Activatable time-temperature indicator system

• US 6,544,925 B1
• Filed: 03/02/2000
• Issued: 04/08/2003
• Est. Priority Date: 03/02/2000
• Status: Expired due to Fees

• Current Assignee: Temptime Corporation (Zebra Technologies Corporation)
• Original Assignee: Lifelines Technology Incorporated (Zebra Technologies Corporation)
• Inventors: Prusik, Thaddeus, Arnold, Raymond M., Piechowski, Allan P.
• Primary Examiner(s): Hess, Bruce H.
• Application Number:
  US09/517,831
• Time in Patent Office: 1,132 Days
• Field of Search: 503/200, 503/226, 503/201, 428/913, 436/2, 436/7, 116/206, 116/207, 116/216, 116/218, 422/56-58, 252/408.1
• US Class Current: 503/201
• CPC Class Codes: B32B 7/06 permitting easy separation
• CPC Class Codes: G01K 3/04 in respect of time
• CPC Class Codes: G01N 31/229 for investigating time/temperature history
• CPC Class Codes: G09F 3/0291 Labels or tickets undergoing a change under particular conditions, e.g. heat, radiation, passage of time

Abstract

An activatable time-temperature indicator system useful in tracking the thermal exposure history of a temperature-sensitive perishable product and providing a visually-distinct signal, such as a change in color density, at the expiration of a predetermined time-temperature integral comprises a first element, such as a direct thermal printing label (11), comprising a composition (13) having at least a first co-reactant of a color-forming reaction. A second, activator element, such as an adhesive tab (21) capable of being affixed to the label element, comprises an activator component (25), such as a second co-reactant of the color-forming reaction or a solubilizing agent for prompting the interaction of the co-reactants of the label composition. The activator tab element is affixed to the label composition to activate for reaction at ambient conditions the normally high-temperature color-forming composition (13) of the label at about the same time as the label is affixed to the perishable product. Such an ability to effect the initiation of the indicator reaction at a given time eliminates any unknown, premature color formation in the indicator system to thereby ensure a true time-temperature history of the perishable product.

Claims

1. An activatable time-temperature monitoring system for indicating the elapse of a combination of time and ambient temperature which exceeds a predetermined time-temperature integral

characterized in that said system comprises

a) a first element comprising a direct thermal color-forming composition comprising at least a pair of co-reactant components capable of reacting in combination to form said color upon the heating of said composition at least to a threshold temperature;

and

b) a second element comprising an activating component capable of, upon contact with said first element composition, initiating said color-forming combination reaction at a second temperature below said threshold and causing said reaction to proceed at an average rate satisfying said predetermined time-temperature integral.

2. A system according to claim 1

characterized in that

a) said first element co-reactant components of said composition are normally maintained in non-reactive separation; and

b) said activating component is capable of effecting reactive contact between said co-reactant components at least at said second temperature.

3. A system according to claim 2

characterized in that

a) said non-reactive separation of said components is effected by an intervening matrix material, and

b) said activating component is capable of effecting a condition in said matrix enabling said reactive component contact.

4. A system according to claim 3 wherein said activating component increases a fluid property of said matrix to enable migrative contact between said co-reactant components.

5. A system according to claim 1 wherein said activating component exhibits at said second temperature a reactant property of at least one of said pair of co-reactant components.

6. A system according to claim 1

characterized in that

a) said first element comprises a pH-sensitive dye-forming composition;

and

b) said activating component is capable of providing at least at said second temperature a condition of pH conducive to the formation of said dye.

7. An activatable time-temperature monitoring system for indicating the accumulation of a combination of time and ambient temperature which exceeds a predetermined time-temperature integral to which an associated perishable product has been exposed

characterized in that said system comprises

a) a first element comprising a direct thermal color-forming composition comprising at least a pair of co-reactant components capable of reacting in combination to form said color upon the heating of said composition at least to a threshold temperature;

and

b) a second element comprising an activating component capable of, upon contact with said first element composition, initiating said color-forming combination reaction at a second temperature below said threshold and causing said reaction to proceed to formation of said color at an average rate satisfying said predetermined time-temperature integral.

8. A system according to claim 7 wherein said activating component exhibits at least at said second temperature a reactant property of at least one of said pair of co-reactant components.

9. A system according to claim 8 wherein

a) said activating component is normally maintained out of contact with said first element composition; and

b) said second element further comprises a component capable of effecting said reaction-initiating contact at least at said second temperature.

10. A system according to claim 7 wherein

a) said first element co-reactant components are normally maintained out of reactive combination;

and

b) said activating component comprises a composition capable of effecting said reactive combination of said co-reactant components.

11. A system according to claim 10 wherein said activating component is capable of effecting a salvation of said direct thermal composition.

12. A system according to claim 7 wherein

a) at least one of said direct thermal composition component pair is reactive in an acid medium to form said color;

and

b) said activating component comprises a source of acid capable of generating said acid medium at least at said second temperature.

13. A system according to claim 12 wherein said activating component further comprises a composition capable of increasing the fluidity of said direct thermal composition.

14. A system according to claim 7 wherein

a) said combination reaction proceeds in response to said activating component at a rate varying within a given range, and

b) said second element further comprises a second activating component capable of so activating said combination reaction at least at a third temperature intermediate said second and threshold temperatures and causing said reaction to proceed at a rate substantially above said given range.

15. A system according to claim 7 wherein said activating component is selectively disposed on said second element in the form of intelligible indicia, thereby providing for a visually-distinct reproduction of said indicia as a result of said initiated color-forming reaction.

16. A system according to claim 7 wherein said activating component is selectively disposed in a position relative to indicia on said first element so as to cause the obscuring or alteration of said indicia as a result of said initiated color-forming reaction.

17. A method of monitoring the useful life of a perishable product which comprises affixing to said product a time-temperature monitoring system for indicating by means of a visually distinct color change signal the accumulation of a combination of time and ambient temperature which exceeds a predetermined time-temperature integral to which an associated, perishable product has been exposed

characterized in that

a) said indicator system comprises

a first element comprising a direct thermal color-forming composition comprising at least a pair of co-reactant components capable of reacting in combination to form said color upon the heating of said composition at least to a threshold temperature, and a second element comprising an activating component capable of, upon contact with said first element composition, initiating said color-forming combination reaction at a second temperature below said threshold and causing said reaction to proceed to the formation of said color at an average rate satisfying said predetermined time-temperature integral;

b) said second element is affixed to said first element to thereby effect said contact between said activator component and said first element color-forming composition;

c) said first element is affixed to said perishable product substantially simultaneously with said affixing of said second element to said first element; and

d) said perishable product is exposed to ambient temperatures for a time within the period up to the formation of said color and the resulting appearance of said visually distinct signal.

18. A method according to claim 17 wherein

a) the activity of said activator component is rendered latent by protective encapsulation; and

b) said method further comprises rupturing said encapsulation to thereby initiate said activity of said activator component.

19. A method according to claim 17 wherein

a) said activator component comprises a latent actinically-activatable compound;

and

b) said method further comprises exposing said compound to actinic radiation to thereby initiate said activity of said activator component.

20. A method according to claim 17 wherein

a) a series of second elements is provided varying in level of time-temperature integral of resulting activated reaction, and

b) a second element to be affixed to said first element is selected from said series according to a designation of a type of perishable product to which said first element is to be affixed.