US4737463A
Expired / Lapsed
US
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Photoactivatable time-temperature indicator
Assignee: Lifelines Technology Inc
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Filing: 1985-10-09
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Granted: 1988-04-12
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Expires: 2005-10-09
Abstract
Abstract A photoactivated time-temperature indicator is based on diacetylenic salts. A thermally unreactive ("inactive") diacetylenic salt (or a mixture of such salts) is mixed, in a polymeric matrix, with a material that generates acid upon exposure to light. Photoexcitation, preferably by UV or near UV light, causes the formation of a thermal reactive ("active") free diacetylenic acid. 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 that require refrigeration.
Inventors
- 👤 Himangshu R. Bhattacharjee
- 👤 James T. Yardley
- 👤 Thaddeus Prusik
- 👤 Ronald R. Chance
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 04:26
CPC Classifications
G; G01; G01N; G01N31/00; G01N31/22; G01N31/229; Y; Y10; Y10S; Y10S436/00; Y10S436/905
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
92 words
A photoactivatable time-temperature indicator, comprising a mixture of (a) a thermally unreactive diacetylenic compound, (b) a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylene to a thermally reactive product, and (c) an aqueous polymeric medium; said mixture forming a solution wherein transport between the diacetylenic compound and photogenerated acid is facilitated; said photoactivatable time-temperature indicator capable of being photoactivated with differing doses of actinic radiation whereby the period of time of the progressive color-developing temperature response to said indicator may be established at preselected ranges.
Claim 2
Dependent Claim
92 words
A photoactivatable time-temperature indicator, comprising a mixture of (a) a thermally unreactive diacetylenic compound, (b) a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylene to a thermally reactive product, and (c) an aqueous polymeric medium; said mixture forming a solution wherein transport between the diacetylenic compound and photogenerated acid is facilitated; said photoactivatable time-temperature indicator capable of being photoactivated with differing doses of actinic radiation whereby the period of time of the progressive color-developing temperature response to said indicator may be established at preselected ranges.
Claim 3
Dependent Claim
12 words
The indicator of claim 1 in which the photosensitive compound is o-nitrobenzaldehyde.
Claim 4
Dependent Claim
12 words
The indicator of claim 1 in which the photosensitive compound is 2,2,2-tribromoethanol.
Claim 5
Dependent Claim
12 words
The indicator of claim 1 in which the polymeric medium comprises gelatin.
Claim 6
Dependent Claim
16 words
The indicator of claim 1 further comprising an absorbent substrate in which the mixture is absorbed.
Claim 7
Dependent Claim
13 words
The indicator of claim 5 in which the absorbent substrate comprises filter paper.
Claim 8
Dependent Claim
21 words
The indicator of claim 1 further comprising a cover sheet over the mixture that is substantially transparent to the actinic radiation.
Claim 9
Dependent Claim
13 words
The indicator of claim 7 in which the cover sheet is a polyester.
Claim 10
Dependent Claim
53 words
The indicator of claim 1 in which the diacetylenic compound is selected from the group consisting of (A) a salt of [HOOC--(CH 2 ) n --C.tbd.C--C.tbd.C--(CH 2 ) 2 --C.tbd.C] 2 (B) a salt of [HOOC--(CH 2 ) n --C.tbd.C--C.tbd.C--CH 2 ] 2 and mixtures thereof, where n is in the range 1-7.
Claim 11
Dependent Claim
8 words
The indicator of claim 9 in which n=3.
Claim 12
Dependent Claim
13 words
The indicator of claim 10 in which the salt comprises a sodium salt.
Claim 13
Dependent Claim
13 words
The indicator of claim 1 in which the polymeric medium comprises polyvinyl alcohol.
Claim 14
Dependent Claim
13 words
The indicator of claim 12 in which the polyvinyl alcohol is 50-100% hydrolyzed.
Claim 15
Dependent Claim
13 words
The indicator of claim 13 in which the polyvinyl alcohol is 70-90% hydrolyzed.
Claim 16
Dependent Claim
23 words
The indicator of claim 12 in which the polyvinyl alcohol has a weight-averaged molecular weight in the range from about 500 to 500,000.
Claim 17
Dependent Claim
18 words
The indicator of claim 15 in which the polyvinyl alcohol has a weight-averaged molecular weight of about 110,000.
Claim 18
Independent Claim
78 words
A method of measuring time-temperature exposure, which comprises the steps: (a) exposing a photoactivatable time-temperature indicator to actinic radiation to render it thermally reactive, (b) measuring the reflectivity of the indicator at a specified wavelength prior to the time-temperature exposure, (c) measuring the reflectivity of the indicator at the specified wavelength after the 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 19
Independent Claim
78 words
A method of measuring time-temperature exposure, which comprises the steps: (a) exposing a photoactivatable time-temperature indicator to actinic radiation to render it thermally reactive, (b) measuring the reflectivity of the indicator at a specified wavelength prior to the time-temperature exposure, (c) measuring the reflectivity of the indicator at the specified wavelength after the 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 20
Dependent Claim
22 words
The method of claim 17 in which the time-temperature exposure comprises a temperature in the range between about 6° and 60° C.
Claim 21
Dependent Claim
28 words
A method of mesuring the time-temperature exposure of a perishable article by applying to the article a photoactivatable time-temperature indicator and then following the steps of claim 17.
Claim 22
Dependent Claim
43 words
The method of claim 17 in which the photoactivatable time-temperature indicator comprises a mixture of a thermally unreactive diacetylenic compound and a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylenic compound to a thermally reactive product.
Claim 23
Dependent Claim
47 words
The method of claim 20 in which the photoactivatable time-temperatue indicator is a mixture of o-nitrobenzaldehyde, (A) a salt of [HOOC--(CH 2 ) 3 --C.tbd.C--C.tbd.C--(CH 2 ) 2 --C.tbd.C] 2 , (B) a salt of [HOOC--(CH 2 ) 3 --C.tbd.C--C.tbd.C--CH 2 ] 2 , and polyvinyl alcohol.
Claim 24
Dependent Claim
27 words
The method of claim 21 in which the actinic radiation is electromagnetic radiation having a wavelength in the range between about 250 nm and about 400 nm.
Claim 25
Dependent Claim
126 words
A sealed photoactivatable time-temperature label that comprises: (a) a mixture of (i) a thermally unreactive diacetylenic compound and (ii) a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylenic compound to a thermally reactive product, (b) an aqueous polymeric medium that contains the mixture and that facilitates transport between the diacetylenic compound and the photogenerated acid, (c) a polyester cover sheet over the mixture, and (d) a base sheet that seals against the cover sheet, sandwiching the polymeric medium and mixture between the sheets wherein said photoactivatable time-temperature indicator-label is capable of being photoactivated with differing doses of actinic radiation whereby the period of time of the progressive color-developing temperature response of said label may be established at preselected ranges.
Claim 26
Dependent Claim
126 words
A sealed photoactivatable time-temperature label that comprises: (a) a mixture of (i) a thermally unreactive diacetylenic compound and (ii) a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylenic compound to a thermally reactive product, (b) an aqueous polymeric medium that contains the mixture and that facilitates transport between the diacetylenic compound and the photogenerated acid, (c) a polyester cover sheet over the mixture, and (d) a base sheet that seals against the cover sheet, sandwiching the polymeric medium and mixture between the sheets wherein said photoactivatable time-temperature indicator-label is capable of being photoactivated with differing doses of actinic radiation whereby the period of time of the progressive color-developing temperature response of said label may be established at preselected ranges.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-12 | 1991-10-12 | 1992-04-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-12 | 1995-10-12 | 1996-04-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-12 | 1999-10-12 | 2000-04-12 | $7700.00 | Window Closed / Lapsed |