Document having a security feature and method of determining the

Details Document having a security feature and method of determining the Document having a security feature and method of determining the

1982-09-28

1985-02-26

Bell, Paul A.

Printed matter

Having revealable concealed information, fraud preventer or...

Utilizing electromagnetic radiation

283 94, 283904, 283 86, 356 71, B42D 1500, G02B 2738

Patent

active

045014396

ABSTRACT:
In a security blank which includes a substrate which has two major surfaces, a thermoplastic layer which has a predetermined refraction index and is suitable for embossing thereon a machine-readable authenticity feature in the form of an optical microstructure, and a transparent layer which has a prearranged refraction index for covering and protecting the microstructure, and wherein the prearranged refraction index has a value different from the predetermined refraction index, and the microstructure generates a characteristic diffraction effect from light incident thereonto, the improvement includes a surface of the substrate facing the thermoplastic layer, which has within a region of the microstructure diffuse reflection characteristics of a predetermined magnitude, and wherein the thermoplastic layer is transparent, and wherein the difference between the refraction indexes is sufficiently small, and the magnitude of the diffuse reflection characteristics is sufficiently large, so that the characteristic diffraction effect of the microstructure is not normally detectable by the eye of an observer.

REFERENCES:
patent: 3571957 (1971-05-01), Cumming et al.
patent: 3614430 (1971-10-01), Berler
patent: 4092526 (1978-05-01), Beck
patent: 4119361 (1978-10-01), Greenaway
patent: 4129382 (1978-12-01), Greenaway
patent: 4140373 (1979-02-01), Rull
patent: 4142674 (1979-03-01), Walton
patent: 4184700 (1980-01-01), Greenaway
patent: 4211918 (1980-07-01), Nyfeler et al.
patent: 4290630 (1981-09-01), Lee

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