Optical recording media having optically-variable security properties

• US 5,549,953 A
• Filed: 04/29/1993
• Issued: 08/27/1996
• Est. Priority Date: 04/29/1993
• Status: Expired due to Fees

• Current Assignee: National Research Council Canada
• Original Assignee: National Research Council Canada
• Inventors: Li, Li
• Primary Examiner(s): Ryan, Patrick J.
• Assistant Examiner(s): MULVANEY, ELIZABETH EVANS
• Application Number:
  US08/053,678
• Time in Patent Office: 1,216 Days
• Field of Search: 428/64, 428/65, 428/457, 428/913, 428/916, 428/64.1, 428/64.2, 428/64.3, 428/64.4, 428/64.5, 428/64.8, 430/270, 430/945, 430/270.1, 430/270.11, 430/270.12, 430/270.13, 430/270.14, 346/7 L, 346/135.1, 369/283, 369/288
• US Class Current: 428/64.1
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G02B 5/288 comprising at least one thin film resonant cavity, e.g. in bandpass filters
• CPC Class Codes: G06K 19/16 the marking being a hologram or diffraction grating
• CPC Class Codes: G07D 7/004 using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: G07D 7/12 Visible light, infrared or ultraviolet radiation
• CPC Class Codes: G07F 7/086 by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer for security documents G07D7/00; for the reading of record-carriers in general G06K7/00; for the design of coded credit-cards G06K19/10
• CPC Class Codes: Y10S 428/913 Material designed to be responsive to temperature, light, moisture
• CPC Class Codes: Y10S 428/916 Fraud or tamper detecting
• CPC Class Codes: Y10S 430/146 Laser beam
• CPC Class Codes: Y10T 428/21 Circular sheet or circular blank

Abstract

The prevention of counterfeiting of currencies, passports, cheques, bank cards, credit cards, optical disks and the like is addressed by introducing thin film structures having both optically-variable security properties and encoded optical data decodable by optical means. The thin film structures comprise a substrate and a multilayer interference coating carried by the substrate, producing an inherent color shift with a change of viewing angle. The multilayer interference coating has a dielectric material which is transparent and the recording layer made of a light absorbing material, a crystalline-structural changing material or a magneto-optic material. The encoded data is in the form of bar codes or digital data. The information is encoded by photolithographic means or by optical recording means. The encoded data is retrieved by an optical recording system having a light source and an optical guiding system and a light detector.

Claims

1. A thin film structure for storing data and having optically-variable properties for the prevention of counterfeiting and forgery, comprising:

a substrate having data encoded therein;

a thin film multilayer interference coating defining a Fabry Perot structure carried by the substrate, the interference coating being of a thickness suitable for providing thin film interference effects such that colours seen vary with a change in viewing angle, said thin film multilayer interference coating including at least one semi-transparent layer, at least a non-absorbing spacer including one or more dielectric layers, and a reflecting layer, the at least one spacer being disposed between the at least one semi-transparent layer and the reflecting layer.

2. A thin film structure as defined in claim 1 wherein the nonabsorbing dielectric layer is made of a transparent material selected from Al₂ O₃, HfO₂, MgF₂, Nb₂ O₅, SiO₂, Ta₂ O₅, TiO₂, Y₂ O₃, ZnS, ZnSe, and ZrO₂.

3. A thin film structure for storing data as is defined in claim 2, wherein the nonabsorbing dielectric layer is between 10 nm and 100 nm in thickness.

4. A thin film structure as defined in claim 1 wherein a recording layer is carried by the thin film multilayer interference coating and is positioned to receive and absorb an external light signal.

5. A thin film structure as defined in claim 4 wherein the optically decodable data is one of the forms comprising bar codes and digital data.

6. A thin film structure as defined in claim 4 wherein the at least one semi-transparent layer is a light absorbing material selected from the group consisting of Al, Cr, Co, Cu, Ge, Au, Hf, Mo, Ni, Nb, Pt, Si, Ag, Ta, Te, Ti, W, Yr, Zr, TeO_x, organic dyes or Ni based alloys.

7. A thin film structure as defined in claim 4, wherein the recording layer is encoded by one of the processes consisting of photolithographic means, local melting, vaporization, ablation, deformation and structural change with a laser beam.

8. A thin film structure for storing data and having optically-variable properties, for the prevention of counterfeiting and forgery, comprising:

a substrate; and

,

a thin film multilayer interference coating defining a Fabry Perot structure carried by the substrate for recording optical decodable data, the interference coating being of a thickness suitable for providing thin film interference effects such that colours seen vary with a change in viewing angle, the thin film multilayer interference coating including at least a recording layer made of a phase changing material for storing information, and a plurality of adjacent layers including a nonabsorbing dielectric layer and at least another layer of another material that is selected from the group consisting of metals, dielectrics, and semiconductors, the nonabsorbing layer being a spacer layer disposed between the recording layer and the at least other layer.

9. A structure as defined in claim 8 wherein the recording 8 wherein the recording layer is positioned to receive and absorb an external light signal.

10. A structure as defined in claim 9 wherein a crystalline microstructural phase of the phase change material of the recording layer changes when energy provided by the external light signal is absorbed by the material.

11. A structure as defined in claim 8 wherein the optically decodable data is encoded in the recording layer by heating the layer to a sufficient temperature to change the phase of the material with a laser beam.

12. A thin film structure for storing data and having optically-variable properties, for the prevention of counterfeiting and forgery, comprising:

a substrate; and

,

a thin film multilayer interference coating carried by the substrate for recording optical decodable data, said interference coating being of a thickness suitable for providing thin film interference effects such that colours seen vary with a change of viewing angle, the thin film multilayer interference coating defining a Fabry Perot structure including at least a transparent dielectric layer and a reflective layer of another material that is selected from the group consisting of metals, dielectrics, and semiconductors the interference coating also including a recording layer, the recording layer being a magnetic-optic material for storing magnetic-optically decodable data, the dielectric layer being disposed between the recording layer and the reflective layer.

13. A thin film structure as defined in claim 12, wherein the optically decodable data encoded in the recording layer is erasable.

14. A thin film structure for storing data and having optically-variable properties, for the prevention of counterfeiting and forgery, comprising:

a substrate; and

,

a thin film multilayer interference coating carried by the substrate for recording optical decodable data, said interference coating defining a Fabry Perot structure and being of a thickness suitable for providing thin film interference effects such that colours seen vary with a change of viewing angle, the thin film multilayer interference coating including at least a spacer layer that is a transparent layer and at least another layer of another material that is reflective selected from the group consisting of metals, dielectrics, and semiconductors, the interference coating also including a recording layer for storing optically decodable data, the recording layer being a light absorbing material selected from the groups of dielectrics, metals and semiconductors, the transparent spacer layer being a dielectric layer disposed between the recording layer and the at least other layer.

15. An optical data storage and retrieval system having security features, comprising:

a source for generating a coherent light signal for reading stored data;

a thin film structure for storing data and having optically-variable properties, comprising;

a substrate;

a multilayer interference coating carried by the substrate being of a thickness suitable for producing an inherent color shift with a change of angle, said interference coating including a dielectric layer, at least another layer being a different dielectric, a metal or a semiconductor and including a recording layer made of a material selected from the group consisting of light absorbing materials, phase change materials and magneto-optic materials, said recording layer having optically decodable data encoded therein and being positioned to receive and absorb the coherent light signal and to reflect an information containing signal; and

, detector means positioned to receive the reflected information containing signal.