Ink with time dependent characteristics
US5759246A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 17, 1996 |
| Grant date | Jun 2, 1998 |
| Priority date | — |
| Expiry date | Dec 17, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/78
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and ink composition are disclosed that utilize two mechanisms for the purpose of indicating the approximate age of an ink that has been deposited on a writing surface. The first mechanism relates to detecting color shifts of pH sensitive compounds in the ink as the result of the evaporation of certain acidic or basic chemicals thereof. The second mechanism relates to the oxidation of compounds in the ink. Spectroscopically generated curves are plotted as the ratio of reactants to products, versus time. The spectral characteristics of the ink are determined in units of percent reflectance of the active compounds in the ink so that the age of the ink can be computed by reference to known reaction rates. A plurality of dyes having differing reaction rates may be added to the ink to enable precise measurements to be made over different time intervals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.