Identification card with embedded halftone image security feature perceptible in transmitted light

• US 6,752,432 B1
• Filed: 06/23/2000
• Issued: 06/22/2004
• Est. Priority Date: 06/23/1999
• Status: Expired due to Term

• Current Assignee: L-1 Secure Credentialing, LLC (Advent International Corporation)
• Original Assignee: Digimarc Corporation
• Inventors: Richardson, Jack T.
• Primary Examiner(s): CARTER, MONICA SMITH
• Application Number:
  US09/602,313
• Time in Patent Office: 1,460 Days
• Field of Search: 402/990.1, 283/67, 283/81, 283/86, 283/91, 283/94, 283/98, 283/101, 283/105, 283/108, 283/110, 428/13, 428/131, 428/137, 428/201, 428/203
• US Class Current: 283/91
• CPC Class Codes: B42D 25/00 Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof printing processes to produce identification or security features B41M3/14
• CPC Class Codes: B42D 25/23 Identity cards
• CPC Class Codes: B42D 25/405 Marking
• CPC Class Codes: B42D 25/465 using chemicals or adhesives
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24851 Intermediate layer is discontinuous or differential
• CPC Class Codes: Y10T 428/24868 Translucent outer layer

Abstract

An information-bearing laminar assembly, suitable for use as an identification card, is disclosed. The assembly is characterized by the provision therein of an embedded halftone image security feature that becomes visible essentially only when the assembly is viewed in transmitted light. The information-bearing laminar assembly comprises an inner information-bearing layer interposed between a first and a second light-transmissive protective outer layer. The inner layer contains both visible information-bearing indicia and an imagewise halftone pattern of laser-ablated microholes. The light-transmissivity of the information-bearing inner layer within said half-tone pattern is imagewise differentiated at each microhole as a function of the microhole'"'"'s penetration depth. Sandwiched between the protective outer layers, the halftone pattern is imperceptible when the information-bearing laminar assembly is viewed in reflection and perceptible when the information-bearing laminar assembly is viewed in transmission.

Claims

1. An information-bearing laminar assembly, comprising an information-bearing inner layer interposed between first and second light transmissive outer layers;

the information-bearing inner layer having imagewise halftone pattern of microholes formed thereon, each microhole penetrating at least partially through the thickness of the information-bearing layer such that the light transmissivity of the information-bearing layer within said half-tone pattern is imagewise differentiated at each microhole;

the first and second light-transmissive outer layers and said information-bearing inner layer being constructed and arranged such that the first and second light transmissive outer layers cover said imagewise half-tone pattern of microholes and permit transmitted light to reach said microholes;

the microholes having sufficiently small structural dimensions such that, under unassisted visual inspection, the imagewise halftone pattern is (a) substantially imperceptible when the information-bearing laminar assembly is viewed in reflection, and (b) substantially perceptible when the information-bearing laminar assembly is viewed in transmission.

2. The information-bearing laminar assembly of claim 1, wherein the first and second light-transmissive outer layers are made of a thermoplastic material, and wherein said thermoplastic material fills said microholes.

3. The information-bearing laminar assembly of claim 1, further comprising first and second layers of an adhesive material, the first adhesive layer being deposited to adhere the information-bearing inner layer to the first light-transmissive outer layer, the second adhesive layer being deposited to adhere the information-bearing inner layer to the second light-transmissive outer layer.

4. The information-bearing laminar assembly of claim 3, wherein said adhesive material fills said microholes.

5. The infomniation-bearing laminar assembly of claim 1, wherein the first and second light-transmissive outer layers comprise amorphous polyethylene terephthalate.

6. The information-bearing laminar assembly of claim 1, wherein the diameters of the microholes are within the range of approximately 0.002 inches to approximately 0.004 inches.

7. The information-bearing laminar assembly of claim 6, wherein the microholes penetrate the information-bearing inner layer at depths within a range of 50 percent to 100 percent of the total depth of the information-bearing inner layer.

8. The assembly of claim 1 wherein the imagewise halftone pattern of microholes is disposed around the periphery of the inner information-bearing layer.

9. The assembly of claim 8 wherein the first and second light transmissive outer layers are coupled to the information-bearing inner layer such that an attempt to decouple either of the first and second light transmissive outer layers from the information-bearing inner layer results in a disruption of the imagewise halftone pattern formed by the of microholes disposed around the periphery of the information-bearing layer, the disruption being substantially perceptible under unassisted visual inspection when light is passed through the information-bearing inner layer.

10. The assembly of claim 1 wherein the imagewise halftone pattern of microholes is generally confined to a periphery of the inner information-bearing layer, the imagewise halftone pattern of microholes defining an identifiable optical pattern capable of indicating whether an attempt has been made to remove the first and second light transmissive outer layer.

11. The assembly of claim 1, wherein the information-bearing layer further comprises visually-perceptible information-bearing indicia on at least a portion of a surface thereof.

12. The information-bearing laminar assembly of claim 11, wherein the imagewise halftone pattern of microholes is disposed in an area of the information-bearing inner layer that contains substantially no visually-perceptible information-bearing indicia.

13. The information-bearing laminar assembly of claim 11, wherein the imagewise halftone pattern of microholes and the visually-perceptible indicia overlap.

14. The assembly of claim 1 wherein the imagewise halftone pattern of microholes is constructed and arranged to vary the density of the inner information-bearing layer such that the intensity of the light transmissive through the inner information-bearing layer is varied.

15. The assembly of claim 1 wherein said imagewise halftone pattern of microholes is constructed and arranged such that the light transmissivity of the information-bearing inner layer within said first portion of said half-tone pattern is imagewise differentiated at each microhole as a function of the penetration depth of the microhole into tie information-bearing inner layer.

16. The assembly of claim 1 wherein said imagewise halftone pattern of microholes is constructed and arranged such that the light transmissivity of the information-bearing inner layer within said half-tone pattern is imagewise differentiated at each microhole as a function of the population of microholes within the imagewise halftone pattern.

17. The assembly of claim 1 wherein the information-bearing inner layer comprises a translucent material having a substantially homogeneous color.

18. The assembly of claim 1 wherein the information-bearing inner layer comprises at least one of TESLIN, a semi-rigid planar material capable of being laser ablated, and a rigid planar material capable of being laser ablated.

19. A method of manufacturing an information-bearing laminar assembly, comprising:

making an information-bearing layer comprising planar material capable of having microholes formed therein; and

forming in said planar material an imagewise halftone pattern of microholes, the microholes having sufficiently small structural dimensions;

such that under unassisted visual inspection, the halftone pattern is substantially imperceptible when the information-bearing laminar assembly is viewed in reflection and substantially perceptible when the information-bearing laminar assembly is viewed in transmission.

20. The method of claim 19, wherein forming microholes comprises forming microholes with diameters within the range of approximately 0.002 inches to approximately 0.004 inches.

21. The method of claim 19, wherein the microholes penetrate the planar material at depths within a range of 50 percent to 100 percent of the total depth of the planar material.

22. The method of claim 19, further comprising interposing the information-bearing layer between first and second light-transmissive outer layers, the first and second light-transmissive outer layers and said information-bearing inner layer being constructed and arranged such that the first and second, light transmissive outer layers cover said imagewise half-tone pattern of microholes and permit transmitted light to reach said microholes.

23. The method of claim 19, further comprising coupling the information-bearing layer between first and second light-transmissive outer layers such that the first and second outer layers cover the imagewise halftone pattern of microholes, the first and second light-transmissive outer layers being configured such that under unassisted visual inspection, the halftone pattern is imperceptible when the information-bearing laminar assembly is viewed in reflection and perceptible when the information-bearing laminar assembly is viewed in transmission.

24. The method of claim 19, wherein the information-bearing layer comprises laser-ablatable material and wherein forming the microholes comprises laser ablating the information-bearing layer to form microholes.

25. The method of claim 24, wherein the laser ablation comprises modulating the intensity and duration of the laser irradiation to imagewise differentiate the penetration depths of said microholes into said planar material.

26. The method of claim 19, further comprising providing visually perceptible information-bearing indicia on at least a portion of the inner information-bearing layer.

27. The method of claim 26 further comprising overlapping the microholes and at least a portion of the visually perceptible information-bearing indicia.

28. An information-bearing laminar assembly, comprising

a first light transmissive layer;

a second light transmissive layer; and

means for providing an imagewise halftone pattern disposed between the fist and second light transmissive layers, such that under unassisted visual inspection, the imagewise halftone pattern is (a) substantially imperceptible when the first light transmissive layer is viewed in reflection, and (b) substantially perceptible when light is transmitted from the second light transmissive layer to the first light transmissive layer.