Long term rapid color changing time indicator employing dye absorbing layer

Abstract

Abstract A time indicator is provided that includes a front layer and a back layer, each having an inner and outer surface. The front layer has a display region on its outer surface. An adhesive means is provided on the inner surface of the front or back layer for adhesively attaching the front layer and back layer to each other. An opaque viewing layer is included on the front or back layer and an activation agent is provided on the other layer. One surface of the opaque viewing layer is viewable from the display region when the front and back layers are adhesively attached to each other. A dye that is substantially non-migrating through the opaque viewing layer, overlies the other surface of the opaque viewing layer. When the inner surfaces of the front and back layers are contacted with each other, the adhesive means adhesively attaches the front and back layers to each other and activates the activation agent. The activation agent migrates to the opaque viewing layer in a predetermined period of time to be absorbed therein. Such absorption activates the dye to enable it to migrate through the opaque viewing layer toward the other side causing an indication in the display region that the predetermined amount of time has expired. Optionally, the activation agent contacts the dye to, for example, solubilize the dye to enable it to migrate through the opaque viewing layer. Preferably, the activating agent is a plasticizer that is absorbed into the polymeric opaque the viewing layer. At a critical concentration of the plasticizer in the viewing layer, the dye is rapidly absorbed into the viewing layer, passing through the viewing layer to the other surface thereof where it becomes visible through the clear display region on, for example, the white background of the viewing layer.

Inventors

• 👤 David J. Haas

Bibliographic Details