Liquid-crystal medium

The present invention relates to a liquid crystal (LC) medium comprising polymerisable compounds, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in flexible LC displays, and to LC displays comprising it.

Background of the Invention Recently liquid crystal (LC) mixtures have been developed for the realization of flexible substrate based LC displays. These LC mixtures contain reactive polymer precursors that allow the formation of polymer walls in the display, which help to maintain the gap distance of the LC layer. This technology thus enables manufacturing of free form and robust displays by using LC materials.

Free form LC displays can either have a permanent shape other than the flat shape of rigid flat panel displays, for example a curved shape, or can even have flexible shape. The simplest form of the first type are curved TVs that have been developed in the recent past and offer the viewer an enhanced viewing experience. Thereby it is possible to provide displays which are not only shaped in one but in two dimensions, and which can be used for example as car dashboards or advertising screens. Flexible displays, another type of free form displays, have also been developed, and have been proposed for example for use in mobile phones or smart watches utilizing the advantages of flexibility. Further potential applications are foldable or rollable mobile phones, as well as extra-large screens for presentations or home entertainment, which, due to their size, require to be rollable or foldable for being transported or stowed.

Advantageously such devices are based on plastic substrates instead of rigid glass substrates as used in conventional, unflexible LC displays.

Another display concept, 'unbreakable' displays, are also based on plastic substrates and refers to a display design featuring particular robustness, durability, and resistance against mechanical impact. One problem that should be solved is that mobile devices have an elevated risk of being dropped accidentally or becoming otherwise damaged during their normal use. In view of the high value of these devices, a solution to this problem would be highly desirable.

There is thus a great demand for free form or unbreakable LC displays.

One of the main technical challenges of LC displays with flexible substrates is that a constant LC layer thickness is critical for proper device operation. A proper combination of defined LC layer thickness and LC material properties ensures that the pixels can be switched between a black state and light transmitting state. In case of a varying layer thickness, unwanted interference with the gap distance between the substrates can result in visible optical defects. It should therefore be ensured that the LC layer thickness is not altered by the bending or the lack of rigidity of flexible plastic substrates.

In conventional LC displays with rigid glass substrates, usually spacer particles are added to the LC layer in order to define and maintain a constant layer thickness. A possible solution for free form displays is to adapt this concept by incorporating supporting structures, like for example polymer walls, that can both resist compression and bind the two substrates together. A suitable manufacturing process is to prefabricate the polymer wall structures, spread the LC mixture on the substrate, and subsequently close the panel with the top substrate. Potential problems with this approach are for example that spreading of the LC mixture is obstructed by the support structures, and that bonding to the top substrate might not be sufficient.

An alternative solution is to create the polymer wall structures by means of a photolithographic process after the display has been assembled. This is schematically illustrated in Fig. 1 showing a polymer wall formation process. Fig. 1 (a) shows an LC mixture consisting of LC host molecules (rods), polymerisable monomer (dots), and photo-initiator (not shown). As shown in Fig. 1 (b) the LC mixture is filled into the display, or the LC mixture is spread on a first substrate and a second substrate applied on top, and UV radiation (indicated by the arrows) is applied through a photomask. Polymerization induced phase separation takes place, as a result of which polymer walls are formed in irradiated regions according to the mask pattern as shown in Fig. 1 (c), while the LC phase of the LC host molecules (rods) in the pixel area is restored. The principle of creating polymer walls by this method for LC display applications is a known technique that has been described in the literature and has been suggested for use in a variety of display modes.

For example, US6130738 and EP2818534 A1 disclose an LC display that comprises polymer walls formed from one or two polymerisable monomers that are contained in the LC host mixture.

However, the currently used LC mixtures and monomers for use in flexible LC displays with polymer wall formation do still have several drawbacks and leave room for further improvement.

For example, it was observed that the polymerisable compounds and LC media used in prior art do often show insufficient phase separation between the polymer walls and the LC molecules of the LC host mixture. This leads on the one hand to the undesired inclusion of LC molecules in the polymer walls, and on the other hand to increased amounts of polymer molecules dissolved or dispersed in the LC host mixture, both of which can negatively influence the display performance. Thus, LC molecules trapped in the polymer wall can lead to reduced transparency and contrast of the display, a deterioration of the electrooptical response due to formation of domains with different switching speed, and decreased adhesion of the polymer walls to the substrates. On the other hand, undesired amounts of polymer molecules in the LC host mixture can negatively affect the LC mixture properties.

Moreover, it was observed that the thickness of the polymer walls is often not constant but varying, which can lead to non-uniform pixel size. Besides the polymer walls do often still not show sufficient stability against mechanical pressure on the one hand and sufficient elasticity on the other hand. Also, the polymer walls are often too thick, which reduces transparency and contrast of the display.

Another problem observed with hitherto used materials is that they do not always fulfil the requirement of good phase separation, thus leading to increased polymerization time, and high degree of crosslinking, thus leading to poor wall stability especially under mechanical stress.

It is therefore desirable to have available improved LC mixtures and

monomers for use in flexible LC displays which can overcome the drawbacks of materials used in prior art as described above.

The present invention is based on the object of providing novel suitable materials, in particular LC host mixtures comprising polymerisable monomers, for use in flexible LC displays with polymer walls, which do not have the disadvantages indicated above or do so only to a reduced extent.

In particular, the invention is based on the object of providing LC media comprising polymerisable monomers, which enable the formation of polymer walls in a time- and cost-effective manner, and which are suitable for mass production. The formed polymer walls should show clear phase separation from the LC host mixture, without or with a reduced amount of defects or LC molecules trapped in the polymer wall, and without or with a reduced amount of polymer molecules dissolved in the LC host mixture. Also, the polymer walls should show constant thickness, high elasticity, high stability against mechanical pressure, and good adhesion to the substrates.

Another object of the invention is to provide improved LC host mixtures for flexible displays which should show high specific resistance values, high VHR values, high reliability, low threshold voltages, short response times, high birefringence, show good UV absorption especially at longer wavelengths, allow quick and complete polymerisation of the monomers contained therein, and reduce or prevent the occurrence of image sticking in the display. Another object of the invention is to provide LC displays with polymer walls that show high transparency in the addressed state, good contrast, high switching speed and a large operating temperature range. Another object of the present invention is to provide an improved technical solution for enabling LCD technology for free form and unbreakable plastic substrate based LC displays.

Another object of the invention is to provide polymerisable LC media for the manufacturing of LC displays with polymer walls, which enable at the same a good phase separation and a high degree of crosslinking.

The above objects have been achieved in accordance with the present invention by materials and processes as described and claimed hereinafter.

Thus, it has surprisingly been found that at least some of the above-mentioned objects can be achieved by using an LC medium which comprises an LC host mixture and one or more polymerisable monomers as disclosed and claimed hereinafter, wherein the LC medium contains a first polymerisable compound comprising at least two polymerisable thiol groups of the formula -SH, and a second polymerisable compound comprising at least two polymerisable groups having an ethylene moiety of the formula -CW=CH2 wherein W is H or for example lower alkyl as defined below, this ethylene moiety hereinafter also being referred to as "-ene group".

It has also been surprisingly found that the polymerisable compounds contained in the LC medium can also be used to form spacers to maintain a constant cell gap between the substrates of the LC display. This can support or even replace the spacer materials that are normally used in prior art.

Summary of the Invention

The invention relates to a liquid crystal (LC) medium comprising a

polymerisable component A) which comprises, and preferably consists of, one or more polymerisable compounds, and a liquid-crystalline component B), hereinafter also referred to as "LC host mixture", which comprises, and preferably consists of, one or more mesogenic or liquid-crystalline

compounds, wherein the polymerisable component A) comprises one or more first polymerisable compounds comprising at least two thiol groups -SH, wherein at least one of the first polymerisable compounds contains an aromatic or heteroaromatic group, said first polymerisable compounds with an aromatic or heteroaromatic group preferably being selected from compounds comprising an aromatic or heteroaromatic group having 4 to 25 ring atoms that may also contain fused rings and is unsubstituted, or mono- or polysubstituted, and connected thereto, optionally via spacer groups, at least two thiol groups -SH, one or more second polymerisable compounds comprising at least two polymerisable groups comprising a terminal ethenyl moiety of the formula - CW=CH ₂ wherein W is H, F, CI, CN, CF ₃ , phenyl or alkyl having 1 to 5 C atoms, preferably H, F, CI , Chb or C2H5, very preferably H or CH3, optionally a polymerisation initiator, optionally a stabiliser.

The liquid-crystalline component B) of an LC medium according to the present invention is hereinafter also referred to as "LC host mixture", and preferably contains LC compounds that are selected only from low-molecular-weight compounds which are unpolymerisable, and optionally contains further additives like stabilisers or chiral dopants.

The invention furthermore relates to an LC medium or LC display as described above and below, wherein the polymerisable compounds, or the compounds of component A), are polymerised.

The invention furthermore relates to a process for preparing an LC medium as described above and below, comprising the steps of mixing an LC host mixture or LC component B) as described above and below, with one or more polymerisable compounds as described above and below, and optionally with further LC compounds and/or additives.

The invention further relates to the use of LC medium in LC displays, preferably in flexible LC displays.

The invention furthermore relates to an LC display comprising an LC medium as described above and below. The invention furthermore relates to an LC display comprising polymer walls obtainable by polymerisation of one or more polymerisable compounds or a polymerisable component A) as described above and below, or comprising an LC medium as described above and below. The invention furthermore relates to an LC display comprising spacers obtainable by polymerisation of one or more polymerisable compounds or a polymerisable component A) as described above and below, or comprising an LC medium as described above and below. The LC display according to the present invention is preferably a flexible LC display, and preferably a TN, OCB, IPS, FFS, posi-VA, VA or UB-FFS display.

The invention furthermore relates to an LC display 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 polymerisable compounds are polymerised between the substrates of the display.

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

compounds. The displays according to the invention have two electrodes, preferably in the form of transparent layers, which are applied to one or both of the substrates. In some displays, for example in TN, OCB or VA displays, one electrode is applied to each of the two substrates. In other displays, for example in IPS, FFS or UB-FFS displays, both electrodes are applied to only one of the two substrates.

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

Brief Description of the Drawings

Fig. 1 schematically illustrates the polymer wall formation process in displays according to prior art and according to the present invention.

Fig. 2-9 show polarization microscope images of test cells containing polymerisable mixtures P1 -P8 according to the invention after polymerization. Fig. 10 shows the polarization microscope image of a test cell containing polymerisable reference mixture CP1 after polymerization.

Terms and Definitions Above and below, the term "free form display" will be understood to mean a display that has either a permanent shape other than a plane-parallel shape, like for example a curved shape, or a flexible display. The term "flexible display" will be understood to mean a display which is bendable without breaking, like for example a display having flexible plastic substrates instead of rigid glass substrates and not comprising any other rigid layers. The term "curved display" will be understood to mean a display which has top and bottom subtrates that are not plane-parallel but curved.

Above and below, the term "flat display with reduced touch Mura sensitivity" will be understood to mean a display wherein irregular luminosity variation defects, which are caused by touching the front screen of a display, are reduced.

Above and below, the term "bi- or polycyclic group" will be understood to mean a group that consists of two or more fused rings, i.e. rings that share at last one common atom (in contrast to rings that are connected via covalent bonds between atoms belonging to different rings), wherein fusion of the rings occurs a) across a sequence of atoms (bridgehead), like for example in

bicyclo[2.2.1 ]heptane (norbornane) or tricyclo[3.3.3.1 ]decane (adamantane), hereinafter also referred to as "bridged bi- or polycyclic groups",

b) across a bond between two atoms, like for example in bicyclo[4.4.0]decane (decalin), hereinafter also referred to as "fused bi- or polycyclic groups" c) at a single atom (spiro atom), like for example in spiro[4.5]decane, hereinafter also referred to as "spirocyclic groups".

Unless indicated otherwise, the abbreviation "RM" is used above and below when referring to a reactive mesogen.

Above and below, polymerisable compounds or RMs with one polymerisable reactive group are also referred to as "monoreactive", polymerisable compounds or RMs with two polymerisable reactive groups are also referred to as "direactive", and polymerisable compounds or RMs with three

polymerisable reactive groups are also referred to as "trireactive". Unless indicated otherwise, the expression "LC mixture" is used when referring to the LC host mixture (i.e. without the RMs or polymerizable compounds), while the expression "LC medium" is used when referring to the LC host mixture plus the RM(s) or polymerizable compounds. Unless stated otherwise, the polymerisable compounds and RMs are preferably selected from achiral compounds.

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

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

As used herein, the term "low-molecular-weight compound" will be

understood to mean to a compound that is monomeric and/or is not prepared by a polymerisation reaction, as opposed to a "polymeric compound" or a "polymer".

As used herein, the term "unpolymerisable compound" will be understood to mean a compound that does not contain a functional group that is suitable for polymerisation under the conditions usually applied for the polymerisation of the RMs or polymerizable compounds.

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

Above and below,

denote a trans-1 ,4-cyclohexylene ring, and

denote a 1 ,4-phenylene ring.

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

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

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

O

I I

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

A carbon or hydrocarbon group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups. A carbon or hydrocarbon radical having more than 3 C atoms can be straight- chain, branched and/or cyclic and may also contain spiro links or condensed rings. The terms "alkyl", "aryl", "heteroaryl", etc., also encompass polyvalent groups, for example alkylene, arylene, heteroarylene, etc. The term "aryl" denotes an aromatic carbon group or a group derived therefrom. The term "heteroaryl" denotes "aryl" as defined above, containing one or more heteroatoms, preferably selected from N, O, S, Se, Te, Si and Ge. Preferred carbon and hydrocarbon groups are optionally substituted, straight- chain, branched or cyclic, alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 20, very preferably 1 to 12, C atoms, optionally substituted aryl or aryloxy having 5 to 30, preferably 6 to 25, C atoms, or optionally substituted alkylaryl, arylalkyl, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 5 to 30, preferably 6 to 25, C atoms, wherein one or more C atoms may also be replaced by hetero atoms, preferably selected from N, O, S, Se, Te, Si and Ge. Further preferred carbon and hydrocarbon groups are C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C20 allyl, C ₄ -C2o alkyldienyl, C ₄ -C2o polyenyl, C6- C20 cycloalkyl, C ₄ -Cis cycloalkenyl, C6-C30 aryl, C6-C30 alkylaryl, C6-C30 arylalkyl, C6-C30 alkylaryloxy, C6-C30 arylalkyloxy, C2-C30 heteroaryl, C2-C30 heteroaryloxy.

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

Further preferred carbon and hydrocarbon groups are straight-chain, branched or cyclic alkyl having 1 to 20, preferably 1 to 12, C atoms, which are unsubstituted or mono- or polysubstituted by F, CI, Br, I or CN and in which one or more non-adjacent CH2 groups may each be replaced, independently of one another, by -C(R ^S1 )=C(R ^S1 )-, -C≡C-, -N(R ^S1 )-, -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 R ^S1 denotes H, F, CI, CN, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non-adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- and in which one or more H atoms may be replaced by F or CI, or denotes an optionally substituted aryl or aryloxy group with 6 to 30 C atoms, or an optionally substituted heteroaryl or heteroaryloxy group with 2 to 30 C atoms.

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

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

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

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

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

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

Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,

[1 ,1 ':3',1 "]terphenyl-2'-yl, naphthyl, anthracene, binaphthyl, phenanthrene, 9,10-dihydro-phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene, spirobifluorene, etc. Preferred heteroaryl groups are, for example, 5-membered rings, such as pyrrole, pyrazole, imidazole, 1 ,2,3-triazole, 1 ,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1 ,2-thiazole, 1 ,3-thiazole, 1 ,2,3- oxadiazole, 1 ,2,4-oxadiazole, 1 ,2,5-oxadiazole, 1 ,3,4-oxadiazole, 1 ,2,3- thiadiazole, 1 ,2,4-thiadiazole, 1 ,2,5-thiadiazole, 1 ,3,4-thiadiazole, 6-membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1 ,3,5-triazine, 1 ,2,4- triazine, 1 ,2,3-triazine, 1 ,2,4,5-tetrazine, 1 ,2,3,4-tetrazine, 1 ,2,3,5-tetrazine, or condensed groups, such as indole, isoindole, indolizine, indazole,

benzimidazole, benzotriazole, purine, naphthimidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phenanthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline, benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquin- oline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimi- dine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazo- thiophene, or combinations of these groups.

The aryl and heteroaryl groups mentioned above and below may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups. The (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those containing exclusively single bonds, and also partially unsaturated rings, i.e. those which may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, O, N, S and Se.

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

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

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

Preferred substituents, hereinafter also referred to as L ^s , are, for example, F, CI, Br, I, -CN, -NO2, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^s ) ₂ , -C(=O)Y ^s , - C(=O)R ^s , -N(R ^S )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 CI, 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 ^s denotes H, F, CI, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent Ch -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 or CI,

Y ^s denotes halogen, preferably F.

"Substituted silyl or aryl" preferably means substituted by halogen, -CN, R°, -OR ⁰ , -CO-R ⁰ , -CO-O-R ⁰ , -O-CO-R ⁰ or -O-CO-O-R ⁰ , wherein R° denotes H or alkyl with 1 to 20 C atoms.

Particularly preferred substituents L are, for example, F, CI, CN, NO2, CH3, C2H5, OCH3, OC2H5, COCH3, COC2H5, COOCH3, COOC2H5, CF ₃ , OCF3, OCHF2, OC2F5, furthermore phenyl.

in which L has one of the meanings indicated above and r is 0, 1 , 2, 3 or 4.

The polymerisable group P, P ^x or Ρ ¹ · ² is a group which is suitable for a polymerisation reaction, such as, for example, free-radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain.

Particular preference is given to groups for chain polymerisation, in particular those containing a C=C double bond or -C≡C- triple bond, and groups which are suitable for polymerisation with ring opening, such as, for example, oxetane or epoxide groups. Preferred groups P, P ^x and Ρ ¹ · ² are selected from the group consisting of

O

CH ₂ =CW ¹ -CO-O-, CH ₂ =CW ¹ -CO-, w HC— CH- , w ² ( ^{C H} ₂ ) _k °- ,

, CH ₂ =CW ² -(O)k3-, CW ¹ =CH-CO-(O) _k3 -,

CW ¹ =CH-CO-NH-, CH ₂ =CW ¹ -CO-NH-, CH ₃ -CH=CH-O-, (CH ₂ =CH) ₂ CH- ₀ OCO-, (CH ₂ =CH-CH ₂ ) ₂ CH-OCO-, (CH ₂ =CH) ₂ CH-O-, (CH ₂ =CH-CH ₂ ) ₂ N-,

(CH ₂ =CH-CH ₂ ) ₂ N-CO-, HO-CWW-, HS-CW ² W ³ -, HW ² N-, HO-CWW-NH-, CH ₂ =CW ¹ -CO-NH-, CH ₂ =CH-(COO)ki-Phe-(O) _k2 -, CH ₂ =CH-(CO) _k i-Phe-(O) _k2 - , Phe-CH=CH-, HOOC-, OCN- and W ⁴ W ⁵ W ⁶ Si-, in which W ¹ denotes H, F, CI, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, CI , CH3 or C ₂ H5, W ² and W ³ each, independently of one another, denote H or alkyl5

having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴ , W ⁵ and W ⁶ each, independently of one another, denote CI, oxaalkyl or

oxacarbonylalkyl having 1 to 5 C atoms, W ⁷ and W ⁸ each, independently of one another, denote H, CI or alkyl having 1 to 5 C atoms, Phe denotes 1 ,4-Q phenylene, which is optionally substituted by one or more radicals L as

defined above which are other than P-Sp-, ki, k ₂ and k3 each, independently of one another, denote 0 or 1 , k3 preferably denotes 1 , and k ₄ denotes an integer from 1 to 10. ₍ - Very preferred groups P, P ^x and Ρ ¹ · ² are selected from the group consisting of

CH ₂ =CW ¹ -CO-O-, CH ₂ =CW ¹ -CO-, w HC— CH- . w ² ,

, CH ₂ =CW ² -O-, CH ₂ =CW ² -, CW ¹ =CH-CO-

(O) _k3 -, CW ¹ =CH-CO-NH-, CH ₂ =CW ¹ -CO-NH-, (CH ₂ =CH) ₂ CH-OCO-,

(CH ₂ =CH-CH ₂ ) ₂ CH-OCO-, (CH ₂ =CH) ₂ CH-O-, (CH ₂ =CH-CH ₂ ) ₂ N-, (CH ₂ =CH- CH ₂ ) ₂ N-CO-, CH ₂ =CW ¹ -CO-NH-, CH ₂ =CH-(COO) _k i-Phe-(O) _k2 -, CH ₂ =CH- (CO)ki-Phe-(O) _k2 -, Phe-CH=CH- and W ⁴ W ⁵ W ⁶ Si-, in which W ¹ denotes H, F, CI, CN, CF3, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, CI, CH3 or C2H5, W ² and W ³ each, independently of one another, denote H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl, W ⁴ , W ⁵ and W ⁶ each, independently of one another, denote CI, oxaalkyl or oxa- carbonylalkyl having 1 to 5 C atoms, W ⁷ and W ⁸ each, independently of one another, denote H, CI or alkyl having 1 to 5 C atoms, Phe denotes 1 ,4- phenylene, ki, k2 and k3 each, independently of one another, denote 0 or 1 , k3 preferably denotes 1 , and k ₄ denotes an integer from 1 to 10.

Very particularly preferred groups P, P ^x and Ρ ¹ · ² are selected from the group consisting of CH ₂ =CW ¹ -CO-O-, in particular CH ₂ =CH-CO-O-, CH ₂ =C(CH ₃ )- CO-O- and CH ₂ =CF-CO-O-, furthe (CH ₂ =CH) ₂ CH-O-CO-,

(CH ₂ =CH) ₂ CH-O-, W ² HC— CH - 0-

Further preferred polymerisable groups P, P ^x and Ρ ¹ · ² are selected from the group consisting of vinyloxy, acrylate, methacrylate, ethacrylate,

fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably from acrylate and methacrylate.

If Sp, Sp ^x or Sp ¹ ' ² is different from a single bond, it is preferably selected of the formula Sp"-X", so that the respective radical P-Sp- conforms to the formula P-Sp"-X"-, wherein

Sp" denotes alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, CI, Br, I or CN and in which, in addition, one or more non-adjacent CH ₂ groups may each be replaced, independently of one another, by -O-, -S-, -NH-, -N(R ⁰ )-, -Si(R°R ⁰⁰ )-, - CO-, -CO-O-, -O-CO-, -O-CO-O-, -S-CO-, -CO-S-, -N(R ⁰⁰ )-CO-O-, -O- CO-N(R ⁰ )-, -N(R°)-CO-N(R ⁰⁰ )-, -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(R ⁰ )-, -N(R ⁰ )- CO-, -N(R°)-CO-N(R ⁰⁰ )-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, - OCF ₂ -, -CF ₂ S-, -SCF ₂ -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH=N-, - N=CH-, -N=N-, -CH=CR ⁰ -, -CY ² =CY ³ -, -C≡C-, -CH=CH-CO-O-, -O-CO- CH=CH- or a single bond, R° and R ⁰⁰ each, independently of one another, denote H or alkyl having 1 to 20 C atoms, and Y ² and Y ³ each, independently of one another, denote H, F, CI or CN.

X" is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ⁰ -, -NR°- CO-, -NR°-CO-NR ⁰⁰ - or a single bond. Typical spacer groups Sp, Sp ^x , Sp ^{1 2} and -Sp"-X"- are, for example, -(CH2) _P i-, -(CH ₂ CH2O)qi-CH ₂ CH2-, -CH2CH2-S-CH2CH2-, -CH2CH2-NH-CH2CH2- or -(SiR°R ⁰⁰ -O)pi-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R° and R ⁰⁰ have the meanings indicated above. Particularly preferred groups Sp, Sp ^x , Sp ^{1 <2} and -Sp"-X"- are -(CH ₂ ) _P i-, -(CH ₂ ) _P i- O-, -(CH ₂ ) _P i-O-CO-, -(CH ₂ ) _P i-CO-O-, -(CH ₂ ) _P i-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. Detailed Description of the Invention

The LC medium according to the present invention is characterized in that it comprises a first monomer with at least two thiol groups and a second polymerisable compound with at least two terminal ethenyl groups (hereinafter also referred to as "-ene group"). The polymerisation of these groups, also known in the literature as thiol-ene reaction, is not a chain-growth

polymerisation reaction but a step-growth polymerisation reaction. In contrast to a chain-growth reaction, where the molecular weight of the forming polymer chain increases quickly after the start of the reaction, in a step-growth reaction the molecular weight of the forming polymer chain increases slowly and steadily. As the LC medium of the present invention contains monomers with at least two polymerisable groups, this results in a nonlinear molecular weight increase and the formation of a polymer network with high degree of crosslinking.

As a result, it was observed that the use of an LC medium according to the present invention for preparing polymer walls shows unexpected

improvements over the LC media of prior art, like for example a better phase separation between the polymer walls and the LC host mixture, and a higher degree of crosslinking of the polymer. The LC medium according to the present invention thus enables polymer walls with improved resistance against mechanical stress and with a pattern having high resolution.

Preferably, the first and second monomers as used in the LC medium according to the present invention are selected from compounds having two, three of four polymerisable groups, more preferably from compounds having two or three polymerisable groups, most preferably from compounds having three polymerisable groups.

Preferably component A) of the LC medium comprises one or more first polymerisable compounds selected of formula I

G ¹ -(Sp ¹ -SH) _g i I wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings

Sp ¹ a spacer group or a single bond,

G ¹ an aromatic or heteroaromatic group having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

L F, CI, -CN, -NO ₂ , -NCO, -NCS, -OCN, -SCN, -C(=O)N(R ^q ) ₂ , -

C(=O)Y ^z , -C(=O)R ^q , -N(R ^q ) ₂ , optionally substituted silyl, optionally substituted aryl or heteroaryl having 5 to 20 ring atoms, or straight- chain or branched alkyl having 1 to 25 C atoms in which, in addition, one or more non-adjacent CH ₂ groups may each be replaced, independently of one another, by -C(R°)=C(R ⁰⁰ )-, -C≡C- , -N(R ⁰ )-, -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, CI,

-CN,

R ^q H, F, CI, CN, or straight chain, branched or cyclic alkyl having 1 to

25 C atoms, wherein one or more non-adjacent CH ₂ -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 or CI, R°, R ⁰⁰ H or alkyl having 1 to 20 C atoms,

Y ^z halogen, preferably F or CI, g1 an integer from 2 to 10, preferably 2, 3, 4, 5 or 6.

In the compounds of formula I Sp ¹ is preferably selected from -(CH2) _P i-, - (CH ₂ ) _P i-O-, -(CH ₂ ) _P i-O-CO-, -(CH ₂ ) _P i-CO-O- or -(CH ₂ ) _P i-O-CO-O-, wherein p1 is an integer from 2 to 12, and wherein Sp ¹ is linked to the adjacent thiol group -SH such that O and S atoms are not directly connected to each other.

In a preferred embodiment G ¹ in formula I is selected from benzene,

biphenylene, terphenylene, naphthalene, phenanthrene, anthracene and perylene, very preferably from benzene, biphenylene, terphenylene and naphthalene, most preferably from benzene and biphenylene.

Preferred compounds of formula I are selected from the following

subformulae

11

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings

Sp ¹ one of the meanings given in formula I, n1 2, 3 or 4, n2 1 , 2 or 3.

Very preferred compounds of formula I are selected from the following subformulae

Preferably component A) of the LC medium comprises at least one compound of formula 11 or I2 or their subformulae.

In another preferred embodiment the present invention component A) of the LC medium does, in addition to the aromatic or heteroaromatic thiol compounds, comprise one or more first polymerisable compounds comprising at least two thiol groups -SH, which are selected of formula II

G ² -(Sp ² -SH)g ₂ II wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings

Sp ² a spacer group or a single bond,

G ² a straight-chain alkyl group with 1 to 20 C atoms, or a branched

alkyl group with 3 to 20 C atoms, or a cyclic alkyl group with 3 to 20 C atoms, wherein each of these groups is optionally mono- or polysubstituted by L, and wherein in each of these groups one or more CH ₂ -groups are optionally replaced by -O-, -S-, -CO-, -O-

CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C-, -N(R ⁰ )- such that O-atoms and /or S-atoms are not directly adjacent to one another,

L, R°, R ⁰⁰ one of the meanings given in formula I above, g2 an integer from 2 to 10, preferably 2, 3, 4, 5 or 6.

In the compounds of formula II Sp ² is preferably selected from -(CH2) _P i-, - (CH ₂ ) _P i-O-, -(CH ₂ ) _P i-O-CO-, -(CH ₂ ) _P i-CO-O- or -(CH ₂ ) _P i-O-CO-O-, wherein p1 is an integer from 2 to 12, and wherein Sp ² is linked to the adjacent thiol group - SH such that O and S atoms are not directly connected to each other.

In a preferred embodiment G ² in formula II is straight-chain alkyl with 1 to 20 C atoms, or branched alkyl with 3 to 20 C atoms, that is optionally mono-, poly- or perfluorinated, and wherein one or more CH ₂ -groups are optionally replaced by -O-, -S-, -CO-, -O-CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C- or -N(R ⁰ )- such that O-atoms and/or S-atoms are not directly adjacent to one another.

In another preferred embodiment G ² in formula II is cyclic alkyl with 3 to 20 C atoms that is optionally mono- or polysubstituted by one or more groups L, preferably F, and wherein one or more CH ₂ -groups are optionally replaced by - O-, -S-, -CO-, -O-CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C- or -N(R ⁰ )- such that O- and/or S-atoms are not directly adjacent to one another. Preferred compounds of formula II are selected from the following

subformulae

HS-R-SH 111 (HS-R)n4C(W ^x )3-n4-CH2-O-CH2-C(W ^x ) ₃ -n4(R-HS)n4 113

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings

Sp ² one of the meanings given in formula II,

R straight-chain or branched alkylene with 2 to 20, preferably 2 to 12

C atoms, or cyclic alkylene with 3 to 20, preferably 3 to 12 C atoms, each of which is optionally mono-, poly- or perfluorinated, and wherein one or more Ch -groups are optionally replaced by - O-, -S-, -CO-, -O-CO-, -CO-O-, -O-CO-O-, -CH=CH-, -C≡C, or - N(R ⁰ )- such that O- and/or S-atoms are not directly adjacent to one another,

W ^x H, OH, or alkyl or alkoxy with 1 to 12 C atoms, preferably H, OH,

CH ₃ , OCHs, or C ₂ H ₅ or OC ₂ H ₅ , n3 3 or 4, n4 2 or 3. Very preferred compounds of formula II are selected from the following subformulae

 -27-

 wherein W ^x is as defined in formula 112 and a is 1 , 2 or 3.

Preferably component A) of the LC medium comprises one or more second polymerisable compounds selected of formula III G ³ -(Sp ³ -P ¹ )g ₃ III wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings P ¹ -(O)si-(CO)s2-CW=CH ₂ ,

W H, F, CI, CN, CF ₃ , phenyl or alkyl having 1 to 5 C atoms,

preferably H, F, CI , CH ₃ or C ₂ H ₅ , Sp ³ a spacer group or a single bond, G ³ a straight-chain alkyl group with 1 to 20 C atoms, or a branched alkyl group with 3 to 20 C atoms, or a cyclic alkyl group with 3 to 20 C atoms, wherein each of these groups is optionally mono- or polysubstituted by L, and wherein in each of these groups one or more CH ₂ -groups are optionally replaced by -O-, -S-, -CO-, -O-

CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C-, -N(R ⁰ )- such that O-atoms and /or S-atoms are not directly adjacent to one another, or an G ³ is an aromatic or heteroaromatic group having 4 to 25 ring atoms, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

L one of the meanings given in formula I, g3 an integer from 2 to 10, preferably 2, 3, 4, 5 or 6, s1 0 or 1 , s2 0 or 1 , with s2 being 0 if s1 is 0. In the compounds of formula III Sp ³ is preferably selected from -(CH2) _P i-, -

(CH ₂ ) _P i-O-, -(CH ₂ ) _P i-O-CO-, -(CH ₂ ) _P i-CO-O- or -(CH ₂ ) _P i-O-CO-O-, wherein p1 is an integer from 2 to 12, and wherein Sp ³ is linked to the adjacent group -(O) _g i- (CO) _g2 -CW=CH ₂ such that O atoms are not directly connected to each other. In a preferred embodiment in formula III s1 is 0 and s2 is 0. In another preferred embodiment in formula III s1 is 1 and s2 is 0. In another preferred embodiment in formula III s1 is 1 and s2 is 1 .

In a preferred embodiment G ³ in formula III is straight-chain alkyl with 1 to 20 C atoms, or branched alkyl with 3 to 20 C atoms, that is optionally mono-, poly- or perfluorinated, and wherein one or more CH ₂ -groups are optionally replaced by -O-, -S-, -CO-, -O-CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C- or -N(R ⁰ )- such that O-atoms and/or S-atoms are not directly adjacent to one another. In another preferred embodiment G ³ in formula III is cyclic alkyl with 3 to 20 C atoms that is optionally mono- or polysubstituted by one or more groups L, preferably F, and wherein one or more Ch -groups are optionally replaced by - O-, -S-, -CO-, -O-CO-, -CO-O-, -O-CO-O-, -C(R°)=C(R ⁰⁰ )-, -C≡C- or -N(R ⁰ )- such that O- and/or S-atoms are not directly adjacent to one another.

In another preferred embodiment G ³ in formula III is aryl or heteroaryl with 4 to 25 ring atoms that is optionally substituted by one or more groups L. If G ³ is aryl or heteroaryl, it is preferably selected from benzene, biphenylene, terphenylene, naphthalene, phenanthrene, anthracene and perylene, very preferably from benzene, biphenylene, terphenylene and naphthalene, most preferably from benzene and biphenylene, all of which are optionally substituted by one or more groups L.

Preferred compounds of formula III are selected from the following

subformulae

P ¹ -(CH ₂ ) _n5 -P ² 1111

(P ¹ -(CH ₂ )n6)n7CW ^x _4- n7 III2

wherein the individual radicals, independently of each other and on each occurrence identically or differently, have the following meanings

P ¹ , P ² , P ³ , P ⁴ -(O)si-(CO)s2-CW=CH ₂ , one of the meanings given in formula III,

W ^x H, OH, or alkyl or alkoxy with 1 to 12 C atoms, preferably H, OH,

CH ₃ , OCHs, or C ₂ H ₅ or OC ₂ H ₅ , n5 an integer from 2 to 15, n6 0 or an integer from 1 to 15, n7 2, 3 or 4,

!0

n8 2, 3 or 4, and wherein in formula 1111 in the group (CH2)n5 one or more of the H atoms may be replaced by F or alkyl with 1 to 6 C atoms, and in formula III2 in the group (CH2)n6 one or more of the CH2 groups are optionally replaced by -O- or -CO-, and one or more of the H atoms are optionally replaced by F or alkyl with 1 to 6 C atoms.

Very preferred compounds are those of formula III2 and its subformulae, especially wherein n7 is 3.

In a preferred embodiment of the present invention the component A) of the LC medium comprises one or more compounds of formula III or its

subformulae wherein all groups P ^1"4 are identical groups. In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more second polymerisable compounds comprising at least two polymerisable groups of formula -(O) _s i-(CO) _S 2- CW=CH2 that are different from each other. Preferably in this preferred embodiment the component A) of the LC medium comprises one or more compounds of formula II or its subformulae with at least two different groups P ^1"4 . Preferably in these compounds of formula II one of P ^1"4 is vinyloxy and the other is acrylate, methacrylate or ethacrylate, most preferably

methacrylate.

In the second polymerisable compounds, the polymerisable groups are preferably selected from acrylate, methacrylate, ethacrylate and vinyloxy groups. Very preferably one of the polymerisable groups is vinyloxy and the other is acrylate or methacrylate, most preferably methacrylate.

Very preferred compounds of formula are selected from the following subformulae

CH2=CW-CO-O-(CH ₂ )n5-O-CW=CH2

CH2=CW-CO-O-(CH ₂ )n5-O-CO-CW=CH2

CH2=CW-O-(CH ₂ )n5-O-CW=CH2

(CH2=CW-O-(CH ₂ )n6)3CW ^x M2a

(CH2=CW-CO-O-(CH ₂ )n6)3CW ^x M2b

(CH ₂ =CW-O-(CH ₂ )n6)4C Il2c

(CH ₂ =CW-CO-O-(CH ₂ )n6)4C M2d

(CH2=CW-O-(CH ₂ )n6)2CW ^X 2 N2e

(CH2=CW-CO-O-(CH ₂ )n6)4CW ^X 2 M2f wherein W, W ^x , s1 , s2, n5 and n6 are as defined above, and wherein in formula 1111 a-c in the group (Ch jni one or more of the H atoms may be replaced by F or alkyl with 1 to 6 C atoms, and in formula MI2a-f in the group (CH2)n6 one or more of the Ch groups are optionally replaced by -O- or -CO- , and one or more of the H atoms are optionally replaced by F or alkyl with 1 to 6 C atoms.

Especially preferred are compounds of formula MI2a and MI2b.

Very preferred compounds of formula III are selected from the following formulae

35







MI4a1

Especially preferred are compounds of formula MI2a1 and MI2a2.

In a preferred embodiment of the present invention component A) of the LC medium comprises one or more first polymerisable compounds, preferably of formula I, having exactly three thiol groups. Preferably the component A) according to this preferred embodiment comprises one or more compounds of formula I wherein g1 is 3.

In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more first polymerisable compounds, preferably of formula I or II, very preferably of formula I, having exactly three thiol groups, and one or more first polymerisabe compounds, preferably of formula I or II, having (exactly) two or four thiol groups. In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more first polymerisable compounds of formula I having contains two or more, preferably exactly three, thiol groups, and one or more first polymerisabe compounds preferably of formula II having two or more thiol groups.

In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more compounds selected from formulae 11 and I2 or their subformulae, wherein at least one compound is selected from formula 11 or its subformulae, wherein preferably n1 is 3.

In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more compounds selected from formula 11 or I2 and its subformulae, and one ore more compounds selected from formulae 111 to II4 and their subformulae.

In another preferred embodiment of the present invention component A) of the LC medium comprises one or more second polymerisable compounds having exactly three polymerisable groups with a terminal ethenyl moiety - CW=CH2. Preferably the component A) according to this preferred embodiment comprises one or more compounds of formula III wherein g3 is 3, and very preferably comprises one or more compounds selected from formulae III2-III4 wherein n7 and n8 denote 3.

In another preferred embodiment of the present invention the component A) of the LC medium comprises two or more second polymerisable compounds as defined above and below. Very preferably the component A) according to this preferred embodiment comprises at least one second polymensable compound having exactly two polymerisable groups with a terminal ethenyl moiety -CW=CH2 and at least one second polymerisable compound having (exactly) three or four polymerisable groups with a terminal ethenyl moiety - CW=CH ₂ .

In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more compounds of formula 1111 and its subformulae and one or more compounds selected from formulae III2-III5 and their subformulae wherein preferably n7 and n8 denote 3 or 4.

In another preferred embodiment of the present invention the component A) of the LC medium comprises one or more compounds selected from formulae III1 -III4 and their subformulae wherein at least one compound is selected from formula III2 and its subformulae, preferably wherein n7 is 3.

In the LC medium according to the present invention, the concentration of each individual first polymerisable compound, preferably of formula I and II, is preferably from 1 to 20%, very preferably from 2 to 15%, most preferably from 5 to 15% by weight.

In the LC medium according to the present invention, the concentration of each individual second polymerisable compound, preferably of formula III, is preferably from 1 to 20%, very preferably from 2 to 15%, most preferably from 5 to 15% by weight.

In the LC medium according to the present invention, the total concentration of the first and second polymerisable compounds, preferably those of formula I, II and III, is preferably from 2 to 30%, very preferably from 3 to 25%, most preferably from 5 to 22% by weight.

In the LC medium according to the present invention, the ratio of the first to the second polymerisable compounds, preferably the ratio of the compounds of formula I and II to the compounds of formula II, is preferably selected such that the LC medium contains equimolar amounts of thiol groups (-SH) and ethenyl groups (-CW=CH ₂ ). The amount of first and second polymerisable compounds can be calculated according to the following formula

wherein

R = ratio of the molar amount of polymerisable groups of the first compound to the molar amount of polymerisable groups of the second compound

A = total amount of the first polymerisable compound (g)

B = total amount of the second polymerisable compound (g) fA = number of thiol groups in the first polymerisable compound fB = number of ethenyl groups in the second polymerisable compound wA = molecular weight of the first polymerisable compound wB = molecular weight of the second polymerisable compound

Preferably R is in the range from 0.5 to 2, very preferably from 0.8 to 1 .25, more preferably from 0.9 to 1 .1 most preferably 1 .

Particular preference is given to LC media wherein the polymerisable component A) comprises one, two or three first polymerisable compounds, preferably of formula I and optionally formula II, and one, two or three second polymerisable compounds, preferably of formula III.

Preferably the polymerisable component A) contains one or more

polymerisation initiators. Suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Preferably the initiator is a photoinitiator. Suitable initiators for free-radical

polymerisation are, for example, the commercially available photoinitiators Irgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocurel 173® (Ciba AG).

Preferably the total concentration of the polymerisation initiators in the LC medium is from 0.001 to 5% by weight, very preferably 0.01 to 1 % by weight, most preferably 0.05 to 0.5% by weight.

Further preferably the LC medium comprises one or more stabilisers in order to prevent undesired spontaneous polymerisation of the polymerisable monomers, 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.

Very preferably the LC medium contains a stabiliser of the following formula (pyrogallol)

Preferably the total concentration of the stabilisers in the LC medium is from

0.001 to 3% by weight, very preferably 0.01 to 1 % by weight, most preferably 0.05 to 0.5% by weight.

Further preferably the polymerisable component A) contains one or more photosensitizers. Example of suitable and preferred photosensitizers include isopropylthioxanthone (ITX) and thioxanthone.

Preferably the concentration of the photosensitizer in the LC medium is from 0.001 to 10% by weight, very preferably 0.01 to 5% by weight, most preferably 0.01 to 2% by weight. Besides the polymerisable component A) as described above, the LC medium according to the present invention comprises an LC component B), or LC host mixture, comprising one or more, preferably two or more LC compounds which are selected from low-molecular-weight compounds that are unpolymerisable. These LC compounds are selected such that they stable and/or unreactive to a polymerisation reaction under the conditions applied to the polymerisation of the polymerisable compounds.

Preference is given to LC media in which the LC component B), or the LC host mixture, has a nematic LC phase, and preferably has no chiral liquid crystal phase. The LC component B), or LC host mixture, is preferably a nematic LC mixture.

Preference is furthermore given to achiral polymerisable compounds, and to LC media in which the compounds of component A) and/or B) are selected exclusively from the group consisting of achiral compounds.

Preferably the proportion of the LC component B) in the LC medium is from 70 to 95% by weight.

The LC media and LC host mixtures of the present invention preferably have a nematic phase range > 80 K, very preferably > 100 K, and preferably a rotational viscosity < 250 mPa s, very preferably < 200 mPa s, at 20°C. The birefringence Δη of LC media and LC host mixtures according to the invention is preferably preferably from 0.07 to 0.15, particularly preferably from 0.08 to 0.15.

In a first preferred embodiment of the present invention, the LC medium contains an component B) or LC host mixture having a positive dielectric anisotropy Δε.

Such LC media are especially suitable for use in TN, OCB-, Posi-VA-, IPS- or FFS-displays or related modes using LC-materials with Δε>0. The LC media and LC host mixtures according to this first preferred embodiment preferably have a positive dielectric anisotropy Δε from +2 to +30, particularly preferably from +3 to +20, at 20°C and 1 kHz.

Particularly preferred is an LC medium of this first preferred embodiment, wherein the liquid-crystalline component B) or LC host mixture comprises one or more compounds selected from formula A and B

in which the individual radicals have, independently of each other and on each occurrence identically or differently, the following meanings: each, independently

of one another, and on each occurrence, identically or differently

each, independently of one another, 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° F, CI, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,

Z ³¹ -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans-

CF=CF-, -CH2O- or a single bond, preferably -CH2CH2-, - COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, trans-CH=CH- or a single bond,

L ²¹ , L ²² , L ³¹ , L ³² each, independently of one another, H or F,

In the compounds of formula A and B, X° is preferably F, CI, CF3, CHF2, OCF3, OCHF2, OCFHCF3, OCFHCHF2, OCFHCHF2, OCF2CH3, OCF2CHF2, OCF2CHF2, OCF2CF2CHF2, OCF2CF2CHF2, OCFHCF2CF3, OCFHCF2CHF2, OCF2CF2CF3, OCF2CF2CCIF2, OCCIFCF2CF3 or CH=CF ₂ , very preferably F or OCF3, most preferably F.

In the compounds of formula A and B, R ²¹ and R ³¹ are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms.

In the compounds of formula A and B, g is preferably 1 or 2.

In the compounds of formula B, Z ³¹ is preferably COO, trans-CH=CH or a single bond, very preferably COO or a single bond.

Preferably component B) of the LC medium comprises one or more compounds of formula A selected from the group consisting of the following formulae:

in which A ²¹ , R ²¹ , X°, L ²¹ and L ²² have the meanings given in formula A, L ²³ and L ²⁴ each, independently of one another, are H or F, and X° is preferably F. Particularly preferred are compounds of formulae A1 and A2.

Particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae:

A1 a -53-

in which R ²¹ , X°, L ²¹ and L ²² have the meaning given in formula A1 , L ²³ , L ²⁴ , L ²⁵ and L ²⁶ are each, independently of one another, H or F, and X° is preferably F.

Very particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae:

Particularly preferred compounds of formula A2 are selected from the group consisting of the following subformulae:

-57-

in which R ²¹ , X°, L ²¹ and L ²² have the meaning given in formula A2, L ²³ , L ²⁴ , L ²⁵ and L ²⁶ each, independently of one another, are H or F, and X° is preferably F.

Very particularly preferred compounds of formula A2 are selected from the group consisting of the following subformulae:

in which R ²¹ and X° are as defined in formula A2.

Particularly preferred compounds of formula A3 are selected from the group consisting of the following subformulae:

in which R ²¹ , X°, L ²¹ and L ²² have the meaning given in formula A3, and X° is preferably F.

Particularly preferred compounds of formula A4 are selected from the group consisting of the following subformulae: in which R ²¹ is as defined in formula A4.

Preferably component B) of the LC medium comprises one or more compounds of formula B selected from the group consisting of the following formulae:

in which g, A ³¹ , A ³² , R ³¹ , X°, L ³¹ and L ³² have the meanings given in formula B, and X° is preferably F. Particularly preferred are compounds of formulae B1 and B2.

Particularly preferred compounds of formula B1 are selected from the group consisting of the following subformulae: in which R ³¹ , X°, L ³¹ and L ³² have the meaning given in formula B1 , and X° is preferably F.

Very particularly preferred compounds of formula B1 a are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B1 .

Very particularly preferred compounds of formula B1 b are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B1 .

Particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae: in which R ³¹ , X°, L ³¹ and L ³² have the meaning given in formula B2, L ³³ , L ³⁴ , L ³⁵ and L ³⁶ are each, independently of one another, H or F, and X° is preferably F.

Very particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae: in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2b are selected from the group consisting of the following subformulae

W F B2b2 in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2c are selected from the group consisting of the following subformulae:

n which R ³¹ is as defined in formula B2. Very particularly preferred compounds of formula B2d and B2e are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2f are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2g are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2h are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2i are selected from the group consisting of the following subformulae:

B2i1 in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2k are selected from the group consisting of the following subformulae:

in which R ³¹ is as defined in formula B2.

Very particularly preferred compounds of formula B2I are selected from the group consisting of the following subformulae:

B2I1 in which R ³¹ is as defined in formula B2.

Alternatively to, or in addition to, the compounds of formula B1 and/or B2 component B) of the LC medium may also comprise one or more compounds of formula B3 as defined above.

Particularly preferred compounds of formula B3 are selected from the group consisting of the following subformulae:

n which R ³¹ is as defined in formula B3.

Preferably component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula C in which the individual radicals have the following meanings: 4 i \ / _Λ 42\_ each, independently of one another, and on each occurrence, identicall or differentl

R ⁴¹ , R ⁴² each, independently of one another, 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,

Z ⁴¹ , Z ⁴² each, independently of one another, -CH2CH2-, -COO-, trans-

CH=CH-, trans-CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably a single bond, h 0, 1 , 2 or 3.

In the compounds of formula C, R ⁴¹ and R ⁴² are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight- chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms.

In the compounds of formula C, h is preferably 0, 1 or 2.

In the compounds of formula C, Z ⁴¹ and Z ⁴² are preferably selected from

COO, trans-CH=CH and a single bond, very preferably from COO and a single bond.

Preferred compounds of formula C are selected from the group consisting of the following subformulae:

 wherein R ⁴¹ and R ⁴² have the meanings given in formula C, and preferably denote each, independently of one another, alkyi, alkoxy, fluorinated alkyi or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyi or fluorinated alkenyl with 2 to 7 C atoms.

In another preferred embodiment of the present invention component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula D in which A ⁴¹ , A ⁴² , Z ⁴¹ , Z ⁴² , R ⁴¹ , R ⁴² and h have the meanings given in formula C or one of the preferred meanings given above. Preferred compounds of formula D are selected from the group consisting of the following subformulae:

in which R ⁴¹ and R ⁴² have the meanings given in formula D and R ⁴¹ preferably denotes alkyl bedeutet, and in formula D1 R ⁴² preferably denotes alkenyl, particularly preferably -(CH ₂ )2-CH=CH-CH ₃ , and in formula D2 R ⁴² preferably denotes alkyl, -(CH ₂ ) ₂ -CH=CH ₂ or -(CH ₂ ) ₂ -CH=CH-CH ₃ .

In another preferred embodiment of the present invention component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula E containing an alkenyl group in which the individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:

R ^A1 alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z denotes cyclohexenyl, also one of the meanings of R ^A2 ,

R ^A2 alkyl having 1 to 12 C atoms, in which, in addition, one or two non- adjacent Ch groups may be replaced by -O-, -CH=CH-, -CO- , -OCO- or -COO- in such a way that O atoms are not linked directly to one another, x 1 or 2.

R ^A2 is preferably straight-chain alkyl or alkoxy having 1 to 8 C atoms or straight-chain alkenyl having 2 to 7 C atoms.

Preferred compounds of formula E are selected from the following sub- formulae:

in which alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl and alkenyl ^* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl ^* preferably denote CH2=CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

Very preferred compounds of the formula E are selected from the following sub-formulae:

E1 a in which m denotes 1 , 2, 3, 4, 5 or 6, i denotes 0, 1 , 2 or 3, and R ^b1 denotes H, CH ₃ or C ₂ H ₅ .

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

Most preferred are compounds of formula E1 a2, E1 a5, E3a1 and E6a1 .

In another preferred embodiment of the present invention component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula F

in which the individual radicals have, independently of each other and on each occurrence identically or differently, the following meanings:

R ²¹ , R ³¹ each, independently of one another, 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° F, CI, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,

721 -CH2CH2-, -CF2CF2-, -COO-, trans-CH=CH-, trans- CF=CF-, -CH2O-, -CF2O-, -C≡C- or a single bond, preferably -CF2O-,

L ²¹ , L ²² , L ²³ , L ²⁴ each, independently of one another, H or F, g 0, 1 , 2 or 3.

Particularly preferred compounds of formula F are selected from the group consisting of the following formulae:

in which R ²¹ , X°, L ²¹ and L ²² have the meaning given in formula F, L ²⁵ and L ²⁶ are each, independently of one another, H or F, and X° is preferably F.

Very particularly preferred compounds of formula F1 -F3 are selected from the group consisting of the following subformulae: In another preferred embodiment of the present invention component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula G containing a cyano group.

in which the individual radicals have the following meanings: each, independently of one another, and

on each occurrence, identically or differently

_R 51 _R 52 each, independently of one another, 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,

751 742 -CH2CH2-, -COO-, frans-CH=CH-, trans-CF=CF-, -CH2O- , -CF2O-, -C≡C- or a single bond, preferably a single bond,

|_51 |_52 each, independently of one another, H or F,

0, 1 , 2 or 3.

Preferred compounds of formula G are selected from the following

subformulae

in which R ⁵¹ is as defined in formula G and L ¹ and L ² are each, independently of one another, H or F.

Very preferred are compounds of formula G1 , G2 and G5.

Preferred compounds of formula G1 -G9 are those wherein L ⁵¹ and L ⁵² are F.

Further preferred compounds of formula G1 -G7 are those wherein L ⁵¹ is F and L ⁵² is H.

Very preferred compounds of formula G are selected from the group consisting of the following subformulae:

G1 a

In the compounds of formula G, G1 -G7 and their subformulae, R ⁵¹ is particularly preferably alkyl or alkoxy having 1 to 8 carbon atoms, or alkenyl having from 2 to 7 carbon atoms.

The concentration of the compounds of formula A and B in the LC host mixture is preferably from 2 to 60%, very preferably from 3 to 45%, most preferably from 4 to 35%.

The concentration of the compounds of formula C and D in the LC host mixture is preferably from 2 to 70%, very preferably from 5 to 65%, most preferably from 10 to 60%.

The concentration of the compounds of formula E in the LC host mixture is preferably from 5 to 50%, very preferably from 5 to 35%.

The concentration of the compounds of formula F in the LC host mixture is preferably from 2 to 30%, very preferably from 5 to 20%.

Further preferred embodiments of the present invention are listed below, including any combination thereof. a) The LC host mixture comprises one or more compounds of formula A and/or B with high positive dielectric anisotropy, preferably with Δε > 15.

The LC host mixture comprises one or more compounds selected from the group consisting of formulae A1 a2, A1 b1 , A1d1 , A1f1 , A2a1 , A2h1 , A2I1 , A2I2, A2k1 , B2h3, B2I1 , F1 a. The proportion of these compounds in the LC host mixture is preferably from 4 to 40%, very preferably from 5 to 35%. The LC host mixture comprises one or more compounds selected from the group consisting of formulae C3, C4, C5, C9 and D2. The proportion of these compounds in the LC host mixture is preferably from 8 to 70%, very preferably from 10 to 60%.

The LC host mixture comprises one or more compounds selected from the group consisting of formulae G1 , G2 and G5, preferably G1 a, G2a and G5a. The proportion of these compounds in the LC host mixture is preferably from 4 to 40%, very preferably from 5 to 35%.

The LC host mixture comprises one or more compounds selected from the group consisting of formulae E1 , E3 and E6, preferably E1 a, E3a and E6a, very preferably E1 a2, E1 a5, E3a1 and E6a1 . The proportion of these compounds in the LC host mixture is preferably from 5 to 60%, very preferably from 10 to 50%.

In a second preferred embodiment of the present invention, the LC medium contains an component B) or LC host mixture having a negative dielectric anisotropy Δε.

Such LC media are especially suitable for use in VA, IPS and UB-FFS displays or related modes using LC-materials with Δε<0. The LC media and LC host mixtures according to this second preferred embodiment preferably have a negative dielectric anisotropy Δε from -0.5 to - 10, very preferably from -2.5 to -7.5, at 20°C and 1 kHz.

Particularly preferred embodiments of an LC medium according to this second preferred embodiment are those of sections a)-z2) below: a) LC medium wherein the component B) or LC host mixture comprises one or more compounds selected from formulae CY and PY: wherein a denotes 1 or 2, b denotes 0 or 1

R ¹ and R ² each, independently of one another, denote alkyl having 1 to

12 C atoms, where, in addition, one or two non-adjacent Ch groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms,

Z ^x and Z ^y each, independently of one another, denote -CH2CH2-,

-CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C ₂ F ₄ -, -CF=CF-, -CH=CH-CH ₂ O- or a single bond, preferably a single bond, each, independently of one another, denote F, CI, OCF3 CF ₃ , CH ₃ , CH ₂ F, CHF ₂ . Preferably, both L ¹ and L ² denote F or one of L ¹ and L ² denotes F and the other denotes CI, or both L ³ and L ⁴ denote F or one of L ³ and L ⁴ denotes F and the other denotes CI. The compounds of the formula CY are preferably selected from the group consisting of the following sub-formulae:

alkenyl— < H >-CH ₂ O

CY31

F F alkyl— { H — H )-CH ₂ O— ( O )— (O)alkyl ^*

CY32

in which a denotes 1 or 2, alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

Especially preferred are compounds selected from formulae CY2, CY8, CYI O and CY16.

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

PY2 alkyl— < O >— < O ^O-alkyP

35 in which alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms, and (O) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH2=CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ - CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

Especially preferred are compounds selected from formulae PY2, PY8, PYI O and PY16.

Preferably the concentration of the compounds of formula CY and PY and their subformulae in the LC medium is from 10 to 70% by weight, very preferably from 15 to 50% by weight.

Preferably the concentration of the compounds of formula CY and its subformulae in the LC medium is from 2 to 40% by weight, very preferably from 3 to 30% by weight.

Preferably the concentration of the compounds of formula PY and its subformulae in the LC medium is from 2 to 50% by weight, very preferably from 3 to 40% by weight. LC medium wherein the component B) or LC host mixture comprises one or more mesogenic or LC compounds comprising an alkenyl group (hereinafter also referred to as "alkenyl compounds"), wherein said alkenyl group is stable to a polymerisation reaction under the conditions used for polymerisation of the polymerisable compounds contained in the LC medium.

Preferably the component B) or LC host mixture comprises one or more alkenyl compounds selected from formulae AN and AY

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

R ^A1 alkenyl having 2 to 9 C atoms or, if at least one of the rings X, Y and Z denotes cyclohexenyl, also one of the meanings of R ^A2 ,

R ^A2 alkyl having 1 to 12 C atoms, in which, in addition, one or two non- adjacent Ch groups may be replaced by -O-, -CH=CH-, -CO- , -OCO- or -COO- in such a way that O atoms are not linked directly to one another,

Z ^x -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-,

-CO-O-, -O-CO-, -C ₂ F ₄ -, -CF=CF-, -CH=CH-CH ₂ O-, or a single bond, preferably a single bond,

L ^1"4 H, F, CI, OCF3, CF ₃ , CH ₃ , CH ₂ F or CHF ₂ , preferably H, F or CI, x 1 or 2,

0 or 1

Preferred compounds of formula AN and AY are those wherein R ^A2 is selected from ethenyl, propenyl, butenyl, pentenyl, hexenyl and heptenyl.

In a preferred embodiment the component B) or LC host mixture comprises one or more compounds of formula AN selected from the following sub-formulae: kenyl" AN2

alkyl O alkenyl AN3 alkenyl alkyl AN4

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl* preferably denote CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ - (CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -. Preferably the the component B) or LC host mixture comprises one or more compounds selected from formulae AN1 , AN2, AN3 and AN6, very preferably one or more compounds of formula AN1 .

In another preferred embodiment the component B) or LC host mixture comprises one or more compounds of formula AN selected from the following sub-formulae:

in which m denotes 1 , 2, 3, 4, 5 or 6, i denotes 0, 1 , 2 or 3, and R ^b1 denotes H, Chb or C2H5.

In another preferred embodiment the component B) or LC host mixture comprises one or more compounds selected from the following sub- formulae:

Most preferred are compounds of formula AN1 a2 and AN1 a5.

In another preferred embodiment the component B) or LC host mixture comprises one or more compounds of formula AY selected from the following sub-formulae:

AY1

AY2

F F

AY3 alkenyl— < O )— ( O — alkyl

F F

AY4 alkenyl— O )— O ^O-alkyl

35

F F alkenyl (O)alkyl ^{* AY31}

in which alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, "(O)" denotes an O- atom or a single bond, and alkenyl and alkenyl ^* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl ^* preferably denote CH2=CH-,

CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ - CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

In another preferred embodiment the component B) or LC host mixture comprises one or more compounds of formula AY selected from the following sub-formulae:

alkenyl AY5a

alkenyl H O AY6a

^" °- ^C m ^H 2m ₊ 1

F F F F alker H O O Vo-C _m H _2m+1 AY10a

in which m and n each, independently of one another, denote 1 , 2, 3, 4, 5 or 6, and alkenyl denotes CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ - CH=CH-(CH ₂ ) ₂ -.

Preferably the proportion of compounds of formula AN and AY in the LC medium is from 2 to 70% by weight, very preferably from 5 to 60% by weight, most preferably from 10 to 50% by weight.

Preferably the LC medium or LC host mixture contains 1 to 5, preferably 1 , 2 or 3 compounds selected from formulae AN and AY.

In another preferred embodiment of the present invention the LC medium comprises one or more compounds of formula AY14, very preferably of AY14a. The proportion of compounds of formula AY14 or AY14a in the LC medium is preferably 3 to 20% by weight. The addition of alkenyl compounds of formula AN and/or AY enables reduction of the viscosity and response time of the LC medium.

LC medium wherein the component B) or LC host mixture comprises one or more compounds of the following formula: in which the individual radicals have the following meanings:

R ³ and R ⁴ each, independently of one another, denote alkyl having 1 to

12 C atoms, in which, in addition, one or two non-adjacent CH ₂ groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that O atoms are not linked directly to one another,

Ζν denotes -CH ₂ CH ₂ -, -CH=CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-,

-OCH ₂ -, -CO-O-, -O-CO-, -C ₂ F ₄ -, -CF=CF-, -CH=CH-CH ₂ O- or a single bond, preferably a single bond.

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

in which alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably denotes CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH3-CH ₂ -CH=CH-, CH3-(CH ₂ )2-CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -. Especially preferred are compounds of formula ZK1 .

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

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

Most preferred are compounds of formula ZK1 a.

LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds of the following formula: in which the individual radicals on each occurrence, identically or differently, have the following meanings:

R ⁵ and R ⁶ each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH ₂ groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms, denotes— < H >— or — ( o

, and e denotes 1 or 2. The compounds of the formula DK are preferably selected from the group consisting of the following sub-formulae:

alkyl— H >— H >— ( O >— O-alkyl* DK2

alkenyl^ H — ⁽ O )— ( O >— alkyl DK6 in which alkyl and alkyl ^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably denotes CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-,

CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -. e) LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds of the following formula: in which the individual radicals have the following meanings:

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

R ¹ and R ² each, independently of one another, denote alkyl having 1 to

12 C atoms, where, in addition, one or two non-adjacent CH ₂ groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another,

Z ^x denotes -CH ₂ CH ₂ -, -CH=CH-, -CF ₂ O-, -OCF ₂ -, -CH ₂ O-,

-OCH ₂ -, -CO-O-, -O-CO-, -C ₂ F ₄ -, -CF=CF-, -CH=CH-CH ₂ O- or a single bond, preferably a single bond,

L ¹ and L ² each, independently of one another, denote F, CI, OCF3,

CF ₃ , CH ₃ , CH ₂ F, CHF ₂ .

Preferably, both radicals L ¹ and L ² denote F or one of the radicals L ¹ and L ² denotes F and the other denotes CI.

The compounds of the formula LY are preferably selected from the group consisting of the following sub-formulae: in which R ¹ has the meaning indicated above, alkyl denotes a straight- chain alkyl radical having 1 -6 C atoms, (O) denotes an oxygen atom or a single bond, and v denotes an integer from 1 to 6. R ¹ preferably denotes straight-chain alkyl having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, in particular CH ₃ , C2H5, n-C ₃ H ₇ , n-C ₄ H9, n-CsHn , CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ - CH=CH-, CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH- (CH ₂ ) ₂ -.

LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds selected from the group consisting of the following formulae:

in which alkyl denotes Ci-6-alkyl, L ^x denotes H or F, and X denotes F, CI, OCF ₃ , OCHF ₂ or OCH=CF ₂ . Particular preference is given to compounds of the formula GG1 in which X denotes F. LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds selected from the group consisting of the following formulae:

YC7 in which R ⁵ has one of the meanings indicated above for R ¹ , alkyl denotes Ci-6-alkyl, d denotes 0 or 1 , and z and m each, independently of one another, denote an integer from 1 to 6. R ⁵ in these compounds is particularly preferably Ci-6-alkyl or -alkoxy or C2-6-alkenyl, d is preferably 1 . The LC medium according to the invention preferably comprises one or more compounds of the above-mentioned formulae in amounts of > 5% by weight.

LC medium wherein component B) or the LC host mixture additionally comprises one or more biphenyl compounds selected from the group consisting of the following formulae:

in which alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl and alkenyl* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl* preferably denote CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ - (CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -. The proportion of the biphenyls of the formulae BP1 to BP3 in the LC host mixture is preferably at least 3% by weight, in particular > 5% by weight. The compounds of the formula BP2 are particularly preferred.

The compounds of the formulae BP1 to BP3 are preferably selected from the group consisting of the following sub-formulae:

in which alkyl ^* denotes an alkyl radical having 1 -6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formulae BP1 a and/or BP2c.

LC medium wherein component B) or the LC host mixture additionally comprises one or more terphenyl compounds of the following formula: in which R ⁵ and R ⁶ each, independently of one another, have one of the meanings indicated above, and each, independently of one another, denote

in which L ⁵ denotes F or CI, preferably F, and L ⁶ denotes F, CI, OCF3, CF ₃ , CH ₃ , CH ₂ F or CHF ₂ , preferably F.

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

F F F F O O O (O)C _m H _2m+1 T4

in which R denotes a straight-chain alkyl or alkoxy radical having 1 -7 C atoms, R ^* denotes a straight-chain alkenyl radical having 2-7 C atoms, (O) denotes an oxygen atom or a single bond, and m denotes an integer from 1 to 6. R ^* preferably denotes CH ₂ =CH-, CH2=CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ - CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

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

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

Particular preference is given to compounds of the formulae T1 , T2, T3 and T21 . In these compounds, R preferably denotes alkyl, furthermore alkoxy, each having 1 -5 C atoms. The terphenyls are preferably employed in LC media according to the invention if the Δη value of the mixture is to be > 0.1 . Preferred LC media comprise 2-20% by weight of one or more terphenyl compounds of the formula T, preferably selected from the group of compounds T1 to T22.

LC medium wherein component B) or the LC host mixture additionally comprises one or more quaterphenyl compounds selected from the group consisting of the following formulae:

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, CI, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,

I_ ^Q I† ₀ |_ ^Q 6 independently of each other are H or F, with at least one of

I_QI _T0 |_Q6 _being p

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 0.1 to 2% by weight, most preferably from 0.2 to 1 .5% by weight.

Preferably the LC host mixture 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 polymerisation, 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.

LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds of formula CC:

wherein

R ^c denotes 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 ^c denotes F, CI, halogenated alkyl or alkoxy having 1 to 6 C

atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, l_ci _^ |_C2 independently of each other denote H or F, with at least one of L ^C1 and L ^C2 being F.

Preferred compounds of formula CC are those wherein R ^c denotes straight-chain alkyl with 2 to 6 C-atoms, very preferably ethyl, n-propyl or n-butyl.

Preferred compounds of formula CC are those wherein L ^C1 and L ^C2 are F. Preferred compounds of formula CC are those wherein X ^c denotes F or OCF3, very preferably F.

Preferred compounds of formula CC are selected from the following formula

wherein R ^c has one of the meanings of formula CC or one of its preferred meanings given above and below, and is preferably ethyl, n- propyl or n-butyl, very preferably n-propyl.

Preferably the proportion of compounds of formula CC in the LC host mixture is from >0 to < 10% by weight, very preferably from 0.1 to 8% by weight, most preferably from 0.2 to 5% by weight.

Preferably the LC host mixture contains 1 to 5, preferably 1 , 2 or 3 compounds of formula CC.

The addition of compounds of formula CC, 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. Besides, the addition of compounds of formula CC enables to reduce the viscosity and the response time of the LC medium.

LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds selected from the group consisting of the following formulae: - 130-

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

Preferred media comprise one or more compounds selected from the formulae 01 , 03 and 04. LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds of the following formula:

in which

R ⁹ denotes H, Chb, C2H5 or n-CsHz, (F) denotes an optional fluorine substituent, and q denotes 1 , 2 or 3, and R ⁷ has one of the meanings indicated for R ¹ , preferably in amounts of > 3% by weight, in particular > 5% by weight and very particularly preferably 5-30% by weight.

 in which R ⁷ preferably denotes straight-chain alkyl, and R ⁹ denotes CH3, C2H5 or n-C3H ₇ . Particular preference is given to the compounds of the formulae FI1 , FI2 and FI3. LC medium wherein component B) or the LC host mixture additionally comprises one or more compounds selected from the group consisting of the following formulae:

F F F F

VK4 in which R ⁸ has the meaning indicated for R ¹ , and alkyl denotes a straight-chain alkyl radical having 1 -6 C atoms.

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

in which

R ¹⁰ and R ^{1 1} each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent Ch groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms, and R ¹⁰ and R ¹¹ preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, and

Z ¹ and Z ² each, independently of one another, denote -C2H ₄ -,

-CH=CH-, -(CH ₂ ) ₄ -, -(CH ₂ ) ₃ O-, -O(CH ₂ ) ₃ -,

-CH=CH-CH ₂ CH ₂ -, -CH ₂ CH ₂ CH=CH-, -CH ₂ O-, -OCH ₂ -, -CO-O-, -O-CO-, -C ₂ F ₄ -, -CF=CF-, -CF=CH-, -CH=CF-, -CH ₂ - or a single bond.

LC medium wherein component B) or the LC host mixture additionally comprises one or more difluorodibenzochromans and/or chromans of the following formulae:

in which

R ¹¹ and R ¹² each, independently of one another, have one of the

meanings indicated above for R ¹¹ ,

ring M is trans-1 ,4-cyclohexylene or 1 ,4-phenylene, Z ^m -C ₂ H ₄ -, -CH ₂ O-, -OCH ₂ -, -CO-O- or -O-CO-, c is 0, 1 or 2,

preferably in amounts of 3 to 20% by weight, in particular in amounts of 3 to 15% by weight. Particularly preferred compounds of the formulae BC, CR and RC are selected from the group consisting of the following sub-formulae: in which alkyi and alkyi ^* each, independently of one another, denote a straight-chain alkyi radical having 1 -6 C atoms, (O) denotes an oxygen atom or a single bond, c is 1 or 2, and alkenyl and alkenyl ^* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl and alkenyl ^* preferably denote CH2=CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₂ - CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -. Very particular preference is given to LC host mixtures comprising one, two or three compounds of the formula BC-2.

LC medium wherein component B) or the LC host mixture additionally comprises one or more fluorinated phenanthrenes and/or dibenzofurans of the following formulae:

in which R ¹¹ and R ¹² each, independently of one another, have one of the meanings indicated above for R ¹¹ , b denotes 0 or 1 , L denotes F, and r denotes 1 , 2 or 3.

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

in which R and R' each, independently of one another, denote a straight-chain alkyl or alkoxy radical having 1 -7 C atoms. LC medium wherein component B) or the LC host mixture additionally comprises one or more monocyclic compounds of the following formula

wherein

R ¹ and R ² each, independently of one another, denote alkyl having 1 to

12 C atoms, where, in addition, one or two non-adjacent Ch groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms,

L ¹ and L ² each, independently of one another, denote F, CI, OCF3,

CF ₃ , CH ₃ , CH ₂ F, CHF ₂ .

Preferably, both L ¹ and L ² denote F or one of L ¹ and L ² denotes F and the other denotes CI,

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

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. Alkenyl and Alkenyl ^* preferably denote CH ₂ =CH-, CH ₂ =CHCH ₂ CH ₂ -, CH ₃ -CH=CH-, CH ₃ -CH ₂ -CH=CH-, CH ₃ - (CH ₂ ) ₂ -CH=CH-, CH ₃ -(CH ₂ ) ₃ -CH=CH- or CH ₃ -CH=CH-(CH ₂ ) ₂ -.

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

wherein Alkoxy preferably denotes straight-chain alkoxy with 3, 4, or 5 C atoms. LC medium which, apart from the polymerisable compounds as described above and below, does not contain a compound which contains a terminal vinyloxy group (-O-CH=CH ₂ ). LC medium wherein component B) or the LC host mixture comprises 1 to 8, preferably 1 to 5, compounds of the formulae CY1 , CY2, PY1 and/or PY2. The proportion of these compounds in the LC host mixture as a whole is preferably 5 to 60%, particularly preferably 10 to 35%.

The content of these individual compounds is preferably in each case 2 to 20%.

LC medium wherein component B) or the LC host mixture comprises 1 to 8, preferably 1 to 5, compounds of the formulae CY9, CY10, PY9 and/or PY10. The proportion of these compounds in the LC host

mixture as a whole is preferably 5 to 60%, particularly preferably 10 to 35%. The content of these individual compounds is preferably in each case 2 to 20%.

LC medium wherein component B) or the LC host mixture comprises 1 to 10, preferably 1 to 8, compounds of the formula ZK, in particular

compounds of the formulae ZK1 , ZK2 and/or ZK6. The proportion of these compounds in the LC host mixture as a whole is preferably 3 to 25%, particularly preferably 5 to 45%. The content of these individual compounds is preferably in each case 2 to 20%.

LC medium in which the proportion of compounds of the formulae CY, PY and ZK in the LC host mixture as a whole is greater than 70%, preferably greater than 80%.

LC medium in which the LC host mixture contains one or more

compounds containing an alkenyl group, preferably selected from formulae AN and AY, very preferably selected from formulae AN1 , AN3, AN6 and AY14, most preferably from formulae AN 1 a, AN3a, AN6a and AY14. The concentration of these compounds in the LC host mixture is preferably from 2 to 70%, very preferably from 3 to 55%.

LC medium wherein component B) or the LC host mixture contains one or more, preferably 1 to 5, compounds selected of formula PY1 -PY8, very preferably of formula PY2. The proportion of these compounds in the LC host mixture as a whole is preferably 1 to 30%, particularly preferably 2 to 20%. The content of these individual compounds is preferably in each case 1 to 20%. z1 ) LC medium wherein component B) or the LC host mixture contains one or more, preferably 1 , 2 or 3, compounds selected from formulae T1 , T2, T3 and T21 , very preferably from formula T2. The content of these compounds in the LC host mixture as a whole is preferably 1 to 20%. z2) LC medium in which the LC host mixture contains one or more,

preferably 1 , 2 or 3, compounds of formula BF1 , and one or more, preferably 1 , 2 or 3, compounds selected from formulae AY14, AY15 and AY16, very preferably of formula AY14. The proportion of the compounds of formula AY14-AY16 in the LC host mixture is preferably from 2 to 35%, very preferably from 3 to 30%. The proportion of the compounds of formula BF1 in the LC host mixture is preferably from 0.5 to 20%, very preferably from 1 to 15%. Further preferably the LC host mixture according to this preferred embodiment contains one or more, preferably 1 , 2 or 3 compounds of formula T, preferably selected from formula T1 , T2 and T3, very preferably from formula T2. The proportion of the compounds of formula T in the LC host mixture medium is preferably from 0.5 to 15%, very preferably from 1 to 10%.

In the LC medium according to the present invention, the use of an LC host mixture together with the use of a polymerisable component comprising a combination of a first, second and third polymerisable compound as described above leads to advantageous properties in LC displays. In particular, one or more of the following advantages could be achieved:

- easy and quick formation of polymer walls by polymerisation-induced phase separation of the polymer formed by the first and second

polymerisable compounds,

- formation of polymer walls with highly defined shape and constant thickness,

- constant cell gap,

- high flexibility of the display cell in case plastic substrates are used, - high resistance of the display cell against mechanical pressure, and low variation of the cell gap under pressure,

- good adhesion of the polymer walls to the substrates,

- low number of defects,

- reduced formation of domains with different electrooptical properties like response time or contrast,

- high transparency,

- good contrast,

- fast response times.

The display manufacture process is known to the skilled person and is described in the literature, for example in US6130738 and EP2818534 A1 .

The present invention also relates to a process for the production of an LC display as described above and below, comprising the steps of providing an LC medium as described above and below into the display, and polymerising the polymerisable compounds in defined regions of the display.

Preferably the polymerisable compounds are photopolymerised by exposure to UV irradiation.

Further preferably the polymerisable compounds are photopolymerised by exposure to UV irradiation through a photomask. The UV radiation can be generated by a variety of light sources which are known to the skilled person, including but not limited to arc lamps, led lights, laser light sources, or others.

The photomask is preferably designed such that it comprises regions that are transparent to the UV radiation used for photopolymerisation, and regions that are not transparent to the UV radiation used for photopolymerisation, and wherein the transparent regions form a pattern or image that

corresponds to the desired shape of the polymer walls. As a result the polymerisable compounds are only polymerised in those parts of the display that are covered by the transparent regions of the photomask, thus forming polymer walls of the desired shape. Alternatively to using a photomask, a light source can be used that emits light with an already shaped profile. Such profile can for example be generated by interference of two laser beams.

In a preferred embodiment of the present invention, the display is subjected to a second UV irradiation step, preferably without a photomask applied, after the first UV irradiation step as described above. Thereby it is possible to complete polymerisation of monomers that were not or only partially polymerised in the first step. The second UV step can have an emission spectrum and/or intensity which is the same as that of the first step, or which is different from the first step.

Alternatively two applying two separate irradiation steps, the intensity is changed during UV exposure. Preferably, the intensity is gradually increased during UV exposure.

For example, an LC display according to the present invention can be manufactured as follows. Polymerisable compounds as described above and below are combined with a suitable LC host mixture. This resulting LC medium can then be included into the display by using conventional manufacturing processes. The resulting LC medium can be filled for example using capillary forces into the cell gap formed by two substrates. Alternatively, the LC medium can be deposited as a layer onto a substrate, and another substrate is placed on top of the LC layer under vacuum in order to prevent inclusion of air bubbles. The LC medium is in either case located in the cell gap formed by the two substrates, as exemplarily illustrated in Fig. 1a. These substrates usually are covered by an alignment layer which is in direct contact with the LC medium. The substrates itself can carry other functional components like TFTs, black matrix, colour filter, or similar.

Subsequently, polymerization induced phase separation is initiated by exposure of the LC medium, which is either in the nematic or the isotropic phase, to UV radiation with collimated light through a photomask, as exemplarily illustrated in Fig. 1 b. This leads to the formation of polymer wall structures, restoration of the LC host, and alignnnent of the LC phase with the alignnnent layer, as exemplarily illustrated in Fig. 1c.

This process can advantageously utilize display manufacturing processes that are established in the industry. Thus, both the display filling process, for example by one-drop-filling (ODF), and the radiation initiated polymerization step after sealing the display, which is known for example from polymer stabilised or PS-type display modes like PS-VA, are established techniques in conventional LCD manufacturing.

A preferred 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 comprising a polymerisable component A) and a liquid-crystalline component B) as described above and below, wherein the polymerisable component A) is polymerised. The LC 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 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. The first and/or second alignnnent layer controls the alignnnent direction of the LC molecules of the LC layer. For example, in TN displays the alignment layer is selected such that it imparts to the LC molecules an orientation direction parallel to the surface, while in VA displays the alignment layer is selected such that it imparts to the LC molecules a homeotropic alignment, i.e. an orientation direction perpendicular to the surface. Such an alignment layer may for example comprise a polyimide, which may also be rubbed, or may be prepared by a photoalignment method. The substrate can be a glass substrate, for example in case of a curved display. The use of an LC medium according to the present invention in an LC display with glass substrates can provide several advantages. For example, the formation of polymer wall structures in the LC medium helps to prevent the so-called "pooling effect" where pressure applied on the glass substrates causes unwanted optical defects. The stabilizing effect of the polymer wall structures also allows to further minimize the panel thickness. Moreover, in bent panels with glass substrates the polymer wall structures enable a smaller radius of curvature. For flexible LC displays preferably plastic substrates are used. These plastic substrates preferably have a low birefringence. Examples are polycarbonate (PC), polyethersulfone (PES), polycyclic define (PCO), polyarylate (PAR), polyetheretherketone (PEEK), or colourless polyimide (CPI) substrates. 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 one-drop-filling (ODF) method. The

polymerisable component of the LC medium is then polymerised for example by UV photopolymerisation.

In case the polymerisable compounds are used as a replacement for spacer particles, the display manufacturing process preferably comprises the following steps:

In a first step, the LC medium containing the LC host and monomer precursor is applied to one of the two substrates, preferably by using one of the following deposition methods: one drop filling, ink jet printing, spin coating, slit coating, flexo printing, or a comparable method. The substrate in that instance may carry a colour filter, TFT devices, a black matrix, a polyimide coating, or other components typically found on a display substrate. The applied LC medium forms a thin, uniform film with the thickness of the targeted cell gap of the final device.

In a second step, the applied film is subjected to UV radiation having an intensity profile. This profile is generated for example by irradiating through a photomask, using laser interference, direct laser writing, or a comparable method. Irradiation of the film can either occour from either side of the substrate. In case of using a photomask, the mask can either placed on the substrate and the LC film is cured by the light passing through the substrate, or the mask is directly brought in close proximity to the LC film and the LC medium is cured directly.

In this second step, polymer wall structures are created that function as spacer.

Subsequently, the second substrate, which may also carry colour filter, TFT devices, a black matrix, a polyimide coating, or other components typically found on a display substarte, is place ontop of the first substrate so that the LC film comes to rest in between the two substrates.

A further irradiation is now optionally possible to convert unreacted monomers, generate adhesion between the two substartes, and/or seal the edges of the display.

The polymerisation of the polymerisable compounds can be carried out in one step or in two or more steps. It is also possible to carry out the polymerisation in a sequence of several UV irradiation and/or heating or cooling steps. For example, a display manufacturing process may include a first UV irradiation step at room temperature to produce a pretilt angle, and subsequently, in a second polymerisation step to polymerise or crosslink the compounds which have not reacted in the first step ("end curing"). Upon polymerisation the polymensable compounds react with each other to a polymer which undergoes macroscopical phase-separation from the LC host mixture and forms polymer walls in the LC medium. Suitable and preferred polymerisation methods are, for example, thermal or photopolymerisation, preferably photopolymerisation, in particular UV induced photopolymerisation, which can be achieved by exposure of the polymerisable compounds to UV radiation. Preferably the LC medium contains one or more polymerisation initiators.

The polymerisable compounds according to the invention are also suitable for polymerisation 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 polymerisation can thus also be carried out without the addition of an initiator. In a preferred embodiment, the LC medium contains a polymerisation initiator. The LC medium may also comprise one or more stabilisers or inhibitors in order to prevent undesired spontaneous polymerisation 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 polymerisable component (component A), is preferably 10-500,000 ppm, particularly preferably 50-50,000 ppm. Preferably the LC medium according to the present invention does essentially consist of a polymerisable component A) and an LC component B) (or LC host mixture) as described above and below. However, the LC medium may additionally comprise one or more further components or additives. 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, polymerisation initiators, inhibitors, stabilisers, sensitizers, surface-active substances or chiral dopants. These may be polymerisable or non-polymerisable. Polymerisable additives, polymerisation initiators and sensitizers are ascribed to the polymerisable component or component A). Other non-polymerisable additives are ascribed to the non-polymerisable component or component B).

Preferred additives are selected from the list including but not limited to co- monomers, chiral dopants, polymerisation initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents,

hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles. In a preferred embodiment the LC media contain one or more chiral dopants, preferably in a concentration from 0.01 to 1 % by weight, very preferably from 0.05 to 0.5% by weight. The chiral dopants are preferably selected from the group consisting of compounds from Table B below, very preferably from the group consisting of R- or S-101 1 , R- or S-201 1 , R- or S-301 1 , R- or S-401 1 , and R- or S-501 1 .

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.

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 tetraphenyl borate or complex salts of crown ethers (cf., for example, Haller et al., Mol. Cryst. Liq. Cryst. 24, 249-258 (1973)), for improving the conductivity, or substances for modifying the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 127,

22 40 864, 23 21 632, 23 38 281 , 24 50 088, 26 37 430 and 28 53 728. 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 polymerisable compounds as defined above, and optionally with further liquid-crystalline compounds and/or additives. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. The 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, CI, 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 concentrations 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 Tables A1 and A2 below. The compounds shown in Table A1 are especially suitable for use in LC mixtures with positive dielectric anisotropy. The compounds shown in Table A2 are especially suitable for use in LC mixtures with negative dielectric anisotropy.

Table A1

In Table A1 , 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 _m H2m+i means CmH2m+1 Or OCmH2m+1.

CBC-nmF

C-n-V C-n-XF C„H_— ( H >— C _m H 2m+1 C _n H _2n+1 - H H

w

C-n-m CC-n-V

CC-n-Vm CC-n-kVm

CC-nV-Vm CCP-nV-m

CCP-Vn-m CCG-V-F

CCVC-n-V CCP-n-m

CP-nV-m CP-Vn-m

CPPC-nV-Vm

CLP-n-T CLP-n-OT

CLP-nVk-m CCGU-n-F CPGU-

CCPU-n-F CPGU-n-OT

CCCQU-n-F

CLUQU-n-F

CPPQU-n-F

CWCG-n-F CWCU-n-F

CWCQU-n-F

DUUQU-n-F

ECCP-nm ECCP-nOCFs

GGP-n-F PGIGI-n-F

GPQU-n-F GUQGU-n-F

PGU-n-OXF MPP-n-F

MUQU-n-F NUQU-n-F

PGU-n-F PPGU-n-F

PQU-n-F PUQU-n-F

PGUQU-n-F

PP-nV-Vm PP-n-kVm

PCH-nOm PCH-nCI

PYP-nF

K3 n M3 n

Table A2

In Table A2, 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 _m H2m+i means

AIK-n-F

F F

O

^C n ^H 2n+1 O OC _m H _2m+1

AIY-n-Om

AY-n-Om

B-nO-Om

B-n-Om

B-nO-05i

CB-n-m

CB-n-Om

PB-n-m

PB-n-Om

BCH-nm

BCH-nmF

BCN-nm

C-1V-V1

CY-n-Om

CY(F,CI)-n-Om

CI F

^C n ^H 2n+1 H O OC _m H _2m+1

CY(CI,F)-n-Om

CCY-n-Om

CCY(F,CI)-n-Om

CCY(CI,F)-n-Om

CCY-n-m

CCY-V-m

F F

C _n H _2n - H H ^{0 C} _m mH 2m+1

CCY-Vn-m

CCY-n-OmV

CBC-nmF

CBC-nm

CCP-V-m

CCP-Vn-m

CCP-nV-m

CCP-n-m

CPYP-n-(0)m

CYYC-n-m F F F F

C _n H _2n+1 - H H o )→ O (0)C _m mH 2m+1

CCYY-n-(0)m

CCY-n-02V

CCH-nOm

C„H _2n+1 — ( H H H C _m H _2m+1

CCC-n-m

CCC-n-V

CY-n-m

CCH-nm

CC-n-V

CC-n-V1

CC-n-Vm

cc-v-v

CC-V-V1

CC-2V-V2

CVC-n-m

CC-n-mV

CCOC-n-m

CP-nOmFF

CVY-V-n

CY-V-On

35

CY-n-OC(CH ₃ )=CH ₂

CCN-nm

CY-n-OV

C _n H _2n+1 — < H H O (CH ₂ ) _k -OC _m H 2m+1

CCY-n-kOm

C _n H _2n+1 — H O O >- OC _m H '2m+1

CPY-n-Om

F F

C _n H _2n+1 - H ( O ) ( O ) C _m H 2m+1

CPY-n-m

CPY-V-Om

CQY-n-(0)m

CQIY-n-(0)m

CCQY-n-(0)m

CCQIY-n-(0)m

CPQY-n-(0)m

CPQIY-n-(0)m

CPYG-n-(0)m

CCY-V-Om

CCY-V2-(0)m

CCY-1V2-(0)m

CCVC-n-V

CCVC-V-V

F F

C _n H _2n+ r H O O O (0)C _m H

CPYG-n-(0)m CPGP-n-m

CY-nV-(0)m

CENaph-n-Om

COChrom-n-Om

COChrom-n-m

CCOChrom-n-Om

CCOChrom-n-m

CONaph-n-Om

CCONaph-n-Om

CCNaph-n-Om

CNaph-n-Om

CETNaph-n-Om

CTNaph-n-Om

CK-n-F

CLY-n-Om

CLY-n-m

LYLI-n-m

CYLI-n-m

LY-n-(0)m

COYOICC-n-m

COYOIC-n-V

CCOY-V-02V

CCOY-V-03V

COY-n-Om

CCOY-n-Om

D-nOmFF

C _n H _2n+1 ^ H O ^C _m H

PCH-nm C _n H _2n+1 ^ H O OC _m H

PCH-nOm

PGIGI-n-F

PGIY-n-Om F F

C _N H _2N+1 → O Y- O >— < O 0C _M H 2m+1

PYP-n-Om

F F F F

C nH 2n+1 o o o o c _M H 2m+1

PPYY-n-m

PPGU-n-F

YPY-n-m

YPY-n-mV

PY-n-Om

PY-n-m

PY-V2-Om

DFDBC-n(0)-(0)m

F F

C _n H _2n+1 0 O ^0C m ^H 2m÷1

Y-nO-Om

Y-nO-OmV

Y-nO-OkVm

YG-n-Om

YG-nO-Om C _n H _2n+1 → O O OC _m H 2m+1

YGI-nO-Om

YY-nO-Om

In a first preferred embodiment of the present invention, the LC media according to the invention, especially those with positive dielectric anisotropy, comprise one or more compounds selected from the group consisting of compounds from Table A1 .

In a second preferred embodiment of the present invention, the LC media according to the invention, especially those with negative dielectric

anisotropy, comprise one or more compounds selected from the group consisting of compounds from Table A2.

Table B

Table B shows possible chiral dopants which can be added to the LC media according to the invention.

CM 21 R/S

R/S-4011 R/S-5011

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.

- 182-

- 183-

- 184-



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.

In addition, the following abbreviations and symbols are used:

Vo threshold voltage, capacitive [V] at 20°C,

n _e extraordinary refractive index at 20°C and 589 nm,

n ₀ ordinary refractive index at 20°C and 589 nm,

Δη 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],

γι rotational viscosity at 20°C [mPa s],

Ki elastic constant, "splay" deformation at 20°C [pN],

K ₂ elastic constant, "twist" deformation at 20°C [pN],

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

Unless explicitly noted otherwise, all concentrations and ratios in the present application are quoted in per cent by weight, and preferably 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 Δη 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 (Vo), also known as the Freedericks threshold, unless explicitly indicated otherwise. In the examples, the optical threshold may also, as generally usual, be quoted for 10% relative contrast (Vio).

Examples

A) Host Mixtures

The nematic LC host mixture N1 is formulated as follows.

CCH-23 3.00 cl.p. 79.5

CCH-34 4.00 Δη 0.1 186

PCH-301 15.00 Δε 9.9

PCH-302 15.00 ^ε ΙΙ 13.8

PGP-2-3 3.00 γι 1 16

PGP-2-4 3.00

PGUQU-3-F 6.00

PGUQU-5-F 6.00

CCGU-3-F 7.00

CCQU-2-F 8.00

CCQU-3-F 8.00

CCQU-5-F 8.00

CPGU-3-OT 6.00

BCH-3F.F.F 8.00

The nematic LC host mixture N2 is formulated as follows.

BCH-3F.F 10.80 cl.p. 102.3

BCH-5F.F 9.00 Δη 0.0980

ECCP-30CF3 4.50 Δε 4.9

ECCP-50CF3 4.50 ^ε ΙΙ 7.8

CBC-33F 1 .80 γι

CBC-53F 1 .80

CBC-55F 1 .80

PCH-6F 7.20 PCH-7F 5.40

CCP-20CF3 7.20

CCP-30CF3 10.80

CCP-40CF3 6.30

CCP-50CF3 9.90

PCH-5F 9.00

CCP-3-2V 10.00

The nematic LC host mixture N3 is formulated as follows.

APUQU-2-F 5.00 cl.p. 84

APUQU-3-F 5.00 Δη 0.1017

CC-3-V 41 .00 Δε 9.7

CC-3-V1 10.00 ^ε ΙΙ 12.9

CCP-20CF3 2.00 γι 73

CCP-30CF3 3.00

CCP-50CF3 5.00

CCP-V-1 5.00

CPGU-3-OT 4.00

PGUQU-3-F 5.00

PGUQU-4-F 6.00

PGUQU-5-F 6.00

PUQU-3-F 3.00

The nematic LC host mixture N4 is formulated as follows.

CCH-35 12.00 cl.p. 90.2

CCP-V-1 1 1 .00 Δη 0.1 121

CCP-V2-1 4.50 Δε 8.2

CCP-2F.F.F 5.00 ^ε ΙΙ 12.0

CCP-3F.F.F 9.50 γι 157

BCH-2F.F 12.00

BCH-3F.F 12.00

BCH-5F.F 8.00

CCGU-3-F 6.00

CGU-2-F 10.00 - 190-

C) Polymerisable Mixtures

Polymerisable mixture preparation: Polymerisable LC media for polymer wall formation are prepared by mixing LC host, monomers, photoinitiator (unless stated otherwise: lrgacure®651 ) and stabilizer (unless stated otherwise: Pyrogallol), and then homogenizing the resulting mixture by heating above the clearing point.

The polymerisable mixture compositions are shown in Tables 1 a-b below.

Polymerisable mixtures P1 -P8 are mixtures according to the present invention which contain an aromatic thiol compound of formula I.

Polymerisable mixture CP1 is a reference mixture which contains a non- aromatic thiol compound.

Table 1 a

Table 1 b

D) Polymer Wall Formation Test Cells: The test cells comprise two glass substrates coated with ITO, which are kept apart by spacer particles or foils at a layer thickness of 3-4 microns and glued together by an adhesive (usually Norland, NEA 123). On top of the electrode layers polyimide alignment layers (Nissan SE-6514 or SE2414) are applied which are rubbed parallel or antiparallel.

Wall formation:

The test cells are filled with the LC medium and placed on a black, non- reflecting surface. A photomask is placed on top of the test cells and the sample is subjected to UV radiation (Hg/Xe arch lamp, LOT QuantumDesign Europe, LS0205). The UV radation is applied in a first step for 30min with 4mW/cm ² intensity, and in a second step for 30min with 10mW/cnn ² intensity (both steps at 365+/-10nm FWHM). Radiation of the emission spectrum below 320nm is removed by a dichroic mirror. The photomask usually has a pattern of equidistant lines of the same thickness. The line thickness is 140 microns and the distance between the lines is 9 microns, unless stated otherwise. Characterization: Samples are analyzed under a polarization microscope. The isotropic polymer walls can clearly be distinguished from areas containing birefringend LC. The width of the walls and inclusions of LC into the polymer walls, and defects in the pixel area caused by contamination of polymer, or misalignment of the LC caused by the wall formation process can be observed.

Mechanical stress test ("pen-tip test"): Test cells are subjected to a mechanical stress by applying pressure to the top substrate by a 0.5mm ² tip with increasing force in steps of 5N for 10s. The test is carried out using a measurement device Model Multitest (Mecmesin). Test cells with glass substrates having a thickness of 0.7mm are used. The tip has a pencil hardness of 0.8. Damages to the polymer wall structure are evaluated for each force (5N step) with the polarization microscope. The force before the first damage is visible is the force for which the test is considered as passed. Electron micrographs: The structure of the polymer walls and

contamination of the pixel area by polymer are investigated by taking electron micrographs. The samples are prepared by either lifting off the top substrate for top-view images, or breaking the glass slides in half for viewing the cross section of the walls. The LC is removed by flushing the sample with ethanol, subsequently the substrates is dried in an air flow and sputter coated with a conductive layer (gold).

Electro-optical characterization: The electro-optical properties of the liquid crystal host are characterized by applying an electrical potential between 0 and 10V in steps of 0.05V. The resulting response is recorded by measuring the transmission change of the sample in between crossed polarizers (DMS 301 equipped with integration sphere).

E) Device Examples

Polymerisable LC mixtures P1 -P8 and CP1 are each filled into a test cell and subjected to UV irradiation under a photomask as described above.

The test cells were then subjected to mechanical stress test. It was observed for all mixtures P1 -P8 that the polymer wall structure did not show significant damages caused by mechanical stress. In case of mixture P1 the pen-tip test was passed at 40N after 5min UV radiation time.

Fig. 2-9 show polarization microscope images of test cells prepared from polymerisable mixtures P1 -P8, respectively, after polymerization. The formed polymer walls can be seen as dark lines.

Fig. 10 shows the polarization microscope image of a test cell prepared from polymerisable mixture CP1 after polymerization. Polymer wall formation could be observed. However, significant orientation defects appeared in the pixels, as can be seen in Fig. 10. This is believed to be due to bad phase separation between polymer and LC host mixture leading to a high amount of polymer remaining in the pixels where it disturbs uniform orientation of the LC molecules.