Tamper-evident electric paper

• US 6,419,618 B1
• Filed: 10/31/2000
• Issued: 07/16/2002
• Est. Priority Date: 01/29/1999
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Emerson, William C., Bobrow, Daniel G., Greene, Daniel H., Smith, Craig A., Mackinlay, Jock D., Sheridon, Nicholas K., Hebel, L. Charles
• Primary Examiner(s): Rada, Rinaldi I.
• Assistant Examiner(s): Tawfik, Sameh
• Application Number:
  US09/699,426
• Time in Patent Office: 623 Days
• Field of Search: 493/379, 493/76, 493/187, 428/206, 428/323, 428/211, 428/411.1, 428/320.2, 359/296, 359/298, 359/288
• US Class Current: 493/379
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]
• CPC Class Codes: Y10T 428/24893 including particulate material
• CPC Class Codes: Y10T 428/24934 including paper layer
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]

Abstract

Tamper-evident electric paper is made of two sheets of electric paper bonded together, the bottom sheet of which includes a pattern. Any attempt to erase a writing on the top sheet of electric paper results in the pattern on the bottom sheet of electric paper being erased. Therefore any tampering by erasure of a writing on the tamper-evident electric paper is revealed by the absence of a portion of the pattern on the bottom sheet of electric paper. Single sheet tamper-evident electric paper has a complex pattern, such as an encryption, printed on a single sheet of electric paper. Any attempt to erase a writing on the electric paper also erases a portion of the encryption, thereby providing evidence of tampering.

Claims

1. A method of forming an electric paper document, comprising:

orienting pixels of a first sheet of electric paper in a first pattern; and

orienting pixels of a second sheet of electric paper in a second pattern different from the first pattern, the second sheet being positioned in relation to the first sheet such that a first electric field that orients the pixels of the first sheet also orients the pixels of the second sheet.

2. The method of claim 1, wherein a second electric field that orients the pixels of the second sheet does not orient the pixels of the first sheet when both the first sheet and the second sheet are subjected to the second electric field.

3. The method of claim 2, wherein the second pattern comprises a glyph.

4. The method of claim 2, wherein the second pattern is an encryption.

5. The method of claim 1, wherein the second pattern comprises a glyph.

6. The method of claim 1, wherein the second pattern is an encryption.