| abstract |
The invention relates to devices for indicating the history of products, e.g., with regard to the temperature progression. The device according to the invention comprises a covering layer, an indicator layer, an activator layer, and an optional delaying layer. By means of heating, moisture is released, which, in the case of some embodiments, migrates first into the delaying layer and then into the activator layer. There, an activator is mobilized and migrates together with the moisture into the indicator layer. By interaction of the indicator with the activator in the presence of moisture, a color conversion occurs, which indicates the exceedance of the critical temperature. The invention further relates to methods for producing the device according to the invention and to applications of the device according to the invention, e.g., in the temperature monitoring of sensitive products. |