RING COMPOUNDS

Abstract: Ring compounds of formula (I), wherein R<1> denotes an alkyl residue of up to 12 carbon atoms wherein one or two CH2 groups may also be replaced by -O- and/or -CH=CH-, m is 1 or 2, L<1>, L<2> and L<3> are each independently H or F, and X is F, Cl, -CN, -CF3, -OCF3 or -OCHF2 or has one of the meanings given for R<1>, are suitable as components of liquid crystal media.

Description: Ring Compounds The invention relates to ring compounds of formula I wherein R denotes an alkyl residue of up to 12 carbon atoms wherein one or two CH- groups may also be replaced by -O- and/or -CH=CH-, m is 1 or 2, 1 2 3 L , and L are each independently H or F, and X is F, Cl, -CN, -CF 3 , -OCF 3 or -OCHF 2 or has one of the meanings given for R . The compounds of the formula I can be used as components of liquid crystal media, in particular for displays which are based on the principle of the twisted nematic cell, including TN cells with a higher twist angle like_ STN, SBE, O I etc., on the guest-host effect, on the effect of deformation of orientated phases or on the effect of dynamic scattering. The compounds of the formula I can also be used for two-frequency switching systems. Compounds similar to those of formula I are known from DE 3040 632. These compounds exhibit on the one hand a neutral or positive dielectric anisotropy. But on the other hand they have a rather small mesophase range and generally show smectic structures. The invention was based on the object of discovering new stable liquid crystalline or mesogenic compounds which show favorable elastic properties and are especially suitable for supertwist displays without exhibiting the shortcomings of the prior art compounds. Surprisingly, it has been found that the compounds accord¬ ing to formula I meet these criteria to an outstanding degree and allow the realization of very steep electro- optic characteristics and simultaneously a low tempera- ture dependency of the threshold voltages in particular in supertwist displays. By providing the compounds of the formula I, the range of liquid crystal substances which are suitable, under various technological aspects for the preparation of nematic mix- tures is also quite generally widened considerably. The compounds of the formula I have a wide field of appli¬ cation. Depending on the selection of the substituents, these compounds can be used as base materials from which liquid crysta! phases are predominantly composed; however, compounds of the formula I can also be added to liquid crystal base materials from other classes of compounds, for example in order to optimize the dielectric and/or optical anisotropy of such a dielectric. SUBSTITUTE SHEET The compounds of the formula I are colourless in the pure state and form liquid crystal mesophases in a temperature range which is favorably placed for electrooptical use. They are very stable towards chemicals, heat and light. The invention thus relates to the compounds of the formula I and the use of these compounds as components of liquid crystal media. The invention furthermore re¬ lates to liquid crystal media containing at least one compound of the formula I and to liquid crystal display elements, in particular electrooptical display elements, which contain media of this type. Above and below R , L , L 2, 3, m and X have the mentioned meaning, unless expressly stated otherwise. The compounds of the formula I accordingly include pre¬ ferred species of the part formulae la to Ic: In the compounds of these formulae R is preferably alkyl, furthermore also alkenyl or alkyl or alkenyl groups in which one CH 2 -group is replaced by oxygen. SUBSTITUTE SHEET If R and/or X are alkyl and/or alkoxy groups, these can be straight-chain or branched. Preferably, they are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms and are accordingly preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, methoxy, octoxy or nonoxy. Oxaalkyl is preferably straight-chain 2-oxapropyl (= methoxymethyl), 2-(= ethoxymethyl) or 3-oxybutyl (= 2- methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxa- hexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl or 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl. If R and/or X are alkenyl groups these can be straight- chain or branched. Preferably, they are straight-chain and have 2 to 8 C atoms. They are accordingly, in particular, vinyl, prop-1- or prop-2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3-, -4-, -5- or -6-enyl or oct-1-, -2.-., -3-, -4-, -5-, -6- or -7-enyl. If R and/or X are alkenoxy groups these can be straight chain or branched. Pre erably they are straight-chain and are given via formula II -0-(C_32) r -CH = CH-C Aχ+1 II wherein r is 1 or 2 and X runs from 0 to 6. Trans-isomers of both the alkenyl and the alkenoxy groups are preferred. Compounds of the formula I with branched terminal groups R and/or X can be of importance because of a better solu¬ bility in the customary liquid crystal base materials, but in particular as chiral doping substances if they are optically active. Branched groups oft this type as a rule contain not more than one chain branching. Preferred branched groups are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2- methylpropyl), 2-methylbutyl, isopentyl, (= 3-methyl- butyl), 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3- methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 1-methyl- heptoxy (= 2-octyloxy), 2-oxa-3-methylbutyl, 3-oxa-4- methylpentyl, 4-methylhexyl and 6-methyloctoxy. In the case of compounds with branched terminal groups, formula I- includes both the optical antipodes and racemates as well as mixtures thereof. X is preferably F, Cl, -CN, -CF 3 , -OCF 3 or -OCHF 2 . -OCF 3 and -OCHF 2 are especially preferred. m is preferably 1. Of the compounds of the formula I and subformulae thereof, those in which at least one of the radicals contained therein has one of the preferred meanings given are pre- ferred. 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), SUBSTITUTESHEET 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 substances 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. A preferred route to make these compounds by is as follows: Heck Reaction Pd/C/B^ Friedel Crafts Reaction Huang M n on reduct on SUBSTITUTESHEET Another preferred route is as follows: (b) Pd/C/H 2 Finally a third preferred route is as follows: SUBSTITUTESHEET Other methods of making compounds of formula I are apparent to those skilled in the art. In addition to one or more compounds of formula I the liquid crystal media according to the invention prefer- ablv contain 2-40 components and in particular 4-30 com¬ ponents. Liquid crystal media being composed of one or more compounds of formula I and 7-25 other components are especially preferred. These additional components are preferably chosen from the nematic or nematogenic (monotropic or isotropic) substances; in particular from the classes of azoxy- benzenes, benzylideneanilines, biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl cyclohexanecarboxylates, phenyl or cyclohexyl cyclo- hexylbenzoates, phenyl or cyclohexyl cyclohexylcyclo- hexanecarboxylates, cyclohexylphenylbenzoates, cyclohexyl- phenyl cyclohexanecarboxylates, cyclohexylphenyl cyclo- hexylcyclohexanecarboxylates, phenylcyclohexanes, cyclohexyl- biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclo- hexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclo- hexene, 1,4-bis-cyclohexylbenzenes, 4,4'-bis-cyclohexyl- biphenyls, phenyl- or cyclohexylpyrimidineε, phenyl- or cyclohexylpyridines, phenyl- or cyclohexyldioxanes, phenyl- or cyclohexyl-l,3-dithianes, 1,2-diphenylethanes, 1,2-di- cyclohexylethanes, l-phenyl-2-cyclohexylethanes, 1-cyclo- hexyl-2-(4-phenyl-cyclohexyl)-ethanes, l-cyclohexyl-2-bi- phenylethanes, l-phenyl-2-cyclohexyl-phenylethanes, optio¬ nally halogenated stilbenes, benzyl phenyl ethers, tolaneε and substituted cinnamic acids. SUBSTITUTESHEET The 1,4-phenylene groups of these compounds may be fluorinated. The most important compounds which are possible consti¬ tuents of liquid crystal media according to the invention can be characterized by the formalae 1, 2, 3, 4 and 5: R'-L-E-R" 1 R'-L-COO-E-R" 2 R f -L-OOC-E-R" 3 R'-L-CH 2 CH 2 -E-R" 4 R'-L-C≡C-E-R" 5 In the formulae 1, 2, 3, 4 and 5 L and E may be equal or different from each other. L and E independently from each other denote a bivalent residue selected from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe-, -G-Cyc- and their mirror images; in this compilation of residues Phe denotes un- substituted or fluorinated 1,4-phenylen, Cyc trans- 1,4- cyclohexylene or 1,4-cyclohexenylen, Pyr pyrimidine-2,5- diyl or pyridine-2,5-diyl, Dio l,3-dioxane-2,5-diyl and G 2-(t ans-l,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or l,3-dioxane-2,5-diyl. One of the residues L and E is preferably Cyc, Phe. or Pyr. E preferably denotes Cyc, Phe or Phe-Cyc. The liquid crystal media according to the invention preferably con- tain one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E meaning Cyc, Phe and Pyr, said liquid crystal media further containing at the same time one ore more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with one of the residues L and E denoting Cyc, Phe and Pyr and the other residue being selected from the group consisting of -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Cyc-, said liquid SUBSTITUTESHEET crystal media containing in addition to this optionally one or more components selected from the compounds of formulae 1, 2, 3, 4 and 5 with L and E being selected from the group consisting of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc. In a preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 1) R 1 and R" are independent¬ ly from each other alkyl, alkenyl, alkoxy, alkenoxy with up to 8 carbon atoms. R' and R" differ from one another in most of these compounds, one of the residues usually being alkyl or alkenyl. In another preferred subgroup of the compounds of formulae 1, 2, 3, 4 and 5 (subgroup 2) R" denotes -CN, -CF 3 , -F, -Cl or -NCS while R 1 has the meaning indicated in subgroup 1 and is preferably alkyl or alkenyl. Other variants of the envisaged substituents in the compounds of formulae 1, 2, 3, 4 and 5 are also customary. Many such substances are commercially available. All these substances are obtainable by methods which are known from the literature or by analogous methods. The liquid crystal media according to the invention pre¬ ferably contain in addition to components selected from subgroup 1 also components of subgroup 2, the percentage of these components being as follows: subgroup 1: 20 to 90 %, in particular 30 to 90 % subgroup 2: 10 to 50 %, in particular 10 to 50 % In these liquid crystal media the percentages of the com¬ pounds according to the invention and the compounds of sub¬ group 1 and 2 may add up to give 100 %. SUBSTITUTE SHEET The media according to the invention preferably contain 1 to 40 %, in particular 5 to 30 % of the compounds according to the invention. Media containing more than 40 %, in particular 45 to 90 % of the compounds accor- ding to the invention are further preferred. The media contain preferably 3, 4 or 5 compounds according to the invention. The media according to the invention are prepared in a manner which is customary per se. As a rule, the com- ponents are dissolved in one another, advantageously at elevated temperature. The liquid crystal media accor¬ ding to the invention can be modified by suitable addi¬ tives so that they can be used in all the types of liquid crystal display devices. Such additives are known to the expert and are described in detail in the literature (H. Kelker/R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, it is possible to add pleochroic dyestuffs to prepare colored guest-host systems or substances for modifying the dielectric aniso- tropy, the viscosity and/or the orientation of the nematic phases. The following examples are to be construed as merely illustrative and not limitative, m.p. = melting point, c.p. = clearing point. In the foregoing and in the fol- lowing.all parts and percentages are by weight and the temperatures are set forth in degrees Celsius. "Custo¬ mary work-up" means that water is added, the mixture is extracted with methylene chloride, the organic phase is seperated off, dried and evaporated, and the product is purified by crystallization and/or chromatography. .j' _. C_ 2 U U t __ snas ■ Further are: C: crystalline-solid state, S: smectic phase (the index denoting the typ of smectic phase), N: nematic phase, Ch: cholesteric phase, I: isotropic phase. The number being embraced by 2 of these symbols denotes the tem¬ perature of phase change. Examples of production Example 1 Reduction of trans-4-n-propylcyclohexylmethyl-[p-2- (3,4-difluorophenyl)-ethyl-phenyl]-ketone (obtained as shown in the scheme above) according to Huang Min¬ ion yields 2-[p-(trans-4-propylcyclohexylethyl)-phenyl]- ethyl-3,4-difluorobenzene, K 34 N 40 I. Examples 2 to 18 The following compounds (m = 1) are obtained analogously: R 1 L 1 L 2 L 3 X (2) n-pentyl H H F F (3) n-pentyl H H H F (4).n-propyl H H H F (5) n-propyl H H H CN (6) n-pentyl H H H CN (7) n-propyl H H F CN (8) n-propyl H H H Cl (9) n-propyl H H H CF 3 (10) n-propyl H H H OCF 3 (11) n-propyl H H H OCHF 2 (12) n-propyl H H H OC 2 H 5 (13) n-pentyl H H H OC 2 H 5 (14) n-pentyl H H H -C 3 H 7 (15) n-propyl H F H -C 3 H 7 (16) n-propyl H H F - C 3 H 7 (17) n-propyl F H H OCF3 (18) n-propyl H H F OCHF 2 Examples 19 - 35 The following compounds (m = 2 ) are obtained analogously: L 1 L 2 L 3 X (19) n-pentyl H H F F (20) n-pentyl H H H F (21).n-propyl H H H F ,K685148N194I (22) n-propyl H H H CN (23) n-pentyl H H H CN (24) n-propyl H H F CN (25) n-propyl H H H Cl (26) n-propyl H H H CF 3 SUBSTITUTE SHEET (27) n-propyl H H H OCF 3 (28) n-propyl H H H OCHF 2 (29) n-propyl H H H 0C 2 H 5 (30) n-pentyl H H H OC 2 H 5 (31) n-pentyl H H H -C 3 H ? (32) n-propyl H F H -C 3 H ? (33) n-propyl H H F "C 3 H 7 (34) n-propyl F H H OCF 3 (35) n-propyl H H F OCHF 2 Example36 A liquid crystalline medium containing 15 % of the three ring compound of example 1 and 85 % of a mix¬ ture consisting of 24 % trans-4-n-propylcyclohexyl- benzonitrile, 36 % of trans-4-n-pentylcyclohexyl-benzo- nitrile, 25 % of txans-4-n-heptylcyclohexyl-benzoni * - trile and 15 % of 4'-cyano-4-(trans-4-n-pentylcyclo- hexyl)-biphenyl shows N 67.6 I and a viscosity of 27 mPa.s at 20 °C. SUBSTITUTE 3HI

Claims: Claims Ring compounds of formula I wherein denotes an alkyl residue,of up to 12 carbon atoms wherein one or two GE groups may also be replaced by -O- and/or -CH=CH-, m is 1 or 2, L 1, L2 and L3 are each independently H or F, and X is F t Cl, -CN, -CF 3 , -OCF 3 or -OCHF 2 or has one of the meanings given for R . 2. Liquid crystalline medium being a mixture of at least two compoxmds, characterized in that at least one compound is a compound according to claim 1. SUBSTITUTE SHEET 3. Liquid crystal display device, characterized in that it contains a liquid crystalline medium according to claim 2. 4. Electrooptical display device, characterized in that it contains a liquid crystalline medium according to claim 2. SUBSTITUTE SHEET

Inventors: BAXTER D, COATES DAVID, GREENFIELD SIMON, HITTICH REINHARD, SAGE IAN CHARLES, WAECHTLER ANDREAS, BAXTER, D., COATES, DAVID, GREENFIELD, SIMON, HITTICH, REINHARD, SAGE, IAN, CHARLES, WAECHTLER, ANDREAS
Applicants: MERCK PATENT GMBH, MERCK PATENT GESELLSCHAFT MIT BESCHRAENKTER HAFTUNG
Application year: 1990
Main classification: C07C255
IPC codes: C07C13, C07C25, C07C43, C07C255, C09K19