Ferroelectric active matrix displays with wide operating temperature range

An active-matrix display containing a ferroelectric (chiral smetic) liquid-crystal mixture in a liquid crystal layer in the form of a monodomain having an unambiguously defined direction of the layer normal z of the SmC* phase, where the layer normal z and the preferential direction n of the nematic or cholestreric phase (M* phase) form an angle of more than 5″, wherein the liquid-crystal mixture comprises at least one compound of the formula (I)

• R1—(A1—M1)a-(A2—M2)b-A3—X—B1—(B2)c-R2 (1)
• where the symbols are as defined below:
• R1, R2 are, independently of one another, identical or different and are each
• a) hydrogen, fluorine or CN a straight-chain or branched alkenyl, alkenyloxy, alkyl or alkyloxy radical (with or without asymmetric carbon atoms) having 2 to 16 carbon atoms, where
• b1) one or two nonterminal —CH2— groups may be replaced by —O—, —OC(═O)—, —(C═O), —C(═O)O—, —Si(CH3)2—, CH(Cl)— and/or one or two —CH2— groups may be replaced by —CH═CH— or —C≡C—
• and one or more H atoms may be replaced by F and/or
• b2) one or more —CH2— groups may be replaced by phenylene-1,4-diyl (unsubstituted, monosubstituted or disubstituted by F), phenylene-1,3-diyl (unsubstituted, monosubstituted or disubstituted by F), cyclohexane-1,4-diyl (unsubstituted or monosubstituted by F or CN) or cyclopropane-1,2-diyl
• and one or more H atoms may be replaced by F
• with the provisos that only one of the radicals R1, R2 can be hydrogen, F or CN and that two adjacent —CH2— groups cannot be replaced by —O—
• M1, M2 are, independently of one another, identical or different and are each —C(═O))—, —OC(═O)—, CH2O—, —OCH2—, —CF2O, —OCF2—, —CH2CH2—, CF2CF2—, —CH═CH—, —CH═CF—, —CF═CF—, —C≡C—, —CH2CH2C(═O)O—, —OC(═O)CH2CH2—, —(CH2)4—, —OCH2CH2CH2—, —CH2CH2CH2O—, —OCH2CF2CH2, —CH2CF2CH2O— or a single bond
• A1, A2, A3 are, independently of one another, identical or different and are each cyclohexane-1,4-diyl (unsubstituted or monosubstituted by F, CH3, CN), cyclohex-1-ene-1,4-diyl, cyclohex-2-ene-1,4-diyl, 2-oxocyclohexane-1,4-diyl, 2-cyclohexen-1-one-3,6-diyl, 1-alkyl-1-silacyclohexane-1,4-diyl, bicyclo[2,2,2]octane-1,4-diyl, spiro[4,5]decane-2,8-diyl, spiro[5,5]undecane-3,9-diyl, phenylene-1,4-diyl (unsubstituted, monosubstituted or disubstituted by CN, CN3, CF3, OCH3, unsubstituted, monosubstituted, disubstituted, trisubstituted or tetrasubstituted by F), phenylene-1,3-diyl (unsubstituted monosubstituted or disubstituted by CN, CH3, CF3, OCF3, unsubstituted, monosubstituted, disubstituted, trisubstituted or tetrasubstituted by F), thiophene-2,5-diyl, thiophene-2,4-diyl, (1,3,4)-oxadiazole-2,5-diyl, (1,3,4)-thiadiazole-2,5-diyl, 1,3-thiazole-2,5-diyl, 1,3-thiazole-2,4-diyl, (1,3)-oxazole-2,5-diyl, isoxazole-2,5-diyl, indane-2,6-diyl, naphthalene-2,6-diyl (unsubstituted, monosubstituted or disubstituted by F or CN), 1,2,3,4-tetrahydronaphthalene-2,6-diyl, decaline-2,6-diyl, pyrimidine-2,5-diyl (unsubstituted or monosubstituted by F), pyridine-2,5-diyl (unsubstituted, monosubstituted or disubstituted by F), pyrazine-2,5-diyl (unsubstituted or monosubstituted by F), pyridazine-3,6-diyl, quinoline-2,6-diyl, quioline-3,7-diyl, isoquinoline-3,7-diyl, quinazoline-2,6-diyl, 5,6,7,8-tetrahydroquinazoline-2,6-diyl, quinoxaline-2,6-diyl, 1,3-dioxane-2,5-diyl (unsubstituted or monosubstituted by CN), benzothiazle-2,6-diyl, piperidine-2,4-diyl, piperazine-1,4-diyl
• B1 is cyclohexane-1,4-diyl (unsubstituted, monosubstituted or disubstituted by F, CH3, CN), perfluorocyclohexane-1,4-diyl, cyclohex-1-ene-1,4-diyl, cyclohex-2-ene-1,4-diyl, 1-alkyl-1-silacyclohexane-1,4-diyl, bicyclo[2,2,2]octane-1,4-diyl, cyclopentane-1,3-diyl, cycloheptane-1,4-diyl, tetrahydrofuran-2,5-diyl, tetrahydrofuran-2,4-diyl, phenylene-1,4-diyl (unsubstituted, monosubstituted or disubstituted by CN, CH3, CF3, OCF3, unsubstituted, monosubstituted, disubstituted, trisubstituted or tetrasubstituted by F), phenylene-1,3-diyl (unsubstituted, monosubstituted or disubstituted by CN, CH3, CF3, OCF3, unsubstituted, monosubstituted, disubstituted or trisubstituted by F), thiophene-2,5-diyl (unsubstituted or monosubstituted by F), thiophene-2,4-diyl (unsubstituted or monosubstituted by F), 1,3-thiazol-2,5-diyl (unsubstituted or monosubstituted by F), 1,3-thiazol-2,4-diyl (unsubstituted or monosubstituted by F) (1,3,4)-thiadiazol-2,5-diyl, 1,3-dioxane-2,5-diyl (unsubstituted or monosubstituted by CN), tetrahydropyran-2,5-diyl, 6,6-difluorotetrahydro pyran-2,5-diyl, 6,6-difluoro-2,3-dihydro-6H-pyran-2,5-diyl, 6-fluoro-3,4-dihydro-2H-pyran-2,5-diyl, piperidine-1,4-diyl, piperazine-1,4-diyl, pyrimidine-2,5-diyl (unsubstituted or monosubstituted by F), pyridine-2,5-diyl (unsubstituted or monosubstituted by F), 1,2,3,4-tetrahydronaphthalene-2,6-diyl, decaline-2,6-diyl
• B2 is cyclohexane-1,4-diyl (unsubstituted, monosubstituted or disubstituted by F, CH3, CN), cyclohex-1-ene-1,4-diyl (unsubstituted or monosubstituted by F), cyclohex-2-ene-1,4-diyl, 1-alkyl-1-silacyclohexane-1,4-diyl, bicyclo[2,2,2]octane-1,4-diyl, phenylene-1,4-diyl (unsubstituted, monosubstituted or disubstituted by CN, CH3, CF3, OCF3, unsubstituted, monosubstituted, disubstituted, trisubstituted or tetrasubstituted by F), phenylene-1,3-diyl (unsubstituted, monosubstituted or disubstituted by CN, CH3, CF3, OCF3, unsubstituted, monosubstituted, disubstituted or trisubstituted by F), thiophene-2,5-diyl, thiophene-2,4-diyl, 1,3-thiazole-2,5-diyl, 1,3-thiazole-2,4-diyl, (1,3,4)-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl (unsubstituted or monosubstituted by CN), tetrahydrofuran-2,5-diyl, tetrahydropyran-2,5-diyl, 6,6-difluorotetrahydropyran-2,5-diyl, 6,6-difluoro-2,3-dihydro-6H-pyran-2,5-diyl, 6-fluoro-3,4-dihyfro-2H-pyran-2,5-diyl, pyrimidine-2,5-diyl (unsubstituted or monosubstituted F), pyridine-2,5-diyl (unsubstituted or monosubstituted F), indane-2,6-diyl, piperidine-1,4-diyl, piperazine-1,4-diyl, pyrimidine-2,5-diyl (unsubstituted or monosubstituted by F)
• X is —(CH2)n—, where
• a) one or two —CH2— groups may be replaced by —O— or —C(═O)— and/or
• b) one —CH2CH2— group may be replaced by —CH═CH— and one or more H of the —CH2— groups may be replaced by F
• with the provisos that
• 1) n is 2, 3 or 4
• 2) two adjacent —CH2— groups cannot be replaced by —O—
• a, b, c are each zero, 1 or 2, with the provisos that
• 1) a must be 1 when R1 is hydrogen, F or CN
• 2) the sum of a+b+c is at least 1
• 3) the radicals A and M, respectively, in the brackets may be identical or different when the corresponding index is 2.