| 摘要 |
PURPOSE:To provide a heating time passage display element using an electron donative, color developing org. cpd. and resin having acidic groups. By use of the element, heating time elapsed can be detected with accuracy by a continuous density rise even after the colorless org. cpd. is colored on heating. CONSTITUTION:An electron donative, color developing org. cpd. such as benzoyl leucomethylene blue and resin having acidic groups such as sulfonic acid, carboxylic acid and phenolic hydroxyl groups are kneaded with suitable solvent to form ink. The org. cpd. is colorless or light colored in a solid state at ordinary temp. and it assumes a dark color on heating. A support is coated or impregnated with the ink to provide a heating time passage display element. By adding coloring matter which gradually melts and evaporates or sublimes on heating, the effect of the org. cpd. can be enhanced furthermore. |
