Tamper evident closure

In accordance with the present invention, an irreversible tamper evident system for a button closure is provided. The irreversible tamper evident system is provided by a color change system carried by the flexible button portion of the closure. The color change system comprises an indicator coating over a dark colored substrate coating. The indicator coat is preferably colored with a light colored transparent colorant such as an orange colored fluorescent dye. The indicator coat is preferably a liquid material which can be cured by evaporation, heat, UV irradiation or the like, to form a solid layer. When the substrate layer and indicator layer are in intimate contact, a first color is observed. Depending upon the relative colors used for this substrate and indicator layers, this first color can be a combination of the colors of the two layer or can be primarily the color of the substrate layer. However, when the layers become separated and the outer layer is spaced from the inner layer, a second color is observed which second color is primarily the color of the indicator coat.

The present invention generally relates to new and useful improvements in 
closures having end panels of which at least an area is formed to flex 
when the closure is applied to a container and, more particularly, to a 
closure wherein the flexible area of the end panel is provided with an 
irreversible tamper indicating system which is actuated when the flexible 
area of the end panel flexes from a sealed condition to an unsealed 
condition. 
BACKGROUND OF THE INVENTION 
Among the various closures made for the food and beverage industry is a 
"button" or "pop top" closure wherein the closure contains a flexible 
portion which assumes a given flexed position to indicate a sealed package 
and a different position when the package seal is breached. These "button" 
or "pop top" closures are commonly used in vacuum sealed food products 
such as baby food products to warn purchasers when the vacuum condition 
under which the food was packaged has been breached. 
Although closures having tamper indicating buttons are predominantly in use 
in vacuum applications, there also have been more recently developed 
closures with buttons which are mechanically actuated so as to move from 
an as formed "down" position to an upwardly projecting "up" position when 
the closure is properly applied to a container. In this "up" position the 
closures are further characterized as having energy stored within the 
closure end panels urging the buttons to their as formed "down" position. 
Removal of these closures from the containers associated therewith results 
in the buttons moving to their as formed "down" position due to the 
release of the energy stored within the end panels. 
Closures having end panels incorporating tamper indicating buttons are used 
extensively for the food industry, especially for vacuum packaged product, 
because they are effective quick-detection means that lets one know some 
very important conditions about the container. Typically in vacuum 
applications, when the container is properly sealed and a vacuum exists 
therein, the button is in a "down" position while when the container has 
been opened and the closure reapplied, or the vacuum within the container 
otherwise lost, the button will be in its "up" position. Additionally, in 
vacuum package applications, when the closure is first opened and the 
vacuum is lost, a hissing sound may be heard. 
Through the extensive commercial use of such button closures, the 
purchasing public has become generally aware that if the deflectable 
section of the button is up then the original seal has been broken and 
that the container should be rejected. Additionally, in the case where the 
button closure is used in conjunction with a vacuum package container, the 
purchasing public has been sensitized to listen for a hiss of air or a 
"popping" sound to determine whether or not that container has been 
previously opened. 
The popping of the top and, in the case of a vacuum packaged product, the 
sound associated with the loss of vacuum are indicating means to warn 
purchasers when the integrity of the package has been breached. These 
indicators, however, are not fool proof and can be intentionally 
overridden. For example, it is known that a button closure for a vacuum 
packaged product can be returned to its "tamper free" state even after the 
package has been opened. This is accomplished by merely heating the open 
container and when the container is hot, recapping the closure. This 
procedure will recreate the vacuum seal and reset the button. 
Separate tamper evident means have been used in association with button 
caps to augment the flip or pop of the button. For example, button caps, 
and other screw top closures, are often used in association with a shrink 
wrap. Also, the button cap may be provided with a band at its base, joined 
to the remainder of the cap through a line of weakness. The band is 
prevented from rotating or from rising up the screw thread when the cap is 
unscrewed, and as a result, upon closure opening, the band becomes 
detached from the remainder of the cap. 
The packaging industry has also recognized the desirability of providing a 
visual means to determine whether the integrity of a sealed container has 
been breached. For example, U.S. Pat. No. 3,736,899 (Manske) is directed 
to a pressure change indicator. The '899 patent discloses a button type 
cap having a flexible panel with a reflective surface and a disk-like 
element which covers up all or most of the flexible panel when the panel 
is flexed inward but which provides a gap around the periphery of the 
panel when it is flexed outward. The gap reveals a highly visible or 
contrasting color which is seen on the flexible panel either by means of a 
color on the panel itself or a color on the underside of the disk-like 
member. The pressure change system of the '899 patent apparently may be 
reestablished by recreating the vacuum in the package and, accordingly, in 
such a case would not be irreversible. 
U.S. Pat. No. 4,429,803 (Butterfield) is directed to tamper evident means 
for multiple dose medical vials of the type having a rubber seal closure. 
The tamper evident means of the '803 patent is a blister-like sac 
containing a harmless dye. According to the '803 patent, the blister-like 
sac will release the dye and thereby color the remaining contents of the 
vial when the vial's seal is broken. 
U.S. Pat. No. 4,511,052 (Klein et al.) is directed to a tamper indicating 
seal for a container. According to the '052 patent a frangible envelope 
containing an indicator is attached to the band and neck of the container 
having a closure so that when the closure is opened the frangible envelope 
will rupture and expose the indicator. The indicator can be a chemical 
substance which undergoes a change in color when exposed to the atmosphere 
such as an oxygen or moisture sensitive substance. 
U.S. Pat. No. 4,526,752 (Perlman et al.) discloses a tamper evident package 
incorporating an oxygen sensitive leuco dye. According to the '752 patent, 
the oxygen sensitive leuco dye is sealed within the package in an 
anaerobic environment. The package can have a transparent cap through 
which the oxygen sensitive leuco dye is visible to show the integrity of 
the package. If oxygen is admitted to the package such as by opening the 
package, the dye will undergo a color change. 
U.S. Pat. No. 4,813,712 (Scopes) is directed to providing a visible 
indication of whether a button cap is in its concave or convex form. 
According to the '712 patent the condition of the button can be determined 
by applying a pattern to the button surface which pattern can display one 
visible form when the surface is concave and a different visible form when 
the surface is convex. The different visible forms can include two 
different colors. In this regard, the '712 patent discloses a button cap 
having an embossed pattern wherein the pattern displays one color when in 
a given orientation such as concave and displays a different color when 
the orientation changes such as to convex. In another embodiment, the 
pattern is formed of superimposed layers which are displaced relative to 
one another when the surface changes between its concave and convex forms. 
Either the layers or the substrate for the layers contains a grid pattern 
which provides the closure with different appearances in the concave and 
convex forms. As noted in the '712 patent, a high degree of accuracy is 
required in laying down the patterns to ensure the colors register 
correctly with the embossed pattern to produce the desired visual result. 
Additionally, the surface indicating systems of the '712 patent appear to 
be reversible. 
U.S. Pat. No. 4,877,143 (Travisano) is directed to a closure such as a 
button cap wherein the button carries an indicator such as a color or an 
imprinted word like "open" thereon. The indicator is covered with a 
translucent layer having a light diffusing surface which is provided by a 
Fresno lens. When the button is in the sealed position, the indicator is 
drawn away from the translucent/light diffusing layer which results in the 
indicator being obscured so that it cannot be seen through the translucent 
layer. When the container is opened and the button flips, the indicator is 
brought into contact with the translucent layer and the indicator becomes 
visible therethrough. Similar to the '712 (Scopes) patent above, the 
tamper evident system of the '143 patent appears to be a reversible system 
rather than an irreversible system. 
Despite recognition of the need for tamper proof or tamper evident button 
closures, and responsive efforts related thereto there still exists the 
need for an improved tamper evident button closure. 
SUMMARY OF THE INVENTION 
The present invention provides an irreversible tamper indicating system for 
use in conjunction with closures having deflectable end panel areas such 
as button closures. The irreversible tamper indicating system of the 
present invention comprises a system which undergoes an irreversible 
change in color upon deflection of the end panel area such as the flipping 
of the button of a button cap. The color change system comprises the 
superimposition of differently colored coatings such as an indicator 
coating of a first color and a background coating of a second color. 
Preferably, the indicator coating is a translucent coating containing a 
light colored colorant and the base coating contains or covers a dark 
colored colorant. The indicator coating and base coating are placed in 
intimate contact, either directly or indirectly through intervening 
coatings such as an adhesive coating, with each other on the surface of 
closure. When the two coatings are in intimate contact with each other a 
first color is perceived which is different from the individual color of 
the indicator coating. 
In this regard, without being limited to any theory of the invention, it is 
believed that when the indicator coating and background coating are in 
intimate contact with each other the perceived color results in large from 
light which passes through both the indicator coating and base coating and 
which is reflected back through those coatings. In accordance with general 
physical principles, the color perceived is a composite of the colors of 
the indicator coat and background or base coat which is a function of the 
absorbance of the light passing through each layer which in-turn is 
dependent upon the color of the colorants, the concentration of the 
colorants and the thickness of the coats. 
In accordance with the present invention, when the flexible portion of the 
end panel of the closure incorporating the color evident system of the 
present invention flexes upon opening of the container, the flexing action 
actuates a color change by causing the indicator coat to separate from the 
base coat. When the indicator coat separates from the base coat, a 
reflection boundary or reflective interface is formed which causes a 
greater portion of light to be reflected at, as opposed to passing 
through, the lower surface of the indicator coat. Accordingly, the 
perceived color is principally the color of the indicator coat rather than 
a composite color of the indicator coat and base coat. 
In accordance with the present invention, the color of the system is 
determined by the adhesion, or lack thereof, between the indicator coating 
and button coating. In practice, such as when used for food products, when 
the sealed container leaves the food packer, the indicator and base 
coatings are in intimate contact with each other. For practical reasons, 
the adhesion between the indicator coat and base coat should be sufficient 
to withstand inadvertent, but tamper free, contact such as that which may 
occur during transportation and stocking of the product without 
unintentional separation of the coatings. On the other hand, the adhesion 
between the indicator coating and button coating must be weak enough so 
that the flipping action of a button closure can activate the tamper 
evident system by causing a sufficient loss of adhesion between the 
indicator coating and base coating. 
In accordance with the present invention, the desired adhesion can be 
achieved through appropriate chemical compositions for the indicator 
coating and base coating and through the physical dimensions and curing 
mechanism for the indicator coating. For example, a closure may have a 
dark inked background and an epoxy ester based coating over its button 
area. Such a base surface coating can be thermally cured and will exhibit 
good adhesion to the closure. Alternatively, a base coating can be 
comprised of other materials, such as an appropriately adhesively backed 
or otherwise bondable polypropylene film, preferably having a thickness of 
one mil or less, which will also exhibit good adhesion to the closure. 
Over the base coating an indicator coating can be applied. 
In accordance with the irreversible aspect of the present invention, the 
coatings must be selected so that once the initial intimate contact 
between the indicator coating and base coating is broken, it can not be 
reestablished. An indicator coating that can be readhered to the base 
coating by drawing the button back down, heat massaging or any other 
method could defeat the tamper evident feature of the present invention. 
Accordingly, preferably the indicator coating of the present invention is 
composed of a resin which can be irreversibly solidified or set. Resins, 
such as thermoset resins which can be irreversibly set such as by chemical 
reaction, heat or radiation are preferred. Once this type of indicator 
coat is fully cured and the intimate adhesion between it and the base coat 
is broken, such intimate contact cannot be reestablished. The indicator 
coating preferably includes a UV resin, a photo initiator, a colorant such 
as a fluorescent dye, flow agents, fillers or other desirable additives. 
The indicator coating is preferably prepared as a viscous liquid mixture 
which is spread over the base coating on the button area of the closure. 
Preferably, the indicator coating has a thickness of between 5 to 20 mils. 
The indicator coat can then be cured such as by passage through a UV oven 
to convert the viscous liquid mixture into a solid indicator coat. 
Examples of materials which can be used for the indicator coating are UV 
curable acrylates such as acrylated epoxies, acrylated urethanes, 
acrylated monomers such as TMPTA or TMPTMA and cationically cured epoxies. 
In accordance with the present invention, when the tamper evident system is 
activated the indicator coating becomes separated from the base coating. 
Therefore, the tamper evident system also preferably includes a flexible 
transparent coating which will seal the indicator coat to the closure and 
prevent the actuated delaminated indicator coat from falling off the 
closure into the container. The overcoat material is selected so that it 
does not restrict the flipping action of the button, or interfere with the 
adhesion or release properties of the indicator coat or with the visual 
appearance of the system. Examples of materials that work well for the 
overcoat layer include clear, low cross-linked density, acrylated 
urethanes, two part epoxy and urethane systems, and UV curable cationic 
systems. Additionally, clear tapes such as polypropylene and polyester 
films which can be bonded to the closure, such as with adhesives or by 
heat sealing, can work well as the overcoat layer. 
In accordance with the preferred embodiment of the present invention, the 
indicator coat is cured in a two stage procedure. The first stage curing 
process transforms the indicator coat mixture from a viscous liquid to a 
flexible solid which can retain its physical dimensions and its adhesion 
to the base coating during shipping, closure application to a container, 
and the inversion of the button when the package vacuum is formed. In this 
embodiment, the base coat, indicator coat and overcoat can be applied to 
the button area of the closure at the closure manufacturer's facilities. 
The closure, with the tamper evident system in place, can then be sent to 
the supplier of the goods for the container such as to a food packer. The 
closure would then undergo relatively normal application processes. Once 
the package is sealed and ready to be cased for shipment, the indicator 
coat would go through a final and complete cure. The final cure step fully 
activates the tamper evident system. If the package is then opened the 
button flips causing the indicator coat to lose adhesion and separate from 
the base coat which in turn causes an irreversible color change to take 
place. UV curable acrylate systems are especially well suited for 
formulating the indicator coat in this application since they lend 
themselves to different degrees of partial cure and can be subsequently 
completely cured. 
It is hypothesized, without being limited to any particular theory of the 
invention, that the liquid mixture of the indicator coat completely wets 
and flows into surface irregularities or disparities such as pores, 
cavities or the like present in the surface of the base coat. On curing, 
it is believed that the indicator coat and base coat form a bond perhaps 
resulting, at least in part, from the mechanical engagement, or 
interlocking, which occurs by virtue of minute areas of the indicator coat 
being forced into the surface irregularities of the base coat. When the 
indicator coat is fully cured and subsequently separated from the base 
coat it cannot re-wet the surface of the button coat and reestablish the 
intimate contact originally present between the two coatings. 
Alternatively, or in combination with the foregoing theory, it is also 
hypothesized that when the indicator coat is applied in liquid form to the 
base coat the indicator coat wets the base coat and upon curing the 
indicator coat sufficiently bonds to the base coat to adhere to the base 
coat while the button closure experiences the compressive type forces 
attendant to a vacuum drawn concave button but the bond between the base 
coat and indicator coat is insufficient to withstand the tension type 
forces attendant to release of the vacuum and flipping of the button. 
In an alternate embodiment of the present invention, a translucent 
bonding-release layer is interposed between the base coat and indicator 
coat. In this embodiment, the bonding-release layer acts as a means to 
bond the indicator coat to the base coat on the button closure prior to 
the integrity of the closed container being breached. When the container 
is opened, the flexible end panel is actuated and imparts enough energy to 
cause the indicator coat to irreversibly separate either alone or along 
with the bonding-release layer from the base layer. In this embodiment, 
the indicator coating can be applied as before as a thermoset resin or the 
indicator coat can be comprised of a preformed colored translucent 
material such as a translucent plastic disk. Preferably, the 
bonding-release layer is a photodegradable adhesive. The photodegradable 
adhesive can be used to sufficiently bond the indicator coat to the base 
coat at the closure manufacturer's facility. The closure can then be 
applied to a container and the flexible end panel portion can be set such 
as by pulling a vacuum thereon during packaging. The closure can then be 
subjected to an appropriate amount of ultraviolet radiation in order to 
degrade and weaken the bonding-release photodegradable adhesive. Upon 
opening of the package, the vacuum seal panel is actuated which imparts 
enough energy in order to fracture the weakened adhesive and thereby 
irreversibly allow the indicator coat to separate from the base coat and 
effect a color change. 
Accordingly, it is a general object of the present invention to provide an 
improved tamper evident closure. 
It is another object of the present invention to provide an improved tamper 
evident button closure. 
It is another object of the present invention to provide an improved tamper 
indicating system in the form of a color change system. 
It is another object of the present invention to provide an irreversible 
tamper evident color change system for a closure which contains a flexible 
portion which assumes a given position to indicate a sealed package and a 
different position when the package seal is breached wherein in the sealed 
position the flexible portion has a first color and in the breach 
condition the flexible portion has a second color. 
These and other objects of the invention will be more fully understood from 
the following description of the invention with references to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring now to the drawings in detail, reference is first made to FIGS. 1 
and 2 which illustrate a typical metallic button closure. The closure is 
generally identified by the numeral 10 and includes an end panel 12 which 
has an upwardly and outwardly sloping peripheral portion 14 defining the 
downwardly opening channel 16. The end panel 12 terminates in a generally 
cylindrical skirt 18 which, in turn, terminates in an inwardly turned curl 
20. 
In order that the closure 10 may be applied to a container (not shown) of 
the type including a neck finish having external threads, the skirt 18 and 
the channel 16 are lined with a suitable sealing compound 22. When the 
closure 10 is pressed down on a neck finish of a container, a seal between 
the closure 10 and the container is formed between that portion of the 
sealing compound 22 underlying the end panel 12 while an interlock is 
formed between the threads of the container by that portion of the sealing 
compound 22 which lines the skirt 18. 
The closure 10 is constructed in a manner wherein the end panel 12 is 
provided with a centrally located button generally indicated by the number 
24. The button 24 includes a central post portion 26 surrounded by an 
upwardly sloping annular portion 28 which, in turn, is surrounded by an 
annular generally flat portion 30. Preferably, the button 24 is 
mechanically reformed after its initial formation to a state of 
compressive residual stress such as by mechanically reforming in the 
manner described in U.S. Pat. No. 5,016,769 which is incorporated by 
reference herein. 
Referring now to FIG. 6, in particular, it will be seen that when a closure 
10 is applied to a container and a vacuum is drawn within such container, 
the button 24 is drawn downwardly. In accordance with the preferred 
embodiment of the invention, by mechanically reforming the button 24 as 
the closure 10 is being formed, the button 24 has certain stored stresses 
which facilitate its being maintained in the "up" normally convexed 
position of FIGS. 1-5 and 7. When the button 24 is drawn down into the 
container as shown in FIG. 6, these compressive stresses increase and 
there is a high tendency for the button 24 to flip upwardly from its 
"down" concave position of FIG. 6 back to its original "up" convex 
position. Thus, when the closure 10 is removed from a container and the 
vacuum applied against the underside of the end panel 12 is released, the 
button 24 will flip, snap or pop upwardly to its original position. It is 
this flipping action of the button 24 that actuates the tamper evident 
color change system of the present invention. 
The present invention particular relates to a button enhancement color 
change system which, as shown in FIG. 3, is generally identified by the 
numeral 32 and which is applied to the button 24. The button color change 
system 32 is particularly constructed to specifically designate that the 
closure 10 has been removed from the container even if the closure 10 is 
again placed on the container in the sealed closed position and thus forms 
tamper evident means for the closure 10. 
The color change system 32 includes a base coat or layer 34 applied to the 
button 24 for movement with the button 24. The base coat 34 is formulated 
to adhere to the surface of the button 24 and move with the button 24 
without separation from the button 24. It has been found that a thermally 
curable epoxy ester based coating provides such characteristics when used 
in conjunction with a metallic closure 10. 
In accordance with the color change aspects of the present invention, base 
coat 34 either contains a colorant, preferably a dark colorant such as a 
black, blue or dark green colorant or is translucent and overlies a 
colored background coat 35 on the button 24. The color of the background 
35 is preferably dark such as a black ink carried by a curable resin such 
as the commercially available ink product LA-10022MK supplied by Flint 
Inc. The background coat 35 can be applied to the button 24 either during 
the formation of the closure 10 such as by appropriate lithographic 
application and placement on the sheet metal used to make closure 10 or it 
can be applied to the button 24 after the closure 10 and button 24 are 
formed. Similarly, the base coat 34 can be applied to the button 24 either 
prior to closure 10 formation or after the closure 10 and button 24 are 
formed. 
The color change system 32 also includes an indicator coat or layer 36 
which overlies the base coat 34. The indicator coat 36 is translucent and 
either inherently has a colored appearance or is formulated so as to 
include a colorant. The color of the indicator coat 36 differs from the 
effective color (i.e. the color observed through base coat 34 either by 
having a colored base coat or a translucent base coat over a colored 
background 35) of the base coat 34 and preferably the color of indicator 
coat 36 is a light color. Colorants for the indicator coat 36 include 
transparent fluorescent dyes such as commercially available Pylakrome Oil 
yellow, Pylakrome pink, Pylam white, Keyfluor blue, Day Glo marigold 
orange and Mobay yellow dyes, transparent non-fluorescent dyes such as 
commercially available Macrolex yellow, Macrolex red, Macrolex blue, and 
Macrolex orange dyes, and opaque non-fluorescent dyes such as commercially 
available green production ink, red production ink, blue production ink, 
orange production ink and yellow production ink dyes. The color of 
indicator coat 36 and the effective color of base coat 34 are chosen so 
that, as shown in FIG. 8, when the indicator coat 36 and base coat 34 are 
in intimate contact the color change system 32 has a first color and when 
the indicator coat separates from the base coat 34 the color change system 
32 has a second color as shown in FIG. 9. Preferably, colors are chosen 
for the effective color of the base coat 34 such as black and the 
indicator coat 36 such as orange/yellow so that when the base coat 34 and 
indicator coat 36 are in intimate contact the color change system 32 
appears greenish (for "GO", safe or untampered) and when the indicator 
coat 36 separates from the base coat 34 the color change system 32 appears 
orangish or yellowish (for "CAUTION", unsafe or tampered). 
As shown in the embodiment of the invention depicted in FIG. 3, the 
indicator coat 36 can be applied to the button 24 while the button is in 
its up convex configuration. Application of the indicator coat 36 to the 
base coat 34 while the button 24 is in its up position allows the color 
change system 32 to be applied to the closure 10 at the closure 
manufacturer's facility. 
In accordance with the principles of the present invention, the indicator 
coat 36 is appropriately formulated and applied to the closure 10 to 
provide a coating which will adhere to the base coat 34 when the button 24 
assumes its downward concave vacuum drawn position as shown in FIG. 6 and 
which will separate from the base coat 34 when the button 24 flips back to 
its original "up" position as shown in FIG. 7. It will be appreciated that 
the use of additives such as release agents, lubricants and the like can 
be incorporated within either the base coat formulation or the indicator 
coat formulation to facilitate separation of the indicator coat 36 from 
the base coat 34. It will be appreciated that such release agents can take 
a variety of forms other than chemical additives, such as scoring the 
surface of the button or the base coat, perforating the indicator coat, or 
incorporating solid matter within one or more of the coatings to create 
stress centers to help initiate separation of the layers. It will also be 
appreciated, however, that closures having color change systems 
incorporating enhanced release formulations may have a greater tendency to 
inadvertently undergo a color change. It will further be appreciated that 
the formulations can include other components to enhance the bonding 
between the base coat 34 and the indicator coat 36 so long as the base 
coat 34 and the indicator coat 36 can still effectively separate to cause 
a color change. For example, an epoxy ester varnish base coat 34 may 
contain phenolic resin components to enhance bonding to an indicator coat 
36. It will be appreciated that enhanced bonding agents and enhanced 
release means can also be used in conjunction. For example, means to 
create a stress center to facilitate release of the indicator coat 36 from 
the base coat 34 can be used in conjunction with formulations for either 
base coat 34 or indicator coat 36 which are designed to enhance the 
bonding between the coats. It is believed that the creation of a stress 
crack in the indicator coat 36 upon button flipping may facilitate 
delamination of the indicator coat 36 from the base coat 34. 
It has been found that the use of resins such as acrylated epoxies, 
acrylated urethanes and cationically cured epoxies which are capable of 
multiple stage curing when used to formulate the indicator coat 36 provide 
a tamper evident system for a closure 10 which can be produced at the 
closure manufacturer's site and can be then fully "armed" at the packaging 
site. As best shown in FIGS. 3-6, the indicator coat 36 can be prepared as 
a liquid mixture which is spread over the base coat 34. Preferably, the 
indicator coating is spread to a thickness of 5 to 20 mils. As 
schematically shown in FIG. 4, the indicator coating 36 is partially cured 
such as by exposure to UV radiation effected by an appropriate UV source 
38. Preferably, partial curing of indicator coat 36 is sufficiently 
effected to provide a relatively non-tacky but flexible solid. It will be 
appreciated, however, that the indicator coat 36 can be precured to lesser 
states such as somewhat tacky and even still wet states as desired. 
As shown in FIG. 5, after the indicator coat 36 has been partially cured, a 
flexible transparent coat 40 is applied over indicator coat 36 to seal the 
indicator coat 36 to the closure 10, to protect color change system 32 
during transit and storage and to prevent the indicator coat 36 from 
falling off closure 10 when the indicator coat 36 delaminates from the 
base coat 34. The transparent overcoat 40 is formulated so that it does 
not restrict the flipping action of the button 24 or interfere with the 
separation of the indicator coat 36 from the base coat 34 upon flipping of 
button 24 or interfere with the visual appearance of the color change 
system 32. Examples of materials that can be used to formulate the 
transparent overcoat 40 include clear, low cross-linked density, acrylated 
urethanes, two part epoxies and urethanes, and UV curable cationic 
systems. Additional materials that can be used for overcoat 40 include 
transparent tape such as clear polypropylene or polyester films which can 
be bonded to closure 10 such as by adhesively fixing or heat sealing the 
film to closure 10. 
Preferably, a material which reduces the interfacial tension or bonding 
between the indicator coat 36 and the overcoat 40 is present between such 
coats to prevent the overcoat 40 from interfering with the separation of 
the indicator coat 36 from the base coat 34. Such materials include 
surface active agents like soaps or soap solutions and other surfactants, 
waxes and other lubricants such as amides and stearates and the like, 
which can be applied to the indicator coat 36 prior to application of the 
overcoat 40. It will be appreciated that the curable compositions used for 
color change system 32 such as the UV curable indicator coat 36 and UV 
curable overcoat 40 may contain different curing agents and different 
amounts of curing agents to control the nature and degree of curing. For 
example, a UV curable indicator coat 36 composition may contain different 
photoinitiators which can be activated by different UV wavelengths to 
facilitate multiple stage curing of the indicator coat 36. Additionally, 
when a UV curable overcoat 40 is used in association with a UV curable 
indicator coat 36 it may be desirable to utilize different photoinitiators 
in the indicator coat 36 and the overcoat 40 so that each of the coats can 
be cured independently of each other and so that the cure of the overcoat 
40 does not untimely cure or otherwise interfere with the cure of the 
indicator coat 36. It will, of course, be appreciated that, if necessary, 
different UV sources and/or different UV lamps may be used to activate the 
photoinitiators, as needed. 
FIG. 6 shows the closure 10 carrying the color change system 32 after the 
closure 10 has been applied to a container and the button 24 has been 
drawn down to its concave position by a vacuum within the container. As 
schematically shown in FIG. 6, the partially cured indicator layer 36 can 
then be fully cured to a very stiff cross-linked polymer such as by 
exposure to higher doses of UV radiation effected by an appropriate UV 
source 42. 
As shown in FIGS. 6 and 8, the fully cured indicator coating 36 is in 
intimate contact with the base coating 34 so that color change system 32 
when viewed through indicator coat 36 has a first color. As noted above, 
when the button 24 is in the down position of FIG. 6, it has stored energy 
and is in a state of stress such that when the vacuum is removed by 
removal of the closure 10 from the container, the button 24 will flex 
upwardly to its original position as shown in FIG. 7. As shown in FIGS. 7 
and 9, when the button 24 flexes upwardly, indicator coat 36 separates 
from the base coat 34 and color change system 32 when viewed through 
indicator coat 36 has a second color. It will be appreciated that the 
separation of indicator coat 36 from base coat 34 creates a reflective 
interface 44 sufficient that the color perceived is the color of the 
indicator coat when color change system 32 is viewed through the indicator 
coat 36. It is believed that a 0.3-0.8 micrometer separation between 
indicator coat 36 and base coat 34 should provide a sufficient reflective 
interface 44 to cause color change system 32 to undergo an effective 
change of color. In accordance with the present invention, if after 
activation of color change system 32, closure 10 is reapplied to the 
container and a further vacuum drawn within the container, even though the 
button 24 will be deflected downwardly, the indicator coat 36 will not 
rewet to base coat 34 sufficient to eliminate interface barrier 44 and 
cause the intimate contact necessary to reestablish the first color of 
color change system 32. 
Examples 1-5 illustrate representative formulations for indicator coat 36 
which formulations are susceptible to two stage curing. It is presently 
contemplated that these formulations and an overcoat layer could be 
applied to the button area 24 of a closure 10 at a closure manufacturer's 
site. The button area 24 of the closure 10 would already have a dark 
background 35 such as a black colored background 35 and an epoxy ester 
varnish base coat 34 applied to the button area 24. After the indicator 
coat 36 is applied over the base coat 34 the indicator coat 36 is 
partially cured sufficiently to allow the color change system 32 to 
withstand application of the closure 10 to the container and the drawing 
down of the button 24 by a vacuum within the container without cracking or 
loss of adhesion of the color change system 32. A transparent overcoat 40 
then can be applied over the precured indicator coat 36. After the closure 
10 is applied to the container and the button 24 is down, the color change 
system 32 is fully activated by fully curing the indicator coat 36. 
EXAMPLE 1 
10 parts by weight of a UV curable diacrylate bisphenol A epoxy such as 
Ebercryl 3700 supplied by Radcure is heated to about 50.degree. C. A photo 
initiator (0.4 parts by weight) such as Irgacure 184 supplied by Ciba 
Geigy, fumed silica (0.5 parts by weight) which acts as a suspension 
agent and opaqifier and an orange fluorescent dye (0.005 parts by weight) 
such as Marigold Orange supplied by Day Glo are added. The composition is 
mixed sufficiently to obtain a homogenous mixture of all the components. A 
cowels mixer can be used to increase the speed and efficiency of the 
mixing. 50 to 100 mg of the material is applied to the center of an up 
button of an approximate two inch diameter non-sealed closure. The button 
portion of the closure would already have a black colored background and 
base coating applied to the button portion of the closure. The material is 
then spread to an appropriate shape and size such as a disk shape with a 
diameter of about 3/4 of an inch. The material can be spread in any number 
of ways to achieve the desired result. One method of spreading is to place 
the cap on a rotating chuck and use a flat ended spatula to apply and 
spread the material on the cap. Another method of application is to use an 
apparatus comprising a motorized rotating chuck into which the cap is 
secured, a doctor blade attached to one end of a stylus arm and profile 
bar. A cap can be secured into the chuck and the material to be spread can 
be applied to the center of the button area. The apparatus motor is 
started and the doctor blade is brought into contact with the material. 
The stylus end of the stylus arm is traced over the profile bar which 
determines the movements of the doctor blade across the cap. After the 
material is applied to the button area of the cap, it can be partially 
cured to a non-tacky but flexible solid by exposing it to a light dose of 
UV radiation and an overcoat layer can be applied. After the cap is 
applied to the container and the button is drawn down, the indicator coat 
can be fully cured to a very stiff cross-linked polymer upon exposure to 
higher doses of UV radiation. When the UV cured indicator coat is in 
intimate contact with the black backgrounded base coat the color change 
system when viewed through the indicator coat appears dark green. Upon the 
button up-flip and activation of the tamper evident coating system, the 
color change system when viewed through the indicator coat appears orange 
due to the separation of the indicator coat from the base coat. 
EXAMPLE 2 
Ebecryl 3700 (7.0 parts by weight)) is heated to about 50.degree. C. An 
opaqifier such as zinc oxide (2.0 parts by weight) and colorants such as 
Marigold Orange fluorescent dye (0.3 parts by weight) and Mobay yellow 
fluorescent dye (0.3 parts by weight) are then added. The formulation is 
mixed with sufficient shearing action to provide a homogenous mixture of 
all of the components. This mixture is made in order to effectively 
disperse the dyes and fillers into the indicator formulation in the 
correct amounts. The main indicator coating can then be formulated by 
heating Ebecryl 3700 (100 parts by weight) to about 50.degree. C. and then 
adding the foregoing premix (0.1 part by weight), fumed silica (0.5 parts 
by weight) and 0.1 part by weight of a long wave length photo initiator 
such as Lucerin TPO supplied by BASF. The resulting material can be 
applied to a button closure having a black colored background and a base 
coat and cured in accordance with the methods set forth in Example 1 
above. When the UV cured indicator coat is in intimate contact with the 
black backgrounded base coat the color change system when viewed through 
the indicator coat appears dark green. Upon activation of the color change 
system the color change system when viewed through the indicator coat 
appears orange/yellow due to separation of the indicator coat from the 
base coat. 
EXAMPLE 3 
100 parts by weight of a phenyl based epoxy novolac such as Tactix 785 
supplied by Dow Co. is heated to the melt state. One part of a cationic 
photo initiator such as FX-512 supplied by 3M is then added and the 
components are mixed. The material is allowed to cool and is then crushed 
into a granular form. 50 to 100 milligrams of the material is applied to 
the center of the up button of a non-sealed cap. The button would have a 
black backgrounded base coat in place. The cap is then heated, on a hot 
plate or with an IR lamp, until the material goes to the melt state. The 
melted material is then spread to a diameter of about 3/4 of an inch with 
a stirring rod or a spatula. Upon cooling, the material solidifies. 
Because the material is solid in its uncured state it is not necessary to 
go through the precure process of Examples 1 and 2 above. Although 
thermoplastic phenol formaldehyde type resins typically are cured with 
cross-linking agents such as amines and anhydrides and heat, this 
formulation can be cured for the present application by exposure to UV 
energy. When this material is UV cured it turns red in color. Accordingly, 
after the closure containing the color change system of the present 
invention incorporating the formulation of Example 3 is applied to the 
container and a vacuum is drawn the indicator coat can be cured by 
exposure to UV radiation. When the UV cured indicator coat is in intimate 
contact with the black colored base coat the color change system when 
viewed through the indicator coat appears dark green. Upon button up-flip 
and activation of the tamper evident coating system, the color change 
system when viewed through the indicator coat appears red due to the 
separation of the indicator coat from the base coat. 
EXAMPLE 4 
A photo initiator and colorant premix is prepared of Darocur 4265 (1.96 
parts by weight) photo initiator supplied by EM Industries, Mobay yellow 
10 GN (1.3 parts by weight) yellow fluorescent dye supplied by Mobay and 
Pylachrome pink (0.043 parts by weight) pink fluorescent dye supplied by 
Pylam Corp. The main indicator coating is prepared by adding Ebecryl 220 
(141 parts by weight) UV curable hexafunctional urethane acrylate to a 
four ounce glass jar. Then a fluoro aliphatic ester surface active agent, 
surfactant (0.214 parts by weight) used to provide good wetting 
characteristics of the uncured system to the cap such as FC430 supplied by 
3M, white pigment such as titanium dioxide (0.214 parts by weight) used to 
provide opacity, the foregoing premix (1.430 parts by weight) and about 
2.4 parts by weight of fumed silica such as Cab-O-Sil supplied by Cabot 
Corporation are added. The mixture is stirred gently with a spatula to 
entrap the silica. An additional amount of 2.4 parts by weight fumed 
silica is added and the mixture is vigorously stirred with a cowels blade 
mixture or otherwise appropriately blended such as by a three roll mill. 
The resulting material can be applied to a button closure having a black 
backgrounded base coat in accordance with the methods set forth in Example 
1 above. The indicator coat can then be precured by exposure to UV 
radiation. For example, a Suncure Photocure 2785 Lab UV curing unit 
housing two 12 inch (200 watts/inch) medium pressure mercury vapor lamps 
can be used to cure the indicator coat. The indicator coat can be precured 
by exposure to approximately 0.029 Joules/cm.sup.2 as measured in the 
wavelength range between about 320 to 390 nm (1.times.150 ft/min at full 
power on the Suncure unit). An overcoat layer can be applied over the 
precured indicator coat. For instance, an acrylated urethane overcoat can 
be prepared using an aliphatic urethane diacrylate such as Photomer 6060 
supplied by Henkel. The acrylated urethane is placed in a four ounce glass 
jar and heated on a hot plate for approximately 7 minutes at about 
200.degree. C. at which time it should be fluid enough to stir with a 
glass stirring rod. About 10 parts by weight isobornylacrylate and about 
2.5 parts by weight N vinylpyrrolidone can be sequentially added to lower 
the viscosity, improve elongation, improve hardness and increase the 
curing speed of formulation. About 1 parts by weight of a photo initiator 
such as Irgacure 184 is added and the components are mixed well. 
Additional additives such as surfactants can be added to provide other 
characteristics such as wetting and scruff resistance to the overcoat 
layer. For instance, about 0.2 parts by weight of surfactants can be 
included in the above overcoat formulation to provide wetting and scruff 
resistance to the overcoat. The overcoat can be applied to the closure 
such as by applying it in a manner similar to that used to apply the 
indicator coat to the closure or in any number of other ways to achieve 
the desired result. The overcoat can then be cured by exposure to 
approximately 0.026 Joules/cm.sup.2 as measured in the wavelength range 
between about 320 to 390 nm (1.times.100 ft/min at low power on the 
Suncure unit). After the closure has been applied to the container and the 
button is drawn down, the indicator coat can be fully cured to a very 
stiff-cross-linked polymer by further exposure to approximately 0.518 
Joules/cm.sup.2 as measured in the wavelength range between about 320 to 
390 nm (5.times.50 ft/min at full power on the Suncure unit). When the UV 
cured indicator coat is in intimate contact with the black backgrounded 
base coat the color change system when viewed through the indicator coat 
appears green. Upon activation of the color change system, the color 
change system when viewed through the indicator coat appears orange due to 
separation of the indicator coat from the base coat. 
EXAMPLE 5 
25 parts by weight of an aromatic diacrylate urethane, PES 198 supplied by 
Polymer Systems, is heated to 50.degree. C. 25 parts by weight of a 
bisphenol A epoxy diacrylate such as Henkel 3016 is added to the heated 
aromatic diacrylate urethane and 50 parts by weight of a hexafunctional 
aromatic urethane acrylate used to increase cross-linked density such as 
Henkel 6022 is added. 2 parts by weight of a photo initiator such as 
Darocur 1173 supplied by EM Industries and 2.5 parts by weight of calcium 
carbonate which is used to provide opacity are added. A desired amount of 
a colorant preferably a light colored fluorescent dye can also be added. 
The formulation can be applied to a dark backgrounded base coat button 
closure and cured in accordance with the procedures set forth in Example 4 
above. When the UV indicator coat is in intimate contact with the black 
backgrounded base coat the color change system when viewed through the 
indicator coat will have a first color. Upon activation of the color 
change system, the color change system when viewed through the indicator 
coat will have a second color different from the first color due to 
separation of the indicator coat from the base coat. 
It will be appreciated that although the formulations set forth in Examples 
1-5, above, have been described in the context of two stage curing systems 
that such formulations can also be used in a single stage curable system 
such as by application to a base coating 34 on a button closure 10 which 
has already been applied to a container and drawn down by a vacuum 
therein. In such a single stage application, the indicator coat 36 would 
be subjected to sufficient curing means, such as chemical curing means, 
thermal curing means or radiation such as UV radiation curing means, to 
effect the desired amount of curing of the indicator coat 36 resin. 
Examples 6 and 7 illustrate further representative formulations for 
indicator coat 36 which formulations are susceptible to single stage 
curing. It is presently contemplated that these formulations could be 
applied to the button area 24 of a closure 10 at the packaging site after 
the closure 10 has been applied to a container and the container is sealed 
and the button 24 has been drawn to its down position. The button 24 would 
have a dark background and base coat 34 such as an epoxy ester varnish 
base coat in place. 
EXAMPLE 6 
62.5 parts by weight of a diglycidyl ether of Bisphenol A such as DER 332 
supplied by Dow Chemical and 62.5 parts by weight of an adduct of 40/60 
carboxy terminated butadiene nitrile rubber and bisphenol A type epoxy 
such as Epirez 58005 supplied by Rohme Poulenc are mixed together until 
they are a homogenous blend. The materials can be heated slightly such as 
to 50.degree. C. to lower viscosity and aid mixing. A glass stirring rod 
can also be used to facilitate mixing of small batches. 2.5 parts by 
weight of a mercaptan terminated liquid polymer which imparts rapid cure 
to epoxy resins in combination with selected amines such as Capcure 3-800 
supplied by Henkel is then added to the blend and mixed well. 1.0 parts by 
weight of a tertiary amine which can be used as a catalyst and curing 
agent such as Capcure EH30 supplied by Henkel is then added and the blend 
is mixed well. Immediately after mixing a small amount, approximately 100 
milligrams of the formulation is deposited over a black backgrounded epoxy 
ester base coat present on the center of the down button of a sealed cap 
(the cap being approximately 2 inches in diameter). The container is 
rotated while the flat end of the spatula is used to spread the material 
to a disk shape with a diameter of about 3/4 of an inch. The indicator 
coat is then allowed to cure at room temperature for 24 hours. Upon 
curing, the indicator coat is relatively transparent and, accordingly, the 
button area when viewed through the indicator coat appears black due to 
the black colored base coat. Upon button up-flip the indicator coat looses 
its adhesion to the base coat and the coating and button area when viewed 
through the indicator coat appears milky white. 
EXAMPLE 7 
140 parts by weight of a water solution of sodium silicate, Na.sub.2 
SiO.sub.3, (Banco 41 degrees Be solution) is mixed with 3 parts of a 
premixed water soluble fluorescent dye solution (red and yellow-green 
fluorescent dyes supplied by Formulas). The dye solution is prepared by 
adding the concentrated dye to water to produce a super saturated 
solution. The dye premix is then added to a volume of sodium silicate at a 
level that will produce the needed degree of color. The proper color 
intensity is preferably one which will produce an obvious green color when 
the indicator coating is in contact with a black backgrounded base coating 
and provides an obvious orange or yellow color when it delaminates from 
the black base coating. 50-100 microliters of the sodium silicate/dye 
solution are applied with a syringe or eye dropper to the center of a 
black backgrounded base coated down button on a sealed cap. The solution 
is spread to a diameter of approximately 3/4 of an inch with a glass 
stirring rod, spatula or doctor blade. The cap is then heated to about 
60.degree. C. to drive-off the water. As previously noted, when dried, the 
color change system when viewed through the indicator coat will appear 
green. Upon button up-flip the adhesion is lost between the button surface 
and the indicator film of sodium silicate which causes the color change 
system to appear to be yellow or orange (depending upon the color of the 
dye used) when viewed through the indicator coat. 
Reference is now made to FIGS. 10 through 12 which illustrate an alternate 
embodiment of the present invention. As shown in FIG. 10, in this 
embodiment of the invention, a button enhancement color change system 
generally identified by the numeral 50 comprises a translucent 
bonding-release layer 56 interposed between a base coat 52 and an 
indicator layer 54. As in the embodiment of the invention illustrated in 
FIGS. 3-7, base coat 52 either contains a colorant or is translucent and 
overlies a colored background coat 53 on the button 24 and base coat 52 is 
formulated to adhere to the surface of the button 24 and move with the 
button 24 without separation from the button 24. The indicator layer 54 is 
translucent and either inherently has a colored appearance or is 
formulated to include the colorant. In accordance with the principles of 
the present invention, the color of the indicator layer 54 differs from 
the effective color of the base coat 52. 
The bonding-release layer 56 is interposed between the indicator layer 54 
and the base coat 52 to bond the indicator layer 54 to the base coat 52 in 
an effective intimate contact relationship prior to the breach of the 
integrity of a container sealed with a closure incorporating the color 
change system 50. In accordance with the objects of the present invention, 
the bonding-release layer 56 is translucent so that when the indicator 
layer 54 and the base coat 52 are in effective intimate contact, the 
perceived color of the color change system 50 is a function of the 
combined colors of the layers comprising the color change system 50. 
It will be appreciated that the indicator layer 54 can be made from a resin 
similar to that used for the indicator coat 36 in the embodiment of the 
invention illustrated by FIGS. 3-7 or the indicator layer 48 can be 
comprised of a preformed colored translucent material such as a color 
translucent plastic disc or a colored translucent plastic film. 
As shown in the embodiment of the invention depicted in FIG. 10, the 
indicator layer 54 can be applied to the button 24 over the 
bonding-release layer 56 while the button 24 is in its up concave 
configuration. Application of the indicator layer 54 while the button 24 
is in its up position allows the color change system 50 to be applied to a 
closure at the closure manufacturer's facility. 
In accordance with the principles of the present invention, the 
bonding-release layer 56 is appropriately formulated and applied to a 
closure so that indicator layer 54 and base coat 52 are in effective 
intimate contact when the button 24 assumes it downward concave vacuum 
drawn position as shown in FIG. 11 and so that indicator layer 54 
irreversibly separates from the base coat 52 when the button 24 flips back 
to its original "up" position as shown in FIG. 12. Suitable materials for 
the bonding-release layer 56 include photodegradable adhesives including 
relatively high molecular weight polymers which can be degraded such as by 
subjection to UV radiation to reduce or weaken their adhesive properties. 
Prior to degradation, the photodegradable adhesive can be used to 
sufficiently bond the indicator layer 54 to the base coat 52 during 
application of the color change system 50 to the button 24 and the arming 
of button 24 such as by pulling a vacuum thereon during packaging. It will 
be appreciated that if a UV curable composition is utilized for the 
indicator layer 54 and a photodegradable adhesive is utilized for the 
bonding-release layer 56 that it may be desirable to utilize 
photoactivators for the indicator layer 54 (e.g. photoinitiator(s) which 
actuates curing of the composition) and for the bonding-release layer 56 
(e.g. photoabsorber which actuates degradation of the composition) which 
are actuated by different wavelengths or mechanisms. Using different 
photoactuators for the indicator layer 54 and for the bonding-release 
layer 56 may be especially desirable to prevent premature degradation of 
the bonding-release layer 56 when the indicator layer 54 is being exposed 
to a UV source to fully cure indicator layer 54. 
FIG. 11 shows the closure 10 carrying the color change system 50 after the 
closure 10 has been applied to a container and the button 24 has been 
drawn down to its concave position by a vacuum within the container. As 
schematically shown in FIG. 11, the photodegradable bonding-release layer 
56 can be degraded to weaken its bonding ability such as by exposure to UV 
radiation effected by an appropriate UV source 58. For example, it has 
been found that a photodegradable polystyrene resin such as commercially 
available Ecolyte PS-2005 resin supplied by Novacor of Leominster, Mass. 
has certain adhesive properties at its starting molecular weight of 
111,000M.sub.n and that after exposure to 12-13 Joules/cm.sup.2 of UV 
energy it is degraded to a molecular weight of 86,000M.sub.n and its 
adhesive properties are concomitantly reduced. 
As illustrated in FIG. 12, when the closure 10 incorporating color change 
system 50 is removed from a container and the vacuum applied against the 
underside of the end panel 12 is released, the button will flip, snap or 
pop upwardly to its original position. This flexing action of the button 
24 is sufficient to disrupt the adhesive ability of the weakened 
bonding-release layer 56 thereby allowing the indicator layer 54 to 
separate from the base layer 52. As illustrated in FIG. 12, the adhesive 
failure of the bonding-release layer 56 results in the creation of a 
reflective interface or reflection barrier 60 between the indicator layer 
54 and the base coat 52 which causes the color change system 50 to undergo 
a change in color. 
As shown in FIGS. 10-12, and as in the embodiment of the invention shown in 
FIGS. 3-7, the color change system 50 can include a flexible transparent 
coat 62 which is applied over indicator layer 54 to seal, the indicator 
layer 54 to the closure 10, to protect the color change system 50 during 
transit and storage and to prevent the indicator layer 56 from falling off 
the closure 10 when the bonding-release layer fails and indicator coat 54 
separates from the base coat 52. 
Although only several preferred embodiments of the invention have been 
specifically illustrated and described herein, it will be understood that 
minor variations may be made in the color change system of the present 
invention without departing from the spirit and scope of the invention as 
defined by the appended claims.