05602804 is referenced by 74 patents and cites 60 patents.

The time indicator device of this invention is provided with a display layer with at least one defined display region therein. A migration layer is provided which overlies and is attached to the display layer. The migration layer has at least one migration region therein and in use each migration region is in contact with at least one display region. An activation layer is provided which has at least one defined activation region therein. The activation region includes a migrating agent capable of migrating laterally through the migration region. When the activation layer overlies the migration layer, each activation region overlies at least one migration region. The migration region connects each activation region with at least one display region which is laterally distal from the activation region. In use and in order to activate the device the activation layer and migration layer are adhesively attached to each other. When the activation layer is contacted with and overlies the migration layer, each activation region contacts at least one migration region. Upon contact the migrating agent is activated to migrate laterally from the activation region through the migrating region to at least one display region in a predetermined amount of time to cause an indication in the display region that the predetermined amount of time has elapsed. Preferably, the device has a plurality of defined display regions, defined activation regions and/or migration regions to provide a means for adjusting the predetermined time, adjusting for environmental conditions and to provide a plurality of elapsed times.

Long term rapid color changing time indicator
Application Number
Publication Number
Application Date
August 3, 1995
Publication Date
February 11, 1997
David J Haas
Michael E Zall
G04B 17/00
View Original Source