A liquid-crystal (LC) medium, characterized in that it comprises a liquid-crystalline host consisting of an LC component H) comprising one or more mesogenic or liquid-crystalline compounds and an optically active component D), wherein component H comprises one or more compounds selected from the group of compounds of the formulae CY and/or PY: in which the individual radicals have the following meanings: a denotes 1 or 2, b denotes 0 or 1, denotes R 1 and R 2 each, independently of one another, denote alkyl having 1 to 12 C atoms, where one or more H atoms may be replaced by fluorine, and where one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that O atoms are not linked directly to one another, Z X denotes -CH=CH-, -CH 2 O-, -OCH 2 -, -CF 2 O-, -OCF 2 -, -O-, -CH 2 -, -CH 2 CH 2 - or a single bond, L 1-4 each, independently of one another, denote F, Cl, OCF 3 , CF 3 , CH 3 , CH 2 F, CHF 2 , L 5 denotes H or has one of the meanings given for L 1-4 , and where component H) further comprises one or more compounds of the following formula ZK in a total concentration in the range of from 10% to 45% and one or more compounds of the following formula DK in a total concentration in the range of from 1% to 30%: in which the individual radicals have the following meanings: denotes denotes R 3 and R 4 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that O atoms are not linked directly to one another, Z y denotes -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -COO-, -OCO-, -C 2 F 4 -, -CF=CF- or a single bond; R 5 and R 6 each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, denotes denotes and e denotes 1 or 2, and wherein the liquid-crystalline host has a helical pitch in the range of from 5 to 50 μm. a liquid-crystalline host consisting of an LC component H) comprising one or more mesogenic or liquid-crystalline compounds and an optically active component D), a denotes 1 or 2, b denotes 0 or 1, denotes R 1 and R 2 each, independently of one another, denote alkyl having 1 to 12 C atoms, where one or more H atoms may be replaced by fluorine, and where one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that O atoms are not linked directly to one another, Z X denotes -CH=CH-, -CH 2 O-, -OCH 2 -, -CF 2 O-, -OCF 2 -, -O-, -CH 2 -, -CH 2 CH 2 - or a single bond, L 1-4 each, independently of one another, denote F, Cl, OCF 3 , CF 3 , CH 3 , CH 2 F, CHF 2 , L 5 denotes H or has one of the meanings given for L 1-4 , R 3 and R 4 each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that O atoms are not linked directly to one another, Z y denotes -CH 2 CH 2 -, -CH=CH-, -CF 2 O-, -OCF 2 -, -CH 2 O-, -OCH 2 -, -COO-, -OCO-, -C 2 F 4 -, -CF=CF- or a single bond; R 5 and R 6 each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH 2 groups may be replaced by -O-, -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, denotes denotes and e denotes 1 or 2, <EOS>