Color change devices activatable by bending

Details Color change devices activatable by bending Color change devices activatable by bending

1992-04-30

1994-02-01

Bell, Paul A.

Printed matter

Having revealable concealed information, fraud preventer or...

Identifier

283100, 283101, 283114, B42D 1500

Patent

active

052826503

ABSTRACT:
Color change devices which are capable of undergoing a color change on bending. The devices comprise a flexible substrate having a color generating metal (e.g. a valve metal such as Ta or Nb) at at least one surface and an intimately contacting optically thin anodic film covering the color generating metal and generating a visible color by light interference and absorption effects. The thin anodic film is produced by anodizing the color generating metal in the presence of an adhesion-reducing agent (e.g. a fluoride) for weakening the normally tenacious bond between the anodic film and the metal. Devices of this kind capable of being activated by bending, as well as by separation of the constituent layers, are produced by carrying out the anodization step in the presence of a particular concentration of the adhesion reducing agent from a narrow range (e.g. 40-350 ppm of fluoride). The devices can be used as tamper evident labels and the like which show evidence of removal of the labels from articles to which they were originally attached as an indication of tampering.

REFERENCES:
patent: 3896965 (1975-07-01), Cornell
patent: 4557505 (1985-12-01), Schaefer et al.
patent: 4763931 (1988-08-01), Matsuguchi et al.
patent: 4837061 (1989-06-01), Smits et al.
patent: 5020831 (1991-06-01), Benardelli

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