FREEZE INDICATOR EMPLOYING LIGHT SCATTERING AND METHOD OF MAKING SAME

• US 20140048010A1
• Filed: 08/16/2013
• Published: 02/20/2014
• Est. Priority Date: 08/16/2012
• Status: Active Grant

• Current Assignee: Temptime Corporation (Zebra Technologies Corporation)
• Original Assignee: Temptime Corporation (Zebra Technologies Corporation)
• Inventors: SMITH, Dawn E., Taylor, Dene H., Huffman, Brian S.
• Granted Patent: US 9,297,706 B2
• Time in Patent Office: Days
• US Class Current: 116/206
• CPC Class Codes: G01K 11/12 using changes in colour, translucency or reflectance
• CPC Class Codes: G01K 3/04 in respect of time

Abstract

A freeze indicator including an indicator dispersion is described herein. Such an indicator dispersion can include: a liquid medium and particles of a colored indicator agent dispersed in the liquid medium. The colored indicator agent particles having an inherent color; wherein the indicator dispersion exhibits the inherent color of the colored indicator agent particles after freezing and is configured to have a less colored appearance before freezing and wherein light scattering masks the inherent color of the colored indicator agent particles before freezing. Some indicator dispersions can be free of color-changing chemical co-reactants. These freeze indicators can be small, have a low cost, and have a simple configuration.

Claims

1. An indicator dispersion comprising:

a liquid medium; and

particles of a colored indicator agent dispersed in the liquid medium, the colored indicator agent particles having an inherent color;

wherein the indicator dispersion exhibits the inherent color of the colored indicator agent particles after freezing and is configured to have a less colored appearance before freezing and wherein light scattering masks the inherent color of the colored indicator agent particles before freezing; and

wherein the indicator dispersion is free of color-changing chemical co-reactants.

4. The indicator dispersion of claim 1, wherein the liquid medium is a hydrophobic liquid medium.

5. The indicator dispersion of claim 1, wherein the liquid medium is an aqueous liquid medium.

6. The indicator dispersion of claim 1, wherein the particles of the colored indicator agent comprise solid particles of a colorant dissolved or dispersed in a solid material.

7. The indicator dispersion of claim 5, wherein the particles of the colored indicator agent comprise a colorant dissolved or dispersed in a hydrophobic liquid.

8. The indicator dispersion of claim 7, wherein the colorant is a dye and the hydrophobic liquid is an oil.

9. The indicator dispersion of claim 1, wherein the indicator dispersion coalesces in response to exposure of the indicator dispersion to a freezing temperature.

12. The indicator dispersion of claim 1, wherein the particles of the colored indicator agent have an absorbance at 500 nm of about 1 to about 30.

13. The indicator dispersion of claim 1, wherein the particles of the colored indicator agent have an average particle size of at least about 100 nm, and of not more than about 2 μ

m.

15. The indicator dispersion of claim 1, wherein the thickness of the dispersion is less than 1 mm.

16. The indicator dispersion of claim 1, wherein the after-freezing appearance of a layer of the indicator dispersion having a thickness of 1 mm is at least 0.4 optical density units darker than the before-freezing appearance of the layer of the indicator dispersion.

17. The indicator dispersion of claim 1, wherein the particles of the colored indicator agent are homogenous and no other indicator particles are present in the indicator dispersion.

18. The indicator dispersion of claim 1, wherein the indicator dispersion comprises an ice-nucleating agent.

19. A freeze indicator comprising:

a housing; and

the indicator dispersion of claim 1 within the housing, the housing being configured for the indicator dispersion to be optically readable externally of the freeze indicator.

20. The freeze indicator of claim 19, comprising a substrate supporting the housing, the housing and substrate optionally being flexible.

28. The article of manufacture of claim 37, which is a host product having the freeze indicator associated with the host product to monitor the host product for exposure to a freezing temperature.

29. The article of manufacture of claim 37, which is a label for a perishable good, comprising the freeze indicator.

30. The article of manufacture of claim 37, which is a package for a perishable good, comprising the freeze indicator.

31. The article of manufacture of claim 37, which is a package containing a perishable good, comprising the freeze indicator.

37. An article of manufacture comprising the freeze indicator of claim 19.

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