Compounds and liquid crystalline medium

Substituted piperidine compounds (I) are new. Substituted piperidine compounds of formula (I) are new. ZG : an organic group with 4 binding sites; Z 1> 1>, Z 1> 2> : -O-, -(C=O)-, -(N-R 1> 4>)- or a single bond, where simultaneously Z 1> 1>and Z 1> 2>are not -O-; either Y 1> 1>-Y 1> 4> : 1-4C-alkyl; or Y 1> 1>Y 1> 2>, Y 1> 3>Y 1> 4> : 3-6C-divalent group; R 1> 1> : O-R 1> 3>, O (preferred) or OH, preferably isopropyloxy, cyclohexyloxy, acetophenyloxy or benzyloxy; R 1> 2> : H, F, OR 1> 4>, NR 1> 4>R 1> 5>, 1-20C-alkyl (in which one or more -CH 2- groups are optionally replaced by -O- or -C(=O)- and two adjacent -CH 2- groups are not optionally replaced by -O-), cycloalkyl or alkylcycloalkyl unit (in which one or more -CH 2- groups are optionally replaced by -O- or -C(=O)-, two adjacent -CH 2- groups are not optionally replaced by -O- and one or more H atoms are optionally replaced by OR 1> 4>, N(R 1> 4>)(R 1> 5>) or R 1> 6>), (hetero)aryl (in which one or more H atoms are optionally replaced by OR 1> 4>, N(R 1> 4>)(R 1> 5>) or R 1> 6>) or hydrocarbyl; R 1> 3> : R 1> 2>, 1,4-cyclohexylene (in which one or more -CH 2- groups are optionally replaced by -O-, -CO or -NR 1> 4>), acetophenyl-isopropyl or 3-heptyl; R 1> 4>, R 1> 5> : 1-10C-alkyl, 1-10C-acyl, 6-12C-aryl hydrocarbyl or 6-12C-carboxylic acid; R 1> 6> : 1-10C-alkyl (in which one or more -CH 2- groups are optionally replaced by -O- or -C(=O)- and two adjacent -CH 2- groups are not optionally replaced by -O-); m : 4-n; r, s : 0 or 1; and n : 1-4, provided that, if n is 1, R 1> 1>is O and -[Z 1> 1>] r-[Z 1> 2>] sis -O-, -(CO)-O-, -O-(CO)-O-, -NR 1> 4>- or -NR 1> 4>-(CO)- and [R 1> 2>] n-ZG is not 1-10C-alkyl, cycloalkyl, cycloalkylalkyl or alkylcycloalkyl (in which one or more -CH 2-groups are optionally replaced by -O- and two O atoms are not directly bonded), and if n is 2, R 1> 1>is O and [R 1> 2>] m-ZG-[Z 1> 1>] r-[Z 1> 2>] s- is not a piperidine group of formula (a), and if n is 2, R 1> 1>is OR 1> 3>and R 1> 3>is not n-1-9C-alkyl. Independent claims are included for: (1) a liquid crystal medium comprising the piperidine compound (I), one or more cyclohexane compound of formula (II) and one or more fluorinated benzene compounds of formula (III1)-(III4); (2) stabilizing the liquid crystalline medium comprising adding (I) and optionally one or more compounds comprising 2,6-di-tert-butyl-4-(4-propyl-cyclohexyl)-phenol, 2,6-di-tert-butyl-4-(5-propyl-[1,3]dioxan-2-yl)-phenol, heptadecanoic acid 3,5-di-ter