Time-temperature indicator
First Claim
1. A time-temperature indicating device comprising:
- a diffusion layer of a material having a first impermeable, crystalline-like state and a second permeable, liquid-crystalline state, said material being capable of transition between said first and said second states at a clearly defined temperature;
an indicator disposed on one side of said diffusion layer; and
a reactant material for said indicator normally maintained out of contact with said indicator by said diffusion layer, said reactant material having a predetermined rate of diffusion through said diffusion layer to contact and react with said indicator when said diffusion layer is in the permeable, liquid-crystalline state.
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Abstract
A time-temperature indicator having a time-temperature sensitive component including a layer of material which at temperatures above a predetermined transition temperature changes from an impermeable, psuedo-crystalline state to a permeable, liquid-crystalline state. A reactant material having a predetermined rate of diffusion through the layer at temperatures above its transition temperature is maintained out of contact with an indicator by the layer at temperatures below the transition temperature. A container for the time-temperature component includes a transparent face for viewing the time-temperature component. The container is adapted for attachment to an object, such as to the package of a time and temperature sensitive product to visually indicate the product has been exposed above a particular temperature far in excess of a certain period of time.
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Citations
21 Claims
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1. A time-temperature indicating device comprising:
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a diffusion layer of a material having a first impermeable, crystalline-like state and a second permeable, liquid-crystalline state, said material being capable of transition between said first and said second states at a clearly defined temperature; an indicator disposed on one side of said diffusion layer; and a reactant material for said indicator normally maintained out of contact with said indicator by said diffusion layer, said reactant material having a predetermined rate of diffusion through said diffusion layer to contact and react with said indicator when said diffusion layer is in the permeable, liquid-crystalline state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A time-temperature indicating device for indicating deterioration of perishable goods and the like, said device comprising:
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a time-temperature sensitive component including a reactant material and an indicator responsive to contact by said reactant to produce a visible reaction, said reactant and indicator being normally separated by a diffusion layer having an impermeable, pseudo-crystalline state and a reactant permeable, liquidcrystalline state, said diffusion layer effecting the transition between said impermeable and permeable states at a clearly defined transition temperature; and container means for enclosing said time-temperature sensitive component, said container means including a transparent face for viewing said time-temperature component. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A time-temperature indicating device for indicating deterioration of perishable goods and the like, said device comprising:
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a time-temperature sensitive component including a reactant material and an indicator responsive to contact by said reactant material to produce a visible reaction, said reactant material being dispersed in a diffusion layer disposed adjacent said indicator, and said diffusion layer having an impermeable, pseudo-crystalline state and a reactant-permeable, liquid-crystalline state, wherein said diffusion layer effects a transition between said impermeable and permeable states at a clearly defined transition temperature; and container means for enclosing said time-temperature sensitive component, said container means including a transparent face for viewing said time-temperature component.
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Specification