Mesogenic media and liquid crystal display

1. Medium comprising one or more bimesogenic compounds, one or more nematogenic compound, one or more chiral compound and one or more compounds of formula I,

R 11 -A 11 -(Z 12 -A 12 ) m -AG  I

in which,

A 11 and A 12 each, independently of one another, denote an aryl-, heteroaryl-, heterocyclic- or alicyclic group optionally being substituted by one or more identical or different groups L,

L in each case, independently of one another, denotes, halogen, —CN, —NO 2 , —NCO, —NCS, —OCN, —SCN, straight-chain or branched alkyl or alkoxy having 1 to 5 C atoms, where, in addition, one or more non-terminal CH 2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF 2 O—, —CH═CH—,

—O—, —CO—O—, —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen,

Z 12 in each case, independently of one another, denotes

—O—, —S—, —CO—, —COO—, —OCO—, —S—CO—, —CO—S—, —O—COO—, —CO—NR 0 —, —NR 0 -CO—, —NR 0 -CO—NR 00 , —NR 0 -CO—O—,

—O—CO—NR 0 —, —OCH 2 —, —CH 2 O—, —SCH 2 —, —CH 2 S—, —CF 2 O—, —OCF 2 —, —CF 2 S—, —SCF 2 —, —CH 2 CH 2 —, —(CH 2 ) 4 —, —CF 2 CH 2 —, —CH 2 CF 2 —, —CF 2 CF 2 —, —CH═N—, —N═CH—, —N═N—,

—CH═CR 0 —, —CY 01 ═CY 02 —, —C≡C—, —CH═CH—COO—,

—OCO—CH═CH—, or a single bond,

Y 01 and Y 02 each, independently of one another, denote H, F, Cl or CN,

R 0 and R 00 each, independently of one another, denote H or alkyl having 1 to 12 C atoms,

R 11 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more non-terminal CH 2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF 2 O—, —CH═CH—,

 —O—, —CO—O—, —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen,

AG denotes -Sp-X 11 ,

Sp denotes —(CH 2 )—,

p denotes 0, 1 or 2,

X 11 denotes a group —NH 2 , —SH, —OH, —(CO)OH or a group of the formulae

and

m denotes 0, 1 or 2;

wherein:

the one or more bimesogenic compound is selected from the group of compounds of formulae A-I to A-III,

wherein

R 1 and R 12 ,

R 21 and R 22 ,

and R 31 and R 32 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH 2 groups to be replaced, in each occurrence independently from one another, by —O—, —S—, —NH—, —N(CH 3 )—, —CO—, —COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another,

MG 11 and MG 12 ,

MG 21 and MG 22 , and

MG 31 and MG 32 are each independently a mesogenic group,

Sp 1 , Sp 2 and Sp 3 are each independently a spacer group comprising 5 to 40 C atoms, wherein one or more non-adjacent CH 2 groups, with the exception of the CH 2 groups of Sp 1 linked to O-MG 11 and/or O-MG 12 , of Sp 2 linked to MG 21 and/or MG 22 and of Sp 3 linked to X 31 and X 32 , may also be replaced by —O—, —S—, —NH—, —N(CH 3 )—, —CO—, —O—CO—,

—S—CO—, —O—COO—, —CO—S—, —CO—O—,

—CH(halogen)-, —CH(CN)—, —CH═CH— or —C≡C—, in such a way that no two O-atoms are adjacent to one another, no two —CH═CH— groups are adjacent to each other, and no two groups selected from —O—CO—, —S—CO—, —O—COO—, —CO—S—, —CO—O— and —CH═CH— are adjacent to each other, and

X 31 and X 32 are independently from one another a linking group selected from —CO—O—, —O—CO—, —CH═CH—,

—C≡C— or —S—, and, alternatively, one of them may also be either —O— or a single bond, and, again alternatively, one of them may be —O— and the other one a single bond;

the one or more nematogenic compound is selected from the group of compounds of formulae B-I to B-III,

wherein

R B1 , R B21 ,

R B22 , R B31 and

R B32 are each independently H, F, Cl, CN, NCS or a straight-chain or branched alkyl group with 1 to 25 C atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more non-adjacent CH 2 groups to be replaced, in each occurrence independently from one another, by —O—, —S—, —NH—, —N(CH 3 )—, —CO—,

—COO—, —OCO—, —O—CO—O—, —S—CO—, —CO—S—, —CH═CH—, —CH═CF—, —CF═CF— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another,

X B1 is F, Cl, CN, NCS,

Z B1 , Z B2 and

Z B3 are in each occurrence independently —CH 2 —CH 2 —,

—CO—O—, —O—CO—, —CF 2 -O—, —O— CF 2 —, —CH═CH— or a single bond,

are in each occurrence independently

alternatively one or more of

are

and

n is 1, 2 or 3; and

the one or more chiral compound is selected from the group of compounds of formulae C-I to C-III,

the latter ones including the respective (S,S) enantiomers,

and wherein

E and F are each independently 1,4-phenylene or trans-1,4-cyclohexylene,

v is 0 or 1,

Z 0 is —COO—, —OCO—, —CH 2 CH 2 — or a single bond, and

R is alkyl, alkoxy or alkanoyl with 1 to 12 C atoms.

2. Medium according to claim 1 , characterized in that the compounds of formula I are selected from the group of compounds wherein the anchor group AG in formula I denotes —NH 2 , —SH, —OH or —(CO)OH.

3. Medium according to claim 1 , characterized in that the compounds of formula I are selected from the group of compounds of the following sub formulae,

R 11 -A 11 -(Z 12 -A 12 ) m -Sp-NH 2   Ia

R 11 -A 11 -(Z 12 -A 12 ) m Sp-SH  Ib

R 11 -A 11 -(Z 12 -A 12 ) m Sp-OH  Ic

R 11 -A 11 -(Z 12 -A 12 ) m Sp-(CO)OH  Id

in which, the groups R 11 , A 11 , A 12 , Z 12 , Sp and parameter m have one of the meanings as indicated in claim 1 .

4. Medium according to claim 1 , characterized in that the compounds of formula I are selected from the following sub formulae,

in which R 11 is a straight chain or branched alkyl, having 1 to 25 C atoms.

5. Medium according to claim 1 , characterized in that the total concentration of compounds of formula I in the medium is from 0.01 to 10% by weight.

6. Medium according to claim 1 , characterized in that the amount of chiral compounds in the medium is from 1 to 20% by weight.

7. Electro-optical device comprising a medium according to claim 1 .

8. Electro-optical device according to claim 7 , characterized in that it is a flexoelectric device.

9. Electro-optical device according to claim 7 , characterized in that it comprises two plane parallel electrodes the inner surfaces of which exhibit planar, anti-parallel alignment conditions.