Tuning the polar anchoring strength by doping graphene flakes and resulting accelerated electro-optic switching in liquid crystal devices

Patent metadata

Field	Value
Publication number	US-2020409194-A9
Application number	US-201816164660-A
Country	US
Kind code	A9
Filing date	Oct 18, 2018
Priority date	Jun 15, 2018
Publication date	Dec 31, 2020
Grant date	—

Abstract

A method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device comprising the steps of providing graphene in an ethanol solvent, adding a liquid crystal to the graphene and ethanol solution, forming a liquid crystal graphene ethanol solution, evaporating the ethanol, and forming a pure liquid crystal graphene mixture. A liquid crystal device with faster electro-optic switching and higher polar anchoring strength comprising an LC cell having a polyimide (PI) alignment layer, the liquid crystal graphene mixture, wherein the graphene flakes preferentially attach to the PI alignment layer; wherein the effective polar anchoring energy in the LC cell is enhanced by an order of magnitude and wherein the electro-optic response of the LC is accelerated.

First claim

What we claim is:

1 . A method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device comprising the steps of:
providing a graphene sample in an ethanol solvent;
wherein the graphene sample comprises monolayer flakes;
mixing the graphene sample and the ethanol solvent and forming a graphene and ethanol solution; adding a liquid crystal to the graphene and ethanol solution; allowing the liquid crystal to dissolve into the graphene and ethanol solution; forming a liquid crystal graphene ethanol solution; evaporating the ethanol from the liquid crystal graphene ethanol solution; forming a liquid crystal graphene mixture; degassing the liquid crystal graphene mixture; and forming a pure liquid crystal graphene mixture.

2 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 1 wherein the liquid crystal comprises liquid crystal E7 comprising nematic-isotropic phase transition temperature (T NI ) of 60.5° C.

3 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 2 wherein the monolayer flakes have an average thickness of 0.35 nm and an average lateral size of 550 nm and wherein the liquid crystal graphene mixture is liquid crystal E7 and pristine graphene mixture.

4 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 3 wherein the graphene concentration in the liquid crystal E7 is 2.5×10 −3 wt %.

5 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 3 wherein the step of degassing the liquid crystal graphene mixture occurs under vacuum.

6 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 3 wherein the graphene sample comprises more than 97% monolayer flakes.

7 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 2 further including the steps of:
filling an LC cell having polyimide (PI) planar-alignment layers with the liquid crystal graphene mixture;
wherein the graphene flakes sediment down from the liquid crystal graphene mixture and preferentially attach to the PI alignment layers during the filling step of the LC cell; and
wherein the graphene modifies the anchoring property of the LC.

8 . The method of achieving higher polar anchoring strength of liquid crystal (LC) using monolayer graphene flakes in an LC device and attaining faster electro-optic switching in an LC device of claim 7 further including the steps of:
enhancing the effective polar anchoring energy in the LC cell by an order of magnitude via the π-π electron stacking between the graphene flakes on the PI planar-alignment layers and LC molecules; and
accelerating the electro-optic response of the LC due to higher anchoring energy in the LC cell.

9 . A Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength using monolayer graphene flakes made from the steps of:
providing a graphene sample in an ethanol solvent;
wherein the graphene sample comprises monolayer flakes;
mixing the graphene sample and the ethanol solvent and forming a graphene and ethanol solution; adding a liquid crystal to the graphene and ethanol solution; allowing the liquid crystal to dissolve into the graphene and ethanol solution; forming a liquid crystal graphene ethanol solution; evaporating the ethanol from the liquid crystal graphene ethanol solution; forming a liquid crystal graphene mixture; degassing the liquid crystal graphene mixture; and forming a pure liquid crystal graphene mixture.

10 . The Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength using monolayer graphene flakes of claim 9 wherein the liquid crystal comprises liquid crystal E7 with a nematic-isotropic phase transition temperature (T NI ) of 60.5° C.

11 . The Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength using monolayer graphene flakes of claim 10 wherein the monolayer flakes have an average thickness of 0.35 nm and an average lateral size of 550 nm and wherein the liquid crystal graphene mixture is liquid crystal E7 and pristine graphene mixture.

12 . A Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength comprising:
a LC cell having a polyimide (PI) alignment layer; a liquid crystal graphene mixture in the LC cell; wherein the graphene flakes sediment down from the liquid crystal graphene mixture and preferentially attach to the PI alignment layer during filling the LC cell; wherein the graphene modifies the anchoring property of the LC; wherein the effective polar anchoring energy in the LC cell is enhanced by an order of magnitude via the π-π electron stacking between the graphene flakes on the PI alignment layer and LC molecules; and wherein the electro-optic response of the LC is accelerated due to the higher anchoring energy in the cell.

13 . The Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength of claim 12 wherein the liquid crystal comprises liquid crystal E7 and wherein the liquid crystal E7 has a nematic-isotropic phase transition temperature (T NI ) of 60.5° C.

14 . The Liquid Crystal device with faster electro-optic switching and higher polar anchoring strength of claim 13 wherein the monolayer graphene flakes have an average thickness of 0.35 nm and an average lateral size of 550 nm; and wherein the liquid crystal graphene mixture is liquid crystal E7 and pristine graphene mixture.

Assignees

• Us Gov Sec Navy

Inventors

• Basu Rajratan

Classifications

• G02F1/1341

  Filling or closing of cells · CPC title

• G02F1/133703 Primary

  by introducing organic surfactant additives into the liquid crystal material · CPC title

• C09K19/582

  Electrically active dopants, e.g. charge transfer agents · CPC title

• G02F1/133723

  Polyimide, polyamide-imide · CPC title

• G02F1/133776

  having structures locally influencing the alignment, e.g. unevenness · CPC title