Thermal indicators
View Patent ↗A thermal indicator using indicia formed by opaque ink applied to a thermal imaging material element is described. The ink is substantially the same color as the imaging element background and remains substantially hidden until the imaging element background changes color when heated. Time-temperature exposure indicating labels can be prepared using a printer with direct thermal type and ink jet type print heads.
1. A method of hiding and revealing a warning message to indicate whether a label has been exposed to a selectable activation temperature, the method comprising:
at a first time, printing with ink of a first color the warning message on a first portion of the label having a thermally sensitive coating of an initial color which substantially matches the first color of the warning message to render the first color of the warning message substantially invisible against the initial color of the thermally sensitive coating and thereby to hide the warning message;
at a second time which is after the first time, applying heat to a second portion of the label which is different from the first portion of the label to provide a non-warning message of a second color on the second portion of the label, wherein the second color of the non-warning message on the second portion of the label is different from the first color of the warning message on the first portion of the label; and
at a third time which is after the second time, exposing the first portion of the label to the selectable activation temperature to change the thermally sensitive coating from the initial color which substantially matches the first color of the warning message to a different color to render the first color of the warning message 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 the selectable activation temperature.
2. The method of claim 1 , wherein (i) the first color is a color which is substantially white, and (ii) the second color is a color which is other than substantially white.
3. The method of claim 2 , wherein the second color is a color which is substantially black.
4. The method of claim 1 , wherein (i) the first color is a color which is substantially white, and (ii) the second color is a color which is substantially black.
5. A method of hiding and revealing a warning message to indicate whether a label has been exposed to a selectable activation temperature, the method comprising:
at a first time, printing with ink of a substantially white color from an ink jet print head the warning message on a first portion of the label having a thermally sensitive coating of an initial color which substantially matches the substantially white color of the warning message to render the substantially white color of the warning message substantially invisible against the initial color of the thermally sensitive coating and thereby to hide the warning message;
at a second time which is after the first time, applying heat from a direct thermal print head to a second portion of the label which is different from the first portion of the label to provide a non-warning message of a color which is other than a substantially white color on the second portion of the label; and
at a third time which is after the second time, exposing the first portion of the label to the selectable activation temperature to change the thermally sensitive coating from the initial color which substantially matches the substantially white color of the warning message to a different color to render the substantially white color of the warning message 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 the selectable activation temperature.
6. The method of claim 5 , wherein the different color to which the thermally sensitive coating changes from the initial color upon exposure to the selectable activation temperature is substantially black.
7. The method of claim 5 , wherein the substantially white color of the ink is a substantially opaque white color.
8. The method of claim 5 , wherein (i) the different color to which the thermally sensitive coating changes from the initial color upon exposure to the selectable activation temperature is substantially black, and (ii) the substantially white color of the ink is a substantially opaque white color.
9. A method of hiding and revealing a warning message to indicate whether a pharmacy label and an associated medication container for containing temperature-sensitive medications have been exposed to a selectable activation temperature, the method comprising:
at a first time, printing with ink of a substantially white color the warning message on a first portion of the pharmacy label having a thermally sensitive coating of an initial color which substantially matches the substantially white color of the warning message to render the substantially white color of the warning message substantially invisible against the initial color of the thermally sensitive coating and thereby to hide the warning message;
at a second time which is after the first time, applying heat to a second portion of the pharmacy label which is different from the first portion of the pharmacy label to provide a non-warning message of a color which is other than a substantially white color on the second portion of the pharmacy label;
at a third time which is after the second time, attaching the pharmacy label including the warning message and the non-warning message to the medication container; and
at a fourth time which is after the third time, exposing the first portion of the pharmacy label to the selectable activation temperature to change the thermally sensitive coating from the initial color which substantially matches the substantially white color of the warning message to a different color to render the substantially white color of the warning message visible against the different color of the thermally sensitive coating and thereby to reveal the warning message to indicate that the pharmacy label and the medication container to which the pharmacy label is attached have been exposed to the selectable activation temperature.
10. The method of claim 9 , wherein the different color to which the thermally sensitive coating changes from the initial color upon exposure to the selectable activation temperature is substantially black.
11. The method of claim 9 , wherein the substantially white color of the ink is a substantially opaque white color.
12. The method of claim 9 , wherein (i) the different color to which the thermally sensitive coating changes from the initial color upon exposure to the selectable activation temperature is substantially black, and (ii) the substantially white color of the ink is a substantially opaque white color.