Display element using a liquid crystal substance and image displaying method using the same

• US 5,721,597 A
• Filed: 02/20/1996
• Issued: 02/24/1998
• Est. Priority Date: 03/01/1995
• Status: Expired due to Term

• Current Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Inventors: Kakinuma, Takeo, Ito, Kensuke, Koshimizu, Minoru
• Primary Examiner(s): Bayerl, Raymond J.
• Assistant Examiner(s): Vail, Seth D.
• Application Number:
  US08/603,158
• Time in Patent Office: 735 Days
• Field of Search: 345/95, 349/10, 349/86, 349/88
• US Class Current: 349/86
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/1392 using a field-induced sign-reversal of the dielectric anisotropy

Abstract

A method and apparatus in which the liquid crystal material having cross-over frequency is used for displaying an image, the liquid crystal material is dispersed in the transparent polymer in a phase-separated state, a first voltage signal having a first frequency lower than the cross-over frequency is applied to the liquid crystal material to orient reversibly the liquid crystal material to a first direction to display temporary information, then a second voltage signal having a magnitude higher than the first voltage is selectively applied to orient permanently the liquid crystal material to the first direction to display permanent information and a third voltage signal having a second frequency higher than the cross-over frequency is selectively applied to orient the liquid crystal material perpendicularly to the first direction, to erase the permanent information. The dynamic image and the memorized static image is displayed interchangeably by selecting the applied voltage signal having a specific frequency range.

Claims

1. A method of erasing information on a display using a polymer liquid crystal device containing a transparent polymer and dual-frequency responsive liquid crystal material, the liquid crystal material having a cross-over frequency, and dispersed in the transparent polymer in a phase-separated state, comprising the steps of:

selectively applying a first voltage signal having a first frequency lower than the cross-over frequency to orient permanently the liquid crystal material to a first direction to display information permanently; and

selectively applying a second voltage signal having a frequency higher than the cross-over frequency to orient the liquid crystal material perpendicularly to the first direction, to erase the permanent information.

2. A method of displaying information on a display using a polymer liquid crystal device containing a transparent polymer and dual-frequency responsive liquid crystal material, the liquid crystal material having cross-over frequency, and dispersed in the transparent polymer in a phase-separated state, comprising the steps of:

selectively applying a first voltage signal having a first frequency lower than the cross-over frequency to orient reversibly the liquid crystal material to a first direction to display temporary information;

selectively applying a second voltage signal having a magnitude higher than the first voltage, and the first frequency to orient permanently the liquid crystal material to the first direction to display permanent information; and

selectively applying a third voltage signal having a second frequency higher than the cross-over frequency to orient the liquid crystal material perpendicularly to the first direction, to erase the permanent information.

3. The method as described in claim 2, wherein the first voltage signal orients a significant portion of liquid crystal molecules in the liquid crystal material to the first direction parallel to a direction of an electric field of the first voltage signal, and the second voltage signal orients substantially all liquid crystal molecules including ones located at an interface portion with the transparent polymer to the first direction.

4. The method as described in claim 2, wherein the third voltage signal re-orients substantially all liquid crystal molecules including ones located in an interface portion with the transparent polymer to a direction perpendicular to the first direction.

5. The method as described in claim 2, wherein the third voltage signal is higher in magnitude than the second voltage signal.

6. A Liquid crystal display device for displaying a dynamic moving image and a static dynamic image interchangeably comprising:

a transparency modulation layer having a transparent polymer and dual-frequency responsive liquid crystal material which has a cross-over frequency, the liquid crystal material is dispersed in the transparent polymer in a phase-separate state to make an interface portion therebetween, the interface portion having an irregular surface portion enough to prevent the free orientation of the liquid crystal material response to an selective electric field;

a plurality of electrodes arranged with respect to the liquid crystal material to apply an electric field thereto; and

a driving source coupled to the electrodes to provide a first voltage selectively providing the electric field having a first frequency lower than the cross-over frequency, a second voltage magnitudely higher than the first voltage having the first frequency and a third voltage having a second frequency higher than the cross-over frequency.

7. A liquid crystal display device claimed in claim 6, wherein the first voltage signal orients a significant portion of liquid crystal molecules in the liquid crystal material to a first direction parallel to a direction of an electric field of the first voltage signal, and the second voltage signal orients substantially all liquid crystal molecules including ones located in an interface portion with the transparent polymer to the first direction.

8. A liquid crystal display device claimed in claim 6, wherein the third voltage signal re-orients substantially all liquid crystal molecules including ones located in an interface portion with the transparent polymer to a direction perpendicular to the first direction.

9. A liquid crystal display device claimed in claim 6, wherein the third voltage is greater in magnitude than the second voltage.