Bistable reflective display and methods of forming the same

• US 5,956,113 A
• Filed: 01/31/1997
• Issued: 09/21/1999
• Est. Priority Date: 01/31/1997
• Status: Expired due to Fees

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Crawford, Greg P.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): KIM, JOANNE H
• Application Number:
  US08/897,210
• Time in Patent Office: 963 Days
• Field of Search: 349/185, 349/186
• US Class Current: 349/185
• CPC Class Codes: C09K 19/52 characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

A bistable reflective display has a stable focal conic or weakly scattering state even when an applied voltage used to transition to the focal conic state is removed. The bistable reflective display includes first and second substrates, a cholesteric liquid crystal material located between the first and second substrates and silica agglomerates dispersed within the cholesteric liquid crystal material.

Claims

1. A bistable reflective display, comprising:

first and second substrates;

a cholesteric liquid crystal material located between the first and second substrates;

silica agglomerates dispersed within the cholesteric liquid crystal material; and

a voltage source that selectively applies a voltage to the first; and

second substrates, wherein when the voltage has a first value, the bistable reflective display operates in a light scattering state and when the voltage has a second value, the bistable reflective display operates in a transparent state.

2. The bistable reflective display of claim 1, wherein the bistable reflective display maintains the light scattering state when the voltage source is operated to transition from applying the first value to applying zero volts.

3. The bistable reflective display of claim 1, wherein the bistable reflective display transitions from the transparent state to a reflective state when the voltage source is operated to remove the voltage having the second value.

4. The bistable reflective display of claim 1, wherein the silica agglomerates are formed from silica particles having an approximately 0.5-1.0 weight percentage of the silica particles to the cholesteric liquid crystal material.

5. The bistable reflective display of claim 1, wherein the bistable reflective display has a reflective state, the reflective state reflecting light of a desired wavelength and transmitting light not of the desired wavelength.

6. The bistable reflective display of claim 5, wherein the desired wavelength is selected by selecting a type of the cholesteric liquid crystal material.

7. The bistable display of claim 1, wherein the silica agglomerates are formed from silica particles and the silica particles have a weight percentage of the silica particles to the cholesteric liquid crystal material selected so as to maintain the light scattering state when the voltage source removes the voltage having the first value.

8. The bistable reflective display of claim 7, wherein the weight percentage of the silica particles to the cholesteric liquid crystal material is selected so as to allow the bistable reflective display to transition from the transparent state to a reflecting slate when the voltage source removes the voltage having the second value.

9. A method of forming a bistable reflective display, comprising:

forming first and second substrates;

forming a cholesteric liquid crystal material located between the first and second substrates;

forming silica agglomerates dispersed within the cholesteric liquid crystal material; and

connecting a voltage source to the first and second substrates, the voltage source selectively applying a voltage, wherein when the voltage has a first value, the bistable reflective display operates in a light scattering state and when the voltage has a second value, the bistable reflective display operates in a transparent state.

10. The method of forming a bistable reflective display of claim 9, further comprising forming the bistable reflective display to maintain the light scattering state when the voltage source is operated to transition from applying the first value to applying zero volts.

11. The method of forming a bistable reflective display of claim 9, further comprising forming the bistable reflective display to transition from the transparent state to a reflective state when the voltage source is operated to remove the voltage having the second value.

12. The method of forming a paper-white reflective display of claim 9,further comprising forming the silica agglomerates from silica particles having an approximately 0.5-1.0 weight percentage of the silica particles to the cholesteric liquid crystal material.

13. The method of forming a bistable reflective display of claim 9, further comprising forming the bistable reflective display to have a reflective state, the reflective state reflecting light of a desired wavelength and transmitting light not of the desired wavelength.

14. The method of forming a bistable reflective display of claim 13, further comprising selecting a type of the cholesteric liquid crystal material to select the desired wavelength.

15. The method of forming a bistable reflective display of claim 9, further comprising forming the silica agglomerates from silica particles, the silica particles having a weight percentage of the silica particles to the cholesteric liquid crystal material selected so as to maintain the light scattering state when the voltage source removes the voltage having the first value.

16. The method of forming a bistable reflective display of claim 15, further comprising selecting the weight percentage of the silica particles to the cholesteric liquid crystal material so as to allow the bistable reflective display to transition from the transparent state to a reflecting state when the voltage source removes the voltage having the second value.