Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-12-04
2001-07-03
Krynski, William (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S206000, C428S207000, C428S474400
Reexamination Certificate
active
06254969
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to shelf life indicating structures and in particular to structures for indicating the shelf life of a product within a package.
BACKGROUND
Shelf life or freshness indicators affixed to food, beverage, and other product packages are useful and beneficial to producers and the public. A common way of indicating the shelf life of a product is to print a “sell by” or “use by” date on the package containing the product. A disadvantage of this type of pre-calculated, shelf life indicator is that it takes no account of the actual conditions (temperature, humidity, etc) under which the product is stored. Further, the pre-calculated, printed shelf life indicator may be easily visually lost in circumstances in which a consumer merely glances at the product, especially if the packaging contains other eye-catching text and graphics.
It is an object of the present invention to provide an “active” indicator, which is also more readily visible to the user, and which more precisely reflects the effects of varying storage conditions.
SUMMARY
Accordingly there is provided a structure for giving a shelf life indication with respect to a product, the structure comprising a first layer including an oxygen sensitive ink which gives a visible indication when exposed to a predetermined minimum quantity of oxygen, and a second layer including an oxygen scavenging material adapted to try and prevent oxygen reaching the oxygen sensitive ink for a predetermined interval, the oxygen scavenging material having a finite scavenging capability such that after the predetermined interval the oxygen scavenging material is unable to prevent oxygen reaching the oxygen sensitive ink, causing the ink to react with the oxygen to give its visible indication so as to provide a shelf life indication.
Thus the shelf life indicator is activated by the actual amount of oxygen to which the package is exposed. When the oxygen scavenging capabilities of the scavenging layer have been exhausted, the indicator will be triggered. Conveniently the visible indication given by the oxygen sensitive ink is a change in color from a first color to a second color when exposed to the predetermined quantity of oxygen. This will also include a change from clear to colored, making the ink visible to the user for the first time. Examples of synthetic oxygen sensitive inks include those based on ferrocene or pyrogallol components, thiazine dyes or other oxygen sensing dyes, whilst naturally occurring substances such as enzymes found in foodstuffs may conceivably also be employed. Examples of oxygen scavenging materials include those described in WO 89/01012, WO 95/11801, and WO 96/29362, although other materials have been proposed.
Preferably there is also provided means for initiating the shelf life indication structure. Conveniently the structure includes an additional oxygen impermeable layer which is removable in order to initiate the shelf life indication structure. Conveniently the oxygen impermeable layer is also impermeable to light, and the oxygen scavenging layer may be photo-initiated, for example by the user removing the impermeable layer and holding the structure to the light for a predetermined time. The impermeable layer is typically a layer of metallic foil, such as aluminum foil. Conveniently the shelf life indicating structure is in the form of a label attached to a package.
The invention further resides in a method of indicating the shelf life of a product comprising the steps of:
a) providing a first substrate layer including or imprinted with an oxygen sensitive ink adapted to give a visible indication when exposed to a predetermined minimum quantity of oxygen,
b) covering the first layer with a second layer including an oxygen scavenging material adapted to prevent oxygen reaching the oxygen scavenging ink for a predetermined interval,
c) covering both first and second layers with a removable layer of oxygen impermeable material,
d) forming the first, second and third layers into a patch or label, and
e) attaching the patch or label to the package to provide a shelf life indication system.
REFERENCES:
patent: 4382700 (1983-05-01), Youngren
patent: 4526752 (1985-07-01), Perlman et al.
patent: 4629330 (1986-12-01), Nichols
patent: 5021515 (1991-06-01), Cochran et al.
patent: 5053339 (1991-10-01), Patel
patent: 5633836 (1997-05-01), Langer et al.
patent: 5639815 (1997-06-01), Cochran et al.
patent: WO 89/01012 (1989-02-01), None
patent: WO 95/11801 (1995-04-01), None
patent: WO 96/29362 (1996-09-01), None
Crown Cork & Seal Technologies Corporation
Krynski William
Shewareged B.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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