Self-verifying security documents

Details Self-verifying security documents Self-verifying security documents

1999-04-09

2000-05-16

Fridie, Jr., Willmon

Printed matter

Having revealable concealed information, fraud preventer or...

283 17, 283 73, 283107, B42D 1500

Patent

active

060626046

DESCRIPTION:

BRIEF SUMMARY
This invention relates to security documents, such as banknotes or the like, and is particularly concerned with providing a security document which includes means for verifying the security document or another similar document.
A wide variety of security devices or features for security documents, such as banknotes, travellers cheques or the like has been proposed previously. Examples of such security devices and features include: optically variable devices, such as holograms and diffraction gratings; security threads or strips; microprint; fine line or "filigree" patterns; Moire inducing patterns; and fluorescent inks, phosphorescent inks, pearlescent inks or other optically variable inks, such as metameric inks.
Metamerism has been described as "the property of the eye and brain to receive the same colour sensation (under specific lighting conditions) from two objects with different spectral energy distributions". Metameric inks have the unique property of appearing to change colour when viewed in different lighting conditions. For example, two inks with different metameric properties may appear to be of an identical colour when viewed in a particular white light environment, say daylight, but when viewed in different lighting conditions, e.g. in incandescent light, or in filtered light, the two inks will appear to have different reflective colours, so that one ink is distinguishable from the other. The optical effect of inks with metameric properties is widely accepted as a security device which inhibits such counterfeiting attempts as computer scanning and colour photocopying. Colour photocopying and colour printing is typically restricted to four different pigments (black, cyan, yellow and magenta) when attempting to match the colour of the original. In the event of reproducing metamerism, the colour distinction of an image with a different colour appearance in a particular lighting environment, is not as evident in the copy when compared to the original. The use of metameric inks as an anti-counterfeiting feature or security device in security documents is also described in U.K. Patent No. GB 1407065.
One disadvantage of metameric inks as a security device is that they require an optical filter or other external aid, to provide the required lighting condition for verification of the security device. Other types of security devices also require external aids for their verification. For example, fluorescent inks may require a source of ultraviolet light for their verification, and microprint, fine line and filigree patterns may require a magnifying lens for verification. Also, Moire inducing patterns, which produce fringes or a Moire effect when there is interference with a superimposed similar pattern, have hitherto only been effective as an anti-counterfeiting device when an attempt is made to reproduce a security document by colour photocopying. Also, a separate viewing device is required to verify that a security document has a Moire inducing pattern.
In Australian Patent Specification No. AU-A-87665/82 there is disclosed a security document and a method of producing a security document, in which opacifying coatings of ink are applied to both sides of a sheet-like substrate formed from a clear plastics film. The security document may be produced with some areas to which no opacifying coating is applied on both sides of the clear plastics substrate. These clear, transparent areas are known as "windows" and are particularly suitable for incorporating security devices, for example diffraction gratings, optically variable devices and embossed images, which can be inspected in the transparent areas or windows from both sides of the security document.
The present invention proposes that a transparent window in a security document may be used as a means for verifying, enhancing or optically varying a security device elsewhere on the document or on another security document.
According to one aspect of the invention, there is provided a security document such as a banknote, comprising a single flexible shee

REFERENCES:
patent: 3227474 (1966-01-01), Hoeflinger
patent: 4100689 (1978-07-01), Broune
patent: 5246375 (1993-09-01), Goede
patent: 5321755 (1994-06-01), Vlaar
patent: 5445417 (1995-08-01), Bromer et al.

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