Tamper evident closure using microcapsules

Abstract: A vacuum identifying button (26) of a closure (16) for containers (10) has encapsulated microcapsules (30) containing a suitable dye. While the button (26) is in its depressed, concave configuration, a coating (28) surrounding the microcapsules (30) is cured and caused to bond to the microcapsules (30). When the button (26) everts to project upwardly and have a convex configuration, the coating (28) is tensioned causing the microcapsules (30) to rupture and release the color forming dye materials thereof. Evidence of button flipping or tampering can be simply forming a colored area, such as a stripe. However, colored areas may be in a design to present a warning or message.

Description: This invention relates in general to new and useful improvements in closures particularly intended to be used in conjunction with vacuum packed products and including an end panel having a tamper evident button which initially projects outwardly from the end panel and which is retracted by the vacuum drawn within the package to indicate tampering particularly by way of loss of the vacuum due to opening of the package. An example of a closure, which employs a safety button and is used to indicate vacuum release when a container is opened, is described in AU-B-74317/81. This concerns a closure which includes a resilient central panel of generally convex configuration. When applied to a container, and under influence of a vacuum, the panel is capable of being drawn into a substantially flat or concave configuration. The flat or concave end panel thus provides a visual indication that the container is properly sealed to maintain a negative pressure within it. These features are described in the preamble of claim 1. This invention particularly relates to an improvement over such a conventional closure by providing the button with rupturable microcapsules which contain reactant materials for defining colored areas. In a preferred embodiment, the colored areas will spell out a message such as "OPENED". Pressure activated materials have been developed by Minnesota Mining and Manufacturing Company of St. Paul, Minnesota. These developments are the subject of Patent Nos. US-A-3,935,960; US-A-4,685,578 and US-A-4,714,656. Of these, US-A-3,935,960 particularly relates to an indicator layer which changes color when flexed thereby indicating whether the closure has been handled or tampered with. This invention, in general, relates to the utilization of a material similar to that found in this patent. Accordingly, in one aspect the present invention provides a closure as set out in the accompanying Claim 1. In another aspect the invention provides a method of applying a visual indicator to a closure as defined in accompanying Claims 8 and 10. In accordance with this invention, the microcapsules are set in a coat which, when cured, is tightly bonded to the microcapsules so that when the coat is tensioned, as occurs when the closure button goes from a retracted concave position to a projecting convex position, the microcapsules will rupture with a mixing of the materials therein to form a colored area or areas. Preferably the colored areas are so arranged so as to define a message such as "OPENED". This disclosure relates generally to two forms of the invention, both of which do not become set until after the closure has been applied to a container to form a vacuum packed package with the button being drawn downwardly generally into the container. With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims, and the several views illustrated in the accompanying drawings. Figure 1 is a top perspective view of a conventional type of closure to which there has been applied a tamper indicating coating in accordance with this invention. Figure 2 is a top plan view of the closure as initially formed with there having been applied thereto a coating containing a plurality of microcapsules. Figure 3 is an enlarged transverse sectional view taken generally along the line 3-3 of Figure 2 and shows in more detail the button and the coating applied to the button. Figure 4 is a fragmentary sectional view showing the button with a second coating applied over the first coating and indicating an initial curing of the first coating by the application of heat. Figure 5 is a further sectional view taken through the center of the closure as it appears after the closure has been applied to the container and a vacuum formed in the container so as to cause the button to evert to a concave state. Figure 6 is a fragmentary sectional view similar to Figure 5 and shows the coating contained in the microcapsules and the second coating as being treated by UV rays in a second curing step which will result in cross linking between the coating carrying the microcapsules and the second coating. Figure 7 is another fragmentary vertical sectional view showing the closure as it appears after the vacuum within the container has been released and the button has everted to its projecting convex state. Figure 8 is a fragmentary top plan view of the closure shown in Figure 7 after the microcapsules have been ruptured and the material contained therein have combined so as to define a message. Figure 9 is an enlarged fragmentary sectional view through a typical coating containing microcapsules. Figure 10 is a fragmentary exploded perspective view of the conventional closure after being applied to a container and a vacuum formed therein to draw the button down and wherein the coating is to be applied to the button when in this state are shown. Referring now to the drawings in detail, it will be seen that there is illustrated in Figure 1 a conventional type of container, for example, a baby food jar, having an upper neck finish portion 14 of reduced diameter connected to the body of the container 10 along a shoulder 12. The container 10 is closed by a conventional closure 16 which is preferably formed of metal, but could feasibly be formed of other materials, including plastic. Referring now to Figure 3, it will be seen that the closure 16 includes an end panel 18 which may have a peripheral portion 20 defining a downwardly opening channel 22 for receiving a suitable sealing compound. The closure 16 also includes a depending peripheral skirt 24 which may be provided with suitable means for effecting the securement of the closure 16 to the neck finish 14. It is to be understood that the above identified features of the closure 16 may vary from closure to closure. However, in accordance with this invention, the end panel 18 must include a button 26. The button 26 is preferably circular in outline and when the closure 16 is formed it projects convexly upwardly as is shown in Figures 2 and 3. In accordance with one form of the invention, there is applied to the convex projecting button 26 a coating 28 in the form of a layer of material having incorporated therein microspheres 30 as is generally shown in Figure 9. The coating 28 may be in the form of a binder and the microcapsules may be filled with a liquid dye precursor on the one hand and finely divided particles of material capable of reacting with the dye precursor to form a dye on the other hand. All as is generally disclosed in US-A-3,935,960 (Cornell). Most specifically, in accordance with this invention, the microcapsules 30 may be related to one another in a pattern so that when the capsules are ruptured, the dye will spread within the coating 28 in a predetermined pattern to present a message. This will be explained in more detail hereinafter. It is to be understood that the capsule coating at this time is relatively soft and pliable and resistant to rupture. Next, as is best shown in Figure 4, a clear coat of a flexible coating is applied over the coating 28. This second coating is identified by the numeral 32 and is initially cured by the application of heat. The second clear coat 32 which will cover the microcapsules would not necessarily be a thermally cured material. It could be for example: a UV curable acrylic resin; a UV curable epoxy resin; or a two part epoxy system that would cure at room temperature or at elevated temperatures. The closure 16, in this state, is shipped to the packer who then closes a filled container 10 with the closure 16. The resultant package will have a vacuum therein of sufficient negative pressure to draw the button 26 downwardly into the container to a concave shape as is best shown in Figure 5. Following the normal processing of the package, at least the button area is subject to UV treatment. At this time it is to be particularly noted that the materials used to form the coating 28 and the second coating 32 are ones that a UV curing step will result in cross linking between the two materials. This is diagrammatically shown in Figure 6. The net result is that the microcapsules are tightly bonded to the coating 28 so that when the coating 28 is placed in tension, the microcapsules will rupture and cause the formation of the colored areas described above. This will occur when the vacuum within the container 10 is released to the extent that the button 26 will evert as shown in Figure 7. The everting of the button 26, results in the coating material 28 to be placed in tension sufficiently to rupture the microcapsules 30. As viewed in Figure 8, the resultant colored areas will be ones which preferably will present a message such as by the word "OPENED" as shown in Figure 8. Of course, other messages may be presented. If desired, the invention may be of separate structure as is shown in Figure 10. The customary closure 16 is applied to the container 10 to seal a product therein with the customary formation of a vacuum. At this time the button 26 is depressed and concaved in shape. Then there is applied to the button 26 a coating 34 containing a plurality of microcapsules 30. The material of the coating 34 is such that it remains relatively flexible after curing and also has a strong adhesive to the microcapsules 30. The coating should be clear or opaque. The action of the button 26 flipping up on opening of the container stretches the coating 34 slightly. Since the coating 34 has strong adhesion to the capsules, this stretching should pull the capsules apart releasing their encapsulated color forming material. The coating 34 should also protect the capsules from rupture due to bumping, or other incidental contact. The stretching of the coating material caused by button flipping would be the rupture mechanism for rupturing the microcapsules 30.

Claims: A closure for use in vacuum packaging of a product, said closure (16) having an end panel (18) provided with a pressure activated button (26) which button (26) when said closure (16) is applied to a vacuum packed container (10) is recessed and which button (26) when the vacuum is relieved everts to project outwardly, characterised by provision of a visual indicator (28,30) on the button (26) which is in the form of a coating (28) having therein a plurality of microcapsules (30) which have combinable contents for forming a colored area on said button (26), said microcapsules (30) being rupturable in response to stretching of said coating (28) as the button (26) everts from its recessed position to its projecting position to form said colored area. A closure according to claim 1 wherein said visual indicator (28,30) is in the form of a message when actuated. A closure according to any preceding claim wherein said coating (28) containing said microcapsules (30) is applied to said closure (16) or set only after said closure (16) is part of a vacuum packed package (10) and while said button (26) is recessed. A closure according to any preceding claim wherein said coating (28) containing said microcapsules (30) has a second coating (32) thereover. A closure according to claim 4, wherein said coating (28) containing said microcapsules (30) and said second coating (32) are cross linked together by curing. A closure according to claim 5, wherein said cross linking exists only when said closure (16) is applied to a vacuum packed container (10) and at a time when said button (26) is recessed. A closure according to claim 4, 5 or 6, wherein said coating (28) containing said microcapsules (30) and said second coating (32) are in separate states on said closure (16), prior to application of said closure (16) to a container (10) and when said button (26) is projecting from said end panel (18). A method of applying a visual indicator to a pressure actuated button of a closure for a container of a vacuum packed product, said method comprising the step of providing a closure (16) of the type including an end panel (18) having a pressure indicating button (26) projecting therefrom, applying the closure (16) to the container (10) and forming a vacuum within said container (10) causing said button (26) to evert to a retracted position, and then applying to said retracted button (26) a coating (28) containing rupturable microcapsules (30) having combinable contents for forming a colored area on said button (26) in response to stretching of said coating (28) by said button (26) returning to said projecting position when vacuum is released in said container (10). A method according to claim 8, wherein said coating (28) is curable and is cured after application to have a strong adhesion both to said button (26) and said microcapsules (30). A method of applying a visual indicator to a pressure actuated button of a closure for a container of a vacuum packed product, said method comprising the step of providing a closure (16) of the type including an end panel (18) having a pressure indicating button (26) projecting therefrom, applying to said projecting button (26) a coating (28) containing rupturable microcapsules (30) having combinable contents for forming colored areas on said button (26), applying over said coating (28) a second coating (32) cross linkable with said coating (28) by curing. A method according to claim 10, wherein said closure (16) is then applied to said container (10) in sealing relation with a vacuum formed in said container (10) causing said button (26) to evert to a retracted position, followed by curing of said second coating (32) and cross linking of said second coating (32) with said coating (28) containing rupturable microcapsules. A method according to claim 11, wherein said second coating (32) is first cured by heating. A method according to claim 11, wherein said second coating (32) is cured by heating prior to application of said closure (16) to a container (10) and while said button (26) still projects from said end panel (18). A method according to any one of claims 8 to 12, wherein said microcapsules (30) are arranged in a pattern wherein said colored areas define a message.

Inventors: ILLER HOWARD DARRELL, ILLER, HOWARD DARRELL
Applicants: CONTINENTAL WHITE CAP INC, CONTINENTAL WHITE CAP, INC.
Application year: 1991
Main classification: B65D79
IPC codes: B65D55, B65D25, B65D79, B65D81