Dual heat-freeze indicator
A dual heat-freeze indicator and methods for making the same are disclosed. The dual heat-freeze exposure indicator includes a substrate, a low temperature indicator material provided in a first initial color state, a high temperature indicator material provided in a second initial color state, both supported by the substrate. The low temperature indicator material is configured to change from the first initial color state to a first exposed color state responsive to the indicator being exposed to a temperature below a low temperature threshold. The high temperature indicator material is configured to irreversibly change from the second initial color state to a second exposed color state responsive to the indicator being exposed to a temperature above a high temperature threshold. The low temperature indicator material returns from the exposed color state to the initial color state responsive to being exposed to a temperature above a reset temperature threshold.
1 . A combined low temperature and high temperature historical temperature exposure indicator, comprising:
a substrate;
a low temperature indicator material supported by the substrate and provided in a first initial color state;
a high temperature indicator material supported by the substrate and provided in a second initial color state;
wherein the low temperature indicator material and the high temperature indicator material are combined in a heterogenous mixture;
wherein the low temperature indicator material is configured to change from the first initial color state to a first exposed color state responsive to the indicator being exposed to a temperature below a low temperature threshold, the low temperature indicator material configured to return from the exposed color state to the initial color state responsive to the low temperature indicator material being subsequently exposed to a temperature above a reset temperature threshold;
wherein the high temperature indicator material is configured to irreversibly change from the second initial color state to a second exposed color state responsive to the indicator being exposed to a temperature above a high temperature threshold, where the high temperature threshold is lower than the reset temperature threshold.
2 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the heterogeneous mixture is light colored or opaque in the first initial color state and a dark background area or indicia is provided on the substrate which is masked by the opacity of the heterogeneous mixture in the first initial color state and visible through the heterogeneous mixture when the heterogeneous mixture is exposed to a high temperature excursion.
3 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the low temperature threshold is in a range from 5° C. to −20° C.
4 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the high temperature threshold is in a range from 35° C. to 80° C.
5 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the reset temperature threshold is in a range from 50° C. to 100° C.
6 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the low temperature indicator material is a memory thermochromic composition that comprises at least one of (i) leuco dye (ii) liquid crystal; (iii) wax; (iv) micro-encapsulated dye; (v) an ester; (vi) an alkane; (vii) an organic polymer; (viii) an inorganic material; (ix) a micro-encapsulated leuco-dye; (x) microencapsulated leuco pigments.
7 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the high temperature indicator material comprises a water-based SCC polymer emulsion.
8 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the substrate includes printed information identifying the location of the low temperature indicator material and the high temperature indicator material on the substrate.
9 . The combined low temperature and high temperature historical temperature exposure indicator of claim 1 , wherein the exposure indicator, includes a second high temperature indicator material supported by the substrate and provided in a third initial color state; and
wherein a second high temperature indicator material configured to irreversibly change from the third initial color state to a third exposed color state responsive to the indicator being exposed to a temperature above a second high temperature threshold, wherein the second high temperature threshold is the same or lower than the reset threshold.
10 . The combined low temperature and high temperature historical temperature exposure indicator of claim 9 , wherein the first high temperature indicator material and the second high temperature indicator material overlay one another on the substrate.
11 . The combined low temperature and high temperature historical temperature exposure indicator of claim 9 , wherein the first high temperature indicator material, the second high temperature indicator material are located in separate regions on the substrate.
12 . The combined low temperature and high temperature historical temperature exposure indicator of claim 9 , wherein the second high temperature indicator material comprises a water-based SCC polymer emulsion.
13 . The indicator of claim 1 , wherein the low temperature indicator material is is microencapsulated separately from the high temperature indicator material.
14 . A combined low temperature and high temperature historical temperature exposure indicator, comprising:
a substrate;
a low temperature indicator material supported by the substrate and provided in a first initial color state;
a high temperature indicator material supported by the substrate and provided in a second initial color state; and
a dark background provided on the substrate behind both the low temperature indicator material and the high temperature indicator material;
wherein at least a portion of the low temperature indicator material overlays at least a portion of the high temperature indicator material;
wherein the low temperature indicator material is configured to change from the first initial color state to a first exposed color state responsive to the indicator being exposed to a temperature below a low temperature threshold, the low temperature indicator material configured to return from the exposed color state to the initial color state responsive to the low temperature indicator material being subsequently exposed to a temperature above a reset temperature threshold;
wherein the high temperature indicator material is configured to irreversibly change from the second initial color state to a second exposed color state responsive to the indicator being exposed to a temperature above a high temperature threshold, where the high temperature threshold is lower than the reset temperature threshold;
wherein the low temperature indicator material is transparent in the first initial color state and dark colored and opaque in the first exposed color state, and wherein the high temperature indicator material is light colored and opaque in the second initial color state and transparent in the second exposed color state, revealing the dark background when both the high temperature indicator material and the low temperature indicator material are transparent, the combined indicator appearing dark after being exposed to either a low temperature excursion below the low temperature threshold or a high temperature excursion above the high temperature threshold.
15 . The combined low temperature and high temperature historical temperature exposure indicator of claim 14 , wherein a symbol is provided in the dark background that is readable by the human eye, wherein a visual indication provided by the low temperature indicator material affects the appearance of the symbol, and wherein the changed appearance of the low temperature indicator material when exposed to a temperature below a low temperature threshold, provides a different visible indication.
16 . The combined low temperature and high temperature historical temperature exposure indicator of claim 15 , wherein the background contains an indicia visible after a high temperature excursion, that is hidden after a low temperature excursion or a reset.
17 . The indicator of claim 14 , wherein the low temperature indicator material is is microencapsulated separately from the high temperature indicator material.
18 . A method of creating a combined low temperature and high temperature historical temperature exposure indicator, the method comprising:
receiving a substrate;
receiving a low temperature indicator material configured to transition from a high temperature color state to a low temperature color state responsive to the indicator being exposed to a temperature below a low temperature threshold, the low temperature indicator material configured to return from the low temperature color state to the high temperature color state responsive to the low temperature indicator material being subsequently exposed to a temperature above a reset temperature threshold;
receiving a high temperature indicator material in an initial color state, the high temperature indicator material configured to irreversibly change from the initial color state to an exposed color state responsive to the indicator being exposed to the temperature above a high temperature threshold, where the high temperature threshold is lower than the reset temperature threshold;
forming a heterogenous mixture of the low temperature indicator material and the high temperature indicator material;
applying the heterogenous mixture to the substrate; and
maintaining the combined low temperature and high temperature indicator materials at a temperature above the low temperature threshold and below the high temperature threshold.
19 . The method of claim 18 , wherein the low temperature indicator material is applied in the low temperature color state, and, after application, the low temperature indicator material is exposed to a temperature above the reset temperature, placing it in the high temperature state.
20 . The method of claim 19 , wherein the low temperature indicator material is applied and exposed to the temperature above the reset temperature, prior to applying the high temperature indicator material.
21 . The method of claim 18 , wherein the low temperature indicator material is a memory thermochromic composition that comprises at least one of (i) leuco dye (ii) liquid crystal; (iii) wax; (iv) micro-encapsulated dye; (v) an ester; (vi) an alkane; (vii) an organic polymer; (viii) an inorganic material; (ix) a micro-encapsulated leuco-dye; (x) microencapsulated leuco pigments.
22 . The method of claim 18 , wherein the high temperature indicator material comprises a water-based SCC polymer emulsion.
23 . The method of claim 18 , wherein the low temperature indicator material is microencapsulated separately from the high temperature indicator material.