2430257-A is referenced by 18 patents and cites 5 patents.

By printing a bar code (comprising dark and light regions) or parts of such a bar code with an ink containing a dye, which changes colour in the presence of an acid or a base to remove the contrast between the regions of the bar code, and a neutral compound which releases an acid or a base on exposure to energising radiation, a bar code can be produced that becomes unreadable after a pre-determined interval. This can be used as a time-temperature indicator to ensure that products, which might be perishable, associated with such a bar code are not used by the public. In one embodiment the dye is a leuco dye, in another embodiment the neutral compound is a cationic photoinitiator.

Bar code having a time-temperature indicator
Application Number
GB20050018948 20050916
Publication Number
Application Date
September 16, 2005
Publication Date
March 21, 2007
Leonard Michael William
Azizian Farid
Sun Chemical
G01N 31/22
G01K 03/00
B65D 79/00
G01K 11/00
G01N 31/22
G01K 03/04
B65D 79/02
G01K 11/12
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