| 摘要 |
<p>A label that changes appearance with time is disclosed. The label comprises a first layer that has different permeabilities to a gas in different lateral areas of the label and which comprises a substance that changes colour when in contact with the gas. The substance is arranged within the label such that the gas permeates across the thickness of the layer at different rates in different lateral areas so as to cause the substance to change colour at different rates in said different areas. Another label that changes appearance with time is disclosed that allows ink to permeate to its surface at different rates in different lateral areas.</p> |
