Variable density verification
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United States of America Patent
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-
May 28, 2002
Issued Date -
N/A
app pub date -
Mar 23, 1998
filing date -
May 25, 1995
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A counterfeit-resistant document comprises a contrasting layer and a dynamic camouflaging layer. The contrasting layer is highly contrastive and includes a latent message that can be reproduced over a broad range of copy device control settings. The dynamic camouflaging layer is applied over the contrasting layer to suppress the latent message. The visual density of the dynamic camouflaging layer, which comprises a camouflage pattern that is printed in thermochromic ink, inversely varies with temperature. In this manner, the dynamic camouflaging layer is inactivated at room temperatures so that the latent message is suppressed on the original document, and activated at scanning temperatures so that the latent message is exhibited on a reproduction of the original document.
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