Patent ID: 8764324

Claim:
A printer for printing of a time-temperature indicator label having a thermally sensitive coating on a substrate, where the thermally sensitive coating changes from an initial color to a different color when the thermally sensitive coating is exposed to heat, the printer comprising: a direct thermal printing print head for applying heat to thermally image a portion of the thermally sensitive coating to provide indicia on a first portion of the label, wherein the indicia provided on the first portion of the label is visible after heat is applied from the direct thermal printing print head to the portion of the thermally sensitive coating; an ink jet print head for printing a warning message on a second portion of the label which is different from the first portion of the label, wherein the warning message is (i) substantially invisible before the thermally sensitive coating is exposed to heat from a source which is other than the direct thermal printing print head, and (ii) visible after the thermally sensitive coating is exposed to heat from a source which is other than the direct thermal printing print head; and a supply of ink for the ink jet print head, wherein the ink comprises a color which (i) substantially matches the initial color of the thermally sensitive coating before the thermally sensitive coating is exposed to heat from a source which is other than the direct thermal printing print head such that the warning message printed on the second portion of the label is substantially invisible against the initial color of the thermally sensitive coating, and (ii) contrasts sufficiently with the different color of the thermally sensitive coating after the thermally sensitive coating is exposed to heat from a source which is other than the direct thermal printing print head such that the warning message printed on the second portion of the label is visible against the different color of the thermally sensitive coating and thereby to reveal the warning message to indicate that the label has been exposed to heat from a source which is other than the direct thermal printing print head.