| 摘要 |
A vacuum closure (10) for a container of a food product is of metal and has a tamper-indicating button (20) formed in the centre of its generally plane closure panel. In order to enhance its visual distinctiveness for tamper-evidence the button is formed with a coating (30) of an embrittled material having a colour developer incorporated in it. The brittle coating acts as matrix in which microcapsules (32) of a dye precursor material are dispersed. Operation of the button when the closure is opened ruptures the microcapsules, so allowing the dye precursor and colour developer to mix intimately and form a colour which is indicative that opening has occurred. |
