Optically sensitive electric paper

• US 6,137,467 A
• Filed: 01/03/1995
• Issued: 10/24/2000
• Est. Priority Date: 01/03/1995
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Richley, Edward A., Sheridon, Nicholas K.
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US08/368,133
• Time in Patent Office: 2,121 Days
• Field of Search: 345/107, 345/105, 345/106, 345/173, 345/175, 345/176, 345/179, 345/182, 345/183, 345/84, 345/85, 178/18, 178/19, 264/4, 264/5, 264/7, 264/8
• US Class Current: 345/107
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

An improved electric paper which allows it to form an image from a light image rather than from an applied electric field. The prior art embodiment had a number of rotatable balls imbedded in a plastic substrate. Each ball had hemispheres that had different electrical characteristics, and were colored differently. Under the influence of an image in the form of an electrical field, the balls would selectively rotate to form a permanent visible image, whereupon the field could be removed. This invention has two conductive surfaces to provide a uniform electric field across the substrate, and then exposes the substrate to light which selectively changes the electrical characteristics of one of the two hemispheres, resulting in the rotation of the selected balls to form the image.

Claims

1. Apparatus for generating an image from a light source comprising:

a light source for generating a light image and

a display medium comprising,

a flat substrate having two sides,

two conductive surfaces, one on each side of said flat substrate,

a source of electrical voltage connected to said surfaces which can be switched so that one or the other of the surfaces is more positive,

a plurality of fluid-filled cavities within said substrate, and

a sphere within each of said cavities, said sphere comprising first and second hemispheres, the surface of the first hemisphere comprising a photoalterable material whose electrical properties are altered by exposure to light, and wherein the second hemisphere is a different color from the first hemisphere.

2. The apparatus of claim 1 wherein said photoalterable material is a photoconductor.

3. The apparatus of claim 1 wherein said photoalterable material is a photoinjector.

4. The apparatus of claim 1 in which said second hemisphere is an insulator.

5. The apparatus of claim 1 in which said second hemisphere is a semiconductor.

6. The apparatus of claim 1 in which said second hemisphere is also a photoalterable material.

7. Apparatus for generating an image from a light source comprising:

a stylus comprising

an electrode for generating an electric field, and

a light source for generating a light beam within said field and

a display medium comprising,

a flat substrate having two sides,

two conductive surfaces, one on each side of said flat substrate,

a plurality of fluid-filled cavities within said substrate, and

a sphere within each of said cavities, said sphere comprising first and second hemispheres, the surface of the first hemisphere comprising a photoalterable material whose electrical properties are altered by exposure to light, and wherein the second hemisphere is a different color from the first hemisphere.

8. Apparatus for generating an image from a light source comprising:

a number of styluses arranged in a row, each comprising

an electrode for generating an electric field, and

a light source for generating a light beam within said field, and

a display medium comprising,

a flat substrate having two sides,

two conductive surfaces, one on each side of said flat substrate,

a plurality of fluid-filled cavities within said substrate, and

a sphere within each of said cavities, said sphere comprising first and second hemispheres, the surface of the first hemisphere comprising a photoalterable material whose electrical properties are altered by exposure to light, and wherein the second hemisphere is a different color from the first hemisphere.