GB2277738A

GB2277738A - 2,2-Difluoro-and 2-halo-2,2-difluoroacetyl terminus liquid-crystalline compoun ds

Info

Publication number: GB2277738A
Application number: GB9408630A
Authority: GB
Inventors: Ekkehard Bartmann; Herbert Plach
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 1993-05-05
Filing date: 1994-04-29
Publication date: 1994-11-09
Anticipated expiration: 2014-04-29
Also published as: GB2277738B; GB9408630D0

Abstract

Fluoromethyl ketones of the formula I <IMAGE> [in which X is H, F or Cl; m is 0, 1 or 2; R is H or a C1-15 alkyl or alkenyl (optionally substituted by a CN, a CF3 or at least one halogen; and where one or more CH2 is optionally replaced by customary linking groups); Z<1> and Z<2> are conventional linking groups, including a direct bond, and one of Z<1> and Z<2> may also be -(CH2)4- or -CH=CH-CH2CH2-; A<1> and A<2> are 1,4-monocyclenes (wherein the ring is monocyclic and six membered; carbocyclic or heterocyclic; saturated or unsaturated or aromatic; and optionally fluorinated) or 1,4-bicyclo(2.2.2)octylene or a naphthalene-2,6-diyl group which may further be partially or completely saturated] are suitable as components of liquid-crystalline media.

Description

Fluoromethyl ketones, and liquid-crystalline medium The invention relates to novel fluoromethyl ketones of the formula I

in which R is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case independently of one another, by -O-, -S-,

-Co-, - CO-O-, -O-CO- or -O-CO-O-, in such a way that 0 atoms are not linked directly to one another, A and A2 are each, independently of one another, a (a) trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH2 groups may be replaced by -0- and/or -S-, (b) 1,4-phenylene radical in which, in addi tion, one or two CH groups may be replaced by N, or (c) radical from the group consisting of 1,4 cyclohexenylene, 1,4-bicyclo(2,2,2)-octy lene, piperidine-1,4-diyl, naphthalene 2, 6-diyl, decahydronaphthalene-2,6-diyl and 1,2, 3,4-tetrahydronaphthalene-2,-6- diyl, it being possible for the radicals (a) and (b) to be substituted by one or two fluorine atoms, Z1 and Z2 are each, independently of one another, -CO-O-, -O-CO-, -CH20-, -OCH2-, -CH2CH2-, -CH=CH-, -C-C- or a single bond, and one of the radicals Z1 and Z2 is alternatively -(CR2)4- or -CH=CH-CH2CH2-, X is H, F or Cl and m is 0, 1 or 2.

The invention furthermore relates to the use of these compounds as components of liquid-crystalline media, and to liquid-crystal and electro-optical display elements containing the liquid-crystalline media according to the invention.

The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering.

The invention had the object of finding novel, stable, liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and, in particular, simultaneously have comparatively low viscosity and relatively high dielectric anisotropy.

It has now been found that compounds of the formula I are eminently suitable as components of liquid crystalline media. In particular, they have comparatively low viscosities. They can be used to obtain stable, liquid-crystalline media having a broad mesophase range and advantageous values for the optical and dielectric anisotropy. These media furthermore have very good lowtemperature behaviour and extremely low threshold voltages.

DE 41 01 600 Al mentions compounds containing a terminal CO-CF2-alkyl group, such as, for example,

Compounds of the formulae

are described in DE-A 40 06 921.

These compounds are in most cases not W-stable and are therefore,not so suitable for practical applications.

However, with respect to the very wide variety of areas of application of such compounds, it was desirable to have available further UV-stable compounds of high nematogeneity which have properties precisely customized to the particular applications.

In addition, the provision of the compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable from various applicational points of view for the preparation of liquid-crystalline mixtures.

The compounds of the formula I have a broad range of applications. Depending on the choice of substituents, these compounds can be used as base materials from which liquid-crystalline media are predominantly composed; however, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compounds in order, for example, to modify the dielectric and/or optical anisotropy of a dielectric of this type and/or to optimize its threshold voltage and/or its viscosity.

In the pure state, the compounds of the formula I are colourless and form liquid-crystalline mesophases in a temperature range which is favourably located for electro-optical use. They are stable chemically, thermally and to light.

The invention thus relates to the compounds of the formula I and to the use of these compounds as components of liquid-crystalline media. The invention furthermore relates to liquid-crystalline media containing at least one compound of the formula I and to liquid-crystalline display elements, in particular electro-optical display elements, which contain such media.

For reasons of simplicity below, Y is CO-CF2-X, A3 is

Cyc is a 1,4-cyclohexyl radical, Che is a 1,4-cyclohexenylene radical, Dio is a 1,3-dioxane-2,5diyl radical, Dit is a 1,3-dithiane-2,5-diyl radical, Phe is a 1,4-phenylene radical, Pyd is a pyridine-2,5-diyl radical, Pyr is a pyrimidine-2,5-diyl radical and Bi is a bicyclo(2,2,2)octylene radical, it being possible for Cyc and/or Phe to be unsubstituted or monosubstituted or disubstituted by F or CN.

A1 and A2 are preferably selected from the group consisting of Cyc, Che, Phe, Pyr, Pyd and Dio, it being preferred if only one of the radicals A1 and A2 present in the molecule is Che, Phe, Pyr, Pyd or Dio.

R is preferably alkyl, furthermore alkoxy. X is preferably F or C1, in particular F.

The compounds of the formula I accordingly embrace bicyclic compounds of the sub-formulae Ia and Ib: R-A-A -Y Ia R-A-Z-A -Y Ib tricyclic compounds of the sub-formulae Ic to If: R-A-A-A -Y Ic R-A-Z-A-Z-A -Y Id R-A-Z-A -A -Y Ie R-A-A-Z-A -Y If and tetracyclic compounds of the sub-formulae Ig to Im: R-A-A-A-A -Y Ig R-A-Z-A-A-A -Y Ih R-A-A-Z-A-A -Y Ii R-A-A-A-Z-A -Y Ij R-A-Z-A-Z-A-A -Y Ik R-A-A-Z-A-Z-A -Y Il R-A-Z-A-Z-A-Z-A -Y Im Of these, particular preference is given to those of the sub-formulae Ia, Ib, Ic, Id, Te, If, Ii and I1.

The preferred compounds of the sub-formula iA embrace those of the sub-formulae Iaa to Iag: R-Phe-A -Y Iaa R-Dit-A3-Y Iab R-Dio-A -Y Iac R-Pyr-A -Y Iad R-Pyd-A -Y Iae R-Cyc-A -Y Iaf R-Che-A -Y Iag Of these, particular preference is given to those of the formulae Iaa, Iad, Iae and Iaf.

The preferred compounds of the sub-formula Ib embrace those of the sub-formulae Iba to Ibc: R-Cyc-CH2CH2-A3-Y Iba R-Cyc-COO-A3-Y Ibb R-Phe-COO-A -Y Ibc The preferred compounds of the sub-formula Ic embrace those of the sub-formulae Ica to Icn: R-Phe-Phe-A -Y Ica R-Phe-Pyd-A3 -Y Icb R-Phe-Dio-A3-Y Ice R-Cyc-Cyc-A3-Y Icd R-Phe-Cyc-A3 -Y Ice R-Cyc-Pyd-A -Y Icf R-Pyd-Phe-A -Y Icg R-Pyr-Phe-A -Y Ich R-Phe-Pyr-A -Y Ici R-Cyc-Pyr-A3 -Y Icj R-Cyc-Phe-A3-Y Ick R-Rio-Phe-A -Y Icl R-Che-Phe-A -Y Icm R-Phe-Che-A3-Y Icn Of these, particular preference is given to those of the formulae Ica, Icb, Tcd, Ice, Ich, Ici and Ick.

The preferred compounds of the sub-formula Id embrace those of the sub-formulae Ida to Idk: R-Phe-Z-Phe-Z2-A -Y Ida R-Phe-Z-Dio-Z-A -Y Idb R-Cyc-Z-Cyc-Z-A -Y Idc R-Cyc-Z-Pyr-Z -A -Y Idd R-Pyd-Z-Phe-Z-A -Y Ide R-Phe-Z-Pyd-Z-A -Y Idf R-Pyr-Z-Phe-Z-A -Y Idg R-Phe-Zl-Pyr-Z2-A3-Y Idh R-Phe-Z1-Cyc-Z2-A3-y Idi R-Cyc-Z-Phe-Z-A -Y Idj R-Dio-Zl-Phe-Z2-A3-Y Idk The preferred compounds of the sub-formula Ie embrace those of the sub-formulae Iea to Iej: R-Pyr-Z-Phe-A -Y Iea R-Dio-Z-Phe-A -Y Ieb R-Phe-Z-Phe-A -Y Iec R-Cyc-Z-Phe-A -Y Ied R-Phe-Z-Cyc-A -Y Iee R-Cyc-Z-Cyc-A -Y Ief R-Phe-Z-Dio-A -Y Ieg R-Pyd-Z-Phe-A -Y Ieh R-Phe-Z-Pyr-A -Y Iei R-Cyc-Z-Pyr-A -Y Iej The preferred compounds of the sub-formula If embrace those of the sub-formulae Ifa to Ifn:: R-Pyr-Phe-Z2-A--Y Ifa R-Pyr-Phe-OCH2-A -Y Ifb R-Phe-Phe-Z-A -Y Ifc R-Phe-Phe-OOC-A -Y Ifd RCyc-Cyc-Z2-A3-Y Ife R-Oyc-Cyc-CH2CH2-A3 -Y 1ff R-Pyd-Phe-Z2-A3-Y Ifg R-Dio-Phe-Z-A -Y Ifh R-Phe-Cyc-Z2-A3-Y Ifi R-Phe-Pyd-Z-A -Y Ifj R-Che-Phe-Z-A -Y Ifk R-Phe-Che-Z-A -Y Ifl R-Cyc-Phe-Z2-A3-Y Ifm R-Cyc-Phe-OOC-A -Y Ifn Preference is also given to compounds of the formula I and all of the sub-formulae in which Al and/or A2 are 1,4-phenylene which is monosubstituted or disubstituted by F or monosubstituted by CN. In particular, these are 2-fluoro-1,4-phenylene, 3-fluoro 1,4-phenylene and 3, 5-difluoro-1,4-phenylene, and 2-cyano-1,4-phenylene and 3-cyano-1,4-phenylene.In a particularly preferred embodiment, A2 is 3,5-difluoro1,4-phenylene and m is 1 or 2.

Zl and Z2 are preferably a single bond, -CO-O-, -O-CO- or -CH2CR2-, secondarily preferably -CH2O- or -OCH2-.

If one of the radicals Z1 and Z2 is - (CH2) 4- or -CH=CH-CH2CH2-, the other radical Z1 or Z2 (if present) is preferably a single bond.

If R is an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.

Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2- (= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8oxanonyl, or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R is an alkyl radical in which one CH2 group has been replaced by -CH=CH-, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 carbon atoms. It is accordingly in particular vinyl, prop-l- or -2-enyl, but-l-, -2- or -3-enyl, pent-l-, -2-, -3- or -4-enyl, hex-l-, -2-, -3-, -4- or -5-enyl, hept-l-, -2-, -3-, -4-, -5- or -6-enyl, oct-l-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-l-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, or dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl.

If R is an alkyl radical in which one CH2 group has been replaced by -0- and one has been replaced by -CO-, these are preferably adjacent. These thus contain an acyloxy group -CO-O- or an oxycarbonyl group -O-CO-.

These are preferably straight-chain and have 2 to 6 carbon atoms.

They are accordingly in particular acetoxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3 -acetoxypropyl, 3 -propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2 - (methoxycarbonyl) ethyl, 2 - (ethoxycarbonyl) ethyl, 2 - (propoxycarbonyl) ethyl, 3 (methoxycarbonyl) propyl, 3 - (ethoxycarbonyl) propyl or 4 (methoxycarbonyl)butyl.

If R is an alkyl radical in which one CH2 group has been replaced by unsubstituted or substituted-CH=CH- and an adjacent CH2 group has been replaced by CO or CO-O or O-CO, this may be straight-chain or branched. It is preferably straight-chain and has 4 to 13 carbon atoms.

It is accordingly in particular acryloyloxymethyl, 2acryloyloxyethyl, 3- acryloyloxypropyl, 4 - acryloyloxy- butyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7acryloyloxyheptyl, 8 -acryloyloxyoctyl, 9 -acryloyloxy- nonyl, 10- acryloyloxydecyl, methacryloyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl, 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryloyloxynonyl.

If R is an alkyl or alkenyl radical which is monosubstituted by CN or CF3, this radical is preferably straight-chain and the substitution by CN or CF3 is in the -position.

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

Compounds of the formula I containing branched wing groups R may occasionally be of importance due to better solubility in the customary liquid-crystalline base materials, but in particular as chiral dopes if they are optically active. Smectic compounds of this type are suitable as components of ferroelectric materials.

Compounds of the formula I having SA phases are suitable, for example, for thermally addressed displays.

Branched groups of this type generally contain not more than one chain branch. Preferred branched radicals R are isopropyl, 2-butyl (= l-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy and 1methylheptoxy.

If R is an alkyl radical in which two or more CE2 groups have been replaced by -0- and/or -CO-O-, this may be straight-chain or branched. It is preferably branched and has 3 to 12 carbon atoms. It is accordingly in particular biscarboxymethyl, 2,2-biscarboxyethyl, 3,3biscarboxypropyl, 4,4-biscarboxybutyl, 5,5-biscarboxypentyl, 6, 6-biscarboxyhexyl, 7,7-biscarboxyheptyl, 8,8biscarboxyoctyl, 9, 9-biscarboxynonyl, 10, 10-biscarboxy- decyl, bis(methoxycarbonyl)methyl, 2,2-bis(methoxycarbonyl) ethyl, 3,3-bis(methoxycarbonyl)propyl, 4,4bis(methoxycarbonyl)butyl, 5,5-bis(methoxycarbonyl)pentyl, 6,6-bis(methoxycarbonyl)hexyl, 7,7 bis(methoxycarbonyl)heptyl, 8,8-bis(methoxycarbonyl)octyl, bis(ethoxycarbonyl)methyl, 2,2bis (ethoxycarbonyl) ethyl, 3, 3-bis (ethoxycarbonyl) propyl, 4,4-bis(ethoxycarbonyl)butyl or 5,5-bis(ethoxycarbonyl)hexyl.

Compounds of the formula I which contain wing groups R which are suitable for polycondensation are suitable for the preparation of liquid-crystalline polycondensates.

The formula I covers the racemates of these compounds and the optical antipodes, and mixtures thereof.

Of these compounds of the formula I and of the sub-formulae, those are preferred in which at least one of the radicals present therein has one of the preferred meanings indicated.

In the compounds of the formula I, the stereoisomers in which the rings Cyc and piperidine are trans1,4-disubstituted are preferred. Those of the abovementioned formulae which contain one or more Pyd, Pyr and/or Dio groups in each case include the two 2,5positional isomers.

Some very particularly preferred smaller groups of compounds are those of the sub-formulae I1 to I20:

The 1,4-cyclohexenylene group preferably has the following structures:

The compounds of the formula I are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie, Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for said reactions.

Use may also be made here of variants which are known per se, but are not described here in greater detail.

The compounds according to the invention can be prepared, for example, by metallating a compound of formula II

in which R, A1, A2, Z, Z2 and m are as defined above, in accordance with the reaction scheme below, and reacting the product with methyl 2,2,2-trifluoro- or 2,2-difluoro2-chloroacetate.

Scheme 1

1. BuLi, THF, -70 C

2. XF2C-CO2C:H3 -70 C Further synthetic methods are evident to the person skilled in the art. For example, appropriately 5substituted 1,3-difluorobenzene compounds can be converted into the 1,3-difluoro compounds (L = H) in accordance with the above scheme, and the radical R-(A1 Z)m-A-Z can subsequently be introduced by reactions which are customary in liquid-crystal chemistry (for example coupling, for example as described in the article by E. Poetsch, Kontakte (Darmstadt), 1988 (2), p. 15).

The compounds of the formula II can be prepared, for example, in accordance with the synthetic schemes below: Scheme 2 (A = -(-A-Z)m-A-/Z = -CH2CH2-)

F R-A-CH2PePh3Ie + QHC c F R-A-Cn"=CH-ffi H2/Pd-C F R-A-CH2CH2 F Scheme 3 (A = -(-A-Z)m-A- / Z2 = Single bond)

1. n-BuLi 2. B(OCH3)3

3. Ho

Scheme 4

Scheme 5

1. n-BuLi 2. B(OCH3)3

3 He

Scheme 6

Esters of the formula I can also be obtained by esterifying corresponding carboxylic acids (or reactive derivatives thereof) using alcohols or phenols (or reactive derivatives thereof) or by the DCC method (DCC = dicyclohexylcarbodiimide).

The corresponding carboxylic acids and alcohols or phenols are known or can be prepared analogously to known processes.

In a further process for the preparation of the compounds of the formula I, an aryl halide is reacted with an olefin in the presence of a tertiary amine and in the presence of a palladium catalyst (cf. R. F. Heck, Acc. Chem. Res. 12 (1979) 146). Examples of suitable aryl halides are chlorides, bromides and iodides, in particular bromides and iodides. The tertiary amines necessary for the success of the coupling reaction, such as, for example, triethylamine, are also suitable as solvent. Examples of suitable palladium catalysts are palladium salts, in particular Pd(II) acetate, with organophosphorus(III) compounds, such as, for example, triarylphosphines.The reaction can be carried out in the presence or absence of an inert solvent at temperatures between about 0 and 1500, preferably between 20 and 1000; examples of suitable solvents are nitriles, such as acetonitrile, or hydrocarbons, such as benzene or toluene. The aryl halides and olefines employed as starting materials are in many cases commercially available or can be prepared by processes known from the literature, for example by halogenation of corresponding parent compounds or by elimination reactions on corresponding alcohols or halides.

Ethers of the formula I are obtainable by etherifying the corresponding hydroxyl compounds, preferably corresponding phenols, the hydroxyl compound expediently first being converted into a corresponding metal derivative, for example into the corresponding alkali metal alkoxide or alkali metal phenoxide by treatment with NaH, NaNH2, NaOR, KOH, Na2CO3 or K2CO3. This can then be reacted with the corresponding alkyl halide, alkyl sulphonate or dialkyl sulphate, expediently in an inert solvent, such as, for example, acetone, 1,2-di- methoxyethane, DMF or dimethyl sulphoxide, or alternatively. with an excess of aqueous or aqueousalcoholic NaOH or KOH, at temperatures between about 200 and 100"C.

The starting materials are either known or can be prepared analogously to known compounds.

The compounds of the formula I where Z2 = -(CR2)4- can be prepared in accordance with the following scheme: Scheme 7

R- (A1-Z1) m-A2-CH2CH2-Br Chain extension by means of ethyl malonate R- (A1 -Z1 ) ,t,-A2- (CH2 ) 9-Br ZnBr2/LI ultrasound [R- (Al-Zi ) ;nA2 (C.2) < ] 2-Zn

In the Pd(II) -catalysed coupling reaction, either the target product I' is formed directly or a precursor is formed into which the radical -Y is introduced entirely analogously to the above methods for compounds of the formula I.

The compounds of the formula I' where Z2 = -CH=CH-CH2CH2- can be prepared by the Wittig method in accordance with the following scheme: Scheme 8

The synthesis of some particularly preferred compounds is shown in greater detail below: Scheme 9

Scheme 10

Scheme 11

The liquid-crystalline media according to the invention preferably contain 2 to 40, in particular 4 to 30, components as further constituents besides one or more compounds according to the invention. These media very particularly preferably contain 7 to 25 components besides one or more compounds according to the invention.

These further constituents are preferably selected from nematic or nematogenic (monotropic or isotropic) substances, in particular substances from the classes of the azoxybenzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl esters of benzoic acid, of cyclohexanecarboxylic acid and of cyclohexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexylbiphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexylcyclohexenes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl - or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-1,3dithianes, 1,2-diphenylethanes, 1,2-dicyclohexylethanes, l-phenyl-2-cyclohexylethanes, 1-cyclohexyl-2- (4-phenyl- cyclohexyl)ethanes, l-cyclohexyl-2-biphenylylethanes, 1-phenyl-2 - cyclohexylphenylethanes optionally halogenated stilbenes, benzyl phenyl ethers, tolans and substituted cinnamic acids. The 1,4-phenylene groups in these compounds may also be fluorinated.

The most important compounds suitable as further constituents of media according to the invention can be characterized by the formulae 1, 2, 3, 4 and 5: R'-L-E-R" 1 R'-L-COO-E-R" 2 R'-L-OOC-E-R" 3 R'-L-CH2CH2-E-R" 4 R'-L-CsC-E-R" 5 In the formulae 1, 2, 3, 4 and 5, L and E, which may be identical or different, are in each case, independently of one another, a bivalent radical from the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -pio-, -G-Phe- and -G-Cyc- and their mirror images, where Phe is unsubstituted or fluorinesubstituted 1, 4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexylene, Pyr is pyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl and G is 2-(traas-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl.

One of the radicals L and E is preferably Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The media according to the invention preferably contain one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which L and E are selected from the group comprising Cyc, Phe and Pyr and simultaneously one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which one of the radicals L and E is selected from the group comprising Cyc, Phe and Pyr and the other radical is selected from the group comprising -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-, and optionally one or more components selected from the compounds of the formulae 1, 2, 3, 4 and 5 in which the radicals L and E are selected from the group comprising -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-.

In a smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5, R' and R" are in each case, independently of one another, alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy having up to 8 carbon atoms. In most of these compounds, R' and R" are different from one another, one of these radicals usually being alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5 which is known as group B, R" is -F, -C1, -NCS or - -(O)iCX3(k+1FkCll, where i is 0 or 1, and k+l is 1, 2 or 3; the compounds in which R" has this meaning are labelled with the sub-formulae ib, 2b, 3b, 4b and 5b. Particular preference is given to those compounds of the sub-formulae 1b, 2b, 3b, 4b and 5b in which R" is -F, -C1, -NCS, -CF3, -OCHF2 or -OCF3. In the case of a 4-substituted benzene ring, H can be substituted by F in one or both ortho-positions.

In the compounds of the sub-formulae ib, 2b, 3b, 4b and 5b, R' is as defined for the compounds of the subformulae la-5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

In a further smaller sub-group of the compounds of the formulae 1, 2, 3, 4 and 5, R" is -CN; this subgroup is known as group C below, and the compounds of this sub-group are correspondingly described by sub-formulae Ic, 2c, 3c, 4c and 5c. In the compounds of the sub-formulae Ic, 2c, 3c, 4c and 5c, R' is as defined for the compounds of the sub-formulae la-5a and is preferably alkyl, alkoxy or alkenyl. In the case of a 4-substituted benzene ring, H can be substituted by F in one or both ortho-positions.

In addition to the preferred compounds of groups A, B and C, other compounds of the formulae 1, 2, 3, 4 and 5 having other variants of the proposed substituents are also customary. All these substances can be obtained by methods which are known from the literature or analogously thereto.

Besides compounds of the formula I according to the invention, the media according to the invention preferably contain one or more compounds selected from group A and/or group B and/or group C. The proportions by weight of the compounds from these groups in the media according to the invention are preferably Group A: 0 to 90%, preferably 4 to 80%, in particular 4 to 50% Group B: 0 to 80%, preferably 5 to 80%, in particular 5 to 65ask Group C: 0 to 80%, preferably 5 to 70%, in particular 5 to 50%, the sum of the proportions by weight of the group A and/or B and/or C compounds present in the particular media according to the invention preferably being 5 to 90% and in particular 10 to 80%.

The media according to the invention preferably contain 5 to 80%, particularly preferably 10 to 55%, of compounds according to the invention. Further preferred media are those which contain more than 60%, in particular 65 to 90%, of compounds according to the invention.

The media preferably contain three, four or five compounds according to the invention.

Preferred embodiments of the liquid-crystalline media are indicated below: - In addition to one or more compounds of the formula I, the medium contains further compounds, preferably selected from the following group:

in which the individual radicals are defined as follows: alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 7 carbon atoms, X': F, C1, CF3, OCF3 or OCHF2, Y' and Z: each, independently of the other, H or F, and O 0 or 1.

In the formulae,

is preferably

R' is preferably straight-chain alkyl having 1 to 7 carbon atoms.

In addition to one or more compounds of the formula I, the medium preferably additionally contains one or more compounds selected from the group consisting of the general formulae II, III and IV. The proportion of compounds of the formulae II to IV in the total mixture is preferably from 30 to 70% by weight. Preference is furthermore given to media which are distinguished by the fact that they essentially comprise compounds of the general formulae I to XIII.

The media according to the invention are prepared in a manner which is customary per se. In general, the components are dissolved in one another, expediently at elevated temperature. By means of suitable additives, the liquid-crystalline phases can be modified in accordance with the invention in a manner such that they can be used in all types of liquid-crystal display elements which have hitherto been disclosed. Additives of this type are known to those skilled in the art and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be added for the production of coloured guest-host systems, or substances can be added to modify the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases.

In the present application and in the examples below, the structures of the liquid-crystal compounds are indicated by acronyms, with the transformation into chemical formulae being carried out in accordance with Tables A and B below. All radicals CnH2n+1 and @mH2m+1 are straight-chain alkyl radicals having n or m carbon atoms respectively. The coding in Table B is self-evident. In Table A, only the acronym for the parent structure is shown.In individual cases, the acronym for the parent structure is followed, separated by a dash, by a code for the substituents R1, R2 L1 and L2: Code for R, R R L L R, L, L nm CnH2n+1 CmH2m+1 H H nOm CnH2n+1 OCmH2m+1 H H nO.m OCnH2n+1 CmH2m+1 H H n CnH2n+1 CN H H nN.F CnH2n+1 ON H F nF CnH2n+l F H H nOF OCnH2nvl F H H nCl CnH2n+1 Cl H H nF.F CnH2n+1 F H F nF.F.F CnH2n+1 F F F nCF3 CnH2n+1 CF3 H H nOCF3 CnH2n+1 OCF3 H H nOCF2 CnH2n+1 OCHF2 H H nS CnH2n+1 NCS H H rVsN CrH2r+1-CH=CH-CsH2s- ON H H rEsN CrH2r+1-O-CsH2s- CN H H nAm CnH2n+1 COOCmH2m+1 H H Table A:

Table B::

BCH-nKCF3.F.F The examples below are intended to illustrate the invention without representing a limitation. Above and below, per cent data are per cent by weight. All temperatures are given in degrees Celsius; mp. = melting point, cp. = clearing point. Furthermore, C = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The data between these symbols are the transition temperatures. An denotes optical anisotropy (589 nm, 200C), and the viscosity (mm2/sec) was determined at 200C.

"Customary work-up" means that water is added, if necessary, the mixture is extracted with dichloromethane, diethyl ether or toluene, the organic phase is separated off, dried and evaporated, and the product is purified by distillation under reduced pressure or by crystallisation and/or chromatography.The following abbreviations are used: DAST diethylaminosulfur trifluoride DCC dicyclohexylcarbodiimide DDQ dichlorodicyanobenzoquinone DIBALH diisobutylaluminium hydride POT potassium tert-butoxide TRF tetrahydrofuran pTSOH p-toluenesulphonic acid TMEDA tetramethylethylenediamine Example 1

0.019 mol of p- [trans-4- (trans-4-pentylcyclo- hexyl)cyclohexyl]-2,6-difluorobenzene in 60 ml of absolute tetrahydrofuran are cooled to -700C, and 0.023 mol of butyllithium (15% in n-hexane) is subsequently added. The mixture is stirred for 1.5 hours, and 0.02 mol of ethyl trifluoroacetate is subsequently added dropwise to the solution. The mixture is stirred at -700C for a further 2 hours, and finally about 6 ml of 12% hydrochloric acid are added.The organic phase is separated off, washed with water and subjected to customary work-up.

C 43 N 103.5 I, An = +0.091, As = 17.45 The following compounds of the formula

are prepared analogously:

R (A1-Z1)=-A2-Z2- X n-C3X7 9 F n-C3H7 e Cl n-C5H11 &commat; F n-CsHll &commat; C1 n-C3H F n-C3H7 C1 n-C5Hl1 9 F n-C5H11 t Cl CH2 = CHCH2CH2 e F CH2O &commat; C1 C2M5 mHHHOH2CH2 F n-C3H &num;mHCM2CH2 F n-C3H7 9 CH2CH2- C1 n-CsH11 H CH2CH2- F n-CsH11 H9 CH2CH2- C1 CM3 0CM2 mHHHCM2CM2 F C2H5 e&commat; -CH2CH2- F C2M o CH2CH2- o )-Cfi2Clri2 - Ci n-C3H7 &commat;9 CH2CH2- F n-C3H7 e9 CH2CH2- C1 n-C4Hg 4&commat; CH2CH2- F n-C4Hg < CH2CH2- C1 n-C5M11 CM2CM2- F n-C5Hl1 < CH2CH2- C1 C2M5 OH2CM2 F C2H5 e -CH2CH2 -(O)- C1

R (Al-zl) ~A2~z2 X n-C3H7 {i)-CH2CH2 < )- F n C3H7 ECH2CH2 e Cl n-C5H11 -(O XCH2CH24} )- F n-C5H11 XCH2CH2-9 Cl CH2 = CHCM2CM2 -CH2CM2 F CH2 = CHCH2CH2 (PCH2CH2 < Cl n-C3H7 kHzCM2CH2- -(H} F n~C3H7 GCH2CH2 C1 n-CsHll XCH2CH249 n-O5M11 )CH2CH2 e C1 n-C3 H7 - F n-C3H7 H Cl n-C5Hll w F n-05H11 < Cl CH3CH2O < F CH3CH2O e&commat; C1 C2H5 Ii 9 F n-C3H7 F 078 N 94.8 I; An=+0.097; & 18.21 n-C3H7 mHM Cl n-C4Hg HDHH F n -C4 Hg 9 C1 n-C5Hll 9 Cl n-C6Hl, 9 F n-C6M12 Cl n-CloH2l w F n-Cl2H2s mDHM F

R -(A1-Zl) -A2-Z2- X F n-C3M7 ThffiMO X F F F n-C3H7 X c n-C4 H9 H4Mo F n-C4h9 < C F n-CSH11 iHf F n-C5Hll X C n-C3H7 < F F n-C3H7 C1 F F n C h < F n-C5M11 C F n-C3K7 ~/7 CH2C12 - F F

R -(A1-Z1)=-A2-Z2- X F n-C3H7 < -CH2CH2- C1 F F n-CSH11 m%HOCM2CN2 most F F n-C5M11 H%0H2CH2 C1 F C2HS F N C2Hs {O)- C1 N N n-C3H7 To )- F N N n-C3H7 CO,- Cl N N n-CsH1l { ,- F N N n-C5Hl 1 Co N

R -(Al-z;;) ~A2~z2 X N C2M5 { ) F c N C2Hs { > 9 C1 N N n-C3H7 { > 9 F N N n-C3H7 { Cl N N n-CsHll {O F F I n-C5M11 { )9 Cl N C2H5 - F N C2H5 e ~ Cl N n-C3H7 e ~ F N n-03H7 9 Cl N n-C5Hll e F N n-C5Hll S Cl N

R (A1~Z1),~A2~ZZ~ X F C2M5 my- F F C2H5 m Cl F F n-C3 H7 < F F F n-C3 H7 m Cl F F n-CsH1l < F F F n-C3M7 ffDoo C1 F C2M5 -QCH2CH2 - P C2M5 e CH2CH2- C1 n-C3H7 e CH2CH2- 2 n-C3H7 9 K .CH2CH2 - C1 n-CsHll -CH2 CM2 n-C5H11 -( h' CH2CH2- C1

R -(Al-Zl) ~A2~z2~ X 0 C2M5 { > ~ F 0 0 C2M5 { > ~ Cl o o n-CjH7 { ) F 0 0 n-C;;H7 { ) Cl o o n-CsH1l { F o 0 n-C5M11 %)- Cl o C2H5 -m) F C2M5 mc Cl F n-C3i7 F n-C3H7 < ~ C1 n-C5Hll X F F n-CsHl1 X Cl Example 2

0.03 mol of p-[4-(trans-4-propylcyclohexyl)phenyl]-2,6-difluorobenzene in 60 ml of absolute tetrahydrofuran is cooled to -700C, and 0.034 mol of butyllithium (15% in n-hexane) is subsequently added. The mixture is stirred at -700C for 2 hours, and 0.031 mol of ethyl trifluoroacetate is added dropwise.The mixture is stirred for a further 2 hours, 5 ml of 12.5% hydrochloric acid are added, and the organic phase is separated off and then subjected to customary work-up.

C 57 N (49.5) I, An = +0.164 The following compounds of the formula

are prepared analogously: n X 1 F 1 C1 1 H 2 F 2 C1 2 H 3 C1 3 H 4 F 4 C1 4 H 5 C1 5 H 6 F n X 6 C1 6 H 8 F 8 C1 8 H 10 F 10 C1 10 H Example 3

2.0 mol of NaOH pellets are dissolved in 500 ml of water, and 0.5 mol of p-[trans-4-pentylcyclohexyl)- phenylboronic acid in 1000 ml of toluene is added.The mixture is subsequently stirred for 40 minutes, during which the temperature of the solution should not exceed 450C. 0.5 mol of 3,5-difluorophenyl bromide and 11.5 g of tetrakis (triphenylphosphine) palladium (0) are then added to the solution. The mixture is refluxed overnight and cooled to room temperature.

The mixture is filtered with suction, the organic phase is separated off, and the aqueous phase is extracted with toluene. The combined organic extracts are washed with water and filtered through a spherical frit filled with silica gel. The solution is subsequently dried over NaSO4. The solvent is removed in vacuo, and the residue is recrystallized from ethanol.

The product (0.03 mol) is dissolved in TRF at room temperature with stirring under a nitrogen atmosphere. The solution is then cooled to -700C, and 0.034 mol of n-BuLi (15% in n-hexane) is added dropwise.

The mixture is stirred at -700C for 2 hours, 0.031 mol of ethyl trifluoroacetate is added dropwise to the suspension, and the mixture is stirred for a further 2 hours. 12.5% hydrochloric acid is subsequently added.

Finally, the mixture is subjected to conventional work up.

C1. pt. 70.50C, As = 22, #n = 0.155 Mixture examples Example A PCH-5F 5.0 Clearing point [ C]: +88 PCH-7F 6.0 An 589 nm, 20 [CO]: +0.0913 CCP-20CF3 11,0 be [1 kHz, 20 C]: 8,6 CCP-30CF3 12.0 V(10,0,20) [V]: 1.49 CCP-4OCF3 10.0 V(90,0,20) [V]: 2.34 CCP-50CF3 12.0 BCH-3F.F.F 12.0 BCH-5F.F.F 11.0 CCP-3F.F.F 12.0 CCP-5KCF3.F.F 9.0 ExamPle B PCH-5F 5.0 Clearing point [ C] +88 PCH-7F 6.0 An [589 nm, 20 OC]: +0.0969 CCP-2OCF3 11.0 ## [1 kHz, 20 OC]: 9.2 CCP-3OCF3 12.0 V(10,0,20) [V]: 1.31 CCP-4OCF3 10.0 V(90,0,20) [V]: 2.10 CCP-5OCF3 12.0 BCH-3KCF3.F.F 12.0 BCH-5F.F.F 11.0 CCP-3F.F.F 12.0 CCP-5F.F.F 9.0 ExamPle C PCH-5F 5.0 % Clearing point [ C]: +87 PCH-7F 6.0 % #n [589 nm, 20 C]: +0.0978 CCP-2OCF3 11.0 % V(10,0,20) [V]: 1.50 CCP-3OCF3 12.0 % V(90,0,20) [V]: 2.30 CCP-4OCF3 10.0 % CCP-5OCF3 12.0 % BCH-3F.F.F 12.0 % BCH-5F.F.F 11.0 % CCP-5KCF3.F.F 21.0 % Example D PCH-5F 5.0 % Clearing point [ C]: +87 PCH-7F 6.0 % An [589 nm, 20 OC]: +0.1008 CCP-20CF3 11.0 % V(10,0,20) [V]: 1.31 CCP-3OCF3 12.0 % V(90,0,20) [V]: 2.05 CCP-4OCF3 10.0 % CCP-5OCF3 12.0 % BCH-3KCF3.F.F 23.0 % CCP-3F.F.F 12.0 % CCP-5F.F.F 9.0 % ExamPle E PCH-SF 5. 0 6 Clearing point [ C]: +87 PCH-7F 6.0 % #n [589 nm, 20 C]: 10.1052 CCP-2OCF3 11.0 % V(10,0,20) [V]: 1.26 CCP-3OCF3 12.0 % V(90,0,20) [V]: 1.99 CCP-4OCF3 10.0 % CCP-5OCF3 12.0 % BCH-3KCF3.F.F 23.0 % CCP-5KCF3.F.F 21.0 % Example F PCH-5F 9.0 % Clearing point [ C]: 90.0 PCH-6F 7.2 % #n [589 nm, 20 C]: 0.1015 PCH-7F 5.4 % ## !1 kHz, 20 C]: 6.57 CCP-2OCF3 7.2 % CCP-30CF3 10,8 % CCP-4OCF3 8.1 % CCP-5OCF3 8.1 % BCH-3F.F 10.8 % BCH-5F.F 9.0 % ECCP-3OCF3 4.5 % ECCP-50CF3 4.5 % CBC-33F 1.8 % CBC-53F 1.8 % CBC-55F 1.8 % CCP-3KCF3.F.F 10.0 % Example G PCH-5F 9.0 % Clearing point [ C]: 91.1 PCH-6F 7.2 % An [589 nm, 20 C]: 0.0964 PCH-7F 5.4 % ## [1 kHz, 20 C]: 6.46 CCP-2OCF3 7.2 % CCP-30CF3 10.8 % CCP-4OCF3 8.1 % CCP-SOCF3 8.1 % BCH-3F.F 10.8 % BCH-5F.F 9.0 % ECCP-3OCF3 4.5 % ECCP-5OCF3 4.5 % CBC-33F 1.8 % CBC-53F 1.8 % CBC-55F 1.8 % CCP-5KCF3.F.F 10,0 % Example H PCH-5F 9.0 % Clearing point [ C]: 88.9 PCH-6F 7,2 % An [589 nm, 20 OC]: 0,1037 PCH-7F 5.4 % ## [1 kHz, 20 C]: 7.17 CCP-2OCF3 7,2 % CCP-3OCF3 10.8 % CCP-4OCF3 8.1 % CCP-5OCF3 9.0 % BCH-3F.F 10.8 % BCH-5F.F ECCP-30CF3 4,5 % ECCP-5OCF3 4.5 % CBC-33F 1.8 % CBC-53F 1,8 % CBC-55F 1.8 % CCP-3KCF3.F.F 10,0 % Example I PCH-2 5.0 % Clearing point [ C]: 61 PCH-3 15.0 % An [589 rim, 20 C]: 0.1270 PCH-4 11.0 % ## [1 kHz, 20 C]: 16.6 PCH-5 21.0 % d.#n [ m]: 1.0 PCH-7 11.0 % V(10,0,20) [V]: 1.53 PCH-32 5.0 % V(90,0,20) [V]: 2.09 BCH-3KCF3.F.F 12.0 % BCH-5KCF3.F.F 10.0 % CBC-33 4.0 % CBC-53 6.0 % Example J PCH-3 14.0 % Clearing point [ C]: 87 PCH-4 10.0 % #n [589 nm, 20 C]: 0.1320 PCH-5 20,0 % A [1 kHz, 20 C]: 15,1 PCH-7 10.0 % d.#n [ m]: 1.0 PCH-32 5.0 % V(10,0,20) [V]: 1.61 BCH-3KCF3.F.F 12.0 % V(90,0,20) [V]: 2.23 BCH-5KCF3.F.F 10.0 % CBC-33 6,0 % CBC-S3 7,0 % CBC-55 6.0 % Example K PCH-3 12,0 % Clearing point [ C]: 86 PCH-4 10.0 % An [589 nm, 20 C]: 0.1321 PCH-5 18.0 % At [1 kHz, 20 C]: 16.5 PCH-7 9.0 % d.#n [ m]: 1.0 BCH-3KCF3.F.F 9.0 % V(10,0,20) [V]: 1.52 BCH-5KCF3.F.F 9.0 % V(90,0,20) [V]: 2.14 CCP-3KCF3.F.F 9.0 % CCP-5KCF3.F.F 9.0 % CBC-33 4.0 % CBC-53 5.0 % CBC-55 6.0 % ExamPle L PCH-3 14, 0 % Clearing point [ C]: 90 C PCH-4 10.0 % An (589 nm, 20 C]: 0.118 PCH-5 20.0 % ## [1 kHz, 20 C]: 13.7 PCH-7 10.0 % d.#n [ m]: 1.0 / 0.5 PCH-32 5.0 % V(10,0,20) [V]: 1.67 / 1.32 BCH-3KCF3.F.F 12.0 % V(90,0,20) [V]: 2.38 / 2.07 BCH-5KCF3.F.F 9.0 % CBC-33 6,0 % CBC-53 7.0 % CBC-55 6.0 % Example M PCH-2 12.0% Clearing point [ C]: 62 PCH-4 13.0 % #n [589 nm, 20 C]: +0.1385 K6 7.0 % ## [1 kHz, 20 C]: 17,3 K9 6.0 % dAn [ m]: 1.0 K12 6,0 % V(10,0,20) [V]: 1,17 ME2N 2.0 % V(90,0,20) [V]: 1.76 ME3N 3.0 % ME2N.F 3,0 % ME3N.F 3,0 % ME5N.F 5.0 % BCH-3KCF3.F.F 8.0 % BCH-5KCF3.F.F 8.0 % HD-34 6.0 % HD-35 7.0 % CH-33 3.0 % CH-35 3.0 % CH-43 3.0 % CH-45 3.0 % Example N PCH-3 7.0 % Clearing point [ C]: 71 PCH-4 4.0 % #n [589 nm, 20 C]: +0.1430 K6 12.0 % ## [1 kHz, 20 C]: 11.0 K12 12.0 % d.#n [ m]: 1.0 PCH-301 4.0 % V(10,0,20) [V]: 1.45 BCH-5KCF3.F.F 8.0 % V(90,0,20) [V]: 2.60 BCH-5KCF3.F.F 7.0 % D-301 8.0 % D-302 7.0 % D-401 6.0 % D-402 6.0 % D-501 7.0 % CBC-33 4,0 % CBC-53 4.0 % CBC-55 4.0 % ExamPle O ME2N.F 3.0 % Clearing point [ C]: # ME3N.F 3.0 % An [589 nm, 20 C]: +0,1580 ME5N.F 6.0 % ## [1 kHz, 20 C]: 17.

ME7N.F 5.0 % HP-3N.F 5.0 % Twist angle 180 (STN) K9 6.0 % V(10.0.20) [V]: 1.26 K15 12.0 % PCH-3 14.0 % V90/V10: 15.7 PCH-301 18.0 % BCH-3KCF3.F.F 6.0 % CBC-33 5.0 % CBC-55 4.0 % CBC-33F 4.0 % CBC-53F 5.0 % CBC-55F 4.0 % Example P PCH-3 9.5 % Clearing point [ C]: 88 PCH-4 6.5 % #n [589 nm, 20 C]: +0.138 PCH-5 13.0 % ## [1 kHz, 20 C]: +15.3 PCH-7 6.5 % d.#n [ m]: 1.0 PCH-302 12.5 % V(10,0,20) [V]: 1.65 BCH-3KCF3.F.F 18.0 % V(90,0,20) [V]: 2.30 BCM-SKCF3.F.F 18.0 % CBC-33 5.0 % CBC-53 5.0 CBC-55 6.0 Example p Multi-bottle system -000 -050 PCH-3 12.0 % PCH-3 11.0 % PCH-4 9,0 % PCH-4 8,0 % PCH-5 18,0 % PCH-5 - 16.0 % PCH-7 9.0 % PCH-7 8.0 % BCH-3KCF3.F.F 3.0 % PCH-302 5.0 % BCH-5KCF3.F.F 3.0 % BCH-3KCF3.F.F 9.0 % CCP-3KCF3.F.F 15.0 % BCH-5KCF3.F.F 9.0 % CCP-5KCF3.F.F 15.0 % CCP-3KCF3.F.F 9.0 % CBC-33 5.0 9s CCP-SKCF3.F.F 9,0 % CBC-53 5.0 % CBC-33 5,0 % CBC-55 6.0 9s CBC-53 5.0 % CBC-55 6, 0 % Clearing point : 87 Clearing point [ C]: : 87 An [589 rim, 20 C]: +0,122 An [589 rim, 20 C]: +0,135 As [1 kHz, 20 C]: 15.7 ## [1 kHz, 20 C]: 15.5 d.#n [ m]: 1.0 d.#n [ m]: 1.0 V(10,0,20) [V]: 1.60 V(10,0,20) [V]: 1.58 V(90,0,20) [V]: 2.35 V(90,0,20) [V]: 2.29 -100 PCH-3 10.0 % Clearing point [ C]: 88 PCH-4 7.0 % ## [1 kHz, 20 C]: +15.4 PCH-5 14.0 % d.#n [ m]: 1.0 PCH-7 7.0 % V(10.0.20) [V]: 1.58 PCH-302 10.0 % V(90,0,20) [V]: 2.24 BCH-3KCF3.F.F 15.0 % BCH-5KCF3.F.F 15.0 % CCP-3KCF3.F.F 3.0 % CCP-5KCF3.F.F 3.0 % CBC-33 5.0 % CBC-53 5.0 % CBC-55 6.0 % Example R PCH-3 20.0 % Clearing point [ C]: 73 PCH-4 9.0 % #n [589 nm, 20 C]: +0.1032 PCH-5 9.0 % ## [1 kHz, 20 C]: 11.8 PCH-301 15.0 % d.#n [ m]: 0.5 CCP-2OCF3 6.0 % Twist angle: 240 (STN) CCP-3OCF3 6.0 % V(10,0,20) [V]: 2.02 CCP-5OCF3 6.0 % V90/V10: 6.5 % CCP-3KCF3.F.F 10.0 % CCO05KCF3.F.F 10.0 % CBC-33F 4,0 % CBC-53F 5.0 % Example S Two-bottle System (STN) -000 -100 PCH-3 20,0 % PCH-3 17.0 % PCH-4 ,0 % K6 6,0 % K9 7,0 % PCH-5 9.0 % PCH-301 20.0 % PCH-301 15.0 % PTP-102 6.0 % CCP-20CF3 6.0 % PTP-201 6,0 % CCP-3OCF3 6.0 % CCP-3OCF3 6.0 % CCP-5OCF3 6.0 % CCP-5OCF3 6.0 % CCP-3KCF3.F.F 10.0 % BCH-3KCF3.F.F 5.0 % CCP-5KCF3.F.F 10,0 % BCH-5KCF3.F.F 5,0 % CCPC-33 3.0 % CPTP-301 5.0 % CCPC-34 3,0 % CPTP-302 6,0 % CCPC-35 3.0 % CPTP-303 5.0 % Clearing point [ C]: 76 Clearing point [ C]: 82 #n [589 nm, 20 C]: +0.0966 #n [589 nm, 20 C]: +0.1785 ## [1 kHz, 20 C]: 11.7 ## [1 kHz, 20 C]: 17.0 d.#n [ m]: 0.5 d.#n [ m]: 0.5 TN STN (240 ) TN(90 )STN(240 ) V(10,0,20) [V]: 1.29 2.03 V(10,0,20) [V]: 1.78 1.98 V(90,0,20) [V]: 2.08 - V(90,0,20) [V]: 2.50 V90/V10: - 6.7 % V90/V10: - 6.5 % ExamDle T PCH-3 17, 0 % Clearing point int [ C]: 81 K6 6.0 % #n [589 nm, 20 C]: +0.182 K9 7.0 % ## [1 kHz, 20 C]: 11.5 PCH-301 18.0 % d.#n [ m]: 1.0 PTP-102 6.0 % TN (90 ) STN (2 PTP-201 6.0 % V(10,0,20) [V]: 1.66 1.90 CCP-3KCF3.F.F 6.0 96 V(90,0,20) [V] 2.34 - CCP-5KCF3.F.F 6.0 % V90/V10: " 6.

BCH-3KCF3.F.F 5.0 % BCH-5KCF3.F.F 5.0 % CPTP-301 6.0 % CPTP-302 6.0 % CPTP-303 6.0 %

Claims

Patent claims 1. Fluoromethyl ketones of the formula I in which R is H, an alkyl or alkenyl radical having

1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen, it also being possible for one or more CH2 groups in these radicals to be replaced, in each case independently of one another, by - O -, - S -,

-CO-O-, -.O-CO- or -O-CO-O-, in such a way that 0 atoms are not linked directly to one another, A1 and A2 are each, independently of one another, a (a) trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH2 groups may be replaced by -0- and/or -S-, (b) 1,4-phenylene radical in which, in addi tion, one or two CH groups may be replaced by N, or (c) radical from the group consisting of 1,4 cyclohexenylene, 1,4-bicyclo(2,2,2)octy lene, piperidine-1,4-diyl, naphthalene 2, 6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6 diyl, it being possible for the radicals (a) and (b) to be substituted by one or two fluorine atoms, Z1 and Z2 are each, independently of one another, -CO-O-, -O-CO-, -CH2O-, -OCH2-, -CH2CH2-, -CH=CH-, -C-C- or a single bond, and one of the radicals Z1 and Z is alternatively -(CH2)4- or -CH=CH-CH2CH2-, X is H, F or C1 and m is 0, 1 or 2.

2. Compounds of the formula I1,

in which R and X are as defined in Claim 1.

3. Compounds of the formula I3,

in which R and X are as defined in Claim 1.

4. Compounds of the formula I4,

in which R and X are as defined in Claim 1.

5. Compounds of the formula I5,

in which R and X are as defined in Claim 1.

6. Compounds according to one of Claims 1 to 5, characterized in that X is fluorine.

7. Use of compounds of the formula I as components of liquid-crystalline media.

8. Liquid-crystalline medium having at least two liquid-crystalline components, characterized in that it contains at least one compound of the formula I.

9. Liquid-crystalline medium according to Claim 8, characterized in that it additionally contains one or more compounds selected from the group consisting of the general formulae II, III and IV:

in which the individual radicals have the following meanings: alkyl, oxaalkyl, fluoroalkyl or alkenyl, in each case having up to 7 carbon atoms, X': F, C1, CF3, OCF3 or OCHF2, Y' and Z: each, independently of another, H or F, and 0 or 1.

10. Liquid-crystal display element, characterized in that it contains a liquid-crystalline medium according to Claim 8.

11. Electro-optical display element, characterized in that it contains, as dielectric, a liquid-crystalline medium according to Claim 8.