Liquid-crystalline medium

A liquid-crystalline medium comprising a mixture of polar compounds having positive dielectric anisotropy, wherein said mixture comprises one or more compounds of formula I:

• in which:
• R is straight-chain alkyl or alkoxy having 2 to 7 carbon atoms or alkenyl radical having 2 to 10 carbon atoms,
• A1 (a) is a trans-1,4-cyclohexylene radical in which, in addition, one or more non-adjacent CH2 groups may be replaced, in each case independently, by —O— or —S—, or a 1,4-cyclohexenylene radical,
• (b) is a 1,4-phenylene radical, in which, in addition, one or two CH groups may be replaced by N,
• (c) is a radical from the group consisting of 1,4-bicyclo[2.2.2]octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydro-naphthalene-2,6-diyl and 1,2,3,4-tetrahydro-naphthalene-2,6-diyl,
• wherein the radicals (a) and (b) may be monosubstituted or polysubstituted by CN, CH3 or F,
• Z1 is —CO—O—, —O—CO—, —CH2—O—, —OCH2—, —CH2CH2—, —CF2O—, —OCF2—, —CH═CH—, —C≡C—, —(CH2)4—, —CH═CH—CH2CH2— or a single bond,
• Y is F, Cl, halogenated alkyl having 1 to 6 carbon atoms, halogenated alkenyl having up to 6 carbon atoms, or halogenated alkoxy having 1 to 6 carbon atoms,
• L is H or F, and
• m is 0 or 1;
• and
• wherein said mixture has a clearing point greater than 90° C.