Time color indicator

Details Time color indicator Time color indicator

1978-02-07

1980-07-15

Weldon, Ulysses

Horology: time measuring systems or devices

Chronological

428353, 428 88, 116216, 116207, G04F 1300

Patent

active

042121531

ABSTRACT:
A laminated indicator which changes in a visually perceptible mode with the passage of time and a method for making such an indicator. At least two layers are provided whereby the molecular migration of an agent in an interior layer to the outermost surface of the exterior layer causes a change which can be visually percepted, e.g., a change in color or shade. Preferred embodiments include the migration of a dye or the migration of an acid or base wherein the outermost layer has the other member of an acid-base pair and a pH indicator.

REFERENCES:
patent: 2337534 (1943-12-01), Barber
patent: 3078182 (1963-02-01), Crone, Jr. et al.
patent: 3520124 (1970-07-01), Myers
patent: 3999946 (1976-12-01), Patel et al.

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