Field activated security articles including polymer dispersed liquid crystals, and including micro-encapsulated field affected materials

• US 6,259,506 B1
• Filed: 06/23/1998
• Issued: 07/10/2001
• Est. Priority Date: 02/18/1997
• Status: Expired due to Term

• Current Assignee: Spectra Science Corp. (Spectra Acquisition Corp.)
• Original Assignee: Spectra Science Corp. (Spectra Acquisition Corp.)
• Inventors: Lawandy, Nabil M
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/102,786
• Time in Patent Office: 1,113 Days
• Field of Search: 349/193-86, 283/72, 283/90, 283/901, 428/29
• US Class Current: 349/193
• CPC Class Codes: G06K 19/06 characterised by the kind of the digital marking, e.g. shape, nature, code
• CPC Class Codes: Y10S 283/901 Concealed data

Abstract

In a first aspect this invention provides a security article comprising an electrically actuated optical switch comprised of a liquid crystal material. In one embodiment the liquid crystal material is disposed in a layer of polymer dispersed liquid crystal material. In a second embodiment the liquid crystal material is micro-encapsulated with an orientable dye. In a second aspect this invention provides a document or currency that comprises a paper matrix that includes at least one security article, i.e. a security thread. In a third aspect this invention provides a device for verifying an authenticity of a document or currency of a type that includes at least one security article, i.e. at least one security thread. The at least one security thread includes the liquid crystal material having a visual characteristic that is switched between two states as a function of a presence or absence of an electric field between first and second electrodes. In one embodiment the device for verifying the authenticity of the document or the currency includes an external pump source for generating a stimulated emission the at least one security article disposed within the document or currency. In one embodiment the external pump source includes a pulsed Nd:YLF laser, a frequency doubling KTP crystal and a device to provide stimulated Raman scattering.

Claims

1. A device for verifying an authenticity of a document or currency of a type that includes at least one security thread, comprising first and second electrodes and an excitation source coupled to said electrodes, said first and second electrodes being spaced apart for accommodating therebetween said document or currency, at least one of said electrodes being transparent, said at least one security thread being comprised of at least one layer of polymer dispersed liquid crystal material having a visual characteristic that is switched between two states as a function of a presence or absence of an electric field between said first and second electrodes, wherein said polymer is comprised of an ink.

2. A security article, comprising at least one layer that contains an optical gain medium and a plurality of micro-capsules that contain an electrically actuated optical switch comprised of liquid crystal material.

3. A security article as set forth in claim 2, wherein when excited said optical gain medium emits a laser-like emission of one of a desired color or a desired wavelength.

4. A security article, comprising at least one layer comprised of a plurality of micro-capsules that contain liquid crystal material and a material for generating a stimulated emission, in response to an optical pump, and electrically activated scattering sites for scattering said stimulated emission.