Display method, device for realizing same and displaying medium used therefor

• US 5,105,185 A
• Filed: 07/11/1990
• Issued: 04/14/1992
• Est. Priority Date: 07/12/1989
• Status: Expired due to Fees

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Sasaki, Kazuyoshi, Tomoyori, Makoto, Nakanowatari, Jun
• Primary Examiner(s): Brier, Jeffery A.
• Assistant Examiner(s): Chin, Jick
• Application Number:
  US07/551,701
• Time in Patent Office: 643 Days
• Field of Search: 350/331 R, 350/342, 350/347 E, 340/765, 340/784, 355/210, 355/211, 430/19, 430/20, 430/31, 430/46, 430/56, 430/138
• US Class Current: 345/94
• CPC Class Codes: G02F 1/135 Liquid crystal cells structurally associated with a photoconducting or a ferro-electric layer, the properties of which can be optically or electrically varied G02F1/133348 takes precedence
• CPC Class Codes: G09F 11/26 of an endless band

Abstract

The present invention relates to a method and a device for displaying letters, images, etc. as well as a displaying medium used therefor, by which a display medium obtained by superposing a photoconductive layer, in which microcapsules are dispersed on a substrate. The microcapsules enclose a liquid crystal material which transitions between a transparent state and an opaque state by the application of an electric field. The substrate has a conductive surface so that charging of the surface causes the microcapsules to become transparent. An electrostatic latent image is formed on the surface of the displaying medium by irradiating selectively the surface with light. An AC electric field is applied to the displaying medium in order to make the microcapsules opaque at the position corresponding to the place, where the electric field is made disappear thereby making the latent image visible.

Claims

1. A method for displaying images comprising the steps of:

forming an electric field in a displaying medium, wherein said displaying medium is obtained by superposing a photoconductive layer on a substrate, said photoconductive layer dispersing microcapsules, said microcapsules enclosing a liquid crystal material, said substrate being conductive at least at a surface portion thereof, said electric field for making said liquid crystal material transparent; and

forming a latent image by making said electric field selectively disappear and by applying an AC electric field selectively to where said electric field has disappeared, said AC electric field for making said liquid crystal material opaque and said latent image visible.

2. The method according to claim 1, wherein said step of forming said electric field in said displaying medium is effected by charging said surface of said displaying medium.

3. The method according to claim 2, wherein said step of forming said latent image is effected by irradiating selectively the surface of said displaying medium with light.

4. A display device comprising:

a displaying medium comprising photoconductive layers, microcapsules dispersed in said photoconductive layers, said microcapsules enclosing a liquid crystal material, and a substrate which is conductive at least at a surface portion thereof, said photoconductive layers being superposed on said substrate;

means for forming a uniform electric field in said displaying medium;

latent image forming means for forming a latent image by making said electric field selectively disappear; and

electric field applying means for applying a uniform AC electric field to said displaying medium in which said latent image is formed and for forming a display image from said latent image.

5. A display device according to claim 4, wherein said electric field forming means is a charging device for uniformly charging the surface of said displaying medium.

6. A display device according to claim 5, wherein said latent image forming means is a light writing device for irradiating the surface of said displaying medium with light.

7. A display medium comprising:

a substrate which is conductive at least at a surface portion thereof;

a photoconductive layer formed on said substrate and comprising a charge generating layer and a charge transporting layer; and

microcapsules containing a liquid crystal material and being dispersed in said charge transporting layer.

8. A display medium according to claim 7, wherein said liquid crystal material is a ferroelectric liquid crystal.