US4812053A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Activatable time-temperature indicator
Assignee: Lifelines Technology Inc
•
Filing: 1987-08-07
•
Granted: 1989-03-14
•
Expires: 2007-08-07
Abstract
Abstract An activatable time-temperature indicator consists of an oxygen-sensitive reaction product of a triarylmethane dye and a decolorant that is coated on a substrate and covered by an oxygen barrier. Optinally, an oxygen-permeable layer is between the coating and the oxygen barrier. The indicator is activated by removing the oxygen barrier. Following this activation step, a progressive color development occurs at a rate that increases with temperature. The indicator is useful for monitoring the freshness of perishable products, particularly those stored at sub-ambient temperature.
Inventors
- 👤 Himangshu R. Bhattacharjee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 19:57
CPC Classifications
G; G01; G01N; G01N31/00; G01N31/22; G01N31/229; G01K; G01K3/00; G01K3/02; G01K3/04; Y; Y10; Y10S; Y10S252/00; Y10S252/962; Y10S428/00; Y10S428/913
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
37 words
An activatable time-temperature indicator comprising: (a) a substrate on which is a coating of an oxygen-sensitive reaction product of a triarylmethane dye and a decolorant for the dye and (b) a removable oxygen barrier over the coating.
Claim 2
Dependent Claim
37 words
An activatable time-temperature indicator comprising: (a) a substrate on which is a coating of an oxygen-sensitive reaction product of a triarylmethane dye and a decolorant for the dye and (b) a removable oxygen barrier over the coating.
Claim 3
Dependent Claim
13 words
The indicator of claim 1 in which the substrate material is absorbent paper.
Claim 4
Dependent Claim
25 words
The indicator of claim 1 in which the substrate material is substantially oxygen-impermeable and is selected from the group consisting of thermoplastics, paper, and metals.
Claim 5
Dependent Claim
13 words
The indicator of claim 1 in which the coating further comprises a binder.
Claim 6
Dependent Claim
12 words
The indicator of claim 4 in which the binder comprises polyvinyl alcohol.
Claim 7
Dependent Claim
13 words
The indicator of claim 4 in which the substrate material is a thermoplastic.
Claim 8
Dependent Claim
28 words
The indicator of claim 1 in which the triarylmethane dye is selected from one or more of the group consisting of brilliant green, malachite green, and crystal violet.
Claim 9
Dependent Claim
13 words
The indicator of claim 7 in which the triarylmethane dye includes brilliant green.
Claim 10
Dependent Claim
24 words
The indicator of claim 1 in which the decolorant is a reducing agent selected from the group consisting of bisulfites, hydroxides, cyanides, and hydrogen.
Claim 11
Dependent Claim
20 words
The indicator of claim 9 in which the decolorant is selected from the group consisting of alkali metal- and ammonium-bisulfites.
Claim 12
Dependent Claim
31 words
The indicator of claim 2 further comprising a first oxygen-permeable layer between the coating and the oxygen barrier and a second oxygen-permeable layer between the substrate and a second oxygen barrier.
Claim 13
Independent Claim
115 words
A method of measuring an incremental time-temperature exposure with an activatable time-temperature indicator comprising a substrate on which is a coating of oxygen-sensitive reaction product of a triarylmethane dye and decolorant for the dye and a removable oxygen barrier over the coating, which comprises the steps of: (a) removing the oxygen barrier from the indicator to expose the indicator to ambient oxygen, thereby activating it, (b) measuring the reflectivity of the indicator at a specified wavelength, (c) measuring the reflectivity of the indicator at the specified wavelength after an incremental time-temperature exposure, and (d) calculating the incremental time-temperature exposure by using a pre-established relationship between a change in reflectivity of the indicator and time-temperature exposure.
Claim 14
Independent Claim
115 words
A method of measuring an incremental time-temperature exposure with an activatable time-temperature indicator comprising a substrate on which is a coating of oxygen-sensitive reaction product of a triarylmethane dye and decolorant for the dye and a removable oxygen barrier over the coating, which comprises the steps of: (a) removing the oxygen barrier from the indicator to expose the indicator to ambient oxygen, thereby activating it, (b) measuring the reflectivity of the indicator at a specified wavelength, (c) measuring the reflectivity of the indicator at the specified wavelength after an incremental time-temperature exposure, and (d) calculating the incremental time-temperature exposure by using a pre-established relationship between a change in reflectivity of the indicator and time-temperature exposure.
Claim 15
Dependent Claim
13 words
The method of claim 12 in which the coating further comprises a binder.
Claim 16
Dependent Claim
13 words
The method of claim 12 in which the substrate material is a thermoplastic.
Claim 17
Dependent Claim
13 words
The method of claim 12 in which the triarylmethane dye includes malachite green.
Claim 18
Dependent Claim
20 words
The method of claim 12 in which the decolorant is selected from the group consisting of alkali metal- and ammonium-bisulfites.
Claim 19
Dependent Claim
25 words
The method of claim 12 in which the oxygen barrier comprises a thermoplastic cover sheet that is separated from the coating to activate the indicator.
Claim 20
Dependent Claim
20 words
The method of claim 12 in which the oxygen barrier comprises an overcoat that is dissolved to activate the indicator.
Claim 21
Dependent Claim
20 words
The method of claim 12 in which the temperature exposure is in the range between about -20° and 60° C.
Claim 22
Independent Claim
120 words
A method of measuring an incremental time-temperature exposure of a perishable article by (a) applying to the article an activatable time-temperature indicator comprising a substrate on which is a coating of an oxygen sensitive reaction product of a triarylmethane dye and a decolorant for the dye and a removable oxygen barrier over the coating, (b) removing the oxygen barrier from the indicator to expose it to ambient oxygen, thereby activating it, (c) measuring the reflectivity of the indicator at a specified wavelength, (d) measuring the reflectivity of the indicator at the specified wavelength after incremental time-temperature exposure, and (e) calculating the incremental time-temperature exposure by using a pre-established relationship between a change in reflectivity of the indicator and time-temperature exposure.
Claim 23
Independent Claim
120 words
A method of measuring an incremental time-temperature exposure of a perishable article by (a) applying to the article an activatable time-temperature indicator comprising a substrate on which is a coating of an oxygen sensitive reaction product of a triarylmethane dye and a decolorant for the dye and a removable oxygen barrier over the coating, (b) removing the oxygen barrier from the indicator to expose it to ambient oxygen, thereby activating it, (c) measuring the reflectivity of the indicator at a specified wavelength, (d) measuring the reflectivity of the indicator at the specified wavelength after incremental time-temperature exposure, and (e) calculating the incremental time-temperature exposure by using a pre-established relationship between a change in reflectivity of the indicator and time-temperature exposure.
References Cited (Backward Citations)
US3018611A
Cited
US3480402A
Cited
US3463532A
Cited
US3768976A
Cited
US3966414A
Cited
US4189399A
Cited
JPS5446186A
Cited
US4212153A
Cited
US4264708A
Cited
US4208186A
Cited
US4276190A
Cited
US4373032A
Cited
US4407960A
Cited
US4466941A
Cited
US4526752A
Cited
EP0117390A2
Cited
US4576795A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-13 | 1992-09-12 | 1993-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-13 | 1996-09-12 | 1997-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-13 | 2000-09-12 | 2001-03-14 | $7700.00 | Window Closed / Lapsed |