Security document having a security element embedded therein wit

Details Security document having a security element embedded therein wit Security document having a security element embedded therein wit

1991-03-07

1993-01-05

Eley, Timothy V.

Printed matter

Having revealable concealed information, fraud preventer or...

And electrically conductive material

283 72, 283 91, 283901, 162106, B42D 1500

Patent

active

051764059

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a security document having a security element in the form of a transparent thread or strip embedded therein bearing visually recognizable marks in the form of characters, printed patterns and the like and designed so as to be electrically conductive for machine-testability.
It is known to protect security documents by embedding therein security elements that exhibit particular machine-detectable physical properties and/or have a visual appearance that permits them to serve as authenticity features for the security document. These security elements are e.g. threads or strips that are embedded directly in the paper layer as it is forming in the course of the paper production.
For example, German laid-open print no. 14 46 851 discloses a safeguarding thread provided on both sides with microprints. To allow for the patterns printed on the front and the back to be checked independently of each other an aluminum layer is placed therebetween. This aluminum layer can also serve as a machine-readable feature if its electric conductivity is determined. In practice this form has not proved to be very useful since the aluminum layer makes the safeguarding thread opaque and the writing can only be recognized in incident light and even then only with great difficulty. It is usually necessary to make the paper transparent by chemical means at least for the time of testing. Furthermore, the microprint of the safeguarding thread overlaps the outer printed pattern, which is likewise felt to be disturbing in many cases.
Since safeguarding threads can only be embedded up to a certain width without holes during sheet forming, it has been proposed to incorporate porous threads, which can be of accordingly wider design (German laid-open print no. 21 52 090). In a special embodiment a safeguarding thread is also described that shows different colors when viewed in incident light and in transmitted light. The thread is provided for this purpose with two color layers having a semitransparent aluminum coating therebetween. When this thread is viewed in incident light after it is embedded in the paper, the color layer located above the reflective aluminum coating is dominant, while in transmitted light the secondary color from the two colors will be the dominant color. However, such threads involve adhesion problems between the color layers and the metal layer located therebetween, whereby the outer color layer can even be detached from the metal layer. Although this thread is thus basically machine-testable with respect to its electric conductivity, this feature is not a reliable authenticity feature due to the lack of durability of the metal coating over the total length of the thread. Cracks or partial detachment of the metal layer will already cause an interruption in the electric conductivity. Such security documents are accordingly classified as forgeries in during machine testing although they are authentic.
A safeguarding thread having very easily tested writing after being embedded in paper is known e.g. from U.S. Pat. No. 4,652,015. This thread comprises a transparent carrier having printing in the form of a plurality of single shiny microcharacters. The known safeguarding thread and the microcharacters located thereon are not recognizable in incident light. In transmitted light, on the other hand, solely the characters are visible as sharply contoured marks since the carrier itself is designed so as to be transparent. Such a safeguarding thread is produced by metalizing a transparent film with an aluminum layer over a large surface, printing the microcharacters on this layer using an acidproof ink, and then etching off the unprinted areas, leaving the characters as single characters separated from one other on a transparent background.
This thread accordingly has an easily recognized visual feature, but loses the property of electric conductivity due to the split into single characters and the resulting interruption in the metal layer. It is thus unsuitable for machine testing.
Non-prepubli

REFERENCES:
patent: 4504084 (1985-03-01), Jarroh
patent: 4652015 (1987-03-01), Crane
patent: 4927180 (1990-05-01), Trundle et al.
patent: 4943093 (1990-07-01), Melling et al.

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