Temperature-sensitive materials and devices
US4996104A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 23, 1989 |
| Grant date | Feb 26, 1991 |
| Priority date | — |
| Expiry date | Mar 23, 2009 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/2984
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A device for indicating whether a rise in temperature above a predetermined value has occurred includes a support member, such as a label, on which a temperature-sensitive material is deposited. The material includes a large number of fracturable microcapsules containing a medium which changes from a solid state to a liquid state at the predetermined temperature value. The viscosity of the medium in its liquid state and the material of the support member are chosen such that the distance d.sub.1 by which the medium flows across the support member after the fracturing of the microcapsules so as to activate the device is indicative of the time between activation of the device and cooling of the device to below the predetermined temperature value. If the temperature is subsequently allowed to rise above the predetermined value, the medium will again assume its liquid state and will flow further across the support member, reaching a distance of, say, d.sub.2, thus indicating that the rise in temperature has occurred. The material may be printed on the label as a bar code, so that any rise above the predetermined temperature level will be indicated by distortion of the bar code which re…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.