GB2258232A - Alkoxymethylene fluoroterphenyls - Google Patents

Abstract

The invention relates to new alkoxymethylene fluoroterphenyls of the formula I, <IMAGE> in which R<1> is alkyl or alkoxy with 1 to 15 C-atoms, R<2> is alkyl with 1 to 10 C-atoms, n is 1 to 7, and L<1> to L<6> are H or F, at least one or two of L<1> to L<6> being F, the others being H and to their use as components of liquid crystalline compositions.

Description

Alkoxymethylene fluoroterphenyls and liquid crystalline medium The invention relates to new alkoxymethylene fluoroterphenyls of the formula I,

in which R1 is alkyl or alkoxy with 1 to 15 C-atoms, R2 is alkyl with 1 to 10 C-atoms, n is 1 to 7, and L1 to L6 are H or F, at least one or two of L1 to L2 being F, the others being H.

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

Liquid crystal materials are well known, and generally exploit the electrooptical switching properties of the nematic (N) or smectic, especially chiral smectic C (Sc*) or smectic I (SI*), phase, the asterisk denoting a chiral phase.

They are used widely in electrooptical display devices.

Such materials are generally mixtures of compounds selected so that the mixture shows desirable properties. In particular such properties include: (i) a broad temperature range over which a suitable liq- uid crystal phase, e.g. SAT SC, Sc*, Si, SI or N persists, this range preferably including room tem perature (ca. 20 C).

(ii) low viscosity (iii) ease of manufacture (iv) good electrooptical response (v) In the case of compounds or mixtures which show an Sc phase, miscibility with one or more optically active compounds, i.e. which contain an asymmetrically sub stituted carbon atom, to form a helical chiral phase having a long pitch and a high spontaneous polarisa tion coefficient Ps. It is also useful if the com pound or mixture shows an SA phase at a higher tem perature than its Sc phase to assist in aligning the 5c phase with the electrodes of a liquid crystal electrooptical device.

Terphenyls are known for use in liquid crystal materials. For example: EP-A-8430494.3 describes the preparation and use of monofluorinated terphenyls of general formula:

where R1 and R2 are independently alkyl or alkoxy, in nematic liquid crystal materials. GB-A-8725928 and WO/07890 disclose the use of these monofluorinated terphenyls in Sc* mixtures.

EP-A-0084194 contains a wholly speculative references to laterally difluorinated terphenyls, including a theoretical reference to the compound

for use in nematic mixture. PCT/EP87/00515 contains a speculative general formula which would include difluoroterphenyls, and also refers specifically to the two compounds

used exclusively in nematic liquid crystal mixtures. Terphenyls of the formula

(X1 = X2; H or F R1, R2 = Alkyl, Alkoxy) have already been disclosed in US 4,594,465. In the GB 2198749 are described ferroelectric mixtures containing terphenyls of the general formula

(Rl, R2 = Alkyl or Alkoxy) wherein X and Y are independently selected from F and H at least one being fluorine.

Therphenyls of the formulae

(R1 = R2 = Alkyl)

are known from the WO 88-00724, but alkoxymethylene fluoroterphenyls are not mentioned at all.

This invention seeks to identify other useful terphenyls, and in particular to investigate their use in smectic liquid crystal materials.

The invention was based on the object of discovering alkoxymethylene terphenyls of the formula I which are suitable as components of liquid crystalline mixtures. Particularly liquid crystalline mixtures with a broad mesophase range and a comparable low viscosity are preparable with their aid.

In addition, the compounds of the formula I are suitable as components for chiral tilted smectic liquid crystlline phases.

Chiral tilted smectic liquid crystalline phases with ferroelectric properties can be prepared by adding a suitable chiral dopant to a base-mixture which exhibits one or more tilted smectic phases (L.A. Veresnev et al., Mol. Cryst. Liq.

Cryst. 89, 327 (1982); H.R. Brand et al., J. Physique 44 (lett.), L-771 (1983).

Such phases can be used as dielectrics for displays based on the SSFLC-technology described by Clark and Lagerwall (N.A.

Clark and S.T. Lagerwall, Appl. Phys. Lett. 36, 889 (1980); U.S. Patent 4,367,924).

The compounds of the formula I have a wide range of application. Depending on the choice of the substituents, these compounds can be used as the base materials from which liquid crystalline mixtures are composed up to 50 %; however, it is also possible for compounds of the formula I to be added to liquid crystalline base materials of other classes of compounds in order to influence the dielectric and/or optical anisotropy and/or for the viscosity and/or the spontanous polarization and/or the mesophase range and/or the tilt angle and/or the pitch of such a dielectric. The compounds of the formula I are furthermore suitable as intermediates for the preparation of other substances, which are useful as components of liquid crystalline dielectrics.

The compounds of the formula I are colourless in the pure state. They are very stable towards chemicals, heat and light.

Accordingly the invention relates to compounds of the formula I and to the use of these compounds as components of liquid crystalline media. In addition, the invention relates to a liquid crystalline media containing at least one compound of the formula I, to liquid crystalline composition, exhibiting a smectic C phase wherein at least one component is a compound of the formula I.

Furthermore, the invention relates to liquid crystalline display elements which contain such compositions.

A few very particularly preferred smaller groups of compounds are those of the subformulae I1 to I12.

Above and below R1 and R2 each preferably denote alkyl with preferably 1 to 10 C atoms, particularly 3 to 10 C atoms.

n is 1 to 7, preferably 1, 2 or 3.

The compounds of the formula I, wherein R1 and R2 have 2 to 10 C atoms, particularly 3 to 9 C atoms, are suitable for liquid crystlline phases exhibiting ferroelectric properties.

If R1 and R2 each are an alkyl radical, these radicals can be straight-chain or branched. Preferably, it is straight-chain and has 2, 3, 4, 5, 6, 7, 8, 9 or 10 C atoms and is accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl. Rl may also be ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, nonoxy or decyloxy.

Compounds of the formula I with branched terminal groups P1 and R2 can occasionally be of importance because of the improved solubility in the costumary liquid crystal base materials, but in particular as chiral doping substances if they are optically active. Smectic compounds of this type are suitable as components for ferro-electric materials.

Branched groups of this type as a rule do not contain more than one chain branching. Preferred branched chain radicals P1 or R2 are isopropyl, 2-butyl (= l-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl and for Ri also isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, l-methylheptoxy, 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxy, 6-methyloctanoyloxy, 2-methylbutyryloxy, 3-methylvaleryloxy, 4-methylhexanoyloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl.

Compounds of the formula I wherein the terminal groups Rl and/or R2 are suitable for poly-condensation reactions are useful for the preparation of liquid crystalline polycondensates. Formula I includes both the racemates of these compounds and the optical antipodes, as well as mixtures thereof.

The compounds of the formula I are prepared by methods which are known per se, such as are described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg Thieme Verlag, Stuttgart), and in particular under reaction conditions which are known and suitable for the reactions mentioned. Variants which are known per se and are not mentioned in more detail here can also be used in this connection.

If desired, the starting materials can also be formed in situ, such that they are not isolated from the reaction mixture but are immediately reacted further to give the compounds of the formula I.

The compounds of the formula I can be prepared from l-alkyl or l-alkoxy subtituted 4-bromobenzenes as starting material.

The terphenyls are for example be mode by adding appropriately 4-substituted phenyl rings to such precursors using routes which couple these rings via known phenyl boronic acids. This reaction sequence is carried out a second time with the so obtained substituted biphenyls.

The terphenyls may, for example, be prepared using general routes shown in the reactions schemes 1-3: Scheme 1

/F /F / F Br + (HO2) B-OCH3 OCH, tBr OCH3 v Br- 9OH DME Pd (PPh3)4 NaHCO3 (aq.) F Rl Xe -OCH3 Br- 9 (CH2)nBr BBr3 /CH2C12 room temperature R2OH, NaH, THF F SOH R1 -;;D- (CF3SO2) 20 Br--(CH2)OR2 (CF3S02) 2 Mg, THF, N2 TMB NVN N~N , 0 OC F O R1-OS1Q-CF3 (HO) 2B} (CH2) n R2 L DME, Pd(PPh3)4 LiCi, Na2CO3 (aq.) F (CH2) 5 c nOR2 Scheme 2

Scheme 3

Compounds of formula I often show nematic or smectic C phases which persist over a broad temperature range and are useful constituents of liquid crystal mixtures.

Therefore according to a second aspect of the invention there is provided a liquid crystal material, being a mixture of compounds, at least one of formula I.

The liquid crystalline phases according to the invention consist of 2 to 25, preferably 3 to 15, components, at least one of which is a compound of the formula I.

The other constituents are preferably chosen from nematic, smectic, nematogenic of smectogenic substances, in particular the known substances, from the classes of azoxybenzenes, benzylideneanilines, biphenyls, p-terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexane carboxylates, phenylcyclohexanes, cyclohexylbiphenyles, cyclohexylcyclohexanes, cyclohexylnaphthalenes, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclohexylpyrimidines, phenyl- or cyclohexyldithianes, phenyl- or cyclohexyldioxanes, 1,2-bis-phenylethanes, 1,2-bis-cyclohexylethane, l-phenyl-2-cyclohexylethanes, optionally halogenated stilbenes, benzylphenyl ethers, tolanes and substituted cinnamic acids.

Important compounds which are possible constituents of liquid crystalline mixtures according to the invention can be characterized by the formula II R' -L-G-E-R" II wherein L and E are each an unsubstituted or laterally fluoro or cyano substituted carbo- or heterocyclic ring system chosen from the group comprising 1,4-di substituted benzene or cyclohexane rings, 1,4 disubstituted 1-cyanocyclohexane rings, 4,4'-di substituted biphenyl, phenylcyclohexyl or bi cyclohexyl systems, 2,5-disubstituted pyrimidine, pyridine and 1,3-dioxane rings, 2,6-disubstituted naphthalene, di- and tetrahydronaphthalene, quin oline and tetrahydroquinazoline, G is -CH=CH-, -CH=CY-, -CC-, -CO-O-, -CO-S-, -CH=N-, -N(O)=N-, -CH=N(O)-, -CH2-CH2-, -CH2-O-, -CH2-S-, -COO-Phe-COO- or a single bond, Y is halogen, preferably chlorine or -CN, R' and R'' are each alkyl, alkoxy, alkanoyloxy, alkoxycarbo nyl or alkoxycarbonyloxy with up to 18, prefera bly up to 10 C atoms, it also being possible for one CH2 group nonadjacent to an oxygen to be replaced by -O-, -CH=CH-, or -C3C-, or one of these radicals R' and R" may also be -CN, -NO2, -CF3, -NCS, -F, -Cl, or -Br.

In the most of these compounds R' and R" are different for one another, one of these radicals usually being an alkyl or alkoxy group. However, other variants of the substituents envisaged can also be used. Many such substances or mixtures thereof are commercially available. All of these substances can be prepared by methods which are known from the literature.

The liquid crystalline mixtures according to the invention are prepared in a manner which is customary per se. As a rule, the components are dissolved in one another, preferably at elevated temperature.

The liquid crystalline mixtures according to the invention can be modified by suitable additives such that they can be used in all the types of liquid crystal display elements disclosed to date.

Such additives are known to the expert and are described in detail in the literature. For example, it is possible to add conductive salts, preferably ethyl-dimethyl-dodecy-ammonium 4-hexyloxybenzoate, tetrabutylammonium tetraphenylboranate or complex salts or crown ethers (compare, for example, I.

Haller et al., Mol.Cryst.Liq.Cryst. Volume 24, pages 249-258 (1973) for improving the conductivity, dichroic dyestuffs for the production of colored guest-host systems or substances for changing the dielectric anisotropy, the viscosity and/or the orientation of the nematic phases. Such substances are described, for example, in German Offenlegungsschrift 2,209,127, 2,240,863, 2,321,632, 2,338,281, 2,450,088, 2,637,430, 2,853,728 and 2,902,177.

When liquid crystal material is a nematic liquid crystal material, the other constituents of the material may be selected from a wide variety of compounds which are known to be useful constituents of nematic liquid crystal materials, for example those structural types of the part formulae 2.1 to 2.6 where Ra and Rb are independently alkyl or alkoxy:

Generally a nematic liquid crystal material of this aspect of the invention contains up to about 25 % by weight of a terphenyl of formula I. For twisted nematic (TN), Freedericksz effect, cholesteric to nematic phase change effect devices, the bulk of the material may usefully comprise compounds selected from formulae 2.1 to 2.6. If a cholesteric phase is required, one or more of the alkyl groups Ra or Rb may contain an asymmetric carbon atom, e.g. in a 2-methylbutyl group.

Certain alkoxymethylene terphenyls of formula I have been found to be particularly useful in liquid crystal materials which employ the electrically controlled birefringence (ECB) effect. In such materials one or more alkoxymethylene terphenyls of formula I may constitute up to about 50 % by weight, typically up to about 25 %. The bulk of such a mixture may usefully comprise compounds of the art formulae 3.1 to 3.6, in which Ra and Rb may be alkyl or alkoxy:

Certain alkoxymethylene terphenyls of formula I have been found to be useful components of liquid crystal materials which exploit the ferroelectric properties of the Sc* phase.

Certain terphenyls of formula I show smectic C phases which persist over a broad temperature range. Therefore this invention provides a liquid crystal material which shows an Se phase which is a mixture containing one or more terphenyls of formula I, and which may consist wholly of two or more terphenyls of formula I. To provide an Sc* phase, one of the constituents of this mixture must contain an asymmetric carbon atoms, and this constituent may itself be a terphenyl of formula I, but it is preferably a compound not of formula I.

Mixtures with an Se phase which contain in addition to one or more terphenyls of the formula I are particularly preferred.

Such a mixture may usefully contain compounds of the part formulae 4.1 to 4.8, in which Ra and Rb may be alkyl or alkoxy and X denotes 0 or S, preferably 0:

In the compounds of the formulae 4.1 to 4.8 one 1,4-phenylene group may be substituted by halogen, preferably by fluorine.

Preferred fluorinated forms of formulae 4.1 to 4.8 are those of the formulae 4.9 and 4.10:

The smectic phases according to the invention may also contain in addition to the compounds of the formula I and of the formulae 4 a component exhibiting a negative value of the dielectric anisotropy (A < -2), e.g. compounds of the formulae 5.1 to 5.12:

In which Ra and Rb are each independently alkyl or alkoxy or partielly fluorinated alkyl or alkoxy, preferably of the formula - -(O)p~(CH2)q-(CF2)p-X in which p is 0 and q is an integer of 0 to 6, p is an integer of 1 to 10 and y is H or F.

In Sc and Sc* mixtures of this aspect of the invention, terphenyls of formulae I,1 to I,6, especially I,1, I,2 and I,4 are preferred constituents as they show useful 5c phases.

When the Sc or Sc* material of this aspect of the invention does not consist wholly of alkoxymethylene terphenyls of formula I, other constituents are compounds which are known to be useful constituents of 5c and/or Sc* liquid crystal materials. A useful Sc* liquid crystal material may comprise a mixture of one or more terphenyls of formula I, plus one or more other compounds which contain an asymmetrically substituted carbon atom.

In an Sc* mixture of this aspect of the invention R1 and R2 are preferably of a longer carbon chain length than would be used for nematic materials, for example each preferably contains 5 or more carbon atoms. R1 and R2 are preferably n-alkyl or n-alkoxy in such mixtures.

The discovery that Sc* mixtures may be prepared using terphenyls of formula I, and their advantages, i.e. good 5c phases and fast switching speeds, are wholly unexpected over the prior art which refers exclusively to nematic or ECB mixtures. Indeed nematic or ECB mixtures are generally designed to exclude compounds which show smectic character.

Preferred compounds containing asymmetric carbon in an Sc* material of this aspect of the invention include the 1-methylheptyl (20ct*) esters disclosed in EP-A-0110299, or one or * more of the compounds containing a -COO.CH(CN) group disclosed in WO 87/07890 or UK Patent Applications 8729502, 8729503, 8729865 or 8729982.

Derivatives of the optical active lactic acid are disclosed in WO 86/02938 or PCT/GB 87/00132. Optical active derivatives of terpinoids are described in WO 85/04328, naphthoic esters in WO 87/06577, madelic acid esters in WO 88/02390 and derivatives of optical active amino acids are disclosed in WO 86/02937 or UK Patent Application 86 20 111.

The ciral dopants of the part formulae 6.1 to 6.6, wherein X denotes an alkoxy- or alkylamino-residue, Y denotes H, CF3 or CH3, m is 0 or 1, n is 1 or 2 and p is 0 or 1 are particularly preferred: Ra-(Phe) n - Phe-COO-20ct* 6.1

Ra-(Phe)n-Phe-CH2CH2-COO-2Oct* 6.4

Ra-(Phe)n-(COO)m-Phe-(CO)p-OC(CN)RR 6.6 In the compounds of the formulae 6.1 to 6.6 one or more group Phe may be substituted by fluorine, Ra and Rb are as defined above, Rb being preferably C1-C4 n-alkyl, cycloalkyl or branched alkyl.

Ra in the last-above formulae is preferably C5-C12 n-alkyl or n-alkoxy, particularly n-octyloxy. Rb is preferably methyl or a group of general formula

where a is 0 or an integer 1-6, and each of b and c are independently integers 1-6, preferably at least one of b or c being 1. R1 and R2 are each alkyl having a different number of carbon atoms or taken together preferably denote an alicyclic group, for example, of the formula:

When the Sc* mixture of this aspect of the invention contains two or more compounds which contain an asymmetric carbon atom, then two or more of these compounds may usefully be of opposite optical handedness, i.e. having (+) and (-) optical rotation or D and L stereoisomerism.In this way the length of the helical Sc* pitch may be controlled, and/or a useful SA phase may be induced, assisting alignment of the liquid crystal material with the electrodes of an electro-optic device.

Generally an Sc* mixture of this aspect of the invention contains 1 to 30 weight % of chiral dopant(s). The rest of the mixture may comprise one or more compounds of the formula I, especially of the formulae I,1 to I,6 or of I,13 and I,17 to I,19. The total being 100 weight %. Alternatively the Sc* mixture may consist of 1 to 30 weight % of chiral dopant(s), the rest being a mixture of compounds of formula I plus one or more of formulae 4,1 to 4,10 or 5,1 to 5,3 and/or other known smectic C components or other suitable additives.

Generally the weight % of the compounds of the formulae 4,1 to 4,10 or 5,1 to 5,3 will not exceed 80 % of the mixture.

The liquid crystal materials of this invention may be used in liquid crystal electro-optical display devices of known construction.

The examples which follow are intended to illustrate the invention without restricting it. Above and below percentages are percentages by weight; all temperatures are given in degree centigrade. "Customary work-up" means that water is added, the mixture is extracted with methylene chloride, the organic phase is separated off, dried and evaporated, and the product is purified by crystallization and/or chromatography.

The following abbreviations are used: m.p.= melting point c.p.= clearing point K = solid crystal N = nematic liquid crystal SA = smectic A liquid crystal Sc = smectic C liquid crystal I = isotropic liquid Example 1 Preparation of 4-n-heptyl-4" -(2-oxapentyl)-2',3'-difluoro-p- terphenyl Step 1.1

A solution of the Grignard Reagent prepared from 4-n-heptyl-1-brombenzene and Mg in dry THF (250 ml) is added dropwise to a stirred, cooled (-78 OC) solution of tri-isopropyl borate in dry THF (40 ml) under dry N2. The stirred mixture is allowed to warm to room temperature overnight and stirred with 10 % HCl at room temperature for 1 h. The product is extracted into ether twice, and the combined etheral extracts are washed with water and dried.

SteP 1.2

A solution of 0.05 mol 4-n-heptyl-1-brombenzene in ethanol is added dropwise to a stirred mixture of 40 ml 0.05 mol 2,3-difluorophenyl boronic acid and 1 g tetrakis (triphenylphosphine) palladium (0) in 100 ml benzene and 50 ml 2M-Na2CO3 at room temperature under dry N2. The stirred mixture is heated under reflux until glc analysis confirmed absence of starting materials. The product is extracted with ether and dried (MgSO4). The solvent is removed and the residue is purified by column chromatography and cristallization.

Step 1.3

A solution n-butyllithium (10.0 M in hexane) is added dropwise to a stirred cooled solution (-78 OC) of 0.5 mol 4'-nheptyl-2,3-difluoro-biphenyl in 100 ml dry THF under dry N2.

The stirred mixture is maintained under these conditions for 2.5 h and then a cooled solution of tri-isopropylborate in dry THF is allowed to warm to room temperature overnight and then stirred for 1 h at room temperature with 10 % HC1. The product is extracted and combined etheral extracts are washed with water and dried. The solvent is removed in vacuo.

Step 1.4

The product of Step 1.3 is coupled with l-bromo-4-(2-oxapentyl)benzene in an analogous manner as described in step 1.

K 57 N 85 I Analogously are obtained the following compounds of the formula

RI R2 L3 L4 L5 L6 n C2H5 CH3 F F H H 1 C2H5 CH3 F F H H 2 C2H5 C2H5 F F H H 1 C2H5 C2H5 F F H H 3 C2H5 n-C3H7 F F H H 1 C2H5 n-C3H7 F F H H 2 R R L L4 L5 L6 n C2H5 n-C5Hg F F H H 1 C2H5 n-C5H9 F F H H 3 n-C3H7 CH3 F F H H 1 n-C3H7 CH3 F F H H 2 n-C3H7 C2M5 F F H H 1 n-C3H7 C2H5 F F H H 2 n-C3H7 C2H5 F F H H 3 n-C3H7 n-C3H7 F F H H 1 n-C3H7 n-C3H7 F F H H 2 n-C3H7 n-C5Hg F F H H 1 n-C3H7 n-C5Hg F F H H 3 n-C5H11 CH3 F F H H 1 n-C5H11 CH3 F F H H 2 n-C5H11 C2H5 F F H H 1 n-C5H11 C2H5 F F H H 3 n-C5H11 n-C3H7 F F H H 1 n-C5H11 n-C3H7 F F H H 2 n-C5H11 n-C3H7 F F H H 1 n-C5H11 n-C3H7 F F H H 2 n-C5H11 n-C5Hg F F H H 1 n-C5H11 n-C5Hg F F H H 2 n-C7Hl5 CH3 F F H H 1 n-C7H11 CH3 F F H H 3 K 59 N 105,2 n-C7H15 C2H5 F F H H 1 n-C7H15 C2H5 F F H H 2 K30N81,1 I n-C7H11 n-C3H7 F F H H 3 R1 R2 L3 L4 L5 L6 n n-C7H15 n-C5H11 F F H H 1 n-C7H15 n-C5H11 F F H H 2 n-C9H19 CH3 F F H H 1 n-C9H19 CH3 F F H H 3 n-C9H19 C2H5 F F H H 1 n-C9H19 C2H5 F F H H 2 n-C9H19 n-C3H7 F F H H 1 n-C9H19 n-C3H7 F F H H 2 n-C9H19 n-C5H11 F F H H 1 n-C9H19 n-C5H11 F F H H 2 OC2H5 CH3 F F H H 1 OC2H5 CH3 F F H H 2 OC2H5 C2H5 F F H H 1 OC2H5 C2H5 F F H H 2 OC2H5 n-C3H7 F F H H 1 OC2H5 n-C3H7 F F H H 3 OC2H5 n-C5H11 F F H H 1 OC2H5 n-C5H11 F F H H 2 OC3H7 n-C5H11 F F H H 1 OC3H7 n-C5H11 F F H H 3 OC3H7 CH3 F F H H 1 OC3H7 CH3 F F H H 2 OC3H7 C2H5 F F H H 1 OC3H7 C2H5 F F H H 3 OC3H7 n-C3H7 F F H H 1 OC3H7 n-C3H7 F F H H 2 R1 R2 L3 L4 L5 L6 n OC5H11 CH3 F F H H 1 OC5H11 CH3 F F H H 3 OC5H11 C2H5 F F H H 1 OC5H11 C2H5 F F H H 2 OC5H11 n-C3H7 F F H H 1 OC5H11 n-C3H7 F F H H 2 OC5H11 n-C5H11 F F H H 1 OC5H11 n-C5H11 F F H H 2 OC5H11 n-C5H11 F F H H 3 n-C3H7 CH3 H H F F 1 n-C3H7 CH3 H H F F 2 n-C3H7 CH3 H H F F 3 n-C3H7 C2H5 H H F F 1 n-C3H7 C2H5 H H F F 2 n-C3H7 n-C3H7 H H F F 1 n-C3H7 n-C3H7 H H F F 2 n-C3H7 n-C3H7 H H F F 3 n-C3H7 n-C5H11 H H F F 1 n-C3H7 n-C5H11 H H F F 2 n-C5H11 CH3 H H F F 1 n-C5H11 CH3 H H F F 2 n-C5H11 CH3 H H F F 3 n-C5H11 C2H5 H H F F .1 n-C5H11 C2H5 H H F F 2 n-C5H11 n-C3H7 H H F F 1 n-C5H11 n-C3H7 H H F F 2 R1 R2 L3 L4 L5 L6 n n-C5H11 n-C3H7 H H F F 3 n-C5H11 n-C5H11 H H F F 1 n-C5H11 n-C5H11 H H F F 2 n-C7H15 CH3 H H F F 1 n-C7H15 CH3 H H F F 2 n-C7H15 C2H5 H H F F 1 n-C7H15 C2H5 H H F F 2 n-C7H11 C2H5 H H F F 3 n-C7H15 n-C3H7 H H F F 1 K ? SC 60 SA 110 1 n-C7H15 n-C3H7 H H F F 2 n-C7H15 n-C3H7 H H F F 3 n-C7H15 n-C5H11 H H F F 1 n-C7H15 n-C5H11 H H F F 2 n-C9H19 CH3 H H F F 1 n-C9H19 CH3 H H F F 2 n-C9H19 CH3 H H F F 3 n-C9H19 C2H5 H H F F 1 n-CgHl9 C2H5 H H F F 2 n-C9H19 n-C3H7 H H F F 1 n-C9H19 n-C3H7 H H F F 2 n-C9H19 n-C3H7 H H F F 3 n-C9H19 n-C5H11 H H F F 1 n-C9H19 n-C5H11 H H F F 2 Example 2 Preparation of 4-n-nonyl-4" -(2-oxapentyl)-2'-fluoroterphenyl SteP 2.1

n-Nonyl-phenyl boronic acid (prepared as described in step 1.1) is coupled with 1-bromo-2-fluorobenzene in an analogous manner as described in step 1.2.

SteP 2.2

A solution of 0.4 mol bromine in 50 ml CHCl3 is added dropwise to a stirred, cooled (0-5 OC) solution of the biphenyl in 200 ml CHCl3. The stirred mixture is allowed to warm to room temperature for 2 h. The product is washed with water and dried.

Step 2.3

The product of step 2.2 is coupled with 4-(2-oxa-pentyl)phenyl boronic acid in an analogous manner as described in step 1.2. K 34 Sc 64 N 96 I Analogously are obtained the following compounds of the formula

R1 R2 n C2H5 CH3 1 C2H5 CH3 2 C2H5 C2H5 1 C2H5 C2H5 2 C2H5 C3H7 1 C2H5 C3H7 3 C2H5 C5Hll 1 C2H5 C5H11 2 C3H CH3 1 C3H7 CH3 2 C3H7 C2H5 1 C3H7 C2H5 3 C3H7 C3H 1 C3H7 C3H7 2 C3H7 C5H11 1 C3H7 C5H11 3 C5H11 CH3 1 C5H11 CH3 2 C5Hll C2H5 1 C5H11 C2H5 3 C5H11 C3H7 1 C5H11 C3H7 2 R1 R2 n C5Hll C5Hll 1 C5H11 C5H11 3 n-C7H15 CH3 1 n-C7H15 CH3 2 n-C7H15 CH3 3 K 43.7 SB 44.3 Sc 71.6 SA 77.2 N 124.0 I n-C7H15 C2H5 1 n-C7H15 C2M5 2 K 28 SB 50 SA 89 N 104 I n-C7H15 C3M7 1 K 27 SC 54 N 100 I n-C7H15 C3H7 2 n-C7H15 C5H11 1 n-C7H15 C5H11 2 n-C9H19 CH3 1 n-C9H19 CH3 3 K 41.7 SB 45.4 SC 68.2 SA 94.6 N 118.0 I n-C9H19 C2H5 1 n-C9H19 C2H5 2 n-C9H19 C5H11 1 n-C9H19 C5H11 2 OC2H5 CH3 1 OC2H5 CH3 3 OC2H5 C2H5 1 OC2H5 C2H5 2 OC2H5 C2H5 3 OC2H5 C3H7 1 OC2H5 C5H11 1 OC3H7 CH3 1 R1 R2 n OC3H7 C2H5 1 OC3H7 C3H7 1 OC3H7 C5H11 1 OC5H11 CH3 1 OC5H11 C2H5 1 OC5H11 C3H 1 OC5H11 C5H11 1 Example 3 Preparation of 4-n-heptyl-4''-(2-oxapentyl)-3'-fluoro- terphenyl step 3.1

4-n-heptylbrombenzene is coupled with 4-methoxy-3-bromo-phenyl boronic acid in an analogous manner as described in step 1.2.

Step 3.2

BBr3 is added to 0,01 mol 4'n-heptyl-3-fluoro-4-methoxybiphe- nyl dissolved in 30 ml CH2Cl2.The reaction is stirred at room temperature and after customary work-up the 4'-n-heptyl-3fluoro-4-hydroxybiphenyl is obtained.

SteP 3.3

0,013 mol 4'-n-heptyl-3-fluoro-4-hydroxybiphenyl is dissolved in 30 ml pyrimidine. 0,014 mol trifluoromethane sulfonic anhydride is added dropwise at 0 OC. This reaction mixture is left to stand for 16 hrs. Then the mixture is added to H2O and after customary work-up the triflate is obtained.

step 3.4

The triflate is coupled with 4-(2-oxa-pentyl)phenyl boronic acid in an analogous manner as described in step 1.2.

Analogously are obtained the following compounds of the formula

R R n C2H5 CH3 1 C2 CH3 2 C2H5 C2H5 1 C2H5 C2H5 3 C2H5 C3H7 1 C2H5 C3H 2 C2H5 C5Hll 1 C2H5 C5H1l 2 C2H5 C5Hll 3 R1 R2 n n-C3H7 CH3 1 n-C3H7 CH3 2 n-C3H7 C2H5 1 n-C3H7 C2H5 2 n-C3H7 C3H7 1 n-C3H7 C3H? 2 n-C3H7 C5Hll 1 n-C3H7 C5H11 2 n-C5H11 CH3 1 n-C5H11 CH3 2 n-C5H11 C2H5 1 n-C5H11 C2H5 3 n-C5H11 C3H7 1 n-C5H11 C3H7 3 nC5H11 C5H11 1 n-C5H11 C5H11 2 n-C5H11 C5H11 3 n-C7H15 CH3 1 n-C7H15 CH3 2 n-C7H15 CH3 3 K ? SB 71.2 SA 99.3 N 118.9 I n-C7H15 C2H5 1 n-C7H15 C2H5 2 K ? SB 73 SA 105 N 105.3 I n-C7H15 C2H5 3 n-C7H15 C5H11 1 n-C7H15 C5H11 2 n-C7H15 C5H11 3 R R n n-C9H19 CH3 1 n-C9H19 CH3 2 n-C9H19 CH3 3 n-C9H19 C2H5 1 n-C9H19 C2H5 2 n-C9H19 C3H7 1 n-C9H19 C3H7 2 n-C9H19 C3H7 3 n-C9H19 C5H11 1 n-C9H19 C5H11 2 n-C9H19 C5H11 3 OC2H5 CH3 1 OC2H5 C2H5 1 OC2H5 C3H7 1 OC2H5 C5Hll 1 OC3H7 CH3 1 OC3H7 C2H5 1 OC3H7 C3H7 1 OC3H7 C5H11 1 OC5H11 CH3 1 OC5H11 C2H5 1 OC5H11 C3H7 1 OC5H11 C5H11 1

Claims (11)

1. Claims 1. Alkoxymethylene fluoroterphenyls of the formula I,

   in which R1 is alkyl or alkoxy with 1 to 15 C-atoms, R2 is alkyl with 1 to 10 C-atoms, n is 1 to 7, and L1 to L6 are H or F, at least one or two of L1 to L6 being F, the others being H.
2. 2. Derivatives of Claim 1 which are selected from the fol lowing group of fluoroterphenyls
3. 3. Use of the compounds of the formula I as components of liquid crystalline phases.
4. 4. Liquid crystalline medium containing at least two liquid crystalline components, characterized in that it contains one component of the formula I.
5. 5. Liquid crystalline composition according to Claim 4 which is a nematic composition.
6. 6. Liquid crystalline composition according to Claim 4 which is a chiral tilted smectic composition.
7. 7. Liquid crystalline display element, characterized in that it contains a liquid crystalline medium according to Claim 4.
8. 8. Electrooptical display element, characterized in that it contains a liquid crystalline phase according to Claim 4.

   AMENDMENTS TO THE CLAYS HAVE BEEN FLED AS FOLLOWS
9. 9. An alkoxymethylene fluoroterphenyl, substantially as hereinbefore described in any of examples 1, 2 or 3.
10. 10. A liquid crystalline medium containing at least two liquid crystalline components, characterised in that one of said components is an alkoxymethylene fluoroterphenyl, as claimed in claim 9.
11. 11. A liquid crystalline display element, or an electrooptical display element, characterised in that it contains a liquid crystalline medium, as claimed in claim 10.