Smart window and method for switching the same

Patent metadata

Field	Value
Publication number	US-11435642-B2
Application number	US-202017106232-A
Country	US
Kind code	B2
Filing date	Nov 30, 2020
Priority date	Nov 11, 2020
Publication date	Sep 6, 2022
Grant date	Sep 6, 2022

Abstract

A smart window includes two transparent substrates and a liquid crystal layer. The two transparent substrates are opposite to each other and are electrically connected to a voltage supply. A first pulse voltage or a second pulse voltage is provided between the two transparent substrates by the voltage supply. The liquid crystal layer is located between the two transparent substrates and has a liquid crystal material. The liquid crystal material has a pitch of at most 250 nanometers or at least 500 nanometers. The liquid crystal material includes a nematic liquid crystal, a rotatory molecule, and a photochromic dye mixed with each other. The liquid crystal material changes a transmittance corresponding to a specific light wavelength range when receiving a light. The liquid crystal material is switched between a planar texture and a focal-conic texture respectively according to the first pulse voltage and the second pulse voltage.

First claim

What is claimed is:

1. A smart window comprising:
two transparent substrates opposite to each other and are electrically connected to a voltage supply, wherein one of a first pulse voltage a second pulse voltage, a third pulse voltage, and a fourth pulse voltage is provided between the two transparent substrates by the voltage supply; and
a liquid crystal layer located between the two transparent substrates and having a liquid crystal material with a pitch of at most 250 nanometers or at least 500 nanometers, wherein the liquid crystal material includes a nematic liquid crystal, a rotatory molecule, and a photochromic dye mixed with each other, wherein the liquid crystal material is configured for changing a transmittance corresponding to a specific light wavelength range when receiving a light, and configured for being switched between a planar texture and a focal-conic texture respectively according to the first pulse voltage and the second pulse voltage;
wherein the smart window is switched from a scattering state to a transparent state when the first pulse voltage is provided;
wherein the smart window is switched from the transparent state to the scattering state when the second pulse voltage is provided;
wherein in the state that the smart window is in the transparent state, the smart window is switched from the transparent state to a transparent absorption state when the light is provided; and then the smart window is switched from the transparent absorption state to the transparent state when the light is not provided;
wherein in the state that the smart window is in the scattering state, the smart window is switched to from the scattering state to a scattering absorption state when the light is provided; and then the smart window is switched from the scattering absorption state to the scattering state when the light is not provided;
wherein the smart window maintains stably in one of the transparent state, the scattering state, the transparent absorption state, and the scattering absorption state when the first pulse voltage or the second pulse voltage is not provided;
wherein the smart window is switched from the scattering absorption state to the transparent absorption state when the third pulse voltage and the light are provided; and then the smart window is switched to the transparent state when the light is not provided; and
wherein the smart window is switched from the transparent absorption state to the scattering absorption state when the fourth pulse voltage and the light are provided; and then the smart window is switched to the scattering state when the light is not provided.

2. The smart window as claimed in claim 1 , wherein the nematic liquid crystal is a positive nematic liquid crystal, and a voltage value of the first pulse voltage is greater than a voltage value of the second pulse voltage.

3. The smart window as claimed in claim 1 , wherein the nematic liquid crystal is a negative nematic liquid crystal, and the liquid crystal material further includes a salt ion, and a frequency value of the first pulse voltage is greater than a frequency value of the second pulse voltage.

4. The smart window as claimed in claim 1 , wherein when the liquid crystal material is in the planar texture, a transmittance corresponding to a visible light wavelength range of the smart window is higher than 80%.

5. The smart window as claimed in claim 1 , wherein a first time period required for the liquid crystal material to be switched from the focal-conic texture to the planar texture is about 20 milliseconds.

6. The smart window as claimed in claim 1 , wherein a second time period required for the liquid crystal material to be switched from the planar texture to the focal-conic texture is less than 300 milliseconds.

7. The smart window as claimed in claim 1 , wherein each of the two transparent substrates includes a transparent conductive film, respectively located on two opposite sides of the liquid crystal layer.

8. The smart window as claimed in claim 1 , wherein the specific light wavelength range includes at least one of a visible light wavelength range and an infrared light wavelength range.

9. The smart window as claimed in claim 1 , wherein the photochromic dye is ethyl 8-((4′-pentylcyclohexylphenyl)-difluoromethylphenyl-4-yl)-2-phenyl-2-(4-pyrrolidinylphenyl)-2H-naphtho [1,2-b] pyran-5-carboxylate.

10. A method for switching a smart window, wherein the smart window comprises two transparent substrates and a liquid crystal layer between the two transparent substrate, the two transparent substrates are opposite to each other and electrically connected to a voltage supply, and the voltage supply provides one of a first pulse voltage, a second pulse voltage, a third pulse voltage, and a fourth pulse voltage, the method comprises:
providing the first pulse voltage to switch the smart window from a scattering state to a transparent state;
providing the second pulse voltage to switch the smart window from the transparent state to the scattering state;
providing the light to switch the smart window from the transparent state to a transparent absorption state, wherein when the light is not provided, the smart window is switched to the transparent state;
providing the light to switch the smart window from the scattering state to a scattering absorption state, wherein when the light is not provided, the smart window is switched to the scattering state;
providing the third pulse voltage and the light to switch the smart window from the scattering absorption state to the transparent absorption state, wherein when the light is not provided, the smart window is switched to the transparent state; and
providing the fourth pulse voltage and the light to switch the smart window from the transparent absorption state to the scattering absorption state, wherein when the light is not provided, the smart window is switched to the scattering state;
wherein when the first pulse voltage or the second pulse voltage is not provided, the smart window maintains stably in one of the transparent state, the scattering state, the transparent absorption state, and the scattering absorption state.

11. The method as claimed in claim 10 , wherein the nematic liquid crystal is a positive nematic liquid crystal, and a voltage value of the third pulse voltage is greater than a voltage value of the fourth pulse voltage.

12. The method as claimed in claim 10 , wherein the nematic liquid crystal is a negative nematic liquid crystal, and the liquid crystal material further includes a salt ion, and a frequency value of the third pulse voltage is greater than a frequency value of the fourth pulse voltage.

13. The method as claimed in claim 10 , wherein the nematic liquid crystal is a positive nematic liquid crystal, and a voltage value of the first pulse voltage is greater than a voltage value of the second pulse voltage.

14. The method as claimed in claim 10 , wherein the nematic liquid crystal is a negative nematic liquid crystal, and the liquid crystal material further includes a salt ion, and a frequency value of the first pulse voltage is greater than a frequency value of the second pulse voltage.

Assignees

• National Sun Yat Sen University

Inventors

• Lin Tsung-Hsien
• Li cheng-chang
• Tseng Heng-Yi
• Jau Hung-Chang
• Chang Li-Min
• Lin Kuan-Wu

Classifications

• G02F2202/14

  photochromic · CPC title

• E06B2009/2464

  featuring transparency control by applying voltage, e.g. LCD, electrochromic panels · CPC title

• G02F2413/02

  Number of plates being 2 · CPC title

• E06B9/24

  Screens or other constructions affording protection against light, especially against sunshine; Similar screens for privacy or appearance; {Slat blinds}(operating, guiding or securing devices or arrangements for roll-type closures E06B9/56; free-hanging flexible screens A47H23/00) · CPC title

• G02F1/13718 Primary

  based on a change of the texture state of a cholesteric liquid crystal · CPC title