LIQUID CRYSTALLINE TRIFLUORO-SUBSTITUTED COMPOUNDS

Abstract: Compounds are provided of the formula for use in a range of liquid crystal display devices (formula I) wherein n may be 0, 1 or 2, A1, A2, A3 are independently chosen from 1,4-disubstituted benzene, 2,5-disubstituted pyridine, 2,6-disubstituted naphthalene; laterally substituted 1,4-disubstituted benzene, laterally substituted 2,5-disubstituted pyrimidine, laterally substituted 2,5-disubstituted pyridine, laterally substituted 2,5-disubstituted naphthalene wherein the lateral substituents are independently selected from F, CI, Br or CN and may be present in any of the available substitution positions; 1,4-disubstituted bicyclo(2.2.2)octane, trans-1,4-disubstituted cyclohexane, trans-2,5-disubstituted dioxane, 1,4-disubstituted piperidine, Z1, Z2 are independently chosen from a direct bond, COO, OOC, C2H4, CH2O, OCH2, C4H8, C3H6O, (E)-CH=CHC2H4, (Z)-CH2CH=CHCH2, (E)-CH=CHCH2O, -C=C-, Z3 may be C4H8, OC3H6, (E)-CH=CHC2H4, (Z)-CH2CH=CHCH2, (E)-OCH2CH=CH, -C=C-, C2H4; R may be alkyl, alkoxy, alkenyl, alkenyloxy, alkanoyloxy, alkenoyloxy or OCmF2m+1, R may contain 1 to 20 carbon atoms and may be branched or a straight chain m is 1-20.

Description: Liquid Crystalline Trifluoro-substituted Compounds The present invention describes new compounds. In particular it describes compounds for use in liquid crystal mixtures and in liquid crystal displays (LCDs) or in applications relating to inter alia thermography utilising nematic liquid crystal or chiral nematic liquid crystal mixtures. LCDs, such as multiplexed Twisted Nematic TN-LCDs, Super Twisted Nematic STN-LCDs, Super Birefringent SBE-LCDs, Electrically Controlled Birefringence ECB-LCDs, or flexoelectric LCDs are currently used or being developed for computer monitors, laptop or notebook computers, portable telephones, video telephones, personal digital assistants, etc. The optical, electrical and temporal performance, e.g., contrast, threshold and driving voltages, and response times, of such displays depends crucially on the ratios of the elastic constants (k 33 , k 22 , k ) and the cell gap, d. Currently commercially available nematic mixtures for sophisticated high-information-content LCDs, such as STN-LCDs, incorporate trans- 1 ,4- disubstituted-cyclohexyl derivatives with a terminal alkenyl chain (i.e., incorporating a carbon-carbon double bond) directly attached to the cyclohexane ring in order to produce the necessary elastic constant ratios for short response times, high multiplexing rates and low driving voltages. Such materials are costly and difficult to synthesise due to the requirement for a trans configuration of the 1 ,4-disubstituted cyclohexane ring and the necessity of synthesising the carbon-carbon double bond stepwise from this trans ,4-disubstituted- cyclohexyl intermediate. If the carbon-carbon double bond is substituted at both carbon atoms, it must have a trans (E) configuration in order to exhibit an advantageous combination of elastic constants and to have an acceptably high nematic-isotropic transition temperature (N-l). The trans configuration is then generally produced by isomerisation of the cis (Z) form generated by the preceding Wittig reaction. These materials exhibit low or intermediate values of birefringence (Δn) due to the presence of the saturated cyclohexane rings. As the ratio d. Δn determines the optical properties of TN-LCDs and is fixed for driving the LCD in the first or second minimum, it is clear that higher values of Δn would allow smaller cell gaps. As the response time, t on of TN-LCDs is inversely proportional to d 2 , smaller cell gaps have a dramatic effect on t on . Low values of t on also allow the use of colour or more shades of colour due to the shorter frame times. Furthermore TN-LCDs using thin film transistors (TFTs) as the backplate for active addressing require nematic liquid crystal mixtures with a positive dielectric anisotropy (Δε) and a very high resistivity (holding ratio >98%) in order to avoid dielectric breakdown and inferior display performance. It has been shown that standard nematic liquid crystals with a terminal cyano group are unsuitable for TN-TFT-LCDs since they lead to low resisitivity values due in part to their ability to solvate ions present in the alignment layers and electrodes. This has led to the wide-spread use of 'super-fluorinated' nematic liquid crystals with terminal trifluoromethoxy (DE 3732284 A1), difluoromethyl (WO 90/01056) or fluorine endgroups (JP2-233626, EPA 0 568 040 A1 , EPA 0 563 981 A2) and/or several lateral fluoro substituents. However, this leads in general to low nematic-isotropic transition temperatures (N-l) for two-ring compounds. This requires a disproportionate use of three-ring compounds resulting in a high viscosity for the nematic mixture. There is therefore a requirement for synthetically readily-accessible nematic liquid crystals of positive dielectric anisotropy, high resistivity and a relatively high value of N-l. Liquid crystals with a trifluoromethyl group are known and are described in for example P. Le Barney, G. Ravaux, J. C. Dubois and J. P. Parneix, Mol. Cryst. Liq. Cryst, (1985), Vol. 127, pp 413 and EPA 0 480 217. Liquid crystal materials comprising fluorine containing end-groups are described in WO 98/13321 , WO 96/05159, WO 90/13610, DE 4415882 and DE 4222371. For all the above applications it is not usual for a single compound to exhibit all of the properties highlighted, normally mixtures of compounds are used which when mixed together induce the desired phases and required properties. The present invention seeks to overcome or alleviate some of the above problems. According to this invention compounds are provided of Formula I: Formula I wherein n may be 0, 1 or 2 A-,, A 2 , A 3 are independently chosen from 1 ,4-disubstituted benzene, 2,5-disubstituted pyrimidine, 2,5-disubstituted pyridine, 2,6-disubstituted naphthalene; laterally substituted 1 ,4-disubstituted benzene, laterally substituted 2,5-disubstituted pyrimidine, laterally substituted 2,5-disubstituted pyridine, laterally substituted 2,6- disubstituted naphthalene wherein the lateral substituents are independently selected from F, Cl, Br or CN and may be present in any of the available substitution positions; 1 ,4-disubstituted bicyclo(2.2.2)octane, trar/s-1 ,4-disubstituted cyclohexane, trans-2,5- disubstituted dioxane, 1 ,4-disubstituted piperidine, Z Z 2 are independently chosen from a direct bond, COO, OOC, C 2 H 4 , CH 2 O, OCH 2 , C 4 H 8 , C 3 H 6 O, (E)-CH=CHC 2 H 4 , (Z)-CH 2 CH=CHCH 2 , (E)-CH=CHCH 2 O, -C≡C- _ Z 3 may be C 4 H 8 , OC 3 H 6 , (E)-CH=CHC 2 H 4 , (Z)-CH 2 CH=CHCH 2 , (£)-OCH 2 CH=CH, -C≡C— _ C 2 H 4; R may be alkyl, alkoxy, alkenyl, alkenyloxy, alkanoyloxy, alkenoyloxy or OC m F 2m+1 , R may contain 1 to 20 carbon atoms and may be branched or a straight chain; m is 1-20. The structural and other preferences are expressed below on the basis of inter alia desirable liquid crystalline characteristics, in particular an advantageous combination of dielectric constants and high resistivity in the nematic phase, a high nematic-isotropic liquid transition temperature and ready synthesis from commercially available starting materials, some of which may already incorporate at least one carbon-carbon double bond with the desired configuration and position. Overall preferred structures for formula I are those listed below: Preferably n is 0 or 1 ; Preferably A^ A 2 , A 3 , are 1 ,4-disubstituted benzene, 2,5-disubstituted pyrimidine, trans-2,5- disubstituted dioxane, 1 ,4-disubstituted piperidine, or trans- 1 ,4-disubstituted cyclohexane; Preferably Z Z 2 are direct bonds, C 2 H 4 or ~ C=C — Preferably Z 3 are (E)-CH=CHC 2 H 4 or (£)-OCH 2 CH=CH; Preferably R is alkyl, alkoxy, alkenyl or alkenyloxy and has one to seven carbon atoms. Especially preferred structures for formula I are those listed below: Preferably Z 3 are (£)-CH=CHC 2 H 4 or (E)-OCH 2 CH=CH; Preferably R is alkyl, alkoxy, alkenyl or alkenyoxy and contains 1-7 carbon atoms. Compounds of formula I can be prepared by various routes. Typically the ethers can be prepared by the Mitsunobu reaction (Synthesis, (1981) pp 1) of a phenol with an ω,ω,ω- trifluoroalcohol in the presence of triphenyl phosphine, a dehydrating agent, such as diethyl azodicarboxylate, and a suitable solvent, such as tetrahydrofuran or N,N'- dimethylformamide. Alternatively they can be synthesised by alkylation of a secondary alkanol with ω,ω,ω-trifluoroalkyl bromide or the tosylate of the appropriate ω,ω,ω- trifluoroaikanol in the presence of a suitable base, such as potassium tert.-butoxide, and a suitable solvent, such as tert. -butyl-methyl ether or 1 ,2-dimethoxyethane (J. Mater. Chem., (1994) Vol. 4, pp 1673). Alternatively they can be synthesised by alkylation of a phenol with ω,ω,ω-trifluoroalkyl bromide or the tosylate of the appropriate ω,ω,ω-trifluoroalkanol in the presence of a suitable base, such as potassium carbonate, and a suitable solvent, such as ethyl methyl ketone or cyclohexanone in a Williamson ether synthesis. The dioxanes can be prepared by reaction of an aldehyde with a 2-substituted 1 ,3-diol in an appropriate solvent such as toluene catalysed by a small amount of an acid such as sulphuric acid or toluene-4- sulphonic acid under azeotropic removal of water. N-Arylpiperidines can be obtained by condensation of a 4-substituted piperidine with an aryl fluoride with an appropriate base such as potassium carbonate in a suitable solvent such as acetonitrile or hexamethylphosphoric triamide (Synthesis, (1981), pp 606). The (£)-5,5,5-trifluropent-1-enyl substituted compounds can be prepared using a Wittig reaction involving a 4,4,4-trifluorobutanal and appropriate Wittig salts (EPA 0 480 217 A2) in a suitable solvent such as tetrahydrofuran or dimethoxyethane with an appropriate base such as potassium tert.-butoxide or butyl lithium. The corresponding 5,5,5-trifluoropentyl substituted compounds can be prepared by hydrogenation of the (E)-5,5,5-trifluropent-1-enyl substituted compounds with hydrogen over a suitable catalyst such as palladium on charcoal in an appropriate solvent such as toluene or ethyl acetate. 1 ,2-Disubstituted acetylenes and tolanes can be prepared by metal catalysed cross-coupling reactions of mono-substituted acetylenes with aryl and cyclohexyl halides or triflates in the presence of an appropriate base such as triethylamine and appropriate metal based catalysts such as tetrakis(t phenylphosphine)palladium(0) and copper(l)iodide or palladium(ll) acetate and triorthotoluylphosphine ligands (Mol. Cryst. Liq. Cryst., (1990), Vol. 148, pp 193; Mol. Cryst. Liq. Cryst., (1995), Vol. 260, pp 93). The esters can be prepared by esterification (Angewandte Chemie (1978) Vol. 90, pp 556) of the appropriate phenol or secondary alcohol with an alkanoic acid or alkenoic acid in the presence of 4-(dimethylamino)pyridine, a dehydrating agent, such as N, N'- dicyclohexylcarbodiiimide, and a suitable solvent, such as dichloromethane or N, N'- dimethylformamide. Alternatively they can be synthesised by esterification of the appropriate phenol or secondary alcohol with an alkanoic or alkenoic acid chloride (produced, for example, from the corresponding alkanoic or alkenoic acid by the action of thionyl chloride or oxalyl chloride) in the presence of a base, such as pyridine or triethylamine, and a suitable solvent, such as toluene or dichloromethane. The invention will now be described, by way of example only, with reference to the following examples and diagrams: Figure 1 is a plan view of a matrix multiplex addressed liquid crystal display; Figure 2 is a cross-section of a display such as Figure 1 used in a transmissive mode; Figure 3 is similar to Figure 2 but operates in a reflective mode. In the following examples K refers to the crystalline state, N the nematic phase, SmA a smectic A phase, SmB a smectic B phase and SmX an undefined crystal smectic phase. Values contained in brackets [ ] are nematic-isotropic transition temperatures extrapolated from mixtures of individual compounds and the commercially available (Merck, Darmstadt) nematic mixture ZLI 3086. Example 1. Preparation of 1-(4-pentylbicyclo[2.2.2]octyl)-4-(4,4,4-trifluorobutyloxy)benzene A mixture of 4,4,4-trifluoro-1-bromobutane (0.19 g), 4-(4-pentylbicyclo[2.2.2]octyl)phenol (0.25 g) [Mol. Cryst. Liq. Cryst, (1985) Vol. 129, pp 301)], potassium carbonate (0.50 g) and butanone (40 crτ)3) was heated under reflux overnight, filtered to remove inorganic material and then evaporated down. The residue was purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.04 g of 1-(4-pentylbicyclo[2.2.2]octyl)-4-(4,4,4-trifluorobutyloxy)benzene, K 65 °C, N 51 °C, I. The following compounds could be obtained analogously: 1-(4-Propylbicyclo[2.2.2]octyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(4-Heptylbicyclo[2.2.2]octyl)-4-(4,4,4-trifluorobutyloxy)benzene. 4-Propyl-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 97 °C, SmB 108 °C, SmA 1 16 °C, I. 4-Pentyl-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 63 °C, SmB 99 °C, SmA 103 °C, I: [N 63°C, I] 4-Heptyl-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 29 °C, SmX 40 °C, SmB 98 °C, I: [N 36 °C, I]. 4-Propyl-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-Pentyl-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-Heptyl-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 56 °C, SmA 52 °C, I: [N -5 °C, I]. 1-(trans-4-Propylcyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene, K 50°C, I. 1-(trat7S-4-Pentylcyclohexyl)-4-(4,4,4-thfluorobutyloxy)benzene, K 49°C, I: [N 21 °C, I]. 1-(trans-4-Heptylcyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-Propylcyclohexyl)-3-fluoro-4-(4,4,4-trifluorobutyloxy)benzene. 1-(tra/7s-4-Pentylcyclohexyl)-3-fluoro-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-Heptylcyclohexyl)-3-fluoro-4-(4,4,4-trifluorobutyloxy)benzene. 1-[2-(t^rat?s-4-Pentylcyclohexyl)-1-ethyl]-4-(4,4,4-trifluorobutyloxy)benzene. 1-[4-(trans-4-Pentylcyclohexyl)-1-butyl]-4-(4,4,4-trifluorobutyloxy)benzene. 1-[4-(£)-(4- t l rat7s-4-Pentylcyclohexyl)-1-but-1-enyl]-4-(4,4,4-trifluorobutyloxy)benzene. 1-[3-(£)-(4-trans-4-Pentylcyclohexyl)-1-prop-2-enyloxy]-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-[(-Ξ)-Prop-1-enyl]cyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-[(E^-Pent-1-enyl]cyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-[(Z)-Pent-2-enyl]cyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-4-[(£)-Pent-3-enyl]cyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trarjs-4-[Pent-4-enyl]cyclohexyl)-4-(4,4,4-trifluorobutyloxy)benzene. 4-(4-Propylbicyclo[2.2.2]octyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Pentylbicyclo[2.2.2]octyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. K 80°C, SmB 205°C, SmA 247°C, 4-(4-Heptylbicyclo[2.2.2]octyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-Propyl-4"-(4,4,4-trifluorobutyloxy)-p-terphenyl. 4-Pentyl-4"-(4,4,4-trifluorobutyloxy)-p-terphenyl, K 203°C, SmA 267°C, I 4-Heptyl-4"-(4,4,4-trifluorobutyloxy)-p-terphenyl. 4-(trans-4-Propylcyclohexyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trans-4-Pentylcyclohexyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 54°C, SmB 113°C, SmA 167°C, N 171 °C, I. 4-(trat?s-4-Heptylcyclohexyl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trans-4-Propylcyclohexyl)-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trans-4-Pentylcyclohexyl)-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl, K 76°C, SmB 119°C, SmA 177°C, I. 4-(trans-4-Heptylcyclohexyl)-3'-fluoro-4'-(4,4,4-trifluorobutyloxy)biphenyl. 1-(5-Propylpyrimidin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(5-Pentylpyrimidin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(5-Heptylpyrimidin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(5-Propylpyridin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(5-Pentylpyridin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(5-Heptylpyridin-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 4-(5-Propylpyrimidin-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(5-Pentylpyhmidin-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(5-Heptylpyrimidin-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 41-(5-Propylpyridin-2-yl)-4'-(4,4,4-thfluorobutyloxy)biphenyl. 4-(5-Pentyipyridin-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(5-Heptylpyridin-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. Example 2. Preparation of 1-(4-pentylbicyclo[2.2.2]octyl)-4-[(E)-4,4,4-trifluorobut-2- enyloxy]benzene. A mixture of (E)-4,4,4-trifluorobut-2-enyl toluene-4-sulfonate (0.7 g), 4-(4- pentylbicyclo[2.2.2]octyl)phenol (0.5 g), potassium carbonate (1.1 g) and butanone (40 cm 3 ) was heated under reflux overnight, filtered to remove inorganic material and then evaporated down. The residue was purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.05 g of 1- (4-pentylbicyclo[2.2.2]octyl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene, K 68 °C, N 42 °C, I. The (E)-4,4,4-trifluorobut-2-enyl toluene-4-sulfonate required as starting material could be prepared as follows: A solution of toluene-4-sulfonyl chloride (11.4 g) in dichloromethane (10 cm 3 ) was added slowly to a solution of (£)-4,4,4-trifluorobut-2-en-1-ol (0.40 g), pyridine (6.3 g) and dichloromethane (40 cm 3 ) at 0°C. The reaction mixture was stirred at 0°C for 24 h, washed with dilute hydrochloric acid (2 x 50 cm 3 ), water (2 x 50 cm 3 ) and dilute sodium carbonate solution (2 x 50 cm 3 ), dried (MgSO4), filtered and then evaporated down to yield 5.4 g of the desired tosylate, which was used without further purification. The following compounds could be obtained analogously: 1-(4-Propylbicyclo[2.2.2]octyl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(4-Heptylbicyclo[2.2.2]octyl)-4-[(£)-4,4,4-trifluorobut-2-enyloxy]benzene. 4-Propyl-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl, K < 25 °C, SmX 106 °C, SmB 136 °C, I. 4-Pentyl-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl, K 66 °C, SmX 116 °C, SmB 123 °C, I: [N 53°C, I]. 4-Heptyl-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl, K < 25 °C, SmX 107 °C, SmB 117 °C, I: [N 48 °C, I]. 4-Propyl-3'-fluoro-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-Pentyl-3'-fluoro-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-Heptyl-3'-fluoro-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl, K 64 °C, SmB 60 °C, SmA 63 °C, I: [N 20 °C, I]. 1-(trans-4-Propylcyclohexyl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene: K 50°C, I. 1-(trans-4-Pentylcyclohexyl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene; K 41 °C, I: [N 15°C, !]• 1-(trans-4-Heptylcyclohexyl)-4-(4,4,4-thfluorobutyloxy)benzene. 1-(trans-4-Propylcyclohexyl)-3-fluoro-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(frans-4-Pentylcyclohexyl)-3-fluoro-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(trat?s-4-Heptylcyclohexyl)-3-fluoro-4-[(£)-4,4,4-trifluorobut-2-enyloxy]benzene. 4-(4-Propylbicyclo[2.2.2]octyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(4-Pentylbicyclo[2.2.2]octyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. K 111 °C, SmA 169°C, N 235°C. 4-(4-Heptylbicyclo[2.2.2]octyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-Propyl-4"-[(£)-4,4,4-trifluorobut-2-enyloxy]-p-terphenyl. 4-Pentyl-4"-[(E)-4,4,4-trifluorobut-2-enyloxy]-p-terphenyl: K 239°C, SmB 245°C, SmA 270°C, I. 4-Heptyl-4"-[(£)-4,4,4-trifluorobut-2-enyloxy]-p-terphenyl. 4-(trar;s-4-Propylcyclohexyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(tra/7S-4-Pentylcyclohexyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl: K 91 °C, SmB 167°C, N 269°C, I. 4-(trans-4-Heptylcyclohexyl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(trat7S-4-Propylcyclohexyl)-3'-fluoro-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(frar)S-4-Pentylcyclohexyl)-3'-fluoro-4'-[(£)-4,4,4-trifluorobut-2-enyloxy]biphenyl: K 94°C, SmB 110°C, SmA 161 I. 4-(trans-4-Heptylcyclohexyl)-3'-fluoro-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 1-(5-Propylpyrimidin-2-yl)-4-[(£)-4,4,4-thfluorobut-2-enyloxy]benzene. 1-(5-Pentylpyrimidin-2-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(5-Heptylpyrimidin-2-yl)-4-[(£)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(5-Propylpyridin-2-yl)-4-[(E)-4,4,4-trifluorobut-2-enyioxy]benzene. 1-(5-Pentylpyridin-2-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(5-Heptylpyridin-2-yl)-4-[(£)-4,4,4-trifluorobut-2-enyloxy]benzene. 4-(5-Propylpyrimidin-2-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(5-Pentylpyrimidin-2-yl)-4'-[(tΞ)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(5-Heptylpyrimidin-2-yl)-4'-[(E)-4,4,4-thfluorobut-2-enyloxy]biphenyl. 41-(5-Propylpyridin-2-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(5-Pentylpyridin-2-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(5-Heptylpyridin-2-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. Example 3. Preparation of 1-(4-propylpiperid-1-yl)-4-(4,4,4-trifluorobutyloxy)benzene A mixture of 4-propylpiperidine (0.7 g), 1-fluoro-4-[4,4,4-trifluorobutyloxy]benzene (0.5 g), potassium carbonate (1.1 g), Aliquat 333 (4 drops) and acetonitrile (40 cm 3 ) is heated at 90 °C overnight, and then poured into water (500 cm 3 ). The organic layer is separated off and the aqueous layer extracted with ethyl acetate (4 x 100 cm 3 ). The combined organic layers were washed with brine (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.6 g of 1-(4- propylpiperid-1-yl)-4-(4,4,4-trifluorobutyloxy)benzene. The 1-fluoro-4-[4,4,4-trifluorobutyloxy]benzene required as starting material could be prepared as follows: A mixture of 4,4,4-trifluorobutyl bromide (0.7 g), 4-fluorophenol (1.0 g), potassium carbonate (1.1 g) and butanone (40 cm 3 ) is heated under reflux overnight, filtered to remove inorganic material and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent to yield 0.8 g of 1-fluoro-4- [4,4,4-trifluorobutyloxy]benzene. The following compounds could be obtained analogously: 1 -(4-Butylpiperid-1 -yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1 -(4-Pentylpiperid-1 -yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1 -(4-Hexylpiperid-1 -yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1 -(4-Heptylpiperid-1 -yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1 -(4-Octylpiperid-1 -yl)-4-(4,4,4-trifluorobutyloxy)benzene. 4-(4-Propylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Butylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Pentylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Hexylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Heptylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(4-Octylpiperid-1-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 1-(4-Propylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(4-Butylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy}benzene. 1-(4-Pentylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(4-Hexylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(4-Heptylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 1-(4-Octylpiperid-1-yl)-4-[(E)-4,4,4-trifluorobut-2-enyloxy]benzene. 4-(4-Propylpiperid-1-yl)-4'-[(£)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(4-Butylpiperid-1-yl)-4'-[(E)-4,4,4-thfluorobut-2-enyloxy]biphenyl. 4-(4-Pentylpiperid-1-yl)-4'-[(£)-4,4,4-thfluorobut-2-enyloxy]biphenyl. 4-(4-Hexylpiperid-1-yl)-4'-[(£)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(4-Heptylpiperid-1-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. 4-(4-Octylpiperid-1-yl)-4'-[(E)-4,4,4-trifluorobut-2-enyloxy]biphenyl. Example 4. Preparation of 1-(trans-5-propyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene A mixture of 1 ,3-dihydroxy-2-propylpropane (0.3 g), 4-[4,4,4-trifluorobutyloxy]benzaldehyde (0.5 g), toluene-4-sulphonic acid (0.1 g) and toluene (40 cm 3 ) is heated under reflux until water is no longer azeotroped off and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.3 g of 1-(trans-5-propyldioxan-2-yl)-4-(4,4,4- trifluorobutyloxy)benzene. The 4-[4,4,4-trifluorobutyloxy]benzaldehyde required as starting material could be prepared as follows: A mixture of 4,4,4-trifluorobutyl bromide (0.7 g), 4-hydroxybenzaldehyde (0.5 g), potassium carbonate (1.1 g) and butanone (40 cm 3 ) is heated under reflux overnight, filtered to remove inorganic material and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.6 g of 4-[4,4,4-trifluorobutyloxy]benzaldehyde. The following compounds could be obtained analogously: 1-(frar/s-5-Butyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trans-5-Pentyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trar/s-5-Hexyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trar/s-5-Heptyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 1-(trar/s-5-Octyldioxan-2-yl)-4-(4,4,4-trifluorobutyloxy)benzene. 4-(trans-5-Propyldioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trar/s-5-Butyldioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trans-5-Pentyidioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trat?s-5-Hexyldioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trans-5-Heptyldioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. 4-(trarjs-5-Octyldioxan-2-yl)-4'-(4,4,4-trifluorobutyloxy)biphenyl. Example 5. Preparation of trans-1-(trans-4-propylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1- enyljcyclohexane A mixture of potassium tert.-butylate (2.9 g) is added portionwise to a mixture of 4,4,4- trifluorobutanal (1.0 g), 4-(trar/s-4-propylcyclohexyl)phenyl)methylphosphoniumbromide (3.1 g) and tetrahydrofuran (100 cm 3 ) at 0 °C. The reaction is stirred for a further 2 h at room temperature and then poured into water (500 cm 3 ). The organic layer is separated off and the aqueous layer extracted with diethyl ether (4 x 100 cm 3 ). The combined organic layers were washed with brine (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The crude isomeric mixture of trans-1-(trans-4-propylcyclohexyl)-4-[(EτZ)-5,5,5-trifluoropent- 1-enyl]cyclohexane is dissolved in a mixture of ethanol (50 cm 3 ), water (1 cm 3 ) and freshly prepared benzene sulphinic acid (2 g), heated at 65 °C for 48 h and then poured into water (500 cm 3 ). The organic layer is separated off and the aqueous layer extracted with diethyl ether (4 x 100 cm 3 ). The combined organic layers were washed with brine (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 1.3 g of trans-1-(trans-4-propylcyclohexyl)-4-[(E)-5,5,5- trifluoropent-1-enyl]cyclohexane. The 4,4,4-trifluorobutanal required as starting material could be prepared as follows A solution of 4,4,4-trifluorobutanol (10 g) in dichoromethane (20 cm 3 ) is added dropwise to a suspension of pyridine chlorochromate (15 g) and dichloromethane (100 cm 3 ) at room temperature. The reaction mixture is stirred at this temperature for 2 h and then diethyl ether (50 cm 3 ) is added. The reaction mixture is stirred for a further 15 min before decanting off the organic layer and washing the residue with ether. The combined organic layers are washed with brine (2 x 100 cm 3 ), dried (MgSO 4 ), filtered and evaporated down to yield (6.2 g) of 4,4,4-trifluorobutanal, which is used without further purification. The following compounds could be obtained analogously: trans-1-(trar/s-4-Butylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]cyclohexane. trans- -(trans-4-Pentylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1-enyl]cyclohexane. tra/?s-1-(trar/s-4-Hexylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]cyclohexane. trar?s-1-(trat)s-4-Heptylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]cyclohexane. trar/s-1-(trans-4-Octylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1-enyl]cyclohexane. 1-(trans-4-Butylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1-enyl]benzene. 1-(trans-4-Pentylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1-enyl]benzene. 1-(trans-4-Hexylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]benzene. 1-(trans-4-Heptylcyclohexyl)-4-[(E)-5,5,5-thfluoropent-1-enyl]benzene. 1-(trar/s-4-Octylcyclohexyl)-4-[(£)-5,5,5-trifluoropent-1-enyl]benzene. 4-(trans-4-Propyicyclohexyl)-4'-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. 4-(trans-4-Butylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. 4-(trans-4-Pentylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. 4-(trans-4-Hexylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. 4-(trans-4-Heptylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. 4-(traA7s-4-Octylcyclohexyl)-4'-[(E)-5,5,5-trifluoropent-1-enyl]biphenyl. Example 6. Preparation of 1-(tra/?s-4-propylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene A mixture of 1-(trat7s-4-propylcyclohexyl)-4-[(E)-5,5,5-trifluoropent-1-enyl]benzene (1.0 g), 10 % palladium on charcoal (0.2 g) and toluene (20 cm 3 ) is hydrogenated until the absorption of hydrogen is completed. The inorganic material was removed by filtration and the filtrate evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.7 g of 1-(trans-4-propylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. The following compounds could be obtained analogously: 1-(trans-4-Butylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. 1-(trat7s-4-Pentylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. 1-(trat7S-4-Hexylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. 1-(trans-4-Heptylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. 1-(trat7s-4-Octylcyclohexyl)-4-(5,5,5-trifluoropentyl)benzene. 4-(trans-4-Propylcyclohexyl)-4'-(5,5,5-trifluoropentyl)biphenyl. 4-(trans-4-Butylcyclohexyl)-4-(5,5,5-trifluoropentyl)biphenyl. 4-(trans-4-Pentylcyclohexyl)-4'-(5,5,5-trifluoropentyl)biphenyl. 4-(trat?s-4-Hexylcyclohexyl)-4'-(5,5,5-trifluoropentyl)biphenyl. 4-(trans-4-Heptylcyciohexyl)-4-(5,5,5-trifluoropentyl)biphenyl. 4-(trar?s-4-Octylcyciohexyl)-4'-(5,5,5-trifluoropentyl)biphenyl. trans-1-(trans-4-Propyicyclohexyl)-4-(5,5,5-trifluoropentyl)cyclohexane. tra/7s-1-(trar/s-4-Butylcyclohexyl)-4-(5,5,5-trifluoropentyl)cyclohexane. trar/s-1 -(trans-4-Pentylcyclohexyl)-4-(5,5,5-trifluoropentyl)cyclohexane. trat7s-1-(trar/s-4-Hexylcyclohexyl)-4-(5,5,5-trifluoropentyl)cyclohexane. trar/s-1 -(trar;s-4-Heptylcyclohexyl)-4-(5, 5, 5-trifluoropentyl)cyclohexane. trans-1-(tra/7s-4-Octylcyclohexyl)-4-(5,5,5-trifluoropentyl)cyclohexane. Example 7. Preparation of 1-(4-tetradecylphenyl)-2-(4-[4,4,4- trifluorobutyloxy]phenyl)acetylene A mixture of 1-iodo-4-(4,4,4-trifluorobutyloxy]benzene (0.50 g), 4-tetradecylphenylacetylene (0.65 g), copper(l)iodide (0.01 g) and triethylamine (20 cm 3 ) is heated at 90 °C overnight, poured into water (500 cm 3 ) and then extracted with diethyl ether (4 x 100 cm 3 ). The combined organic layers are washed with brine (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.7 g of 1-(4-tetradecylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. The following compounds could be obtained analogously: 1-(4-Propylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene: K 106°C, I: [N 83°C, I]. 1-(4-Butylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetyiene: K 98°C, SmX 86°C, I: [N 85°C, I]. 1-(4-Hexylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Heptylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene: K 76°C, SmX 91 °C, I: [N 85°C, I]. 1-(4-Octylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Nonylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Decylphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetyiene. 1-(4-Propylphenyl)-2-(4-[(£)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene: K 130°C, I: [67°C] 1-(4-Butylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene: K 106°C, SmB 120°C, I: [N 74°C, I]. 1-(4-Hexylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Heptylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene: K 87°C, SmB 121 °C, I: [N 76°C, I]. 1-(4-Octylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Nonylphenyl)-2-(4-[(£)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Decylphenyl)-2-(4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Propylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Butylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Hexylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Heptylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Octylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Nonylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Decylphenyl)-2-(4-[5,5,5-trifluoropentyl]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(3,5-difluoro-4-[(£)-4,4,4-t fluorobut-2-enyloxy]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(3-fluoro-4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(2-Fluoro-4-pentylphenyl)-2-(3-fluoro-4-[(E)-4,4,4-trifluorobut-2-enyloxy]phenyl)acetylene. 1-(2,6-Difluoro-4-pentylphenyl)-2-(3-fluoro-4-[(E)-4,4,4-trifluorobut-2- enyloxy]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(3,5-difluoro-4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Pentylphenyl)-2-(3-fluoro-4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(2-Fluoro-4-pentylphenyl)-2-(3-fluoro-4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(2,6-Difluoro-4-pentylphenyl)-2-(3-fluoro-4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. Example 8. Preparation of 1-(4-[(E)-hex-2-enoyloxy]phenyl)-2-(4-[4,4,4- trifluorobutyloxy]phenyl)acetylene A solution of N, N-dicyclohexylcarbodiimide (0.22 g) in dichloromethane (10 cm 3 ) is added to a solution of (£)-hex-2-enoic acid (0.10 g), 1-(4-hydroxyphenyl)-2-(4-[4,4,4- trifluorobutyloxy]phenyl)acetylene (0.32 g), 4-(dimethylamino)pyridine (0.04 g) in dichloromethane (20 cm 3 ), cooled in an ice bath (0°C) under an atmosphere of nitrogen. The reaction mixture is stirred overnight, filtered to remove precipitated material and the filtrate is evaporated down under reduced pressure. The crude product is purified by column chromatography on silica gel using a 9:1 petroleum ether (40-60°C)/ethyl acetate mixture as eluent, followed by recrystallisation from ethanol to yield 1-(4-[(E)-hex-2-enoyloxy]phenyl)-2- (4-[4,4,4-trifluorobutyloxy]phenyl)acetylene (0.26 g). The 1-(4-hydroxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene required as starting material could be prepared as follows: A mixture of sodium ethoxide (0.7 g), 1 ,2-di(4-hydroxyphenyl)acetylene (0.5 g), and toluene (40 cm 3 ) is stirred for 2 h, 4,4,4-trifluorobutyl bromide (0.7 g), is added and the resultant mixture heated under reflux for 3 h. The reaction mixture is poured into water (500 cm 3 ) and the organic layer separated off. The aqueous layer is then extracted with toluene (2 x 50 cm 3 ). The combined organic layers are washed with water (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.3 g of 1-(4-hydroxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. The following compounds could be obtained analogously: 1-(4-[(E)-But-2-enoyloxy]phenyl)-2-(4-[4,4,4-t fluorobutyloxy]phenyl)acetylene. 1-(4-[(E)-Pent-2-enoyloxy]phenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-[(E)-Hept-2-enoyloxy]phenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-[(E)-Oct-2-enoyloxy]phenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Acetoxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Propanoyloxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Butanoyloxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Pentanoyloxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Hexanoyloxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Heptanoyloxyphenyl)-2-(4-[4,4,4-trifluorobutyloxy]phenyl)acetylene. 1-(4-Octanoyloxyphenyl)-2-(4-[4,4,4-thfluorobutyloxy]phenyl)acetylene. Example 9. Preparation of 1-(4-[trans-4-pentylcyclohexyl]phenyl)-2-(3,3,3- trifluoropropyl)acetylene A mixture of 1-iodo-3,3,3-trifluoropropane (0.50 g), (4-[trans-4- pentylcyclohexyl]phenyl)acetylene (0.65 g), copper(l)iodide (0.01 g) and triethylamine (20 cm 3 ) is heated at 90 °C overnight, poured into water (500 cm 3 ) and then extracted with diethyl ether (4 x 100 cm 3 ). The combined organic layers are washed with brine (2 x 200 cm 3 ), dried (MgSO 4 ), filtered and then evaporated down. The residue is purified by column chromatography on silica gel using a 95:5 hexane/ethyl acetate mixture as eluent and recrystallisation from ethanol to yield 0.7 g of 1-(4-[trat7s-4-pentylcyclohexyl]phenyl)-2-(3,3,3- trifluoropropyl)acetylene. The following compounds could be obtained analogously: 1-(4-[trans-4-Propylcyclohexyl]phenyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(4-[tra/7s-4-Butylcyclohexyl]phenyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(4-[trat?s-4-Pentylcyclohexyl]phenyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(4-[trat7S-4-Hexylcyclohexyl]phenyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(4-[tra/ιs-4-Heptylcyclohexyl]phenyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(trat7s-4-[trar?s-4-Propylcyclohexyl]cyclohexyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(trar/s-4-[trans-4-Butylcyclohexyl]cyclohexyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(trans-4-[trans-4-Pentylcyclohexyl]cyclohexyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(trar/s-4-[trar;s-4-Hexyicyclohexyl]cyclohexyl)-2-(3,3,3-trifluoropropyl)acetylene. 1-(trar/s-4-[trans-4-Heptylcyclohexyl]cyclohexyl)-2-(3,3,3-trifluoropropyl)acetylene. Some of the compounds described by the current invention were investigated in the host mixture DOP-017 which is a mixture of alkylcyclohexyl-COO-phenylOR and alkylcyclohexylphenylCN. The compounds were individually doped 10% into the host and the clearing points determined. The structure of the compounds and the phase behaviour of the mixtures is detailed in Table 1. A compound WD30 is shown for comparison. Table 1 The dielectric permittivities and elastic constants were determined and are shown in Table 2. Table 2 The birefringence and refractive indices of the mixtures were determined and the results are shown in Table 3 with DOP-017 for comparison. Table 3 One known device in which the materials of the current invention may be incorporated is the twisted nematic (TN) device which uses a thin layer of a nematic material between glass slides. The slides are unidirectionally rubbed and assembled with the rubbing directions orthogonal. The rubbing gives a surface alignment to the liquid crystal molecules resulting in a progressive 90° twist across the layer. When placed between polarisers, with their optical axis perpendicular or parallel to a rubbing direction the device rotates the plane of polarised light in its OFF state and transmits without rotation in the ON state. Small amounts of cholesteric material may be added to the nematic material to ensure the 90° twist is of the same sense across the whole area of the device as explained in UK patents 1 ,472,247 and 1 ,478,592. An improvement in the performance of large, complex, nematic LCDs occurred in 1982 when it was observed that the voltage dependence of the transmission of nematic LC layers with twist angles in the range 180° to 270° could become infinitely steep, see CM. Waters, V. Brimmell and E.P. Raynes, Proc. 3rd Int. Display Res. Conf., Kobe, Japan, 1983, 396. The larger twist angles are produced by a combination of surface alignment and making the nematic mixture into a long pitch cholesteric by the addition of a small amount of a chiral twisting agent. The increasing twist angle steepens the transmission/voltage curve, until it becomes bistable for 270° twist; for a specific twist angle between 225° and 270° the curve becomes infinitely steep and well suited to multiplexing. The larger twist angles present have resulted in the name supertwisted nematic (STN) for these LCDs. Liquid Crystal Devices describing the use of STNs may be found in patent application GB 8218821 and resulting granted patents including US 4596446. SID M6/1-37 volume 1 seminar lecture notes, May 1998 describes both active and passive STNs in which the materials of the current invention may be incorporated. 16 Two types of device are commonly known as passive matrix and active matrix liquid crystal devices. The display of Figures 1 and 2 comprises a liquid crystal cell 1 formed by a layer 2 of cholesteric liquid crystal material contained between glass walls 3,4. A spacer ring 5 maintains the walls typically 6μm apart. For passive matrix devices strip like row electrodes 6-, to 6 m , e.g. of SnO 2 are formed on one wall 3 and similar column electrodes 7, to 7 n formed on the other wall 4. With m-row electrodes and n-column electrodes this forms an mxn matrix of addressable elements. Each element is formed by the interaction of a row and column electrode. For active matrix devices a discrete nonlinear device eg a transistor or diode is associated with each pixel. For the passive matrix device a row driver supplies voltage to each row electrode 6. Similarly a column drive 9 supplies voltages to each column electrode 7. Control of applied voltages is from a control logic 10 which receives power from a voltage source 11 and timing from a clock 12. For an active device e.g., a thin film transistor active matrix liquid crystal device (TFT AMLCD) three types of electrodes are present, pixel, scanning and signal electrodes as well as a common electrode on the opposite side of the liquid crystal. The control electrode operates the gate such that the voltage on the signal electrode is applied to the relevant pixel electrode. An example of the use of a material and device embodying the present invention will now be described with reference to Figure 2. The liquid crystal device consists of two transparent plates, 3 and 4, for example made from glass, in the case of an active matrix device these will usually be ofaluminosilicate (alkali free) glass often with a passivation layer of SiO 2 . For an active matrix display the active devices eg thin film transistors, are fabricated and the colour filter layer is added for a full colour display. These plates are coated on their internal face with transparent conducting electrodes 6 and 7, often ITO which is patterned using photolithography techniques. An alignmentlayer is introduced onto the internal faces of the cell so that a planar orientation of the molecules making up the liquid crystalline material will be approximately parallel to the glass plates 3 and 4. This is done by coating the glass plates 3,4 complete with conducting electrodes; the intersections between each column and row electrode form an x, y matrix of addressable elements or pixels. For some types of display the alignment directions are orthogonal. Prior to the construction of the cell the alignment layers are rubbed with a roller covered in cloth (for example made from velvet) in a given direction, the rubbing directions being arranged parallel (same or opposite direction) upon construction of the cell. A spacer 5 e.g. ofpolymethyl methacrylate separates the glass plates 3 and 4 to a suitable distance e.g. 2-7 microns preferably 4-6 microns. Liquid crystal material 2 is introduced between glass plates 3,4 by filling the space in between them. This may be done by flow filling the cell using standard techniques. The spacer 5 is sealed with an adhesive in a vacuum using an existing technique. Polarisers 13 may be arranged in front of and behind the cell. Alignment layers may be introduced onto one or more of the cell walls by one or more of the standard surface treatment techniques such as rubbing, oblique evaporation or as described above by the use of polymer aligning layers. In alternative embodiments the substrates with the aligning layers on them are heated and sheared to induce alignment, alternatively the substrates with the aligning layers are thermally annealed above the glass transition temperature and below the liquid crystal to isotropic phase transition in combination with an applied field. Further embodiments may involve a combination of these aligning techniques. With some of these combinations an alignment layer may not be necessary. It is also possible to use so-called non-contact alignment layers in both passive and active devices described by the current invention. The device may operate in atransmissive or reflective mode. In the former, light passing through the device, e.g. from a tungsten bulb, is selectively transmitted or blocked to form the desired display. In the reflective mode a mirror, or diffuse reflector, (16) is placed behind the second polariser 13 to reflect ambient light back through the cell and twopolarisers. By making the mirror partly reflecting the device may be operated both in atransmissive and reflective mode. The alignment layers have two functions, one to align contacting liquid crystal molecules in a preferred direction and the other to give a tilt to these molecules - a so called surface tilt - of a few degrees typically around 4° or 5°. The alignment layers may be formed by placing a few drops of the polyimide on to the cell wall and spinning the wall until a uniform thickness is obtained. The polyimide is then cured by heating to a predetermined temperature for a predetermined time followed by unidirectional rubbing with a roller coated with a nylon cloth. In an alternative embodiment a single polariser and dye material may be combined. The materials of the current invention may also be used in LCDs with an actively addressed matrix e.g. thin film transistors (TFT-LCDs) or a passively addressed matrix e.g., dual scan STN. SID M3/1-52 volume 1 seminar lecture notes, May 1998 describes a typical AMLCD in which the materials of the current invention may be incorporated.

Claims: Claims 1. Compounds given by Formula I: Formula I wherein n may be 0, 1 or 2 Ai, A 2 , A 3 are independently chosen from 1 ,4-disubstituted benzene, 2,5-disubstituted pyrimidine, 2,5-disubstituted pyridine, 2,6-disubstituted naphthalene; laterally substituted 1 ,4-disubstituted benzene, laterally substituted 2,5-disubstituted pyrimidine, laterally substituted 2,5-disubstituted pyridine, laterally substituted 2,6- disubstituted naphthalene wherein the lateral substituents are independently selected from F, Cl, Br or CN and may be present in any of the available substitution positions; 1 ,4-disubstituted bicyclo(2.2.2)octane, trar/s-1 ,4-disubstituted cyclohexane, trans-2,5- disubstituted dioxane, 1 ,4-disubstituted piperidine, Z , Z 2 are independently chosen from a direct bond, COO, OOC, C 2 H 4 , CH 2 O, OCH 2 , C 4 H 8 , C 3 H 6 O, (E)-CH=CHC 2 H 4 , (Z)-CH 2 CH=CHCH 2 , (£)-CH=CHCH 2 O, -C≡C— _ Z 3 may be C 4 H 8 , OC 3 H 6 , (E)-CH=CHC 2 H 4 , (Z)-CH 2 CH=CHCH 2 , (E)-OCH 2 CH=CH, -C≡C- f C 2 H 4; R may be alkyl, alkoxy, alkenyl, alkenyloxy, alkanoyloxy, alkenoyloxy or OC m F 2m+1 , R may contain 1 to 20 carbon atoms and may be branched or a straight chain; m is 1-20. . Compounds of the following formulae: F wherein Z 3 are (E)-CH=CHC 2 H 4 or (E)-OCH 2 CH=CH; R is alkyl, alkoxy, alkenyl or alkenyoxy and contains 1-7 carbon atoms. 3. A liquid crystal mixture comprising at least one of the compounds of claim 1 or claim 2. 4. A device comprising two spaced cell walls each bearing electrode structures and treated on at least one facing surface with an alignment layer, a layer of a liquid crystal material enclosed between the cell walls, characterised in that it comprises a compound of claim 1 or 2. 5. A device comprising two spaced cell walls each bearing electrode structures and treated on at least one facing surface with an alignment layer, a layer of a liquid crystal mixture enclosed between the cell walls, characterised in that it incorporates a liquid crystal mixture of claim 3. 6. A liquid crystal device according to claim 4 or 5 wherein the device is an Active Matrix Device. 7. A liquid crystal device according to any of claims 4, 5 and 6 wherein the device is an STN device. 8. A liquid crystal device according to any of claims 4, 5 and 6 wherein the device is a TN device.

Inventors: KELLY STEPHEN MALCOLM, SKELTON GRAHAM WILLIAM, KELLY, STEPHEN, MALCOLM, SKELTON, GRAHAM, WILLIAM
Applicants: KELLY STEPHEN MALCOLM, SECR DEFENCE, SKELTON GRAHAM WILLIAM, KELLY, STEPHEN, MALCOLM, SKELTON, GRAHAM, WILLIAM, THE SECRETARY OF STATE FOR DEFENCE
Application year: 1999
Main classification: C07C43
IPC codes: C07C17, C07C22, C07C43, C07C45, C07D211, C07D213, C07D239, C07D295, C07D319, C09K19, G02F1