Method of making color change devices activatable by bending and

Details Method of making color change devices activatable by bending and Method of making color change devices activatable by bending and

1990-06-20

1992-08-04

Niebling, John

Printed matter

Having revealable concealed information, fraud preventer or...

Utilizing superposed layers

205152, 205199, 205200, 205322, 283 81, 283 95, 428915, 428916, C23C 2800, C25D 1126, B65D 5502

Patent

active

051352621

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 are originally attached as an indication of tampering.

REFERENCES:
patent: 3896965 (1975-07-01), Cornell
patent: 4763931 (1988-08-01), Matsuguchi et al.
patent: 4837061 (1989-06-01), Smits et al.
patent: 4890763 (1990-01-01), Curiel
patent: 5020831 (1991-06-01), Benardelli
World Patents Index Latest, Accession No. 84-162105, week 26, Derwent Publications Ltd., London GB; and JP-A-59 087 149 (Mitsubishi Chem. Ind. K.K.), May 19, 1984.

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