Liquid-crystalline medium for use in a switching element

Patent metadata

Field	Value
Publication number	US-11760931-B2
Application number	US-201816770181-A
Country	US
Kind code	B2
Filing date	Dec 3, 2018
Priority date	Dec 6, 2017
Publication date	Sep 19, 2023
Grant date	Sep 19, 2023

Abstract

The present invention relates to liquid-crystalline media comprising one or more mesogenic compounds of formula I as set forth hereinafter, wherein the one or more compounds of formula I are contained in the medium in an amount, based on the overall contents of the medium, of at least 15% by weight. The present invention further relates to a switching layer, a switching element and a window element containing the liquid-crystalline medium.

First claim

The invention claimed is:

1. A window element, comprising a switching element, which switching element comprises a switching layer, which switching layer comprises a liquid-crystalline medium, wherein the switching layer is arranged between two substrates, and wherein the switching element is electrically switchable and operable in an optically transparent state and a scattering state, wherein the liquid-crystalline medium comprises
one or more mesogenic compounds of formula I

wherein
R 1 and R 2 denote, independently of one another, F, Cl, CF 3 , OCF 3 , a straight-chain alkyl or alkoxy having 1 to 15 carbon atoms, a branched alkyl or alkoxy having 3 to 15 carbon atoms, a straight-chain alkenyl having 2 to 15 carbon atoms, or a branched alkenyl having 3 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF 3 or mono- or polysubstituted by halogen and wherein one or more CH 2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another,

denotes

n denotes 0 or 1, and

denote, independently of one another,

wherein L is on each occurrence, identically or differently, halogen selected from the group consisting of F, Cl and Br,

and
one or more chiral compounds,

wherein the one or more compounds of formula I are contained in the medium in an amount, based on the overall contents of the medium, of at least 15% by weight, and
wherein the medium exhibits a clearing point of 98° C. or more.

2. The window element according to claim 1 ,
wherein the medium exhibits a pitch of 0.55 μm or more.

3. The window element according to claim 1 , in which the medium exhibits
an optical anisotropy Δn, determined at 20° C. and 589 nm, of 0.13 or more.

4. The window element according to claim 1 , in which the medium further comprises one or more mesogenic compounds of formulae II and/or III

wherein
R 3 , R 4 , R 5 and R 6 denote, independently of one another, F, CF 3 , OCF 3 , CN, a straight-chain alkyl or alkoxy having 1 to 15 carbon atoms, a branched alkyl or alkoxy having 3 to 15 carbon atoms, a straight-chain alkenyl having 2 to 15 carbon atoms or a branched alkenyl having 3 to 15 carbon atoms, which is unsubstituted, monosubstituted by CN or CF 3 or mono- or polysubstituted by halogen and wherein one or more CH 2 groups may be, in each case independently of one another, replaced by —O—, —S—, —CO—, —COO—, —OCO—, —OCOO— or —C≡C— in such a manner that oxygen atoms are not linked directly to one another, and
L 1 , L 2 , L 3 , L 4 and L 5 denote, independently of one another, H or F.

5. The window element according to claim 1 , wherein in the one or more mesogenic compounds of formula I L is F and R 1 and R 2 are not Cl.

6. The window element according to claim 1 , wherein the one or more chiral compounds in the medium have an absolute value of the helical twisting power of 5 μm −1 or more.

7. The window element according to claim 1 , wherein the medium further comprises one or more polymerisable compounds.

8. The window element according to claim 7 , wherein the one or more polymerisable compounds are contained in the medium in an amount, based on the overall contents of the medium, of 10% by weight or less.

9. The window element according to claim 7 , wherein one or more of the one or more polymerisable compounds comprise one, two or more acrylate and/or methacrylate groups.

10. The window element according to claim 7 , wherein one or more of the one or more polymerisable compounds are polymerisable mesogenic compounds.

11. The window element according to claim 1 , wherein the medium further comprises a polymeric component.

12. The window element according to claim 11 , wherein the polymeric component is contained in the medium in an amount, based on the overall contents of the medium, of 10% by weight or less.

13. A method for preparing the window element of claim 1 , therein a switching layer or a switching element, comprising
(a) providing the medium comprising the one or more mesogenic compounds of formula I and the one or more chiral compounds and which medium further comprises one more polymerisable compounds as a layer, and
(b) polymerising the one or more polymerisable compounds of said medium.

14. The window element according to claim 11 , wherein the polymeric component is obtained by polymerising one or more polymerisable compounds.

15. A cholesteric liquid crystal scattering device, comprising the window element according to claim 1 .

16. An automobile, comprising the window element according to claim 1 .

17. An architectural building, comprising the window element according to claim 1 .

18. A privacy window, comprising the window element according to claim 1 .

Assignees

• Merck Patent Gmbh

Inventors

• Junge Michael
• Beyer Andreas
• Fischer Mila
• Ptak Ewa

Classifications

• C09K19/14 Primary

  linked by a carbon chain · CPC title

• C09K19/04 Primary

  characterised by the chemical structure of the liquid crystal components {, e.g. by a specific unit} · CPC title

• C09K19/12

  at least two benzene rings directly linked, e.g. biphenyls · CPC title

• C09K19/586

  Optically active dopants; chiral dopants · CPC title

• C09K2019/0448

  the end chain group being a polymerizable end group, e.g. -Sp-P or acrylate · CPC title