Low haze switchable window

Patent metadata

Field	Value
Publication number	US-10921672-B2
Application number	US-201715467189-A
Country	US
Kind code	B2
Filing date	Mar 23, 2017
Priority date	Mar 23, 2016
Publication date	Feb 16, 2021
Grant date	Feb 16, 2021

Abstract

A switchable window includes an electro-optical layer of or including an anisotropic gel of polymer stabilized highly chiral liquid crystal, for example, blue phase liquid crystal, encapsulated in, for example, a mesogenic polymer inclusive shell, that forms a self-assembled, three-dimensional photonic crystal that remains electro-optically switchable under a moderate applied voltage (e.g., electric field). The liquid crystal (LC) arrangement may be achieved via a polymer assembled blue phase liquid crystal system having a substantially continuous polymer structure case surrounding well-defined discrete bodies of liquid crystal material arranged in a cellular manner. These assembled structures globally connect to form a matrix. This provides for reduction of angular birefringence of highly chiral LC systems, which advantageously reduces haze in applications such as switchable windows.

First claim

What is claimed is:

1. A switchable window, comprising:
first and second transparent substrates supporting first and second transparent conductive electrodes, respectively;
an electro-optical layer comprising a plurality of microcell cores dispersed in a connective polymer based matrix, each said microcell core comprising polymer stabilized highly chiral liquid crystal and being encapsulated in a polymer inclusive shell;
wherein the electro-optical layer is sandwiched between the first and second substrates, and between the first and second transparent conductive electrodes;
wherein np<nc<ns for all angles of incidence from 0-80 degrees in the ON state, where np, nc and ns are the effective refractive indices of the polymer, core, and shell, respectively, in a transmissive ON state; and
wherein across angles of incidence ranging from 0 to 80 degrees in the ON state of the electro-optical layer each of np, nc, and ns do not change by more than 0.1.

2. The switchable window of claim 1 , wherein the polymer stabilized highly chiral liquid crystal comprise nematic liquid crystal doped with a chiral dopant.

3. The switchable window of claim 2 , wherein the chiral dopant comprises first and second different chiral dopants, each chiral dopant having a different respective twist, so that the first and second chiral dopants provide for different twists relative to each other.

4. The switchable window of claim 3 , wherein the liquid crystal forms a double twist cylinder.

5. The switchable window of claim 4 , wherein a plurality of double twist cylinders are arranged in a matrix structure.

6. The switchable window of claim 5 , wherein the microcell cores each comprise blue phase liquid crystal comprising a plurality of double twist cylinders arranged in a matrix structure.

7. The switchable window of claim 1 , wherein the switchable window is configured to form an electric field between the first and second transparent electrodes, the electric field causing the polymer stabilized highly chiral liquid crystal to align to put the switchable window in a transmissive ON state in which the switchable window is substantially transparent.

8. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤6% at a viewing angle of 45 degrees from a normal viewing angle.

9. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤4% at a viewing angle of 45 degrees from a normal viewing angle.

10. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤3% at a viewing angle of 45 degrees from a normal viewing angle.

11. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤2% at a viewing angle of 45 degrees from a normal viewing angle.

12. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤6% at a viewing angle of 60 degrees from a normal viewing angle.

13. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤4% at a viewing angle of 60 degrees from a normal viewing angle.

14. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤3% at a viewing angle of 60 degrees from a normal viewing angle.

15. The switchable window of claim 7 , wherein a haze value for the switchable window in the transmissive state is ≤2% at a viewing angle of 60 degrees from a normal viewing angle.

16. The switchable window of claim 1 , wherein a haze value of the switchable window in a non-transmissive state, when the electro-optical layer is in an OFF state, is at least 90% at substantially all viewing angles.

17. The switchable window of claim 1 , wherein a haze value of the switchable window in a non-transmissive state is at least 95% at substantially all viewing angles.

18. The switchable window of claim 1 , wherein a haze value of the switchable window in a non-transmissive state is in a range of 100%±3% at substantially all viewing angles.

19. The switchable window of claim 1 , wherein the polymer inclusive shell is substantially spherical.

20. The switchable window of claim 1 , wherein a thickness of the polymer inclusive shell is in a range of 0.25 to 1 μm.

21. The switchable window of claim 1 , wherein a diameter of the liquid crystal material encapsulated in the polymer inclusive shell is in a range of 1 to 10 μm.

22. The switchable window of claim 1 , wherein the first and second transparent substrates are glass substrates.

23. The switchable window of claim 1 , wherein the first and second transparent substrates each comprise PET.

24. The switchable window of claim 1 , wherein the electro-optical layer is an anisotropic gel.

25. The switchable window of claim 1 , wherein the window has a visible transmission of at least 60% when the electro-optical layer is in the transmissive state.

26. The switchable window of claim 1 , wherein the window has a visible transmission of at least 70% when the electro-optical layer is in the transmissive state.

27. The switchable window of claim 1 , wherein the electro-optical layer is an anisotropic gel, and a ratio of polymer/LC in the anisotropic gel is from about 10-30%.

28. The switchable window of claim 1 , wherein polymer distribution in the electro-optical layer is not uniform, so that there is a greater percentage of polymer, compared to liquid crystal, in a middle plane between the first and second electrodes, and there is a lesser percentage of polymer, compared to liquid crystal, closer to the electrodes.

29. The switchable window of claim 1 , wherein the polymer inclusive shell is mesogenic.

30. The switchable window of claim 1 , wherein the polymer inclusive shell comprises a mixture of the polymer and liquid crystal.

31. The switchable window of claim 1 , wherein the first substrate supports the first transparent conductive electrode and a first dielectric layer comprising an oxide of silicon and/or silicon oxynitride, wherein the first dielectric layer comprising the oxide of silicon and/or silicon oxynitride is located between and contacting the electro-optical layer and the first transparent conductive electrode.

32. The switchable window of claim 1 , wherein the second substrate supports the second transparent conductive electrode and a second dielectric layer comprising an oxide of silicon and/or silicon oxynitride, wherein the second dielectric layer comprising the oxide of silicon and/or silicon oxynitride is located between and contacting the electro-optical layer and the second transparent conductive electrode.

33. The switchable window of claim 1 , wherein at all angles of incidence from 0-80 degrees in the ON state ns is from 1.62 to 1.71.

34. The switchable window of claim 1 , wherein at all angles of incidence from 0-80 degrees in the ON state ns is from 1.63 to 1.69.

35. The switchable window of claim 1 , wherein at all angles of incidence from 0-80 degrees in the ON state nc is from 1.57 to 1.66.

36. The switchable window of claim 1 , wherein at all angles of incidence from 0-80 degrees in

Assignees

• Guardian Glass Llc

Inventors

• Veerasamy Vijayen S

Classifications

• G02F1/13793

  Blue phases · CPC title

• G02F1/13775

  Polymer-stabilized liquid crystal layers · CPC title

• G02F1/13756

  the liquid crystal selectively assuming a light-scattering state (G02F1/1334, G02F1/13718 take precedence) · CPC title

• G02F1/1334 Primary

  based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals · CPC title

• G02F1/13345

  Network or three-dimensional gels · CPC title