS-IPS (in-plane switching) or PS-FFS (fringe-field switching) mode or modes derived therefrom, or self-aligned (SA) modes like SA-VA which are polymer stabilized. In the PS or PSA mode a small amount, typically from 0.1 to 1% of one or more polymerizable mesogenic compounds, also known as RMs (reactive mesogens), is added to the LC medium. After filling the LC medium into the display the RMs are then polymerized in situ by UV photopolymerization, while a voltage is applied to the electrodes of the display. Thereby a small tilt angle is generated in the LC molecules of the LC medium, which is stabilized by the polymerized RMs. The UV polymerization process, also referred to as “PSA process”, is usually carried out in two steps, a first UV exposure step ("UV1 step"), with application of a voltage, to generate the tilt angle, and a second UV exposure step ("UV2 step"), without application of a voltage, to complete polymerization of the RMs. In the SA-VA mode the alignment layers are omitted in the display. Instead, a small amount, typically 0.1 to 2.5 %, of a self alignment (SA) additive is added to the LC medium, which induces the desired alignment, for example homeotropic or planar alignment, in situ by a self assembling mechanism. The SA additive usually contains an organic, mesogenic core group and attached thereto one or more polar anchor groups, for example hydroxy, carboxy, amino or thiol groups, which are capable of interacting with the substrate surface, causing the additives on the substrate surface to align and induce the desired alignment also in the LC molecules. The SA additive may also contain one or more polymerizable groups that can be polymerised under similar conditions as the RMs used in the PSA process. The LC medium may in addition to the SA additive also contain one or more RMs. One method to reduce the response times in LC media for the PSA mode is for example by using compounds with an alkenyl group as components of the LC host mixture. However, this may lead to a decrease of the reliability of the mixture when being exposed to the UV light need to polymerize the RMs additives, which is believed to be caused by a reaction of the alkenyl compound with the polyimide of the alignment layer, which is especially problematic when using shorter UV wavelengths of less than 320nm. Therefore there is a tendency to use longer UV wavelengths for the PSA process. UV-LED lamps have also been proposed for use in the PSA process, as they show less energy consumption, longer lifetime and more effective optical energy transfer to the LC medium due to the narrower emission peak, which allows to reduce the UV intensity and/or UV irradiation time. This enables a reduced tact time and savings in energy and production costs. The UV lamps currently available have higher wavelength emission, for example at 365nm. Therefore, there is a need for polymerizable LC media which contain RMs that can be effectively polymerized at longer UV wavelengths. In addition, there is a great demand for PSA or SA displays, and LC media and polymerizable compounds for use in such PSA or SA 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 tilt angle, a high tilt stability, 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 polymerizable compounds, have low melting points and a high solubility in the LC host mixtures. In displays for mobile applications, it is especially desired to have available LC media that show low threshold voltage and high birefringence. The present invention is based on the object of providing novel suitable materials, in particular RMs and LC media comprising the same, for use in PSA or SA 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 comprising RMs for use in PSA or SA displays, which enable very high specific resistance values, high VHR values, high reliability, low threshold voltages, short response times, high birefringence, show good UV absorption especially at longer UV wavelengths, preferably in the range from 340 to 380 nm, enable quick and complete polymerization of the RMs, allow the generation of a low tilt angle, preferably as quickly as possible, enable a high stability of the tilt angle even after longer time and/or after UV exposure, reduce or prevent the occurrence of "image sticking" and "ODF mura" in the display, and in case of the RMs polymerize as rapidly and completely as possible and show a high solubility in the LC media which are typically used as host mixtures in PSA or SA displays. A further object of the invention is to provide LC media for use in PSA displays wherein the RMs exhibit both fast polymerization speed and good reliability parameters, like high VHR or tilt stability. A further object of the invention is the provision of novel LC media containing RMs, in particular for optical, electro-optical and electronic applications, and of suitable processes and intermediates for the preparation thereof. A further object of the invention is to provide LC media containing RMs which show one or more of the following advantageous effects: - they generate a tilt angle to a desired degree after exposure to UV-light, - they lead to high tilt stability, - they show good UV absorption especially at longer UV wavelengths, especially in the range from 340 to 400 nm, and enable quick and complete polymerization of the RMs at these wavelengths, - they are suitable for use in PSA displays prepared by a polymerization process using UV B-type or UV-LED lamps, especially with longer wavelength than the currently used UV C-type lamps, especially in the second UV step of the PSA procress which takes longer irradiation times, thereby reducing damage on the molecules of the LC medium, - they enable good control of the the time range of the first UV-step in which the tilt angle is generated during UV-processing, - they enable using UV-LED lamps with long lifetime and low energy consumption and more effective optical energy transfer than the commonly used fluorescent type UV lamps, - they enable and keeping the time range of the second UV-step, in which any residual RM is polymerized and the tilt angle is stabilized, as short as possible to minimize production cost and energy consumption, - after the first and second UV-exposure step, the residual RMs have less or no negative effects on the LC-mixture performance parameters, such as VHR, tilt stability, etc., - they show good solubility and stability in LC-mixtures in a broad temperature range, preferably from -40 to 140°C. It was found that one or more of these objects could be achieved by providing LC media comprising polymerizable compounds as disclosed and claimed hereinafter. The invention relates to an LC medium comprising two or more polymerizable compounds, at least one of which is selected from formula I

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings R^a, R^b P-Sp- or R, wherein at least one of R^a and R^b denotes P-Sp-, A^a, A^b phenylene-1,4,-diyl or naphthalene,2-6-diyl which is optionally substituted by one or more groups L, Z^a, Z^b -CH=CH-, -CF=CF-, -C ≡C- or a single bond, preferably a single bond, P a polymerizable group, Sp a spacer group that is optionally substituted by one or more groups P, or a single bond, R 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-, CR⁰=CR⁰⁰-, -C ≡C-,

in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, L F, Cl, Br, -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-, -N(R⁰)-, -Si(R⁰R⁰⁰)-, -CH=CH- or -C≡C- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, R⁰, R⁰⁰ H or alkyl with 1 to 12 C atoms, a, b 0, 1 or 2, preferably 0 or 1, r4 0, 1, 2, 3 or 4, preferably 0, 1 or 2. The invention further relates to an LC medium having negative dielectric anisotropy and comprising two or more polymerizable compounds, at least one of which is a compound of formula I, and preferably shows absorption in the range from 340 to 400 nm, very preferably from 350 to 380 nm, and further comprising one or more compounds of formula II

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings R¹ and R² 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-, CR⁰=CR⁰⁰-, -C ≡C-,

in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, preferably alkyl or alkoxy having 1 to 6 C atoms, R⁰, R⁰⁰ H or alkyl with 1 to 12 C atoms, preferably H, A¹ and A² a group selected from the following formulae

preferably from formulae A1, A2, A3, A4, A5, A6, A9 and A10, very preferably from formulae A1, A2, A3, A4, A5, A9 and A10, Z¹ and Z² -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CO-O-, - O-CO-, -C₂F₄-, -CF=CF-, -CH=CH-CH₂O- or a single bond, preferably a single bond, L¹, L², L³ and L⁴ F, Cl, OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F or Cl, very preferably F, Y H, F, Cl, CF₃, CHF₂ or CH₃, preferably H or CH₃, very preferably H, L^C CH₃ or OCH₃, preferably CH₃, a1 1 or 2, a2 0 or 1. The invention further relates to the use of the LC medium as described above and below in LC displays of the PSA or SA mode. 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 polymerizable compounds of formula I with one or more compounds of formula II and optionally with further LC compounds and/or additives. The invention furthermore relates to an LC display comprising an LC medium according to the invention as described above and below, which is a PSA or SA display, preferably a PS-VA, PS-IPS, PS-FFS or SA-VA display. The invention furthermore relates to an LC display comprising an LC medium as described above and below wherein the polymerizable compounds are present in polymerized form, which is preferably a PSA or SA display, very preferably a PS-VA, PS-IPS, PS-FFS or SA-VA display. The invention furthermore relates to an LC display of the 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 as described above and below, wherein the polymerizable compounds are polymerized between the substrates of the display by UV photopolymerization. The invention furthermore relates to a process for the production of an LC display as described above and below, comprising the steps of filling or otherwise providing an LC medium as described above and below between the substrates of the display, and polymerizing the polymerizable compounds, preferably by irradiation with UV light, preferably having a wavelength >340 nm, preferably >360 nm, preferably in the range from 340 to 400 nm, more preferably in the range from 350 to 390 nm, very preferably in the range from 360 to 380 nm, most preferably in the range from 360 to 368 nm, and preferably while a voltage is applied to the electrodes of the display. The invention furthermore relates to a process for the production of an LC display as described above and below, wherein irradiation of the polymerizable compounds is carried out using a UV B-type lamp or an UV- LED lamp, preferably an UV-LED lamp. The invention furthermore relates to an energy saving process for the production of an LC display which is as described above and below. The LC media according to the present invention show the following advantageous properties when used in PSA displays: - 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, - sufficient solubility in organic solvents typically used in display manufacture. In addition the LC media according to the present invention show one or more of the following advantageous properties: - they generate a tilt angle to a desired degree after exposure to UV-light, - they provide a high tilt stability, - they show good UV absorption especially at longer UV wavelengths, preferably in the range from 340 to 400 nm, more preferably in the range from 350 to 390 nm, very preferably in the range from 360 to 380 nm, most preferably in the range from 360 to 368 nm, and enable quick and complete polymerization of the RMs at these wavelengths, - they are suitable for use in PSA displays prepared by a polymerization process using UV-LED lamps, which have longer lifetime, lower energy consumption and more effective optical energy transfer than conventional UV lamps, - they enable to control the time range of the first UV-step in which the tilt angle is generated during UV-processing, - they keep the time range of the second UV-step as short as possible to minimize production cost and energy consumption, - they enable using a UV B-type lamp with longer emission wavelength than a UV C-type lamp in the second, longer UV-step to minimize damage on the compounds in the LC medium, - after the first and second UV-exposure step, they reduce or avoid any negative effects of the residual RM on the LC mixture performance parameters, such as VHR, tilt stability, etc. - they have high stability in a broad temperature range, preferably from - 40°C to ca.140°C, and high low temperature stability (LTS) against crystallization. An alkenyl group in the compounds of formula II or other components of the LC medium as disclosed below is not considered to be within the meaning of the term “polymerizable group” as used herein. The conditions for the polymerization of the polymerizable compounds of the LC medium are preferably selected such that alkenyl substituents do not participate in the polymerization reaction. Preferably the LC media disclosed and claimed in the present application do not contain an additive that initiates or enhances the participation of the alkenyl group in a polymerization reaction. Unless stated otherwise, the polymerizable compounds and the compounds of formula II are preferably selected from achiral compounds. As used herein, the expression “UV light having a wavelength of” followed by a given range of wavelengths (in nm), or by a given lower or upper wavelength limit (in nm), means that the UV emission spectrum of the respective radiation source has an emission peak, which is preferably the highest peak in the respective spectrum, in the given wavelength range or above the given lower wavelength limit or below the given upper wavelength limit and/or that the UV absorption spectrum of the respective chemical compound has a long or short wavelength tail that extends into the given wavelength range or above the given lower wavelength limit or below the given upper wavelength limit. As used herein, the term “full width half maximum” or “FWHM” means the width of a spectrum curve measured between those points on the y-axis which are half the maximum amplitude. As used herein, the term "substantially transmissive" means that the filter transmits a substantial part, preferably at least 50% of the intensity, of incident light of the desired wavelength(s). As used herein, the term "substantially blocking" means that the filter does not transmit a substantial part, preferably at least 50% of the intensity, of incident light of the undesired wavelengths. As used herein, the term "desired (undesired) wavelength" e.g. in case of a band pass filter means the wavelengths inside (outside) the given range of λ, and in case of a cut-off filter means the wavelengths above (below) the given value of λ. 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), and will be understood to be inclusive of "pretilt" and "pretilt angle". 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 absolute 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 polymerization and are also referred to as "polymerizable group" or "P". Unless stated otherwise, the term "polymerizable compound" as used herein will be understood to mean a polymerizable monomeric compound. An SA-VA display according to the present invention will be of the polymer stabilised mode as it contains, or is manufactured by use of, an LC medium containing RMs of formula I and II. Consequently as used herein, the term "SA-VA display" when referring to a display according to the present invention will be understood to refer to a polymer stabilised SA-VA display even if not explicitly mentioned. 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 polymerization reaction, as opposed to a "polymeric compound" or a "polymer". As used herein, the term "unpolymerizable compound" will be understood to mean a compound that does not contain a functional group that is suitable for polymerization under the conditions usually applied for the polymerization 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 com- pounds) 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 polymerization. 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. 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 polymerizable group(s) in a polymerizable mesogenic compound. Above and below, denotes a trans-1,4-cyclohexylene ring,

and

denotes a 1,4-phenylene ring. In a group

the single bond shown between the two ring atoms can be attached to any free position of the benzene ring. If in the formulae shown above and below a group R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L denotes an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy or tetradecyloxy. If in the formulae shown above and below a group R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L denotes an alkyl radical wherein one or more CH₂ groups are replaced by S, this may be straight- chain or branched. It is preferably straight-chain, has 1, 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes thiomethyl, thioethyl, thiopropyl, thiobutyl, thiopentyl, thiohexyl or thioheptyl. Oxaalkyl preferably denotes straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7- oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxa- decyl. If in the formulae shown above and below a group R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L denotes an alkoxy or oxaalkyl group it may also contain one or more additional oxygen atoms, provided that oxygen atoms are not linked directly to one another. In another preferred embodiment, one or more of R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L are selected from the group consisting of

, -S¹-F, -O-S¹-F, -O-S₁-O-S₂, wherein S¹ is C_1-12-alkylene or C_2-12-alkenylene and S² is H, C_1-12-alkyl or C_2-12-alkenyl, and very preferably are selected from the group consisting of

,

, -OCH₂OCH₃, -O(CH₂)₂OCH₃, -O(CH₂)₃OCH₃, - O(CH₂)₄OCH₃, -O(CH₂)₂F, -O(CH₂)₃F, -O(CH₂)₄F. If in the formulae shown above and below a group R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L denotes an alkyl radical in which one CH₂ group has been replaced by -CH=CH-, this may be straight- chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. Accordingly, it denotes, in particular, vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, - 2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3- , -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl. If in the formulae shown above and below a group R^1-13, R⁵¹, R⁵², R^Q, R, R^2A, R^2B, R^IIIA, R^1N, R^2N, R^B1, R^B2, R^CR1, R^CR2, R or L denotes an alkyl or alkenyl radical which is at least monosubstituted by halogen, this radical is preferably straight-chain, and halogen is preferably F or Cl. In the case of polysubstitution, halogen is preferably F. The resultant radicals also include perfluorinated radicals. In the case of monosubstitution, the fluorine or chlorine substituent may be in any desired position, but is preferably in the ^-position. Halogen is preferably F or Cl, very preferably F. The group -CR⁰=CR⁰⁰- is preferably -CH=CH-. -CO-, -C(=O)- and -C(O)- denote a carbonyl group, i.e.

Preferred substituents L, are, for example, F, Cl, Br, I, -CN, -NO₂, -NCO, - NCS, -OCN, -SCN, -C(=O)N(R^x)₂, -C(=O)Y¹, -C(=O)R^x, -N(R^x)₂, 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 O- 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. 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.

is preferably

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

CH₂=CW²-(O)_k3-, CW¹=CH-CO-(O)_k3-, CW¹=CH-CO-NH-, CH₂=CW¹-CO-NH-, CH₃-CH=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, HO-CW²W³-, HS-CW²W³-, HW²N- , HO-CW²W³-NH-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)_k1-Phe-(O)_k2-, CH₂=CH-(CO)_k1-Phe-(O)_k2-, Phe-CH=CH-, HOOC-, OCN- and W⁴W⁵W⁶Si-, in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, which is optionally substituted by one or more radicals L as defined above which are other than P-Sp-, k₁, k₂ and k₃ each, independently of one another, denote 0 or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10. Very preferred groups P are selected from the group consisting of CH₂=CW¹-CO-O-, CH₂=CW¹-CO-,

, CH₂=CW²-O-, CH ²

₂=CW -, CW¹=CH-CO-(O)_k3-, CW¹=CH-CO-NH-, CH₂=CW¹-CO-NH-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, CH₂=CW¹-CO-NH-, CH₂=CH-(COO)_k1-Phe-(O)_k2-, CH₂=CH-(CO)_k1-Phe-(O)_k2-, Phe-CH=CH- and W⁴W⁵W⁶Si-, in which W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ each, independently of one another, denote Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 C atoms, W⁷ and W⁸ each, independently of one another, denote H, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1,4-phenylene, k₁, k₂ and k₃ each, independently of one another, denote 0 or 1, k₃ preferably denotes 1, and k₄ denotes an integer from 1 to 10. Very particularly preferred groups P are selected from the group consisting of CH₂=CW¹-CO-O-, in particular CH₂=CH-CO-O-, CH₂=C(CH₃)-CO-O- and CH₂=CF-CO-O-, furthermore CH₂=CH-O-, (CH₂=CH)₂CH-O-CO-, (CH₂=CH)₂CH-O-,

Further preferred polymerizable groups P are selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate. Very preferably all polymerizable groups in the polymerizable compound have the same meaning. If the spacer group Sp is different from a single bond, it is preferably of the formula Sp"-X", so that the respective radical P-Sp- conforms to the formula P-Sp"-X"-, wherein Sp" denotes linear or branched alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and in which, in addition, one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by -O-, -S-, -NH- , -N(R⁰)-, -Si(R⁰R⁰⁰)-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S- , -N(R⁰⁰)-CO-O-, -O-CO-N(R⁰)-, -N(R⁰)-CO-N(R⁰⁰)-, -CH=CH- or -C ≡C- in such a way that O and/or S atoms are not linked directly to one another, X" denotes -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -CO-N(R⁰)-, -N(R⁰)- CO-, -N(R⁰)-CO-N(R⁰⁰)-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, - OCF₂-, -CF₂S-, -SCF₂-, -CF₂CH₂-, -CH₂CF₂-, -CF₂CF₂-, -CH=N-, - N=CH-, -N=N-, -CH=CR⁰-, -CY²=CY³-, -C ≡C-, -CH=CH-CO-O-, -O-CO- CH=CH- or a single bond, R⁰ and R⁰⁰ each, independently of one another, denote H or alkyl having 1 to 20 C atoms, and Y² and Y³ each, independently of one another, denote H, F, Cl or CN. X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR⁰-, -NR⁰- CO-, -NR⁰-CO-NR⁰⁰- or a single bond. Typical spacer groups Sp and -Sp"-X"- are, for example, -(CH₂)_p1-, -(CH₂)_p1-O-, -(CH₂)_p1-O-CO-, -(CH₂)_p1-CO-O-, -(CH₂)_p1-O-CO-O-, -(CH₂CH₂O)_q1-CH₂CH₂-, - CH₂CH₂-S-CH₂CH₂-, -CH₂CH₂-NH-CH₂CH₂- or -(SiR⁰R⁰⁰-O)_p1-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R⁰ and R⁰⁰ have the meanings indicated above. Particularly preferred groups Sp and -Sp"-X"- are -(CH₂)_p1-, -(CH₂)_p1-O-, - (CH₂)_p1-O-CO-, -(CH₂)_p1-CO-O-, -(CH₂)_p1-O-CO-O-, in which p1 and q1 have the meanings indicated above. Particularly preferred groups Sp" are, in each case straight-chain, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methylimino- ethylene, 1-methylalkylene, ethenylene, propenylene and butenylene. In a preferred embodiment of the invention the compounds of formula I and its subformulae contain a spacer group Sp that is substituted by one or more polymerizable groups P, so that the group Sp-P corresponds to Sp(P)_s, with s being ≥2 (branched polymerizable groups). Preferred compounds of formula I according to this preferred embodiment are those wherein s is 2, i.e. compounds which contain a group Sp(P)₂. Very preferred compounds of formula I according to this preferred embodiment contain a group selected from the following formulae: -X-alkyl-CHPP S1 -X-alkyl-CH((CH₂)_aaP)((CH₂)_bbP) S2 -X-N((CH₂)_aaP)((CH₂)_bbP) S3 -X-alkyl-CHP-CH₂-CH₂P S4 -X-alkyl-C(CH₂P)(CH₂P)-C_aaH_2aa+1 S5 -X-alkyl-CHP-CH₂P S6 -X-alkyl-CPP-C_aaH_2aa+1 S7 -X-alkyl-CHPCHP-C_aaH_2aa+1 S8 in which P is as defined in formula I, alkyl denotes a single bond or straight-chain or branched alkylene having 1 to 12 C atoms which is unsubstituted or mono- or polysubstituted by F, Cl or CN and in which one or more non-adjacent CH₂ groups may each, independently of one another, be replaced by -C(R⁰)=C(R⁰)-, -C ≡C-, -N(R⁰)-, -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, where R⁰ has the meaning indicated above, aa and bb each, independently of one another, denote 0, 1, 2, 3, 4, 5 or 6, X has one of the meanings indicated for X", and is preferably O, CO, SO₂, O-CO-, CO-O or a single bond. Preferred spacer groups Sp(P)₂ are selected from formulae S1, S2 and S3. Very peferred spacer groups Sp(P)₂ are selected from the following subformulae: -CHPP S1a -O-CHPP S1b -CH₂-CHPP S1c -OCH₂-CHPP S1d -CH(CH₂-P)(CH₂-P) S2a -OCH(CH₂-P)(CH₂-P) S2b -CH₂-CH(CH₂-P)(CH₂-P) S2c -OCH₂-CH(CH₂-P)(CH₂-P) S2d -CO-NH((CH₂)₂P)((CH₂)₂P) S3a P is preferably selected from the group consisting of vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, very preferably from acrylate and methacrylate, most preferably from methacrylate. Further preferably all polymerizable groups P that are present in the same compound have the same meaning, and very preferably denote acrylate or methacrylate, most preferably methacrylate. Sp preferably denotes a single bond or -(CH₂)_p1-, -(CH₂)_p2-CH=CH-(CH₂)_p3-, - O-(CH₂)_p1-, -O-CO-(CH₂)_p1, or -CO-O-(CH₂)_p1, wherein p1 is 2, 3, 4, 5 or 6, preferably 2 or 3, p2 and p3 are independently of each other 0, 1, 2 or 3 and, if Sp is -O-(CH₂)_p1-, -O-CO-(CH₂)_p1 or -CO-O-(CH₂)_p1 the O-atom or CO- group, respectively, is linked to the benzene ring. Further preferably at least one group Sp is a single bond. Further preferably at least one group Sp is different from a single bond, and is preferably selected from -(CH₂)_p1-, -(CH₂)_p2-CH=CH-(CH₂)_p3-, -O-(CH₂)_p1-, - O-CO-(CH₂)_p1, or -CO-O-(CH₂)_p1, wherein p1 is 2, 3, 4, 5 or 6, preferably 2 or 3, p2 and p3 are independently of each other 0, 1, 2 or 3 and, if Sp is -O- (CH₂)_p1-, -O-CO-(CH₂)_p1 or -CO-O-(CH₂)_p1 the O-atom or CO-group, respectively, is linked to the benzene ring. Very preferably Sp is different from a single bond, and is selected from - (CH₂)₂-, -(CH₂)₃-, -(CH₂)₄-, -O-(CH₂)₂-, -O-(CH₂)₃-, -O-CO-(CH₂)₂ and -CO-O- (CH)₂-, wherein the O atom or the CO group is attached to the benzene ring. Preferably the polymerizable compounds of formula I have absorption in the range from 330 to 390 nm. Very preferably they have an extinction coefficient of at least 0.5 at a wavelength in the range from 330 to 390 nm, more preferably in the range from 340 to 380 nm, very preferably in the range from 350 to 370 nm, most preferably in the range from 355 to 365 nm. The extinction coefficient and absorption wavelength are measured unless stated otherwise in a solution of the compound in DCM at a concentration of 3g/L. Preferably in the compounds of formula I a and b are independently of each other 0 or 1. In a preferred embodiment of the invention a+b=1 or 2. Preferred compounds of formula I are selected from formula I1

wherein P, Sp, L and r4 have independently of each other one of the meanings given in formula I1 or one of their preferred meanings as given above and below. P is preferably acrylate or methacrylate, very preferably methacrylate. Sp is preferably a single bond. r4 is preferably 0, 1 or 2, very preferably 0 or 1. L is preferably F or OCH₃. Preferably all groups P in the formulae I and I1 have the same meaning, and very preferably denote methacrylate. Very preferred compounds of formula I and I1 are selected from the following subformulae.

Further preferred compounds of formula I and I1 are those selected from one or more of the following embodiments: - the groups P denote independently of each other acrylate or methacrylate, very preferably methacrylate, - all groups P in one compound have the same meaning, - Sp is a single bond, - at least one, preferably one or two of the groups Sp is a single bond and the other groups Sp are different from a single bond, - Sp when being different from a single bond, and Sp', are selected from the group consisting of -(CH₂)_p1-, -(CH₂)_p2-CH=CH-(CH₂)_p3-, -O-(CH₂)_p1-, -O- CO-(CH₂)_p1, or -CO-O-(CH₂)_p1, wherein p1 is 2, 3, 4, 5 or 6, preferably 2 or 3, p2 and p3 are independently of each other 0, 1, 2 or 3 and, if Sp is -O- (CH₂)_p1-, -O-CO-(CH₂)_p1 or -CO-O-(CH₂)_p1 the O-atom or CO-group, respectively, is linked to the benzene ring, - Sp when being different from a single bond, and Sp', are selected from the the group consisting of -(CH₂)₂-, -(CH₂)₃-, -(CH₂)₄-, -O-(CH₂)₂-, -O-(CH₂)₃-, -O-CO-(CH₂)₂ and -CO-O-(CH)₂-, wherein the O atom or the CO group is attached to the benzene ring, - a=b=0, - r4 is 0 or 1, - L is selected from the group consisting of F, Cl, Br, CN, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy each having 1 to 6 C atoms or alkenyl having 2 to 6 C atoms, in which one or more H atoms are optionally replaced by F or Cl, - L is selected from F, CH₃, OCH₃, OC₂H₅, C₂H₅, CH=CH₂ and C(CH₃)=CH₂, very preferably from F and OCH₃. For use in PSA displays the total proportion of the polymerizable compound of formula I or its subformulae in the LC medium is preferably from 0.01 to 2.0%, more preferably from 0.02 to 1.5%, very preferably from 0.025 to 1.0%. For use in SA-VA displays the total proportion of the polymerizable compound of formula I or its subformulae in the LC medium is preferably from > 0 to < 3%, very preferably from > 0 to < 2%, more preferably from 0.05 to 2.5, most preferably from 0.05 to 1.5%. The LC medium comprises, in addition to the polymerizable compound of formula I or its subformulae, at least one further polymerizable compound. In a preferred embodiment the at least one further polymerizable compound is a compound of formula I or its subformulae, more preferably selected from formula I1, very preferably selected from formulae I1-1 to I1-18, or from the preferred embodiments of formula I and its subformulae as disclosed above and below. In another preferred embodiment the LC medium comprises, in addition to the polymerizable compound(s) of formula I or its subformulae, at least one further polymerizable compound selected from the following formulae:

in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: P¹, P², P³ a polymerisable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxy, Sp¹, Sp², Sp³ a single bond or a spacer group where, in addition, one or more of the radicals P¹-Sp¹-, P²-Sp²- and P³-Sp³- may denote R^aa, with the proviso that at least one of the radicals P¹-Sp¹-, P²-Sp² and P³-Sp³- present is different from R^aa, preferably -(CH₂)_p1-, -(CH₂)_p1-O-, -(CH₂)_p1-CO-O- or -(CH₂)_p1- O-CO-O- bedeuten, wherein p1 is an integer from 1 to 12, R^aa H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by -C(R⁰)=C(R⁰⁰)-, -C ≡C-, -N(R⁰)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms), and wherein R^aa does not denote or contain a group P¹, P² or P³, R⁰, R⁰⁰ H or alkyl having 1 to 12 C atoms, R^y and R^z H, F, CH₃ or CF₃, X¹, X², X³ -CO-O-, -O-CO- or a single bond, Z^M1 -O-, -CO-, -C(R^yR^z)- or -CF₂CF₂-, Z^M2, Z^M3 -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂- or -(CH₂)_n-, where n is 2, 3 or 4, L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy hav- ing 1 to 12 C atoms, L', L" H, F or Cl, k 0 or 1, r 0, 1, 2, 3 or 4, s 0, 1, 2 or 3, t 0, 1 or 2, x 0 or 1. Very preferred are compounds of formulae M2 and M13, especially direactive compounds containing exactly two polymerizable groups P¹ and P². Further preferred are compounds selected from formulae M17 to M32, in particular from formulae M20, M22, M24, M27, M30 and M32, especially trireactive compounds containing exactly three polymerizable groups P¹, P² and P³. In the compounds of formulae M1 to M31 the group is preferably

or

wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, Cl, CN, NO₂, CH₃, C₂H₅, C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH₃)C₂H₅, OCH₃, OC₂H₅, COCH₃, COC₂H₅, COOCH₃, COOC₂H₅, CF₃, OCF₃, OCHF₂, OC₂F₅ or P-Sp-, very preferably F, Cl, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, more preferably F, Cl, CH₃, OCH₃, COCH₃ or OCF₃ , most preferably F or OCH₃. Preferred compounds of formulae M1 to M32 are those wherein P¹, P² and P³ denote an acrylate, methacrylate, oxetane or epoxy group, very preferably an acrylate or methacrylate group, most preferably a methacrylate group. Further preferred compounds of formulae M1 to M32 are those wherein Sp¹, Sp² and Sp³ are a single bond. Further preferred compounds of formulae M1 to M32 are those wherein one of Sp¹, Sp² and Sp³ is a single bond and another one of Sp¹, Sp² and Sp³ is different from a single bond. Further preferred compounds of formulae M1 to M32 are those wherein those groups Sp¹, Sp² and Sp³ that are different from a single bond denote - (CH₂)_s1-X"-, wherein s1 is an integer from 1 to 6, preferably 2, 3, 4 or 5, and X" is X" is the linkage to the benzene ring and is -O-, -O-CO-, -CO-O, -O-CO- O- or a single bond. Further preferred compounds of formulae M1 to M32 are those selected from Table D below, especially those selected from the group consisting of formulae RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-58, RM-64, RM-74, RM-76, RM- 88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM-122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM-147, RM-149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-183. Particularly preferred are LC media comprising, in addition to the compound of formula I, one, two or three polymerizable compounds of formulae M1 to M32. Further preferred are LC media comprising, in addition to the compound(s) of formula I, one or more direactive polymerizable compounds selected from formulae M1 to M16, very preferably selected from formulae M2 and M13. Further preferred are LC media comprising, in addition to the compound(s) of formula I, one or more direactive polymerizable compounds selected from formulae M1 to M16, very preferably from formulae M2 and M13, and/or one or more trireactive polymerizable compounds selected from formulae M17 to M32, very preferably from formulae M20, M22, M24, M27, M30 and M32. Further preferred are LC media comprising, in addition to the compound(s) of formula I, one or more polymerizable compounds of formulae M1 to M32 wherein at least one r is not 0, or at least one of s and t is not 0, very preferably selected from formulae M2, M13, M22, M24, M27, M30 and M32, and wherein L is selected from the preferred groups shown above, most preferably from F and OCH₃. Further preferred are polymerizable compounds which show absorption in the wavelength range from 320 to 380nm, preferably selected from formulae M1 to M32, more preferably from the group consisting of the above- mentioned formulae from Table D, most preferably from the group consisting of RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM- 41, RM-48, RM-52, RM-54, RM-57, RM-58, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM-121, RM- 122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM-147, RM- 149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-183. Further preferred additional polymerizable compounds are selected from the compounds used in the mixture examples below. In another preferred embodiment the LC medium comprises, in addition to the polymerizable compounds of formula I or its subformulae, one or more polymerizable compounds having two polymerizable groups selected from formula CM

in which the individual radicals, on each occurrence identically or differently, and each, independently of one another, have the following meaning: P, Sp one of the meanings given in formula I or its subformulae or one of their preferred meanings as given above and below, L F, Cl, CN or straight-chain or branched, optionally mono- or poly- fluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, r1, r2 0, 1, 2, 3 or 4, preferably 0, 1 or 2, very preferably 0 or 1. Preferred compounds of formula CM are selected from the following subformulae

wherein P and Sp, L, r1 and r2 have independently of each other one of the meanings given in formula CM or one of their preferred meanings as given above and below, and Sp' has one of the meanings given for Sp that is different from a single bond. Preferably at least one of r1 and r2 is not 0. P is preferably acrylate or methacrylate, very preferably methacrylate. Preferably all groups P in the formulae CM, CM-1 and CM-2 have the same meaning, and very preferably denote methacrylate. Sp' is preferably selected from -(CH₂)₂-, -(CH₂)₃-, -(CH₂)₄-, -O-(CH₂)₂-, -O-(CH₂)₃-, -O-CO-(CH₂)₂ and - CO-O-(CH)₂-, wherein the O atom or the CO group is attached to the benzene ring. L is preferably selected from F, CH₃, OCH₃, OC₂H₅, C₂H₅, CH=CH₂ and C(CH₃)=CH₂, very preferably from F. Very preferred are the compounds of formula CM-1. More preferred compounds of formula CM are selected from the following subformulae

wherein P, Sp' and L have one of the meanings as given in formula CM-1 and CM-2. P is preferably acrylate or methacrylate, very preferably methacrylate. Preferably all groups P in the formulae CM-1-1 to CM-2-9 have the same meaning, and very preferably denote methacrylate. Sp' is preferably selected from -(CH₂)₂-, -(CH₂)3-, -(CH₂)₄-, -O-(CH₂)₂-, -O-(CH₂)3-, - O-CO-(CH₂)₂ and -CO-O-(CH)₂-, wherein the O atom or the CO group is attached to the benzene ring. L is preferably selected from F, CH₃, OCH₃, OC₂H₅,C₂H₅, CH=CH₂ and C(CH₃)=CH₂, very preferably from F and OCH₃. Very preferred are the compounds of formula CM-1-1, CM-1-2, CM-1-3, CM- 1-4, CM-1-5, CM-1-6 and their subformulae. Most preferred are the compounds of formula CM-1-1. Very preferred compounds of formula CM are selected from the following subformulae:

Very preferred are the compounds of formula CM-1-1a, CM-1-2a and CM-1- 3a. Most preferred are the compounds of formula CM-1-1a. Further preferred are the compounds of formulae CM-1-1a to CM-2-9a wherein one or two of the methacrylate groups are replaced by acrylate groups, and the compounds of formulae CM-1-1a to CM-2-9a wherein all methacrylate groups are replaced by acrylate groups. Further preferred compounds of formula CM are selected from Table D below, very preferably from the group consisting of RM-1, RM-2, RM-3 and RM-7 to RM-49, very preferably selected from the group consisting of RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM-40, RM-41 and RM-48. In another preferred embodiment the LC medium comprises, in addition to the polymerizable compounds of formula I or its subformulae, one or more polymerizable compounds having three polymerizable groups selected from formula MT

wherein P, Sp, L, r1 and r2 independently of each other have the meanings given in formula CM or one of their preferred meanings as given above and below, k is 0 or 1, and r3 is 0, 1, 2 or 3, preferably 0, 1 or 2, very preferably 0 or 1. Preferred compounds of formula MT are selected from the following subformulae

wherein P, Sp, L, r1, r2 and r3 have independently of each other one of the meanings given in formula MT or one of their preferred meanings as given above and below. Preferably at least one of r1, r2 and r3 is not 0. P is preferably acrylate or methacrylate, very preferably methacrylate. L is preferably selected from F, CH₃, OCH₃, OC₂H₅, C₂H₅, CH=CH₂ and C(CH₃)=CH₂, very preferably from F. Preferably all groups P in the formulae MT and MT-1 to MT-6 have the same meaning, and very preferably denote methacrylate. Very preferred are the compounds of formula MT-1, MT-4 and MT-5. More preferred compounds of formula MT are selected from the following subformulae

wherein P, Sp and L have one of the meanings as given in formula MT and Sp' has one of the meanings given for Sp that is different from a single bond. P is preferably acrylate or methacrylate, very preferably methacrylate. Preferably all groups P in the formulae MT-1-1 to MT-6-12 have the same meaning, and very preferably denote methacrylate. Sp' is preferably selected from -(CH₂)₂-, -(CH₂)₃-, -(CH₂)₄-, -O-(CH₂)₂-, -O-(CH₂)₃-, -O-CO-(CH₂)₂ and - CO-O-(CH)₂-, wherein the O atom or the CO group is attached to the benzene ring. L is preferably selected from F, CH₃, OCH₃, OC₂H₅, C₂H₅, CH=CH₂ and C(CH₃)=CH₂, very preferably from F and OCH₃. Very preferred are the compounds of formula MT-1-1, MT-1-6, MT-5-1 and their subformulae. Very preferred compounds of formula MT are selected from the following subformulae:

Ċ

Of the compounds of formula MT-1 to MT-3 very preferred are the compounds of formula MT-1-1a, MT-1-2a, MT-1-2b, MT-2-1a, MT-2-2a, MT- 2-2b, MT-3-1a, MT-3-2a and MT-3-2b. Most preferred are the compounds of formula MT-1-1a, MT-1-2a, MT-1-2b, MT-2-1a, MT-2-2a and MT-2-2b. Of the compounds of formula MT-4 to MT-6 very preferred are the compounds of formula MT-4-1a, MT-4-2a, MT-4-3a, MT-4-4a, MT-4-5a, MT- 4-6a, MT-4-7a, MT-4-7b, MT-4-8a, MT-4-9a, MT-4-10a, MT-4-11a, MT-4- 12a, MT-5-1a, MT-5-2a, MT-5-4a, MT-5-5a, MT-5-6a, MT-5-7a, MT-5-7b, MT-5-8a, MT-5-9a, MT-5-10a, MT-5-11a and MT-5-12a. Most preferred are the compounds of formula MT-4-1a, MT-4-7a, MT-4-7b, MT-5-1a, MT-5-7a and MT-5-7b. Further preferred are the compounds of formulae MT-1-1a to MT-6-11a wherein one or two of the methacrylate groups are replaced by acrylate groups. Further preferred are the compounds of formulae MT-1-1a to MT-6- 11a wherein all methacrylate groups are replaced by acrylate groups. Further preferred compounds of formula MT are selected from Table D below, preferably selected from the group consisting of formulae RM-120 to RM-144. The total proportion of the additional polymerizable compounds of formulae M1 to M32, CM and MT in the LC medium according to the present invention is preferably from 0.01 to 1.0%, more preferably from 0.1 to 0.8%, very preferably from 0.1 to 0.5%. The polymerizable compounds of the formulae I and M1 to M32 can be prepared analogously to processes known to the person skilled in the art and described in standard works of organic chemistry, such as, for example, in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart. For example, acrylic or methacrylic esters can be prepared by esterification of the corresponding alcohols with acid derivatives like, for example, (meth)acryloyl chloride or (meth)acrylic anhydride in the presence of a base like pyridine or triethyl amine, and 4-(N,N-dimethylamino)pyridine (DMAP). Alternatively the esters can be prepared by esterification of the alcohols with (meth)acrylic acid in the presence of a dehydrating reagent, for example according to Steglich with dicyclohexylcarbodiimide (DCC), N-(3- dimethylaminopropyl)-N'-ethylcarbodiimide (EDC) or N-(3- dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and DMAP. The invention furthermore relates to an LC medium or LC display as described above, wherein the polymerizable compounds are present in polymerized form. The LC display is preferably a PS-VA, PS-IPS, PS-FFS, or SA-VA display. For the production of PSA or polymer stabilised SA displays, the polymerizable compounds contained in the LC medium are polymerized by in-situ polymerization in the LC medium between the substrates of the LC display, preferably while a voltage is applied to the electrodes. The structure of the 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. A preferred PSA type LC display of the present invention comprises: - a first substrate including a pixel electrode defining pixel areas, the pixel electrode being connected to a switching element disposed in each pixel area and optionally including a micro-slit pattern, and optionally a first alignment layer disposed on the pixel electrode, - a second substrate including a common electrode layer, which may be disposed on the entire portion of the second substrate facing the first substrate, and optionally a second alignment layer, - an LC layer disposed between the first and second substrates and including an LC medium as described above and below, wherein the polymerizable compounds may also be present in polymerized form. The first and/or second alignment layer controls the alignment direction of the LC molecules of the LC layer. For example, in PS-VA displays the alignment layer is selected such that it imparts to the LC molecules homeotropic (or vertical) alignment (i.e. perpendicular to the surface) or tilted alignment. Such an alignment layer may for example comprise a polyimide, which may also be rubbed, or may be prepared by a photoalignment method. The LC layer with the LC medium can be deposited between the substrates of the display by methods that are conventionally used by display manufacturers, for example the so-called one-drop-filling (ODF) method. The polymerizable component of the LC medium is then polymerized for example by UV photopolymerization. The polymerization can be carried out in one step or in two or more steps. The PSA display may comprise further elements, like a colour filter, a black matrix, a passivation layer, optical retardation layers, transistor elements for addressing the individual pixels, etc., all of which are well known to the person skilled in the art and can be employed without inventive skill. The electrode structure can be designed by the skilled person depending on the individual display type. For example for PS-VA displays a multi-domain orientation of the LC molecules can be induced by providing electrodes having slits and/or bumps or protrusions in order to create two, four or more different tilt alignment directions. Upon polymerization the polymerizable compounds form a copolymer, which causes a certain tilt angle of the LC molecules in the LC medium. Without wishing to be bound to a specific theory, it is believed that at least a part of the crosslinked polymer, which is formed by the polymerizable compounds, will phase-separate or precipitate from the LC medium and form a polymer layer on the substrates or electrodes, or the alignment layer provided thereon. Microscopic measurement data (like SEM and AFM) have confirmed that at least a part of the formed polymer accumulates at the LC/substrate interface. The polymerization can be carried out in one step. It is also possible firstly to carry out the polymerization, optionally while applying a voltage, in a first step in order to produce a tilt angle, and subsequently, in a second polymerization step without an applied voltage, to polymerize or crosslink the compounds which have not reacted in the first step ("end curing"). Suitable and preferred polymerization methods are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV induced photopolymerization, which can be achieved by exposure of the polymerizable compounds to UV radiation. A preferred process of preparing a PSA display includes one or more of the following features: - the polymerizable medium is exposed to UV light in the display in a 2-step process, including a first UV exposure step ("UV1 step"), with application of a voltage, to generate the tilt angle, and a second UV exposure step ("UV2 step"), without application of a voltage, to complete polymerization, - the polymerizable medium is exposed to UV light in the display generated by an UV-LED lamp, preferably at least in the UV2 step, more preferably both in the UV1 and UV2 step. - the polymerizable medium is exposed to UV light in the display generated by a UV lamp with a radiation spectrum that is shifted to longer wavelengths, preferably ≥340nm, more preferably from 350 to <370 nm, very preferably from 355 to 368 nm, to avoid short UV light exposure in the PS-VA process. Both using lower intensity and a UV shift to longer wavelengths protect the organic layer against damage that may be caused by the UV light. A preferred embodiment of the present invention relates to a process for preparing a PSA display as described above and below, comprising one or more of the following features: - the polymerizable LC medium is irradiated by UV light in a 2-step process, including a first UV exposure step ("UV1 step"), with application of a voltage, to generate the tilt angle, and a second UV exposure step ("UV2 step"), without application of a voltage, to complete polymerization, - the polymerizable LC medium is irradiated by UV light generated by a UV lamp having an intensity of from 0.5 mW/cm² to 10 mW/cm² in the wavelength range from 300-380nm, preferably in the UV2 step, and optionally also in the UV1 step, - the polymerizable LC medium is irradiated by UV light having a wavelength of ≥340 nm and ≤420 nm, preferably >350 nm, preferably in the range from 340 to 400 nm, more preferably in the range from 350 to 390 nm, very preferably in the range from 360 to 380 nm, most preferably in the range from 360 to 368 nm, - the polymerizable LC medium is irradiated by UV light while a voltage is applied to the electrodes of the display, - irradiation by UV light is carried out using a UV-LED lamp. This preferred process can be carried out for example by using the desired UV lamps or by using a band pass filter and/or a cut-off filter, which are substantially transmissive for UV light with the respective desired wavelength(s) and are substantially blocking light with the respective undesired wavelengths. For example, when irradiation with UV light of wavelengths λ of 300-400nm is desired, UV exposure can be carried out using a wide band pass filter being substantially transmissive for wavelengths 300nm < λ < 400nm. When irradiation with UV light of wavelength λ of more than 340 nm is desired, UV irradiation can be carried out using a cut-off filter being substantially transmissive for wavelengths λ > 340 nm. Preferably UV irradiation is carried out using a UV-LED lamp. The use of UV-LED lamps, which have with only one narrow emission peak, in the PSA process proivdes several advantages, like for example a more effective optical energy transfer to the polymerizable compounds in the LC medium, depending on the choice of the suitable polymerizable compounds that shows absorption at the emission wavelength of the LED lamp. This allows to reduce the UV intensity and/or the UV irradiation time, thus enabling a reduced tact time and savings in energy and production costs. Another advantage is that the narrow emission spectrum of the lamp allows an easier selection of the appropriate wavelength for photopolymerization. Very preferably the UV light source is an UV-LED lamp emitting a wavelength in the range from 340 to 400 nm, more preferably in the range from 350 to 390 nm, very preferably in the range from 360 to 380 nm, most preferably in the range from 360 to 368 nm. UV-LED lamps emitting UV light with a wavelength of 365 nm are especially preferred. Preferably the UV-LED lamp emits light having an emission peak with a full width half maximum (FWHM) of 30 nm or less. UV-LED lamps are commercially available, for example from Dr. Hoenle AG, Germany or Primelite GmbH, Germany, or IST Metz GmbH, Germany, with emission wavelengths e.g. of 365, 385, 395 and 405 nm. This preferred process enables the manufacture of displays by using longer UV wavelengths, thereby reducing or even avoiding the hazardous and damaging effects of short UV light components. UV radiation energy is in general from 6 to 100 J, depending on the production process conditions. Preferably the total amount of all polymerizable compounds, in the LC medium is from 0.02 to 1.5%, more preferably from 0.05 to 1.2%, most preferably from 0.15 to 1.0%. In a first preferred embodiment, the LC medium according to the present invention contains one or more polymerizable compounds of formula I or its subformulae in a concentration from 0.01 to 0.12%, more preferably from 0.01 to 0.1%, very preferably from 0.025 to 0.075%, and further contains one or more polymerizable compounds that are different from formula I, and are preferably selected from formulae M1 to M32, very preferably from formulae CM and MT, or their subformulae, in a concentration from 0.15 to 0.7%, more preferably from 0.15 to 0.5%, very preferably from 0.2 to 0.4%, and the concentration of the polymerizable compounds of formula I is smaller than the concentration of the polymerizable compounds that are different from formula I. The LC medium according to this first preferred embodiment is especially suitable, and preferably used, in a PSA display or PSA display manufacturing process where polymerization is carried out using a fluorescent type UV lamp, preferably a fluorescent C-type UV lamp in the UV1 step and a fluorescent B-type UV lamp in the UV2 step as described above. In a second preferred embodiment, the LC medium according to the present invention contains one or more polymerizable compounds of formula or its subformulae in a concentration from 0.2 to 1.2%, more preferably from 0.2 to 1.0%, very preferably from 0.3 to 0.8%, and one or more polymerizable compounds that are different from formula I, and are preferably selected from formulae M1 to M32, very preferably from formula CM and MT, or their subformulae, in a concentration from 0.1 to 0.5%, more preferably from 0.15 to 0.5%, very preferably from 0.2 to 0.4%, and preferably in these LC media the concentration of the polymerizable compounds of formula I is at least equal to, and very preferably higher than, the concentration of the polymerizable compounds that are different from formula I. In a third preferred embodiment, the LC medium according to the present invention contains two or more polymerizable compounds of formula I or its subformulae in a total concentration from 0.2 to 1.5%, more preferably from 0.3 to 1.2%, very preferably from 0.4 to 1.0%. The LC medium according to these second and third preferred embodiments is especially suitable, and preferably used, in a PSA display or PSA display manufacturing process where polymerization is carried out using a UV LED lamp, preferably a UV LED lamp in the UV1 step and a UV LED lamp in the UV2 step as described above, preferably with a wavelength in the preferred ranges as described above, most preferably of 365 nm. The LC medium according to the present invention may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, chiral dopants, polymerization 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 medium has preferably a nematic LC phase. In a preferrd embodiment the LC medium contains one or more polymerization initiators. Suitable conditions for the polymerization and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerization are, for example, the commercially available photoinitiators Irgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocure1173® (Ciba AG). If a polymerization initiator is employed, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight. The polymerizable compounds according to the invention are also suitable for polymerization without an initiator, which is accompanied by considerable advantages, such, for example, lower material costs and in particular less contamination of the LC medium by possible residual amounts of the initiator or degradation products thereof. The polymerization can thus also be carried out without the addition of an initiator. Thus, in another preferred embodiment, the LC medium does not contain a polymerization initiator. In another preferred embodiment the LC medium additionally comprises one or more stabilisers in order to prevent undesired spontaneous polymerization of the RMs, for example during storage or transport. Suitable types and amounts of stabilisers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, the commercially available stabilisers from the Irganox® series (Ciba AG), such as, for example, Irganox® 1076. If stabilisers are employed, their proportion, based on the total amount of RMs or the polymerizable component (com- ponent A), is preferably 10-50,000 ppm, particularly preferably 50-5,000 ppm. In a preferred embodiment the LC medium contains one or more chiral dopants, preferably in a concentration from 0.01 to 1% by weight, very preferably from 0.05 to 0.5% by weight. The chiral dopants are preferably selected from the group consisting of compounds from Table B below, very preferably from the group consisting of R- or S-1011, R- or S-2011, R- or S- 3011, R- or S-4011, and R- or S-5011. In another preferred embodiment the LC media contain a racemate of one or more chiral dopants, which are preferably selected from the chiral dopants mentioned in the previous paragraph. In another preferred embodiment of the present invention the LC media contain one or more further stabilisers, preferably selected from the the group consisting of the following formulae

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings R^a-d straight-chain or branched alkyl with 1 to 10, preferably 1 to 6, very preferably 1 to 4 C atoms, most preferably methyl, X^S H, CH₃, OH or O^•, A^S straight-chain, branched or cyclic alkylene with 1 to 20 C atoms which is optionally substituted, n an integer from 1 to 6, preferably 3. Preferred stabilisers of formula S3 are selected from formulaS3A

wherein n2 is an integer from 1 to 12, and wherein one or more H atoms in the group (CH₂)_n2 are optionally replaced by methyl, ethyl, propyl, butyl, pentyl or hexyl. Very preferred stabilisers are selected from the group consisting of the following formulae

In a preferred embodiment the LC medium comprises one or more stabilisers selected from the group consisting of formulae S1-1, S2-1, S3-1, S3-1 and S3-3. In a preferred embodiment the LC medium comprises one or more stabilisers selected from Table C below. Preferably the proportion of stabilisers, like those of formula S1-S3, in the LC medium is from 10 to 500 ppm,very preferably from 20 to 100 ppm. In another preferred embodiment the LC medium according to the present invention contains a self alignment (SA) additive, preferably in a concentration of 0.1 to 2.5 %. In another preferred embodiment the LC medium according to the present invention contains a self alignment (SA) additive, preferably in a concentration of 0.1 to 2.5 %. In a preferred embodiment the SA-VA display according to the present invention does not contain a polyimide alignment layer. In another preferred embodiment the SA-VA display according to preferred embodiment contains a polyimide alignment layer. Preferred SA additives for use in this preferred embodiment are selected from compounds comprising a mesogenic group and a straight-chain or branched alkyl side chain that is terminated with one or more polar anchor groups selected from hydroxy, carboxy, amino or thiol groups. Further preferred SA additives contain one or more polymerizable groups which are attached, optionally via spacer groups, to the mesogenic group. These polymerizable SA additives can be polymerized in the LC medium under similar conditions as applied for the RMs in the PSA process. Suitable SA additives to induce homeotropic alignment, especially for use in SA-VA mode displays, are disclosed for example in US 2013/0182202 A1, US 2014/0838581 A1, US 2015/0166890 A1 and US 2015/0252265 A1. In another preferred embodiment an LC medium or a polymer stabilised SA- VA display according to the present invention contains one or more self alignment additives selected from Table E below. In another preferred embodiment the LC medium according to the present invention contains one or more SA additives, preferably selected from formula II or its subformulae or selected from Table E, in a concentration from 0.1 to 5%, very preferably from 0.2 to 3%, most preferably from 0.2 to 1.5%. Besides the polymerizable compounds and additives described above, the LC medium for use in the LC displays according to the invention comprises an LC mixture ("host mixture") comprising one or more, preferably two or more LC compounds which are selected from low-molecular-weight compounds that are unpolymerizable, and at least one of which is a compound of formula II. These LC compounds are selected such that they stable and/or unreactive to a polymerization reaction under the conditions applied to the polymerization of the polymerizable compounds. Particularly preferred embodiments of such an LC medium are shown below. Preferably the LC medium contains one or more compounds of formula II selected from the group consisting of compounds of the formulae IIA, IIB, IIC and IID

in which R^2A and R^2B each, independently of one another, denote H, an alkyl or alkenyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF₃ or at least monosubstituted by halogen, where, in addition, one or more CH₂ groups in these radicals may be replaced by -O-, -S-,

-C ≡C-, -CF₂O-, -OCF₂-, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, L¹ to L⁴ each, independently of one another, denote F, Cl, CF₃ or CHF₂, Y denotes H, F, Cl, CF₃, CHF₂ or CH₃, preferably H or CH₃, particularly preferably H, Z², Z^2B and Z^2D each, independently of one another, denote a single bond, -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CO O-, -OCO-, -C₂F₄-, -CF=CF-, -CH=CHCH₂O-, p denotes 0, 1 or 2, and q on each occurrence, identically or differently, denotes 0 or 1. Preferred compounds of the formulae IIA, IIB, IIC and IID are those wherein R^2B denotes an alkyl or alkoxy radical having up to 15 C atoms, and very preferablydenotes (O)C_vH_2v+1 wherein (O) is an oxygen atom or a single bond and v is 1, 2, 3, 4, 5 or 6. Further preferred compounds of the formulae IIA, IIB, IIC and IID are those wherein R^2A or R^2B denotes or contains cycloalkyl or cycloalkoxy radical, preferably selected from the group consisting of

wherein S¹ is C_1-5- alkylene or C_2-5-alkenylene and S² is H, C_1-7-alkyl or C_2-7-alkenyl, and very preferably selected from the group consisting of

Further preferred compounds of the formulae IIA, IIB, IIC and IID are indicated below:

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 (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂-CH=CH-, CH₃-(CH₂)₂- CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH-(CH₂)₂-. Particularly preferred LC medium according to the invention comprises one or more compounds of the formulae IIA-2, IIA-8, IIA-10, IIA-16, II-18, IIA-40, IIA-41, IIA-42, IIA-43, IIB-2, IIB-10, IIB-16, IIC-1, and IID-4. The proportion of compounds of the formulae IIA and/or IIB in the mixture as a whole is preferably at least 20 % by weight. In another preferred embodiment the LC medium comprises one or more compounds of formula III

in which R¹¹ and R¹² each, independently of one another, denote H, an alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH₂ groups in these radicals may each be replaced, independently of one another, by

-C ≡C-, -CF₂O-, -OCF₂-, -CH=CH-, by -O-, -CO-O- or -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, A³ on each occurrence, independently of one another, denotes a) 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH₂ groups may be replaced by - O- or -S-, b) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, or c) a radical selected from the group consisting of spiro[3.3]heptane-2,6-diyl, 1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7- diyl and fluorene-2,7-diyl, wherein the radicals a), b) and c) may be mono- or polysubsti- tuted by halogen atoms, n denotes 0, 1 or 2, preferably 0 or 1, Z¹ on each occurrence independently of one another denotes -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□C- or a single bond, and L¹¹ and L¹² each, independently of one another, denote F, Cl, CF₃ or CHF₂, preferably H or F, most preferably F, and W denotes O or S. In a preferred embodiment of the present invention the LC medium comprises one or more compounds of the formula III-1 and/or III-2

in which the occurring groups have the same meanings as given under formula III above and preferably R¹¹ and R¹² each, independently of one another, an alkyl, alkenyl or alkoxy radical having up to 15 C atoms, more preferably one or both of them denote an alkoxy radical and L¹¹ and L¹² each preferably denote F. In another preferred embodiment the LC medium comprises one or more compounds of the formula III-1 selected from the group of compounds of formulae III-1-1 to III-1-10, preferably of formula III-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 straight-chain alkoxy radical having 1-6 C atoms, and L¹¹ and L¹² each, independently of one another, denote F or Cl, preferably both F. In another preferred embodiment the LC medium comprises one or more compounds of the formula III-2 selected from the group of compounds of formulae III-2-1 to III-2-10, preferably of formula III-2-6,

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 straight-chain alkoxy radical having 1-6 C atoms, and L¹ and L² each, independently of one another, denote F or Cl, preferably both F. In another preferred embodiment of the present invention the LC medium comprises one or more compounds of the formula IIIA-1 and/or IIIA-2

in which L¹¹ and L¹² have the same meanings as given under formula III, (O) denotes O or a single bond, R^IIIA denotes alkyl or alkenyl having up to 7 C atoms or a group Cy- C_mH_2m+1-, m and n are, identically or differently, 0, 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, very preferably 1, and 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 or cyclopentyl. The compounds of formula IIIA-1 and/or IIIA-2 are contained in the LC medium either alternatively or additionally to the compounds of formula III, preferably additionally. Very preferred compounds of the formulae IIIA-1 and IIIA-2 are the following:

in which alkoxy denotes a straight-chain alkoxy radical having 1-6 C atoms. In a preferred embodiment of the present invention, the LC medium comprises one or more compounds of formula III-3

in which R¹¹, R¹² 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

-O-, -CO-O- or -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. The compounds of formula III-3 are preferably selected from the group of compounds of the formulae III-3-1 to III-3-10:

in which R¹² denotes alkyl having 1 to 7 C-atoms, preferably ethyl, n-propyl or n-butyl, or alternatively cyclopropylmethyl, cyclobutylmethyl or cyclopentylmethyl. In another preferred embodiment of the present invention, the LC medium comprises one or more compounds of the formulae III-4 to III-6, preferably of formula III-5,

in which the parameters have the meanings given above, R¹¹ preferably denotes straight-chain alkyl and R¹² preferably denotes alkoxy, each having 1 to 7 C atoms. In another preferred embodiment the LC medium comprises one or more compounds of the formula I selected from the group of compounds of formulae III-7 to III-9, preferably of formula III-8,

in which the parameters have the meanings given above, R¹¹ preferably denotes straight-chain alkyl and R¹² preferably denotes alkoxy each having 1 to 7 C atoms. 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. 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 LC medium comprises one or more compounds selected from the compounds of the formulae IV-1-1 to IV-1-4

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

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

Very preferably, the LC medium according to the invention comprises a compound of formula IV-4, in particular selected from the compounds of the formulae IV-4-1 and IV-4-2

The LC medium preferably additionally 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 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-. Preferred compounds of the formula IVa are indicated below:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 to 6 C atoms. The LC medium according to the invention preferably comprises at least one compound of the formula IVa-1and/or formula IVa-2. The proportion of compounds of the formula IVa in the mixture as a whole is preferably at least 5 % by weight Preferably, the LC medium comprises one or more compounds of formula IVb-1 to 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 straight-chain alkenyl radical having 2 to 6 C atoms. The proportion of the biphenyls of the formulae IV-1 to IV-3 in the mixture as a whole is preferably at least 3 % by weight, in particular ≥ 5 % by weight. Of the compounds of the formulae IVb-1 to IVb-3, the compounds of the formula IVb-2 are particularly preferred. Particularly preferred biphenyls are

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

in which R⁵¹ and R⁵² independently of one another, have one of the meanings given for R⁴¹ and R⁴² and preferably denote alkyl having 1 to 7 C atoms, preferably n-alkyl, particularly preferably n-alkyl having 1 to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy, particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to 4 C atoms, preferably alkenyloxy, identically or differently, denote

in which

preferably denotes

Z⁵¹ , Z⁵² each, independently of one another, denote -CH₂-CH₂-, -CH₂-O-,-CH=CH-, -C≡C-, -COO- or a single bond, preferably - CH₂-CH₂-, -CH₂-O- or a single bond and particularly preferably 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-16:

in which R¹ and R² have the meanings indicated for R^2A above. R¹ and R² preferably each, independently of one another, denote straight- chain alkyl or alkenyl. Preferred LC 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, and/or V-16 LC media according to the invention very particularly preferably comprise the compounds of the formula V-10, V-12, V-16 and/or IV-1, in particular in amounts of 5 to 30 %. Preferred compounds of the formulae V-10 are indicated below:

The LC medium according to the invention particularly preferably comprises the tricyclic compounds of the formula V-10a and/or of the formula V-10b in combination with one or more bicyclic compounds of the formulae IV-1 The total proportion of the compounds of the formulae V-10a and/or V-10b in combination with one or more compounds selected from the bicyclohexyl compounds of the formula IV-1 is 5 to 40 %, very particularly preferably 15 to 35 %. Very particularly preferred LC media comprise compounds V-10a and IV-1-1

The compounds V-10a and IV-1-1 are preferably present in the mixture in a concentration of 15 to 35 %, particularly preferably 15 to 25 % and especially preferably 18 to 22 %, based on the mixture as a whole. Very particularly preferred LC media comprise the compounds V-10b and IV-1-1:

The compounds V-10b and IV-1-1 are preferably present in the mixture in a concentration of 15 to 35 %, particularly preferably 15 to 25 % and especially preferably 18 to 22 %, based on the mixture as a whole. Very particularly preferred LC media comprise the following three compounds:

The compounds V-10a, V-10b and IV-1-1 are preferably present in the mixture in a concentration of 15 to 35 %, particularly preferably 15 to 25 % and especially preferably 18 to 22 %, based on the mixture as a whole. Preferred LC media comprise at least one compound selected from the group of the compounds

in which R⁴¹ and R⁴², and R⁵¹ and R⁵² have the meanings indicated above. Preferably in the compounds V-6, V-7 and IV-1, R⁴¹ and R⁵¹ denotes alkyl or alkenyl having 1 to 6 or 2 to 6 C atoms, respectively, and R⁴² and R⁵² denotes alkenyl having 2 to 6 C atoms. Preferred LC media comprise at least one compound of the formulae V-6a, V-6b, V-7a, V-7b, IV-4-1, IV-4-2, IV-3a and IV-3b:

in which alkyl denotes an alkyl radical having 1 to 6 C atoms and alkenyl denotes an alkenyl radical having 2 to 6 C atoms. The compounds of the formulae V-6a, V-6b, V-7a, V-7b, IV-4-1, IV-4-2, IV-3a and IV-3b are preferably present in the LC media according to the invention in amounts of 1 to 40 % by weight, preferably 5 to 35 % by weight and very particularly preferably 10 to 30 % by weight. In a preferred embodiment of the present invention the LC medium additionally comprises one or more compounds of the formulae VI-1 to VI-9

in which R⁷ each, independently of one another, have one of the meanings indicated for R^2A in formula IIA, and w and x each, independently of one another, denote 1 to 6. Particular preference is given to LC media comprising at least one compound of the formula V-9. In a preferred embodiment of the present invention the LC medium additionally comprises one or more compounds of the formulae VII-1 to VII-25,

in which R denotes a straight-chain alkyl or alkoxy radical having 1 to 6 C atoms, (O) denotes -O- or a single bond, X denotes F, Cl, OCF₃ or OCHF₂, L^x denotes H or F, m is 0, 1, 2, 3, 4, 5 or 6 and n is 0, 1, 2, 3 or 4. R preferably denotes methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy. X preferably denotes F or OCH₃, very preferably F. The LC medium according to the invention preferably comprises the ter- phenyls of the formulae VII-1 to VII-25 in amounts of 2 to 30 % by weight, in particular 5 to 20 % by weight. Particular preference is given to compounds of the formulae VII-1, VII-2, VII-4, VII-20, VII-21, and VII-22 wherein X denotes F. In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having 1 to 5 C atoms. In the compounds of the formula VII-20, R preferably denotes alkyl or alkenyl, in particular alkyl. In the compounds of the formula VII-21, R preferably denotes alkyl. In the compounds of the formulae VII-22 to VII-25, X preferably denotes F. The terphenyls of formula VII-1 to VII-25 are preferably employed in the LC media according to the invention if the Δn value of the mixture is to be ≥ 0.1. Preferred LC media comprise 2 to 20 % by weight of one or more terphenyl compounds selected from the group of the compounds of formulae VII-1 to VII-25. Further preferred embodiments are listed below: a) LC medium comprising at least one compound of the formulae Z-1 to Z-7,

in which R, (O) and alkyl have the meanings indicated above for formula III. b) Preferred LC 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^1N 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 LC media 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. The LC media according to the invention preferably comprise the com- pounds of the formulae BC, CR, PH-1, PH-2 in amounts of 3 to 20 % by weight, in particular in amounts of 3 to 15 % by weight. Particularly preferred compounds of the formulae BC and CR are the compounds BC-1 to BC-7 and CR-1 to CR-5,

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 straight-chain alkenyl radical having 2 to 6 C atoms. Very particular preference is given to LC media comprising one, two or three compounds of the formula BC-2, BF-1 and/or BF-2. d) Preferred LC media comprise one or more indane compounds of the formula In,

in which R¹¹, R¹², R¹³ each, independently of one another, denote a straight- chain alkyl, alkoxy, alkoxyalkyl or alkenyl radical having 1 to 6 C atoms, R¹² and R¹³ additionally denote halogen, preferably F, denotes

i denotes 0, 1 or 2. Preferred compounds of the formula In are the compounds of the formulae In-1 to In-16 indicated below:

Particular preference is given to the compounds of the formulae In-1, In- 2, In-3 and In-4. The compounds of the formula In and the sub-formulae In-1 to In-16 are preferably employed in the LC media according to the invention in concentrations ≥ 5 % by weight, in particular 5 to 30 % by weight and very particularly preferably 5 to 25 % by weight. e) Preferred LC media additionally comprise one or more compounds of the formulae L-1 to L-5,

in which R and R¹ each, independently of one another, have the meanings indicated for R^2A in formula IIA 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-5 are preferably employed in concentrations of 5 to 50 % by weight, in particular 5 to 40 % by weight and very particularly preferably 10 to 40 % by weight. f) Preferred LC media 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 IIA above, and L¹ and L², identically or differently, denote F or Cl. Preferred compounds of the formula IIA-Y are selected from the group consisting of the following subformulae

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

in which Alkoxy and Alkoxy* have the meanings defined above and preferably denote methoxy, ethoxy, n- propyloxy, n-butyloxy or n- pentyloxy. g) LC medium which additionally comprises one or more quaterphenyl compounds selected from the following formula:

wherein R^Q is alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated, X^Q is F, Cl, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, L^Q1 to L^Q6 independently of each other are H or F, with at least one of L^Q1 to L^Q6 being F. Preferred compounds of formula Q are those wherein R^Q denotes straight-chain alkyl with 2 to 6 C-atoms, very preferably ethyl, n-propyl or n-butyl. Preferred compounds of formula Q are those wherein L^Q3 and L^Q4 are F. Further preferred compounds of formula Q are those wherein L^Q3, L^Q4 and one or two of L^Q1 and L^Q2 are F. Preferred compounds of formula Q are those wherein X^Q denotes F or OCF₃, very preferably F. The compounds of formula Q are preferably selected from the following subformulae

wherein R^Q has one of the meanings of formula Q or one of its preferred meanings given above and below, and is preferably ethyl, n-propyl or n- butyl. Especially preferred are compounds of formula Q1, in particular those wherein R^Q is n-propyl. Preferably the proportion of compounds of formula Q in the LC host mixture is from >0 to ≤5% by weight, very preferably from 0.05 to 2% by weight, more preferably from 0.1 to 1% by weight, most preferably from 0.1 to 0.8% by weight. Preferably the LC medium contains 1 to 5, preferably 1 or 2 compounds of formula Q. The addition of quaterphenyl compounds of formula Q to the LC host mixture enables to reduce ODF mura, whilst maintaining high UV absorption, enabling quick and complete polymerization, enabling strong and quick tilt angle generation, and increasing the UV stability of the LC medium. Besides, the addition of compounds of formula Q, which have positive dielectric anisotropy, to the LC medium with negative dielectric anisotropy allows a better control of the values of the dielectric constants ε_|| and ε_┴, and in particular enables to achieve a high value of the dielectric constant ε_|| while keeping the dielectric anisotropy Δε constant, thereby reducing the kick-back voltage and reducing image sticking. The LC media according to the invention preferably comprise - one or more compounds of formula I, preferably of formula I1, very preferably selected from formulae I1-1 to I1-10, preferably in a total concentration in the range of from 0.01% to 2.0%, more preferably from 0.1% to 1.0%, most preferably from 0.2% to 0.8%, and/or - one or more compounds of formula IIA, preferably in a total concentration in the range of from 5% to 30%, more preferably from 7% to 25%, particularly preferably from 10% to 20%; and/or - one or more compounds of formulae IIA and IIB, preferably in a total concentration in the range of from 30% to 45%; and/or - one or more compounds of formula IV, preferably in a total concentration in the range of from 35% to 70%, more preferably from 40 % to 65%, particularly preferably from 45% to 60%; and/or - one or more compounds of formula IV-3, preferably in a total concentration in the range of from 35% to 60%, more preferably from 40 % to 55%, particularly preferably from 45% to 50%; and/or - one or more compounds of formula III-2, preferably of formula III-2-6, preferably in a total concentration in the range of from 2% to 25%, more preferably from 5% to 15%, particularly preferably from 5 to 12%. In particular, the medium comprises - one or more compounds CY-n-Om, in particular CY-3-O4, CY-5-O4 and/or CY-3-O2, preferably in a total concentration in the range of from 5% to 30%, preferably 10% to 20%; and/or - one or more compounds PY-n-Om, in particular PY-3-O2 and/or PY-1-O2, preferably in a total concentration in the range of from 5% to 30%, preferably 5% to 20%; and/or - CPY-n-Om, in particular CPY-2-O2, CPY-3-O2 and/or CPY-5-O2, pref- erably in concentrations > 5%, in particular 7% to 20%, based on the mixture as a whole, and/or - one or more compounds CCY-n-Om, preferably CCY-4-O2, CCY-3-O2, CCY-3-O3, CCY-3-O1 and/or CCY-5-O2, preferably in concentrations > 3%, in particular 5 to 15%, based on the mixture as a whole; and/or - one or more compounds CPY-n-Om, preferably CPY-2-O2 and/or CPY-3- O2, preferably in concentrations > 3%, in particular 5 to 15%, based on the mixture as a whole; and/or - CLY-n-Om, preferably CLY-2-O4, CLY-3-O2 and/or CLY-3-O3, preferably in concentrations > 5%, in particular 10 to 30%, very preferably 15 to 20%, based on the mixture as a whole; and/or - CPY-n-Om and CY-n-Om, preferably in concentrations of 10 to 80%, based on the mixture as a whole, and/or - CPY-n-Om and PY-n-Om, preferably CPY-2-O2 and/or CPY-3-O2 and PY- 3-O2 or PY-1-O2, preferably in concentrations of 5 to 20%, more preferably 10 to 15% to based on the mixture as a whole, and/or - CC-3-V, preferably in concentrations of 5 to 50%, based on the mixture as a whole. and/or - the compound of the formula CC-3-V1, in a total concentration in the range of from 5 to 40%, more preferably from 15% to 35%, particularly preferably from 20% to 30%, and/or - one or more compounds of formula B-nO-Om and/or B(S)-nO-Om, in particular the compound B(S)-2O-O4 and/or B(S)-2O-O5, preferably in a concentration in the range of from 2 to 12 %. and/or - 0.1% to 3% of the compound PPGU-3-F. The invention furthermore relates to an electro-optical display having active- matrix addressing, characterised in that it contains, as dielectric, a LC medium according to claim 1 and wherein the display is a VA, SA-VA, IPS, U-IPS, FFS, UB-FFS, SA-FFS, PS-VA, PS-OCB, PS-IPS, PS-FFS, PS-UB- FFS, PS-posi-VA, PS-TN, polymer stabilised SA-VA or polymer stabilised SA-FFS display. It is advantageous for the LC medium according to the invention to preferably have a nematic phase from ≤ -20°C to ≥ 70°C, particularly preferably from ≤ -30°C to ≥ 80°C, very particularly preferably from ≤ -40°C to ≥ 90°C. The medium according to the invention has a clearing temperature of 70°C or more, preferably of 74°C or more. The expression "have a nematic phase" here means on the one hand that no smectic phase and no crystallisation are observed at low temperatures at the corresponding temperature and on the other hand that clearing still does not occur on heating from the nematic phase. The investigation at low temperatures is carried out in a flow viscometer at the corresponding tem- perature and checked by storage in test cells having a layer thickness cor- responding 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 tempera- tures 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 con- ventional methods in capillaries. The liquid-crystal mixture preferably has a nematic phase range of at least 60 K and a flow viscosity ν₂₀ 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 values of the birefringence Δn in the liquid-crystal mixture are generally between 0.07 and 0.16, preferably between 0.08 and 0.15, very preferably between 0.09 and 0.14. In a preferred embodiment of the present invention, the medium has a birefringence in the range of from 0.090 to 0.110, preferably from 0.095 to 0.105, in particular from 0.100 to 0.105. In another preferred embodiment, the medium according to the invention has a birefringence of 0.120 or more, preferably in the range of from 0.125 to 0.145, more preferably from 0.130 to 0.140. The liquid-crystal mixture according to the invention has a dielectric anisotropy Δε of -1.5 to -8.0, preferably of -2.0 to – 4.0, in particular -2.5 to -3.5, The rotational viscosity γ₁ at 20°C is preferably ≤ 120 mPa ·s, in particular ≤ 100 mPa ·s. In a preferred embodiment, the rotational viscosity γ₁ at 20°C is ≤ 100mPa ·s, in particular ≤ 95 mPa ·s. The liquid-crystal media according to the invention have relatively low values for the threshold voltage (V₀). They are preferably in the range from 1.7 V to 3.0 V, particularly preferably ≤ 2.7 V and very particularly preferably ≤ 2.5 V. For the present invention, the term "threshold voltage" relates to the capa- citive threshold (V₀), also called the Freedericks threshold, unless explicitly indicated otherwise. In 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 Δε > 1.5, the term "dielectrically neutral com- pounds" denotes those having -1.5 ≤ Δε ≤ 1.5 and the term "dielectrically negative compounds” denotes those having Δε < -1.5. The dielectric ani- sotropy of the compounds is determined here by dissolving 10 % of the compounds in a LC host and determining the capacitance of the resultant mixture in at least one test cell in each case having a layer thickness of 20 µm 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 LC media according to the invention are suitable for all VA-TFT (vertical alignment-thin film transistor) applications, such as, for example, VAN (vertically aligned nematic), MVA (multidomain VA), (S)-PVA (super patterned VA), ASV (advanced super view, or axially symmetric VA), PSA (polymer sustained VA) and PS-VA (polymer stabilized VA). They are fur- thermore suitable for IPS (in-plane switching) and FFS (fringe field switching) applications having negative Δε. The nematic LC media in the displays according to the invention generally comprise two components A and B, which themselves consist of one or more individual compounds. Component A has significantly negative dielectric anisotropy and gives the nematic phase a dielectric anisotropy of ≤ -0.5. Besides one or more com- pounds of the formula I, it preferably comprises the compounds of the for- mulae IIA, IIB and/or IIC, furthermore one or more compounds of the formula IV-1. The proportion of component A is preferably between 45 and 100 %, in par- ticular between 60 and 85 %. For component A, one (or more) individual compound(s) which has (have) a value of Δε ≤ -0.8 is (are) preferably selected. This value must be more negative, the smaller the proportion A in the mixture as a whole. Component B has pronounced nematogeneity and a flow viscosity of not greater than 30 mm² · s^-1, preferably not greater than 25 mm² · s^-1, at 20°C. A multiplicity of suitable materials is known to the person skilled in the art from the literature. Particular preference is given to compounds of the formula O-17. Particularly preferred individual compounds in component B are extremely low-viscosity nematic liquid crystals having a flow viscosity of not greater than 18 mm² · s^-1,ε preferably not greater than 12 mm² · s^-1, at 20°C. Component B is monotropically or enantiotropically nematic, has no smectic phases and is able to prevent the occurrence of smectic phases down to very low temperatures in LC media. For example, if various materials of high nematogeneity are added to a smectic liquid-crystal mixture, the nemato- geneity of these materials can be compared through the degree of sup- pression of smectic phases that is achieved. The mixture may optionally also comprise a component C, comprising compounds having a dielectric anisotropy of Δε ≥1.5. These so-called posi- tive compounds are generally present in a mixture of negative dielectric anisotropy in amounts of ≤ 20 % by weight, based on the mixture as a whole. Besides one or more compounds of the formula I1, I2 and optionally I3, the medium preferably comprises 4 to 15, in particular 5 to 12, and particularly preferably < 10, compounds of the formulae IIA, IIB and/or IIC and optionally one or more compounds of the formula IV-1 Besides compounds of the formula I1, I2 and optionally I3 and the compounds of the formulae IIA, IIB and/or IIC and optionally IV-1, other constituents may also be present, for example in an amount of up to 45 % of the mixture as a whole, but preferably up to 35 %, in particular up to 10 %. The other constituents are preferably selected from nematic or nematogenic substances, in particular known substances, from the classes of the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclo- hexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenyl- cyclohexanes, cyclohexylbiphenyls, cyclohexylcyclohexanes, cyclo- hexylnaphthalenes, 1,4-biscyclohexylbiphenyls or cyclohexylpyrimidines, phenyl- or cyclohexyldioxanes, optionally halogenated stilbenes, benzyl phenyl ethers, tolanes and substituted cinnamic acid esters. The most important compounds which are suitable as constituents of liquid- crystal phases of this type can be characterised by the formula OC R²⁰-L-G-E-R²¹ OC in which L and E each denote a carbo- or heterocyclic ring system from the group formed by 1,4-disubstituted benzene and cyclohexane rings, 4,4'- disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane systems, 2,5-disubstituted pyrimidine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, quinazoline and tetra- hydroquinazoline, G denotes -CH=CH- -N(O)=N- -CH=CQ- -CH=N(O)- -C ≡C- -CH₂-CH₂- -CO-O- -CH₂-O- -CO-S- -CH₂-S- -CH=N- -COO-Phe-COO- -CF₂O- -CF=CF- -OCF₂- -OCH₂- -(CH₂)₄- -(CH₂)₃O- or a C-C single bond, Q denotes halogen, preferably chlorine, or -CN, and R²⁰ and R²¹ each denote alkyl, alkenyl, alkoxy, alkoxyalkyl or alkoxycarbonyl- oxy having up to 18, preferably up to 8, carbon atoms, or one of these radicals alternatively denotes CN, NC, NO₂, NCS, CF₃, SF₅, OCF₃, F, Cl or Br. In most of these compounds, R²⁰ and R²¹ are different from one another, one of these radicals usually being an alkyl or alkoxy group. Other variants of the proposed substituents are also common. Many such substances or also mixtures thereof are commercially available. All these substances can be prepared by methods known from the literature. 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 combination of compounds of the preferred embodiments mentioned above with the polymerized compounds described above causes low threshold voltages, low rotational viscosities and very good low-temperature stabilities in the LC media according to the invention at the same time as constantly high clearing points and high HR values, and allows the rapid establishment of a particularly low tilt angle (i.e. a large tilt) in PSA displays. In particular, the LC media exhibit significantly shortened response times, in particular also the grey-shade response times, in PSA displays compared with the LC media from the prior art. The LC media according to the invention may also comprise further additives which are known to the person skilled in the art and are described in the literature, such as, for example, polymerization initiators, inhibitors, stabilisers, surface-active substances or chiral dopants. These may be polymerizable or non-polymerizable. Polymerizable additives are accordingly ascribed to the polymerizable component or component A). Non- polymerizable additives are accordingly ascribed to the non-polymerizable component or component B). Furthermore, it is possible to add to the LC media, for example, 0 to 15% by weight of pleochroic dyes, furthermore nanoparticles, conductive salts, preferably ethyldimethyldodecylammonium 4-hexoxybenzoate, tetrabutyl- ammonium tetraphenylborate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst.24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Sub- stances of this type are described, for example, in DE-A 2209127, 2240 864, 2321632, 2338281, 2450088, 2637430 and 2853728. The individual components of the above-listed preferred embodiments of the LC media according to the invention are either known or methods for the preparation thereof can readily be derived from the prior art by the person skilled in the relevant art, since they are based on standard methods described in the literature. Corresponding compounds of the formula CY are described, for example, in EP-A-0364538. Corresponding compounds of the formula ZK are described, for example, in DE-A-2636684 and DE-A-3321 373. The LC media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned compounds with one or more polymerizable compounds as defined above, and optionally with further liquid-crystalline compounds and/or additives. In general, the desired amount of the com- ponents used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. The invention furthermore relates to the process for the preparation of the LC media according to the invention. It goes without saying to the person skilled in the art that the LC media according to the invention may also comprise compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes like deuterium etc. The following examples explain the present invention without restricting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective con- centrations thereof and combinations thereof with one another. In addition, the examples illustrate which properties and property combinations are accessible. Preferred mixture components are shown in Table A below. Table A In Table A, m and n are independently of each other an integer from 1 to 12, preferably 1, 2, 3, 4, 5 or 6, k is 0, 1, 2, 3, 4, 5 or 6, and (O)C_mH_2m+1 means C_mH_2m+1 or OC_mH_2m+1.



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

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In a preferred embodiment of the present invention, the LC media according to the invention comprise one or more compounds selected from the group consisting of compounds from Table A. Table B Table B shows possible chiral dopants which can be added to the LC media according to the invention.

The LC media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight, particularly preferably 0.1 to 3% by weight, of dopants. The LC media preferably comprise one or more dopants selected from the group consisting of compounds from Table B. Table C Table C shows possible stabilisers which can be added to the LC media according to the invention. Therein n denotes an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8, and terminal methyl groups are not shown.

The LC media preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1% by weight, of stabilisers. The LC media preferably comprise one or more stabilisers selected from the group consisting of compounds from Table C. Table D Table D shows illustrative reactive mesogenic compounds which can be used in the LC media in accordance with the present invention.

In a preferred embodiment, the mixtures according to the invention comprise one or more polymerizable compounds, preferably selected from the polymerizable compounds of the formulae RM-1 to RM-182. Of these, compounds RM-1, RM-4, RM-8, RM-17, RM-19, RM-35, RM-37, RM-39, RM- 40, RM-41, RM-48, RM-52, RM-54, RM-57, RM-58, RM-64, RM-74, RM-76, RM-88, RM-91, RM-102, RM-103, RM-109, RM-116, RM-117, RM-120, RM- 121, RM-122, RM-139, RM-140, RM-142, RM-143, RM-145, RM-146, RM- 147, RM-149, RM-156 to RM-163, RM-169, RM-170 and RM-171 to RM-183 are particularly preferred. Table E Table E shows self-alignment additives for vertical alignment which can be used in LC media for SA-VA and SA-FFS displays according to the present invention together with the polymerizable compounds of formula I:

In a preferred embodiment, the LC media, SA-VA and SA-FFS displays according to the present invention comprise one or more SA additives selected from formulae SA-1 to SA-48, preferably from formulae SA-14 to SA-48, very preferably from formulae SA-20 to SA-34 and SA-44, in combination with one or more RMs of formula I. Examples The following examples explain the present invention without restricting it. However, they show the person skilled in the art preferred mixture concepts with compounds preferably to be employed and the respective con- centrations thereof and combinations thereof with one another. In addition, the examples illustrate which properties and property combinations are accessible. In addition, the following abbreviations and symbols are used: V₀ threshold voltage, capacitive [V] at 20°C, n_e extraordinary refractive index at 20°C and 589 nm, n_o ordinary refractive index at 20°C and 589 nm, Δn optical anisotropy at 20°C and 589 nm, ε_┴ dielectric permittivity perpendicular to the director at 20°C and 1 kHz, ε|| dielectric permittivity parallel to the director at 20°C and 1 kHz, Δε dielectric anisotropy at 20°C and 1 kHz, cl.p., T(N,I) clearing point [°C], γ₁ rotational viscosity at 20°C [mPa ^s], K₁ 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 Δn is determined at 589 nm and Δε at 1 kHz, unless explicitly indicated otherwise in each case. The term "threshold voltage" for the present invention relates to the capa- citive threshold (V₀), 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, the process of polymerizing the polymerizable compounds in the PSA displays as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably is carried out at room temperature. 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 usually consists of two plane-parallel glass outer plates at a separation of 25 µm, each of which has on the inside an electrode layer and an unrubbed poly- imide alignment layer on top, which effect a homeotropic edge alignment of the liquid-crystal molecules. The PSVA display or PSVA test cell used for measurement of the tilt angles usually consists of two plane-parallel glass outer plates at a separation of 4 µm unless stated otherwise, each of which has on the inside an electrode layer and a polyimide alignment layer on top, where the two polyimide layers are rubbed antiparallel to one another and effect a homeotropic edge alignment of the liquid-crystal molecules. The SAVA display or test cell has the same structure but wherein one or both polyimide layers are omitted. The polymerizable compounds are usually polymerized in the display or test cell by irradiation with UV light of defined intensity for a prespecified time, with a voltage simultaneously being applied to the display (usually 10 V to 30 V alternating current, 1 kHz). The intensity is measured using a standard meter (Hoenle UV-meter high end with UV sensor). The tilt angle is usually determined using the Mueller Matrix Polarimeter “AxoScan” from Axometrics. A low value (i.e. a large deviation from the 90° angle) corresponds to a large tilt here. Unless stated otherwise, the term "tilt angle" means the angle between the LC director and the substrate, and "LC director" means in a layer of LC molecules with uniform orientation the preferred orientation direction of the optical main axis of the LC molecules, which corresponds, in case of calamitic, uniaxially positive birefringent LC molecules, to their molecular long axis. Example 1 The nematic LC host mixture N1 is formulated as follows B(S)-2O-O4 4.50 % cl.p. 76°C B(S)-2O-O5 5.00 % Δn 0.1120 BCH-32 6.00 % n_e 1.6002 CC-3-V 47.50 % n_o 1.4882 CLY-3-O2 6.00 % Δε -3.0 CPY-2-O2 10.50 % ε|| 3.5 CPY-3-O2 10.50 % ε_┴ 6.6 PY-1-O2 10.00 % γ₁ 74 mPa.s K₁ 14.2 K₃ 14.5 K₃/K₁ 1.03 V₀ 2.31 V Polymerizable mixture P1 according to the present invention is prepared by adding 0.05% of polymerizable compound 1 of formula I and 0.3% of polymerizable compound RM-1 to nematic LC host mixture N1. For comparison purpose polymerizable mixture C1 is prepared by adding only 0.3% of polymerizable compound RM-1 to nematic LC host mixture N1.

The absorption wavelength λ of compounds RM-1 and 1 at an extinction coefficient of E = 0.5 is measured in a solution in DCM at a concentration of 3g/L. The results are shown in Table 1. Table 1 –UV Absorption

From Table 1 it can be seen that compound 1 of formula I has a long absorption wavelength which is higher than that of compound RM-1. Compound 1 is thus better suitable for UV photopolymerization at longer wavelengths. Based on the UV-Vis absorption data shown in Table 1 above, it can be expected that compound RM-1 will not show good polymerization when exposed with a UV-LED lamp having an emission centered around 365 nm because of the lack of overlap of its absorption spectrum with the UV-LED emission spectrum of the UV-LED lamp. Therefore, unless stated otherwise in the following experiments mixtures containing only compound RM-1 are polymerized using a C-type fluorescent lamp with an emission peak at 313 nm, while mixtures containing only compounds of formula I are polymerized using an UV-LED lamp showing emission centered around 365 nm, and mixtures of containing compounds of formula I are compound RM-1 are polymerized using a C-type lamp in the UV1 step and using a B-type lamp in the UV2 step.. For polymerization of polymerizable compound 1 test cells containing the polymerizable mixture P1 are exposed to UV light in a two step process, the first step (UV1) for generating a tilt angle and the second step (UV2) for polymerizing any residual monomer that was not polymerized in the first step. In UV1 step a voltage is applied (20 V_pp square wave, 200 Hz). In UV2 step no voltage is applied. The other conditions are as follows, unless stated otherwise: UV1 (C-type lamp): 4.5 mW/cm² at room temperature for 30-200s UV2 (B-type lamp): 2.5 mW/cm² at RT, 120 min For polymerization of polymerizable compound RM-1 test cells containing the polymerizable mixture C1 are irradiated using conventional lamps to polymerize the compound in two steps as described above. The conditions are as follows. UV1 (C-type fluorescent lamp): 4.5 mW/cm² at room temperature for 30-300s UV2 (C-type fluorescent lamp): 0.5 mW/cm² at room temperature, 120 min Tilt Angle Generation The tilt angle generated in the test cells after the UV1 step above is measured using an Otsuka T_RETS-10 system. The time that is required for generating a tilt angle of 88° is shown in Table 2 below. Table 2 – Tilt Angle Generation

From Table 2 it can be seen that polymerizable mixture P1 according to the invention shows a significantly faster tilt angle generation than reference mixture C1. Tilt Stability Tilt stability, i.e. the change of the tilt angle after repeated electric stress, is a criterion for evaluating the risk of image sticking. A low value for the change of the tilt angle indicates a high tilt stability and a low potential risk of image sticking. For determining the tilt stabillity the test cells after polymerization as described above are electrically stressed with a square wave of 60VPP at 60 Hz for 72 h. After a relaxation time of 5-10 min the tilt angles are measured using the Otsuka T_RETS-10 system. The change of the tilt angle Δtilt is determined according to equation (1) tilt_{after stress} – tilt_{after tilt generation} = Δtilt (1) and is shown in Table 3 below. The lower the value of ^tilt, the higher is the tilt stability. Table 3 – Tilt Stability

From Table 3 it can be seen that polymerizable mixture P1 according to the invention shows significantly better tilt stability than reference mixture C1. Voltage Holding Ratio (VHR) The VHR of the polymerizable LC media is measured at 60°C with application of a voltage of 1 V / 0.6 Hz initial and after UV exposure. Light stress usually causes the decrease of VHR in LC mixtures, therefore the smaller the absolute decrease of VHR value after stress, the better performance for display applications. The results are shown in Table 4. Table 4 - VHR

From Table 4 it can be seen that the VHR of polymerizable mixture P1 according to the invention is significantly higher after UV stress than that of polymerizable mixture C1. Overall, the above results demonstrate that the addition of a small amount of a polymerizable compound of formula I to a polymerizable LC medium comprising the polymerizable compound RM-1 from prior art leads to significant improvements of the tilt angle generation, tilt stability and VHR after UV stress. Examples 2 & 3 The nematic LC host mixture N2 is formulated as follows BCH-32 6.50 % cl.p. 74.7°C CC-3-V1 8.00 % Δn 0.1039 CCH-23 17.00 % ne 1.5900 CCH-34 6.50 % no 1.4861 CCY-3-O1 3.50 % Δε -3.0 CCY-3-O2 12.50 % ε|| 3.4 CPY-2-O2 5.50 % ε_┴ 6.3 CPY-3-O2 10.00 % γ₁ 106 mPa.s CY-3-O2 15.50 % K₁ 14.8 PCH-301 4.50 % K₃ 15.8 PP-1-2V1 5.00 % K₃/K₁ 1.07 PY-3-O2 5.50 % V₀ 2.43 V Polymerizable mixtures P2 and P3 according to the present invention are prepared by adding polymerizable compound 1 of formula I and polymerizable compound RM-1 to the nematic LC host mixture N2 in different concentrations. For comparison purposes polymerizable reference mixture C2 is prepared by adding only polymerizable compound RM-1 to nematic LC host mixture N2. The compositions of the polymerizable mixtures are shown in Table 5 below. Table 5 - Polymerizable mixture compositions

The mixtures are polymerized as described in Example 1, using a C-type lamp in UV 1 step and a B-type lamp in UV2 step. Tilt Angle The tilt angle generated in the test cells after the UV1 step is determined as described in Example 1. The time that is required for generating a tilt angle of 88° is shown in Table 6 below. Table 6 – Tilt Angle

From Table 6 it can be seen that polymerizable mixtures P2 and P3 according to the invention show significantly faster generation of the tilt angle than mixture C2. Tilt Stability The change of the tilt angle Δtilt is determined as described in Example 1 and is shown in Table 7 below. Table 7 – Tilt Stability

From Table 7 it can be seen that polymerizable mixtures P2 and P3 according to the invention show good tilt stability similar to mixture C2. The above results demonstrate that the addition of only a small amount of a polymerizable compound of formula I renders the LC media suitable for use in PSA displays prepared by polymerization with longer UV wavelengths, for example by using a UV B-type lamp in the UV2 step. Examples 4 – 9 Polymerizable mixtures P4 – P9 according to the present invention are prepared by adding polymerizable compound 1 or 2 and polymerizable compound RM-1 to nematic LC host mixture N1 in various concentrations.

The compositions of the polymerizable mixtures are shown in Table 8 below. Table 8 - Polymerizable mixture compositions

The absorption wavelength λ of compound 2 at an extinction coefficient of E = 0.5 is measured as 361nm for a solution in DCM at a concentration of 3g/L. Thus compound 2 of formula I, like compound 1, has a long absorption wavelength which is higher than that of compound RM-1. Compound 2 is thus better suitable for UV photopolymerization at longer wavelengths. Since the polymerizable mixtures contain higher amounts of compounds of formula I than compound RM-1, it is possible to polymerize the compounds using a UV LED lamp with high emission wavelength for both UV1 and UV2 steps. For polymerization test cells containing the polymerizable mixtures P4 – P9 are exposed to UV light in a two step process, the first step (UV1) for generating a tilt angle and the second step (UV2) for polymerizing any residual monomer that was not polymerized in the first step. In UV1 step a voltage is applied (20 V_pp square wave, 200 Hz). In UV2 step no voltage is applied. The other conditions are as follows, unless stated otherwise: UV1 (LED lamp): 20 mW/cm² at room temperature for 30-300s UV2 (LED lamp): 20 mW/cm² at room temperature, 90 min Tilt Stability The change of the tilt angle Δtilt is determined as described in Example 1 and is shown in Table 9 below in comparison to mixture C1. Table 9 – Tilt Stability

From Table 9 it can be seen that polymerizable mixtures P5 – P9 according to the invention show significantly better tilt stability than reference mixture C1. Voltage Holding Ratio (VHR) The VHR of the polymerizable LC media is measured at 60°C with application of a voltage of 1 V / 0.6 Hz initial and after UV exposure. Light stress usually causes the decrease of VHR in LC mixtures, therefore the smaller the absolute decrease of VHR value after stress, the better performance for display applications. The results are shown in Table 10. Table 10 - VHR

From Table 10 it can be seen that the VHR of the polymerizable mixtures P4 – P9 according to the invention after UV stress is significantly higher than that of reference mixture C1. The above results demonstrate that LC media containing a polymerizable compound of formula I are highly suitable for use in PSA displays prepared by a polymerization process using long UV wavelengths >350nm, and especially using UV-LED lamps. Examples 10 & 11 Polymerizable mixtures P10 and P11 according to the present invention are prepared by adding polymerizable compound 1, 2 and RM-139 to nematic LC host mixture N1 in various concentrations.

Compound RM-139 has an absorption wavelength λ of 360nm at an extinction coefficient of E = 0.5 in a solution of DCM with a concentration of 3g/L, and is thus suitable for UV photopolymerization at long wavelengths. The compositions of the polymerizable mixtures are shown in Table 11 below. Table 11 - Polymerizable mixture compositions

Tilt Stability The change of the tilt angle Δtilt is determined as described in Example 1 and is shown in Table 12 below. Table 12 – Tilt Stability

From Table 12 it can be seen that polymerizable mixtures P10 and P11 according to the invention show good tilt stability. Voltage Holding Ratio (VHR) The VHR of the polymerizable LC media is measured at 60°C with application of a voltage of 1 V / 0.6 Hz initial and after UV exposure. Light stress usually causes the decrease of VHR in LC mixtures, therefore the smaller the absolute decrease of VHR value after stress, the better performance for display applications. The results are shown in Table 13. Table 13 - VHR

From Table 13 it can be seen that the VHR of the polymerizable mixtures P10 and P11 according to the invention is high even after UV exposure. The above results demonstrate that LC media containing two polymerizable compounds, at least one of which is of formula I, are highly suitable for use in PSA displays prepared by a polymerization process using long UV wavelengths >350nm, and especially using UV-LED lamps. Example 12 The nematic LC host mixture N3 is formulated as follows B(S)-2O-O4 5.00 % cl.p. 74.3 B(S)-2O-O5 5.00 % Δn 0.1302 BCH-32 9.00 % n_e 1.625 CC-3-V 15.00 % n_o 1.4948 CC-3-V1 7.50 % Δε -2.9 CC-4-V1 13.00 % ε|| 3.6 CCP-3-1 10.00 % ε_┴ 6.5 CLY-3-O2 2.50 % γ₁ 89 CPY-3-O2 2.00 % K₁ 15.1 PY-1-O2 12.00 % K₃ 15 PY-3-O2 10.00 % K₃/K₁ 0.99 PYP-2-3 9.00 % V₀ 2.42 V Polymerizable mixture P12 is prepared by adding 0.45% of the polymerizable compound 1, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N3.

Example 13 Polymerizable mixture P13 is prepared by adding 0.45% of the polymerizable compound 2, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N3. Example 14 The nematic LC host mixture N4 is formulated as follows CC-3-V1 9.00 % cl.p. 74.6°C CCH-301 3.50 % Δn 0.0984 CCH-34 8.00 % n_e 1.5804 CCH-35 8.00 % n_o 1.4820 CCP-3-1 6.00 % Δε -3.6 CCY-3-O1 6.50 % ε|| 3.6 CCY-3-O2 12.50 % ε_┴ 7.1 CPY-3-O2 10.00 % γ₁ 119 mPa.s CY-3-O2 15.50 % K₁ 14.1 PCH-301 8.50 % K₃ 17.0 PY-3-O2 12.50 % K₃/K₁ 1.21 V₀ 2.31 V Polymerizable mixture P14 is prepared by adding 0.45% of the polymerizable compound 1 and 0.2% of the compound RM-1 to the nematic LC host mixture N4. Example 15 Polymerizable mixture P15 is prepared by adding 0.45% of the polymerizable compound 2, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N4. Example 16 The nematic LC host mixture N5 is formulated as follows B(S)-2O-O4 4.50 % cl.p. 75.5°C B(S)-2O-O5 5.00 % Δn 0.1120 BCH-32 6.00 % n_e 1.6001 CC-3-V 30.00 % n_o 1.4881 CC-3-V1 8.00 % Δε -4.1 CCY-3-O1 7.50 % ε|| 3.8 CCY-3-O2 11.00 % ε_┴ 8.0 CLY-3-O2 8.00 % γ₁ 92 mPa.s PY-1-O2 10.50 % K₁ 14.8 PY-2-O2 9.50 % K₃ 15.7 K₃/K₁ 1.06 V₀ 2.06 V Polymerizable mixture P16 is prepared by adding 0.4% of the polymerizable compound 1, 0.3% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N5. Example 17 Polymerizable mixture P17 is prepared by adding 0.45% of the polymerizable compound 2, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N5. Example 18 The nematic LC host mixture N6 is formulated as follows B(S)-2O-O4 4.50 % cl.p. 74.9°C B(S)-2O-O5 5.00 % Δn 0.1122 B(S)-2O-O6 2.00 % n_e 1.5993 CC-3-V 30.00 % n_o 1.4871 CC-4-V1 17.50 % Δε -3.7 CLY-3-O2 8.00 % ε|| 3.7 CPY-2-O2 10.00 % ε_┴ 7.4 CPY-3-O2 10.00 % γ₁ 85 mPa.s PY-1-O2 3.00 % K₁ 14.5 PY-2-O2 10.00 % K₃ 14.2 K₃/K₁ 0.98 V₀ 2.07 V Polymerizable mixture P18 is prepared by adding 0.45% of the polymerizable compound 1, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N6. Example 19 The nematic LC host mixture N7 is formulated as follows B(S)-2O-O4 4.00 % cl.p. 74.7 B(S)-2O-O5 5.00 % Δn 0.1122 BCH-32 7.00 % n_e 1.5977 CC-3-V1 8.00 % n_o 1.4855 CC-4-V1 11.00 % Δε -3.8 CCH-34 8.00 % ε|| 3.9 CCH-35 6.00 % ε_┴ 7.7 CCY-3-O2 11.00 % γ₁ 109 mPa.s CPY-2-O2 3.00 % K₁ 15.0 CPY-3-O2 5.00 % K₃ 15.4 CY-3-O2 15.00 % K₃/K₁ 0.97 PCH-302 5.00 % V₀ 2.13 PPGU-3-F 1.00 % PY-1-O2 4.00 % PY-2-O2 7.00 % Polymerizable mixture P19 is prepared by adding 0.4% of the polymerizable compound 1, 0.1% of the compound RM-1 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N7.

Example 20 The nematic LC host mixture N8 is formulated as follows CC-3-V1 8.50 % cl.p. 75.1°C CC-4-V1 19.00 % Δn 0.1123 CCY-3-O1 6.00 % n_e 1.5969 CCY-3-O2 11.00 % n_o 1.4846 CLY-3-O2 5.00 % Δε -3.9 CPY-3-O2 11.00 % ε|| 3.7 CY-3-O2 6.00 % ε_┴ 7.5 PCH-302 13.50 % γ₁ 124 mPa.s PY-1-O2 6.00 % K₁ 15.2 PY-2-O2 6.00 % K₃ 18.3 PY-3-O2 8.00 % K₃/K₁ 1.20 V₀ 2.29 V Polymerizable mixture P20 is prepared by adding 0.3% of the polymerizable compound 1, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N8. Example 21 The nematic LC host mixture N9 is formulated as follows B(S)-2O-O4 2.00 % cl.p. 73.9 B(S)-2O-O5 2.50 % Δn 0.1165 BCH-32 8.00 % n_e 1.6084 CC-3-V 30.00 % n_o 1.4919 CC-4-V1 7.00 % Δε -2.7 CCP-3-1 11.00 % ε|| 3.6 CLY-3-O2 3.00 % ε_┴ 6.3 CPY-2-O2 2.00 % γ₁ 79 mPa.s CPY-3-O2 12.00 % K₁ 14.1 PY-1-O2 11.50 % K₃ 14.7 PY-2-O2 11.00 % K₃/K₁ 1.04 V₀ 2.46 V Polymerizable mixture P21 is prepared by adding 0.45% of the polymerizable compound 1, 0.3% of the compound RM-1 and 0.6% of the SA additive SA23 to the nematic LC host mixture N9.

Example 22 The nematic LC host mixture N10 is formulated as follows B(S)-2O-O4 4.50 % cl.p. 75.6°C B(S)-2O-O5 3.00 % Δn 0.1049 CC-3-V 51.00 % ne 1.5904 CCP-3-1 1.00 % no 1.4855 CLY-3-O2 9.00 % Δε -3.1 CPY-2-O2 10.00 % ε|| 3.5 CPY-3-O2 12.00 % ε_┴ 6.6 PY-1-O2 9.50 % γ₁ 72 mPa.s K₁ 14.1 K₃ 15.0 K₃/K₁ 1.06 V₀ 2.34 V Polymerizable mixture P22 is prepared by adding 0.4% of the polymerizable compound 2, 0.2% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N10. Example 23 The nematic LC host mixture N11 is formulated as follows CC-3-V1 9.00 % cl.p. 75.4°C CCH-23 14.00 % Δn 0.1055 CCH-34 6.00 % n_e 1.5907 CCH-35 6.00 % n_o 1.4852 CCP-3-1 7.00 % Δε -2.8 CCY-3-O1 5.00 % ε|| 3.3 CCY-3-O2 10.00 % ε_┴ 6.1 CPY-3-O2 12.00 % γ₁ 102 mPa.s CY-3-O2 9.50 % K₁ 16.2 PP-1-2V1 8.50 % K₃ 17.3 PY-3-O2 12.00 % K₃/K₁ 1.07 PY-4-O2 1.00 % V₀ 2.67 V Polymerizable mixture P23 is prepared by adding 0.4% of the polymerizable compound 1, 0.1% of the compound RM-1 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N11. Example 24 The nematic LC host mixture N12 is formulated as follows CC-3-V1 9.00 % cl.p. 74.7°C CCH-23 18.00 % Δn 0.0982 CCH-34 3.00 % n_e 1.5800 CCH-35 7.00 % n_o 1.4818 CCP-3-1 5.50 % Δε -3.4 CCY-3-O2 11.50 % ε|| 3.5 CPY-2-O2 8.00 % ε_┴ 6.9 CPY-3-O2 11.00 % γ₁ 108 mPa.s CY-3-O2 15.50 % K₁ 14.9 PY-3-O2 11.50 % K₃ 15.9 K₃/K₁ 1.07 V₀ 2.28 V Polymerizable mixture P24 is prepared by adding 0.4% of the polymerizable compound 1, 0.15% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N12. Example 25 The nematic LC host mixture N13 is formulated as follows BCH-32 10.00 % cl.p. 74.6°C CC-3-V1 6.50 % Δn 0.1113 CCH-34 8.00 % n_e 1.5981 CCH-35 8.00 % n_o 1.4868 CCY-3-O2 12.00 % Δε -3.3 CPY-2-O2 6.50 % ε|| 3.5 CPY-3-O2 11.00 % ε_┴ 6.8 CY-3-O2 15.00 % γ₁ 128 mPa.s CY-5-O2 13.00 % K₁ 14.5 PP-1-4 10.00 % K₃ 15.3 K₃/K₁ 1.06 V₀ 2.28 V Polymerizable mixture P25 is prepared by adding 0.4% of the polymerizable compound 2, 0.1% of the compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N13. Example 26 The nematic LC host mixture N14 is formulated as follows CC-3-V1 8.00 % cl.p. 74.6°C CCH-23 15.0 % Δn 0.0899 CCH-34 5.00 % n_e 1.5694 CCH-35 6.00 % n_o 1.4795 CCP-3-1 3.00 % Δε -3.3 CCY-3-O1 8.00 % ε|| 3.5 CCY-3-O2 10.00 % ε_┴ 6.8 CCY-3-O3 6.00 % γ₁ 114 mPa.s CCY-4-O2 6.00 % K₁ 13.9 CY-3-O2 12.0 % K₃ 14.6 CY-3-O4 3.75 % K₃/K₁ 1.05 PCH-301 3.00 % V₀ 2.22 V PY-3-O2 2.75 % PY-4-O2 6.50 % PYP-2-3 5.00 % Polymerizable mixture P26 is prepared by adding 0.4% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N14. Example 27 The nematic LC host mixture N15 is formulated as follows B(S)-2O-O4 0.25 % cl.p. 74.6°C BCH-32 4.50 % Δn 0.1034 CC-3-V1 13.00 % n_e 1.5883 CCH-23 15.00 % n_o 1.4849 CCH-301 1.00 % Δε -2.9 CCH-34 2.00 % ε|| 3.4 CCH-35 0.50 % ε_┴ 6.3 CCY-3-O2 6.50 % γ₁ 103 mPa.s CPY-2-O2 12.00 % K₁ 13.0 CPY-3-O2 15.00 % K₃ 15.3 CY-3-O2 15.50 % K₃/K₁ 1.18 CY-3-O4 0.25 % V₀ 2.44 V PCH-301 13.00 % PP-1-2V1 0.50 % PYP-2-3 1.00 % Polymerizable mixture P27 is prepared by adding 0.3% of the polymerizable compound 2, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S3-1 to the nematic LC host mixture N15.

Example 28 The nematic LC host mixture N16 is formulated as follows CCH-301 6.00 % cl.p. 109.9°C CCH-303 10.00 % Δn 0.0976 CCH-501 4.00 % ne 1.5806 CCP-3-1 7.00 % no 1.4830 CCPC-33 3.00 % Δε -3.6 CCPC-34 3.00 % ε|| 3.4 CCY-3-O1 5.50 % ε_┴ 7.0 CCY-3-O2 9.50 % γ₁ 233 mPa.s CCY-3-O3 7.00 % K₁ 16.9 CCY-4-O2 8.50 % K₃ 19.6 CPY-2-O2 3.00 % K₃/K₁ 1.16 CPY-3-O2 12.50 % V₀ 2.47 V CY-3-O4 9.50 % PCH-301 11.50 % Polymerizable mixture P28 is prepared by adding 0.45% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N16. Example 29 The nematic LC host mixture N17 is formulated as follows BCH-32 8.00 % cl.p. 74.6°C CC-3-V1 13.00 % Δn 0.1042 CC-4-V1 2.50 % n_e 1.5897 CCH-301 10.00 % n_o 1.4855 CCH-34 5.00 % Δε -3.1 CCH-35 5.00 % ε|| 3.5 CLY-3-O2 12.50 % ε_┴ 6.6 CPY-2-O2 11.50 % γ₁ 104 mPa.s CPY-3-O2 4.00 % K₁ 13.7 CY-3-O2 15.00 % K₃ 15.4 PCH-301 6.50 % K₃/K₁ 1.12 PY-1-O2 7.00 % V₀ 2.37 V Polymerizable mixture P29 is prepared by adding 0.45% of the polymerizable compound 1, 0.4% of the polymerizable compound 2 and 50ppm of the stabilizer S3-2 to the nematic LC host mixture N17.

Example 30 The nematic LC host mixture N18 is formulated as follows B(S)-2O-O5 0.25 % cl.p. 74.5°C BCH-32 5.50 % Δn 0.1028 CC-3-V 10.00 % ne 1.5880 CC-3-V1 7.50 % no 1.4852 CC-4-V1 16.50 % Δε -3.1 CCH-35 0.25 %ε|| 3.6 CCP-3-1 7.50 % ε_┴ 6.7 CCY-3-O2 11.00 % γ₁ 96 mPa.s CCY-3-O3 1.00 % K₁ 13.8 CCY-4-O2 7.00 % K₃ 15.5 CCY-5-O2 2.00 % K₃/K₁ 1.12 CY-3-O2 9.00 % V₀ 2.37 V PY-1-O2 9.00 % PY-2-O2 9.00 % PY-3-O2 4.50 % Polymerizable mixture P30 is prepared by adding 0.3% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N18. Example 31 The nematic LC host mixture N19 is formulated as follows BCH-32 4.50 % cl.p. 74.8°C CC-3-V 15.00 % Δn 0.1030 CC-3-V1 7.50 % n_e 1.5889 CC-4-V1 12.50 % n_o 1.4859 CCP-3-1 7.00 % Δε -3.1 CCY-3-O1 7.00 % ε|| 3.6 CCY-3-O2 10.50 % ε_┴ 6.8 CCY-4-O2 6.50 % γ₁ 94 mPa.s CY-3-O2 4.50 % K₁ 13.8 PY-1-O2 9.50 % K₃ 15.4 PY-2-O2 9.00 % K₃/K₁ 1.12 PY-3-O2 6.50 % V₀ 2.35 V Polymerizable mixture P31 is prepared by adding 0.45% of the polymerizable compound 2, 0.1% of the polymerizable compound RM-1 and 100ppm of the stabilizer S1-1 to the nematic LC host mixture N19. Example 32 The nematic LC host mixture N20 is formulated as follows CC-3-V 10.50 % cl.p. 74.5°C CC-3-V1 5.50 % Δn 0.1033 CC-4-V1 20.00 % n_e 1.5875 CCH-34 2.00 % n_o 1.4842 CCH-35 1.50 % Δε -3.3 CCY-3-1 2.00 % ε|| 3.6 CCY-3-O1 7.50 % ε_┴ 6.9 CCY-3-O2 11.00 % γ₁ 96 mPa.s CCY-4-O2 8.50 % K₁ 14.4 CLY-2-O4 1.00 % K₃ 15.1 CLY-3-O2 2.00 % K₃/K₁ 1.05 PP-1-2V1 3.50 % V₀ 2.29 V PY-1-O2 9.50 % PY-2-O2 9.50 % PY-3-O2 6.00 % Polymerizable mixture P32 is prepared by adding 0.45% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N20.

Example 33 The nematic LC host mixture N21 is formulated as follows CC-3-V1 7.50 % cl.p. 74.5°C CC-4-V1 20.00 % Δn 0.1030 CCH-34 5.00 % n_e 1.5861 CCH-35 7.50 % n_o 1.4831 CCP-3-1 2.00 % Δε -3.5 CCY-3-O1 8.00 % ε|| 3.6 CCY-3-O2 12.00 % ε_┴ 7.1 CCY-4-O2 3.00 % γ₁ 103 mPa.s CLY-3-O2 4.00 % K₁ 15.1 CY-3-O2 1.50 % K₃ 15.4 PY-1-O2 9.50 % K₃/K₁ 1.02 PY-2-O2 9.50 % V₀ 2.23 V PY-3-O2 10.50 % Polymerizable mixture P33 is prepared by adding 0.4% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N21. Example 34 The nematic LC host mixture N22 is formulated as follows CC-3-V1 7.50 % cl.p. 75°C CC-4-V1 19.50 % Δn 0.1041 CCH-301 5.50 % n_e 1.5884 CCH-34 5.00 % n_o 1.4843 CCP-3-1 11.00 % Δε -3.1 CLY-3-O2 5.00 % ε|| 3.6 CPY-2-O2 6.00 % ε_┴ 6.7 CPY-3-O2 11.50 % γ₁ 101 mPa.s CY-3-O2 15.00 % K₁ 14.0 PY-1-O2 6.50 % K₃ 15.7 PY-2-O2 7.50 % K₃/K₁ 1.12 V₀ 2.37 V Polymerizable mixture P34 is prepared by adding 0.8% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 0.6% of the SA additive SA32 to the nematic LC host mixture N22.

Example 35 The nematic LC host mixture N23 is formulated as follows CC-3-V1 2.50 % cl.p. 105.9°C CC-4-V1 10.00 % Δε -3.6 CCH-301 3.00 % ε|| 3.4 CCH-34 4.00 % ε_┴ 7.0 CCH-35 4.00 % CCP-3-1 6.00 % CCP-3-3 6.00 % CCY-3-O1 4.00 % CCY-3-O2 4.00 % CCY-3-O3 4.00 % CCY-4-O2 4.00 % CCY-5-O2 4.00 % CPY-2-O2 10.00 % CPY-3-O2 10.00 % CY-3-O2 6.50 % CY-3-O4 10.00 % PYP-2-3 5.00 % PYP-2-4 3.00 % Polymerizable mixture P35 is prepared by adding 0.45% of the polymerizable compound 2, 0.1% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N23. Example 36 The nematic LC host mixture N24 is formulated as follows BCH-52 9.00 % cl.p. 105°C CC-3-V1 2.00 % Δε -3.6 CC-4-V1 12.50 % ε|| 3.4 CCH-301 2.00 % ε_┴ 7.0 CCH-34 3.50 % CCH-35 4.00 % CCP-3-1 7.50 % CCY-3-O1 4.00 % CCY-3-O2 4.00 % CCY-3-O3 4.00 % CCY-4-O2 4.00 % CCY-5-O2 4.00 % CPY-2-O2 10.00 % CPY-3-O2 10.00 % CY-3-O4 12.50 % PY-1-O2 7.00 % Polymerizable mixture P36 is prepared by adding 0.45% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1 and 100ppm of the stabilizer S2-1 to the nematic LC host mixture N24. Example 37 The nematic LC host mixture N25 is formulated as follows B(S)-2O-O5 0.25 % cl.p. 75.1°C BCH-32 1.50 % Δn 0.1038 CC-3-V1 8.00 % n_e 1.5864 CC-4-V1 20.00 % n_o 1.4826 CCH-303 1.50 % Δε -3.0 CCH-34 6.00 % ε|| 3.4 CCH-35 8.00 % ε_┴ 6.5 CCY-3-O2 9.50 % γ₁ 99 mPa.s CPY-2-O2 6.00 % K₁ 15.6 CPY-3-O2 11.00 % K₃ 16.0 CY-3-O2 12.50 % K₃/K₁ 1.03 PP-1-2V1 2.75 % V₀ 2.44 V PY-1-O2 5.50 % PY-2-O2 4.50 % PY-3-O2 3.00 % Polymerizable mixture P37 is prepared by adding 0.3% of the polymerizable compound 2, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N25. Example 38 The nematic LC host mixture N26 is formulated as follows BCH-32 0.50 % cl.p. 74.8°C CC-3-V1 7.00 % Δn 0.1036 CC-4-V1 19.50 % n_e 1.5884 CCH-301 12.00 % n_o 1.4848 CCH-34 1.50 % Δε -3.1 CCP-3-1 9.00 % ε|| 3.6 CCY-3-O1 1.50 % ε_┴ 6.7 CCY-3-O2 9.50 % γ₁ 102 mPa.s CPY-2-O2 3.00 % K₁ 13.8 CPY-3-O2 11.00 % K₃ 15.6 CY-3-O2 6.50 % K₃/K₁ 1.13 PY-1-O2 9.00 % V₀ 2.39 V PY-2-O2 9.00 % PY-3-O2 1.00 % Polymerizable mixture P38 is prepared by adding 0.3% of the polymerizable compound 2, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S3-1 to the nematic LC host mixture N26. Example 39 The nematic LC host mixture N27 is formulated as follows B-2O-O5 4.00 % cl.p. 74.2°C BCH-32 8.00 % Δn 0.1091 CC-3-V1 9.00 % n_e 74.2 CCH-301 2.00 % n_o 1.4862 CCH-34 8.00 % Δε -3.1 CCH-35 7.00 % ε|| 3.6 CCP-3-1 8.00 % ε_┴ 6.7 CCP-V2-1 5.00 % γ₁ 108 mPa.s CCY-3-O2 10.50 % K₁ 14.5 CLY-3-O2 1.00 % K₃ 16.5 CPY-3-O2 2.50 % K₃/K₁ 1.14 CY-3-O2 11.50 % V₀ 2.41 V PCH-301 5.50 % PY-3-O2 18.00 % Polymerizable mixture P39 is prepared by adding 0.3% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N27. Example 40 The nematic LC host mixture N28 is formulated as follows CC-3-V1 3.00 % cl.p. 74.8°C CCH-301 9.00 % Δn 0.0891 CCH-303 5.00 % n_e 1.5681 CCH-34 9.00 % n_o 1.4790 CCH-35 9.00 % Δε -3.2 CCP-3-1 8.00 % ε|| 3.5 CCY-3-O2 11.50 % ε_┴ 6.7 CCY-5-O2 9.00 % γ₁ 115 mPa.s CPY-3-O2 6.00 % K₁ 14.2 CY-3-O2 15.00 % K₃ 16.3 PCH-301 4.50 % K₃/K₁ 1.15 PY-3-O2 11.00 % V₀ 2.38 V Polymerizable mixture P40 is prepared by adding 0.3% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N28. Example 41 The nematic LC host mixture N29 is formulated as follows BCH-32 10.50 % cl.p. 74.5°C CCH-34 9.00 % Δn 0.1090 CCH-35 9.00 % n_e 1.5953 CCP-3-1 8.00 % n_o 1.4863 CCY-3-O2 9.50 % Δε -3.4 CCY-4-O2 5.50 % ε|| 3.7 CPY-3-O2 5.50 % ε_┴ 7.0 CY-3-O2 15.00 % γ₁ 128 mPa.s CY-5-O2 5.00 % K₁ 14.0 PCH-301 7.00 % K₃ 15.7 PY-3-O2 16.00 % K₃/K₁ 1.12 V₀ 2.25 V Polymerizable mixture P41 is prepared by adding 0.4% of the polymerizable compound 2, 0.1% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N29. Example 42 The nematic LC host mixture N30 is formulated as follows B(S)-2O-O5 4.00 % cl.p. 74.7°C BCH-32 5.00 % Δn 0.1024 CC-3-V1 6.00 % n_e 1.5885 CCH-34 9.00 % n_o 1.4861 CCH-35 9.00 % Δε -3.2 CCP-3-1 8.00 % ε|| 3.6 CCY-3-O1 6.50 % ε_┴ 6.7 CCY-3-O2 9.00 % γ₁ 109 mPa.s CLY-3-O2 1.00 % K₁ 13.5 CPY-3-O2 4.50 % K₃ 16.5 CY-3-O2 13.00 % K₃/K₁ 1.22 PCH-301 15.00 % V₀ 2.39 V PY-1-O2 8.00 % PY-2-O2 2.00 % Polymerizable mixture P42 is prepared by adding 0.3% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N30. Example 43 The nematic LC host mixture N31 is formulated as follows CCH-301 9.00 % cl.p. 110.9°C CCH-34 9.00 % Δn 0.1022 CCH-35 8.00 % n_e 1.5867 CCOC-4-3 3.00 % n_o 1.4845 CCP-3-1 6.00 % Δε -3.0 CCP-3-3 6.00 % ε|| 3.3 CCPC-33 3.00 % ε_┴ 6.3 CCY-3-1 3.50 % γ₁ 199 mPa.s CCY-3-O2 4.50 % K₁ 18.8 CCY-3-O3 6.00 % K₃ 19.6 CCY-4-O2 6.00 % K₃/K₁ 1.04 CCY-5-O2 5.00 % V₀ 2.69 V CPY-2-O2 10.50 % CPY-3-O2 6.50 % CY-3-O2 1.00 % PCH-302 4.00 % PY-2-O2 9.00 % Polymerizable mixture P43 is prepared by adding 0.7% of the polymerizable compound 2, 0.3% of the polymerizable compound RM-1 and 0.6% of the SA additive SA23 to the nematic LC host mixture N31. Example 44 The nematic LC host mixture N32 is formulated as follows BCH-32 3.00 % cl.p. 109.8°C CCH-301 9.00 % Δn 0.1020 CCH-34 9.00 % n_e 1.5867 CCH-35 2.50 % n_o 1.4847 CCOC-4-3 3.00 % Δε -3.0 CCP-3-1 6.00 % ε|| 3.3 CCP-3-3 5.00 % ε_┴ 6.2 CCY-3-1 3.00 % γ₁ 204 mPa.s CCY-3-O2 6.00 % K₁ 18.4 CCY-3-O3 6.00 % K₃ 20.3 CCY-4-O2 6.00 % K₃/K₁ 1.10 CCY-5-O2 6.00 % V₀ 2.75 V CPY-2-O2 10.00 % CPY-3-O2 8.50 % CY-3-O2 6.00 % PCH-302 11.00 % Polymerizable mixture P44 is prepared by adding 0.9% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA23 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N32. Example 45 The nematic LC host mixture N33 is formulated as follows B(S)-2O-O5 2.00 % cl.p. 74.3°C BCH-32 9.50 % Δn 0.1080 CC-3-V1 6.50 % n_e 1.5962 CCH-301 8.50 % n_o 1.4882 CCH-34 3.00 % Δε -3.3 CCP-3-1 9.50 % ε|| 3.7 CCY-3-O1 6.50 % ε_┴ 7.0 CCY-5-O2 9.50 % γ₁ 121 mPa.s CLY-3-O2 1.00 % K₁ 12.9 CPY-3-O2 5.50 % K₃ 15.9 CY-3-O2 15.50 % K₃/K₁ 1.23 PCH-301 5.00 % V₀ 2.31 V PCH-302 6.50 % PY-2-O2 11.50 % Polymerizable mixture P45 is prepared by adding 1.0% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S3-1 to the nematic LC host mixture N33. Example 46 The nematic LC host mixture N34 is formulated as follows BCH-32 6.50 % cl.p. 74.7 °C CC-3-V1 8.00 % Δn 0.1039 CCH-23 17.00 % Δε -3.0 CCH-34 6.50 % ε_┴ 3.4 CCY-3-O1 3.50 % K₃/K₁ 1.07 CCY-3-O2 12.50 % γ₁ 106 mPa s CPY-2-O2 5.50 % V₀ 2.43 V CPY-3-O2 10.00 % CY-3-O2 15.50 % PCH-3O1 4.50 % PP-1-2V1 5.00 % PY-3-O2 5.50 % Polymerizable mixture P46 is prepared by adding 1.0% of the polymerizable compound 2, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32and 50ppm of the stabilizer S3-2 to the nematic LC host mixture N34. Example 47 The nematic LC host mixture N35 is formulated as follows BCH-32 2.00 % cl.p. 74.7 °C CC-3-V 22.50 % Δn 0.1039 CC-3-V1 9.50 % Δε -3.0 CCP-3-1 3.00 % ε|| 3.5 CCY-3-O2 3.50 % K₃/K₁ 1.17 CCY-4-O2 4.00 % γ₁ 99 mPa s CPY-2-O2 12.00 % V₀ 2.39 CPY-3-O2 12.50 % CY-3-O2 15.50 % CY-3-O4 4.00 % PCH-3O1 7.00 % PP-1-2V1 1.50 % PYP-2-3 3.00 % Polymerizable mixture P47 is prepared by adding 0.8% of the polymerizable compound 2, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA23and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N35. Example 48 The nematic LC host mixture N36 is formulated as follows CY-3-O4 12.00 % cl.p. 77°C PY-3-O2 9.00 % Δn 0.088 CPY-3-O2 12.00 % Δε -3.1 CCOY-2-O2 8.00 % CCY-5-O2 10.00 % CC-3-V 20.00 % CCH-32 30.00 % Polymerizable mixture P48 is prepared by adding 0.8% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA23 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N36. Example 49 The nematic LC host mixture N37 is formulated as follows CY-3-O4 12.00 % cl.p. 77°C PY-3-O2 9.00 % Δn 0.088 CPY-3-O2 12.00 % Δε -3.1 CCOY-2-O2 8.00 % CCY-5-O2 10.00 % CC-3-V 20.00 % CCH-32 30.00 % Polymerizable mixture P49 is prepared by adding 0.7% of the polymerizable compound 2, 0.3% of the polymerizable compound RM-1, 0.6% of the SA additive SA23 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N37. Example 50 The nematic LC host mixture N38 is formulated as follows CCH-32 10.00 % cl.p. 86°C COY-3-O2 10.00 % Δn 0.105 COY-3-O1 10.00 % Δε -5.9 CCOY-2-O2 9.00 % CCY-3-O1 7.00 % CCY-3-O2 6.00 % CCY-4-O2 6.00 % CPY-5-O2 8.00 % CPY-3-O1cpr 10.00 % CPY-2-O2 10.00 % CY-3-O2 7.00 % CY-3-O4 7.00 % Polymerizable mixture P50 is prepared by adding 0.8% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N38. Example 51 The nematic LC host mixture N39 is formulated as follows CCH-32 11.00 % cl.p. 79°C CC-3-V 10.00 % Δn 0.112 PP-5-O2 5.00 % Δε -4.3 COY-3-O2 8.00 % COY-3-O1 7.00 % CCOY-2-O2 13.00 % CPY-cp-O2 7.00 % CPY-3-O2 10.00 % CPY-2-O2 10.00 % PY-3-O2 10.00 % CCP-3-1 2.00 % CCP-V-1 4.00 % CCP-V2-1 4.00 % Polymerizable mixture P51 is prepared by adding 0.9% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA23and 50ppm of the stabilizer S3-2 to the nematic LC host mixture N39. Example 52 The nematic LC host mixture N40 is formulated as follows CY-5-O2 11.00 % cl.p. 60°C PY-3-O2 9.00 % Δn 0.097 COY-3-O2 17.00 % Δε -2.8 B(S)-cp1O-O4 4.00 % PP-1-5 10.00 % CC-3-V1 26.00 % CCH-32 5.00 % CCP-3-1 12.00 % BCH-32 6.00 % Polymerizable mixture P52 is prepared by adding 1.0% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N40. Example 53 The nematic LC host mixture N41 is formulated as follows CCH-23 16.50 % cl.p. 75°C CCH-34 3.00 % Δn 0.112 PCH-3O1 15.00 % Δε -3.0 PP-1-3 9.00 % BCH-32 8.00 % COY-3-O1 8.50 % CCOY-3-O2 17.00 % CPY-2-O2 6.50 % CPY-3-O2 8.00 % CPY-3-O4 8.50 % Polymerizable mixture P53 is prepared by adding 0.9% of the polymerizable compound 1, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N41. Example 54 The nematic LC host mixture N42 is formulated as follows CCH-23 12.00 % cl.p. 111°C CCH-34 8.00 % Δn 0.097 CCH-35 7.00 % Δε -3.1 PCH-3O1 8.00 % CCP-3-1 7.00 % CCP-3-3 4.00 % BCH-32 5.00 % CCOY-2-O2 15.00 % CCOY-3-O2 15.00 % CPY-2-O2 5.00 % CPY-3-O2 5.00 % CPY-3-O3 5.00 % CPY-3-O4 4.00 % Polymerizable mixture P54 is prepared by adding 1.0% of the polymerizable compound 2, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N42. Example 55 The nematic LC host mixture N43 is formulated as follows CC-3-V 32.00 % cl.p. 74°C PP-1-3 11.00 % Δn 0.104 CCP-3-1 8.00 % Δε -2.9 CY-5-O2 2.00 % COY-3-O1 11.50 % CCY-3-O2 11.50 % CPY-2-O2 7.00 % CPY-3-O2 8.00 % CPY-3-O4 9.00 % Polymerizable mixture P55 is prepared by adding 0.7% of the polymerizable compound 2, 0.3% of the polymerizable compound RM-1, 0.6% of the SA additive SA23 and 50ppm of the stabilizer S3-2 to the nematic LC host mixture N43. Example 56 The nematic LC host mixture N44 is formulated as follows CCH-23 21.50 % cl.p. 75°C CCH-34 9.50 % Δn 0.103 PP-1-3 13.50 % Δε -2.8 CCP-3-1 6.00 % COY-3-O1 11.50 % CCOY-3-O2 14.00 % CPY-2-O2 7.00 % CPY-3-O2 8.00 % CPY-3-O4 9.00 % Polymerizable mixture P56 is prepared by adding 0.9% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA23 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N44. Example 57 The nematic LC host mixture N45 is formulated as follows CEY-3-O2 7.00 % cl.p. 89°C CCY-3-O2 8.00 % Δn 0.115 CCOY-3-O2 5.00 % Δε -1.9 CLY-2-O2 8.00 % CAIY-3-O2 3.00 % CAIY-5-O2 4.00 % PYP-2-3 7.00 % PYP-2-4 7.00 % CC-4-V 15.00 % CC-3-V1 6.00 % CC-1-2V1 6.00 % CC-3-2V1 4.00 % PP-1-2V 5.00 % PP-1-2V1 5.00 % CCP-3-1 6.00 % CBC-33F 4.00 % Polymerizable mixture P57 is prepared by adding 0.8% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S3-1 to the nematic LC host mixture N45. Example 58 The nematic LC host mixture N46 is formulated as follows B(S)-2O-O5 2.00 % cl.p. 74°C BCH-32 9.50 % Δn 0.108 CCP-3-1 9.50 % Δε -3.6 CCY-3-O1 6.50 % CCY-5-O2 9.50 % CLY-3-O2 1.00 % CPY-3-O2 5.50 % CC-3-V1 6.50 % CCH-301 8.50 % CCH-34 3.00 % COY-3-O2 15.50 % PCH-3O1 5.00 % PCH-3O2 6.50 % PY-2-O2 11.50 % Polymerizable mixture P58 is prepared by adding 0.7% of the polymerizable compound 2, 0.2% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S2-1 to the nematic LC host mixture N46. Example 59 The nematic LC host mixture N47 is formulated as follows B(S)-2O-O4 4.0 % cl.p. 75°C B(S)-2O-O4 4.0 % Δn 0.114 BCH-32 7.5 % n_e 1.606 CC-3-V 25.75 % n_o 1.492 CC-3-V1 10.0 % Δε -2.6 CCP-3-1 13.0 % ε|| 3.6 CCP-3-3 3.25 % ε_┴ 6.1 CLY-3-O2 2.0 % K₁ 13.7 CPY-2-O2 9.5 % K₃ 14.2 PY-2-O2 11.0 % PY-2-O1 10.0 % Polymerizable mixture P59 is prepared by adding 1.0% of the polymerizable compound 1, 0.1% of the polymerizable compound RM-1, 0.6% of the SA additive SA32 and 50ppm of the stabilizer S3-3 to the nematic LC host mixture N47. Example 60 The nematic LC host mixture N48 is formulated as follows BCH-32 7.50 % cl.p. 75.5°C CC-3-V1 6.50 % Δn 0.1105 CCH-34 8.00 % n_e 1.5970 CCH-35 8.00 % n_o 1.4865 CCY-3-O2 12.00 % Δε -3.3 CPY-2-O2 9.50 % ε|| 3.5 CPY-3-O2 11.00 % ε_┴ 6.8 CY-3-O2 12.00 % γ₁ 130 mPa.s CY-5-O2 13.00 % K₁ 14.2 PCH-301 4.00 % K₃ 15.4 PP-1-4 8.50 % K₃/K₁ 1.08 V₀ 2.28 V Polymerizable mixture P60 is prepared by adding 0.4% of the polymerizable compound 1 and 0.1% of the polymerizable compound RM-1 to the nematic LC host mixture N48. Example 61 Polymerizable mixture P61 is prepared by adding 0.45% of the polymerizable compound 1 and 0.2% of the polymerizable compound RM-35 to the nematic LC host mixture N1.

Example 62 Polymerizable mixture P62 is prepared by adding 0.45% of the polymerizable compound 2 and 0.2% of the polymerizable compound RM-37 to the nematic LC host mixture N2.

Example 63 Polymerizable mixture P63 is prepared by adding 0.45% of the polymerizable compound 1 and 0.2% of the polymerizable compound RM-17 to the nematic LC host mixture N1.

Example 64 Polymerizable mixture P64 is prepared by adding 0.45% of the polymerizable compound 2 and 0.2% of the polymerizable compound RM-19 to the nematic LC host mixture N2.

Example 65 Polymerizable mixture P65 is prepared by adding 0.45% of the polymerizable compound 1 and 0.2% of the polymerizable compound RM-120 to the nematic LC host mixture N1.

Example 66 Polymerizable mixture P66 is prepared by adding 0.45% of the polymerizable compound 2, 0.3% of the polymerizable compound RM-139 and 50ppm of the stabilizer S1-1 to the nematic LC host mixture N1. Example 67 Polymerizable mixture P67 is prepared by adding 0.45% of the polymerizable compound 1 and 0.2% of the polymerizable compound RM-142 to the nematic LC host mixture N2.

Claims

Claims 1. An LC medium comprising two or more polymerizable compounds, at least one of which is selected from formula I:

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings R^a, R^b P-Sp- or R, wherein at least one of R^a and R^b denotes P-Sp-, A^a, A^b phenylene-1,4,-diyl or naphthalene,2-6-diyl which is optionally substituted by one or more groups L, Z^a, Z^b -CH=CH-, -CF=CF-, -C ≡C- or a single bond, P a polymerizable group, Sp a spacer group that is optionally substituted by one or more groups P, or a single bond, R 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-, CR⁰=CR⁰⁰-, -C ≡C-,

or in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, L F, Cl, Br, -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-, -N(R⁰)-, -Si(R⁰R⁰⁰)-, -CH=CH- or -C ≡C- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, R⁰, R⁰⁰ H or alkyl with 1 to 12 C atoms, preferably H, a, b 0, 1 or 2, preferably 0 or 1, r4 0, 1, 2, 3 or 4, preferably 0, 1 or 2. 2. The LC medium according to Claim 1, wherein the compound of formula I is selected from formula I1:

wherein P, Sp, L and r4 have independently of each other one of the meanings given in Claim 1. 3. The LC medium according to Claim 1, wherein the compound of formula I is selected from the following subformulae:

4. The LC medium according to one or more of Claims 1 to 3, characterized in that it comprises one or more compounds of formula I as defined in claims 1 to 3, and one or more polymerizable compounds which are different of formula I.

5. The LC medium according to one or more of Claims 1 to 4, characterized in that it comprises one or more polymerizable compounds selected from the following formulae:

in which the individual radicals, on each occurrence identically or differ- ently, and each, independently of one another, have the following meaning: P¹, P², P³ a polymerisable group, preferably selected from vinyloxy, acrylate, methacrylate, fluoroacrylate, chloro- acrylate, oxetane and epoxy, Sp¹, Sp², Sp³ a single bond or a spacer group where, in addition, one or more of the radicals P¹-Sp¹-, P²-Sp²- and P³-Sp³- may denote R^aa, with the proviso that at least one of the radicals P¹-Sp¹-, P²-Sp² and P³-Sp³- present is different from R^aa, preferably -(CH₂)_p1-, -(CH₂)_p1-O-, -(CH₂)_p1-CO- O- or -(CH₂)_p1-O-CO-O- bedeuten, wherein p1 is an integer from 1 to 12, R^aa H, F, Cl, CN or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non- adjacent CH₂ groups may each be replaced, indepen- dently of one another, by -C(R⁰)=C(R⁰⁰)-, -C ≡C-, - N(R⁰)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, Cl, CN or P¹-Sp¹-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms), and wherein R^aa does not denote or contain a group P¹, P² or P³, R⁰, R⁰⁰ H or alkyl having 1 to 12 C atoms, R^y and R^z H, F, CH₃ or CF₃, X¹, X², X³ -CO-O-, -O-CO- or a single bond, Z^M1 -O-, -CO-, -C(R^yR^z)- or -CF₂CF₂-, Z^M2, Z^M3 -CO-O-, -O-CO-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂- or - (CH₂)_n-, where n is 2, 3 or 4, L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, L', L" H, F or Cl, k 0 or 1, r 0, 1, 2, 3 or 4, s 0, 1, 2 or 3, t 0, 1 or 2, x 0 or 1. 6. The LC medium according to one or more of Claims 1 to 5, characterized in that it comprises one or more polymerizable compounds selected from formula CM:

in which the individual radicals, on each occurrence identically or differ- ently, and each, independently of one another, have the following meaning: P, Sp one of the meanings given in formula I or its subformulae or one of their preferred meanings as given above and below, L F, Cl, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, r1, r2 0, 1, 2, 3 or 4, preferably 0, 1 or 2, very preferably 0 or 1. 7. The LC medium according to one or more of Claims 1 to 6, characterized in that it comprises one or more polymerizable compounds selected from formula MT:

wherein P, Sp, L, r1 and r2 independently of each other have the meanings given in Claim 6, k is 0 or 1, and r3 is 0, 1, 2 or 3, preferably 0, 1 or 2, very preferably 0 or 1. 8. The LC medium according to one or more of Claims 1 to 7, characterized in that it comprises one or more compounds of formula II:

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings R¹ and R² 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-, CR⁰=CR⁰⁰-, -C ≡C-,

in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or Cl, preferably alkyl or alkoxy having 1 to 6 C atoms, R⁰, R⁰⁰ H or alkyl with 1 to 12 C atoms, A¹ and A² a group selected from the following formulae:

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings Z¹ and Z² -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -CO- O-, -O-CO-, -C₂F₄-, -CF=CF-, -CH=CH-CH₂O- or a single bond, preferably a single bond, L¹, L², L³ and L⁴ F, Cl, OCF₃, CF₃, CH₃, CH₂F or CHF₂, preferably F or Cl, very preferably F, Y H, F, Cl, CF₃, CHF₂ or CH₃, preferably H or CH₃, very preferably H, L^c CH₃ or OCH₃, preferably CH₃, a1 1 or 2, a2 0 or 1. 9. The LC medium according to one or more of Claims 1 to 8, characterized in that it contains one or more compounds of formula II selected from the group consisting of compounds of the formulae IIA, IIB, IIC and IID:

-C ≡C-, -CF₂O-, -OCF₂-, -OC-O- or -O-CO- in such a way that O atoms are not linked directly to one another, L¹ to L⁴ each, independently of one another, denote F, Cl, CF₃ or CHF₂, Y denotes H, F, Cl, CF₃, CHF₂ or CH₃, preferably H or CH₃, particularly preferably H, Z², Z^2B and Z^2D each, independently of one another, denote a single bond, -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, - COO-, -OCO-, -C2F4-, -CF=CF-, -CH=CHCH₂O-, p denotes 0, 1 or 2, and q on each occurrence, identically or differently, denotes 0 or 1. 10. The LC medium according to one or more of Claims 1 to 9, characterized in that it comprises one or more compounds of formula III:

, -C ≡C-, -CF₂O-, -OCF₂-, -CH=CH-, by - O-, -CO-O- or -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, A³ on each occurrence, independently of one another, denotes a) 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH₂ groups may be replaced by - O- or -S-, b) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, or c) a radical selected from the group consisting of spiro[3.3]heptane-2,6-diyl, 1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7- diyl and fluorene-2,7-diyl, wherein the radicals a), b) and c) may be mono- or polysubstituted by halogen atoms, n denotes 0, 1 or 2, preferably 0 or 1, Z¹ on each occurrence independently of one another denotes - 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^C- or a single bond, L¹¹ and L¹² each, independently of one another, denote F, Cl, CF₃ or CHF₂, preferably H or F, most preferably F, and W denotes O or S. 11. The LC medium according to to one or more of Claims 1 to 10, characterized in that it comprises one or more compounds of 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. 12. The LC medium according to one or more of Claims 1 to 11, characterized in that it comprises one or more compounds of formula V:

in which R⁵¹ and R⁵² independently of one another, have one of the meanings given for R⁴¹ and R⁴² and preferably denote alkyl having 1 to 7 C atoms, preferably n-alkyl, particularly preferably n-alkyl having 1 to 5 C atoms, alkoxy having 1 to 7 C atoms, preferably n-alkoxy, particularly preferably n-alkoxy having 2 to 5 C atoms, alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms, preferably having 2 to 4 C atoms, preferably alkenyloxy, , identically or differently, denote

in which preferably denotes

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

13. The LC medium according to one or more of Claims 1 to 12, characterized in that it additionally comprises one or more additives selected from the group consisting of stabilizers, chiral dopants, polymerization initiators and self alignment additives. 14. A process of preparing an LC medium according to one or more of Claims 1 to 13, comprising the steps of mixing one or more one or more polymerizable compounds as defined in one or more of Claims 1 to 7 with one or more compounds of formula II, III, IV and/or V as defined in one or more of Claims 8 to 12, and optionally with further liquid- crystalline compounds and/or additives, and optionally polymerizing the polymerizable compounds. 15. An LC display comprising an LC medium as defined in one or more of Claims 1 to 13. 16. The LC display according to Claim 15, which is a PS-VA, PS-IPS, PS- FFS or SA-VA display. 17. The LC display according to Claim 15 or 16, characterized in that it comprises two substrates, at least one of 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 according to one or more of Claims 1 to 13, wherein the polymerizable compounds are polymerized between the substrates of the display by UV photopolymerization. 18. A process for the production of an LC display according to Claim 17, comprising the steps of providing an LC medium according to one or more of Claims 1 to 13 between the substrates of the display, and polymerizing the polymerizable compounds by irradiation with UV light, preferably while a voltage is applied to the electrodes of the display. 19. The process according to Claim 18, characterized in that the UV light has a wavelength >360 nm.

20. The process according to Claim 18 or 19, characterized in that irradiation with UV light is carried out using an UV-LED lamp. 21. An energy saving process for the production of an LC display, characterized in that is as defined in any one of claims 18 to 20.