AU687373B2 - Improved novel tamper evident closure - Google Patents

Description

AUSTRALIA

Patents Act 1990 THE KENDALL COMPANY

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: *o a a..

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IMPROVED NOVEL TAMPER EVIDENT CLOSURE The following statement is a full description of this invention including the best method of performing it known to us:a a as 2 Background of the Invention The present invention relates to flexible tamper-evident tapes wherein the evidence of tampering is either a transfer of a pattern tot he tampered product, revelation of a pattern on the backing of the closure, or tearing of the closure and/or the product over a wide temperature range on the order of -320°F where other so-called tamper-evident seals do not exhibit tampering when removed and replaced later.

Tamper proofing has been of concern throughout the ages in the financial and security sectors. However recently it has taken on new proportions due to tampering of food, cosmetic and pharmaceutical products.

The following patents are illustrative of the prior art, yet are by no means intended as a complete survey of the prior art.

The earliest patent, US Patent No. 2,845,728 issued to HIuber, discloses a self-destroying label having pressure sensitive adhesive on one 15 surface thereof. The principal object of this invention provided for a pressure sensitive label readily e ee 3 applicable to items of various kinds. Yet, when an attempt is made to remove such labels from the article, the label is damaged or disintegrates to a sufficient extent so that the condition of the label, if removed from one article and applied to another.

readily and visibly will serve to indicate that the label has been tampered with.

Essentially, the invention consists of weakening means comprising either interrupted rows of incisions or substantially continuous partial incisions.

U.S. Patent No. 3,383,121 discloses a self-adhesive copy label comprising a laminate construction consisting c.f a first layer such as a sheet of paper, a second pressure sensitive adhesive layer, preferentially adhered to the first layer so that it separates with the first layer when the first and third layers are separated, and a third layer consisting of a sheet of material constructed to he impact sensitive in that it carries, in normally separate states, chemicals which intermix upon impact to produce a color change in the impact area in or on the third layer itself. Thus the tamper evidence here is a color change.

15 U.S. Patent No. 4,082,873 issued to Williams discloses a "laminate comprising a transparent or translucent outer sheet having an information-containing pattern printed on its inner surface, the printed inner surface having a coating of pressure sensitive adhesive film coated thereon. The affinity of the adhesive for the surface to which the laminated label is adhered and to the printed pattern is greater than the affinity of the printed pattern for the outer sheet. Once applied to a substrate, if removal of the label is attempted, the label delaminates in a manner such that the outer sheet separates, leaving at least a portion of the adhesive layer having at least a portion of the printed 4 pattern adhering thereto, adhered to the substrate." U.S. Patent No. 4,121.003 issued to Williams modifies Patent No. 4.082.873. by providing that at least a portion of the information-containing pattern he printed with an ink which is not dried into an integral film form so as to form a disruptable pattern when tampered with. Thus when the top sheet is delaminated from the adhesive, a portion of the pigmentation in the disruptable pattern adheres to the top sheet as well as the adhesive layer, resulting in a "diminution of interruption of the coloration of the disruptable pattern on the top shezt sufficient to give visual indication of tampering." U.S. Patent No. 4.184.701 issued to Franklin et al discloses a label comprising "a laminate comprising a transparent or translucent outer sheet having an information containing pattern printed on its inner surface, said printed film having a discontinuous coating of transparent plasticized organic polymeric material thereon, with said printed and coated surface having a coating of a color containing pressure sensitive adhesive film thereon." Upon removal the label delaminates such that at least portions of the colored adhesive in register with the transparent discontinuous plasticized polymer coating remain on the substrate to which the label is adhered. Thus the evidence of tampering is a visual change in at least portions of background color.

U.S. Patent N'o. 4,608,288 issued to Spindler discloses a label comprising a cover foil with an adhesive layer laminated onto a base foil. The cover foil is made of a material which is irreversibly deformable or easily breakable upon tampering.

Moreover, the cover foil extends beyond the periphery of the base loil, thereby creating a safety rim which makes access to the base foil difficult.

5 U.S. Patent No. 4.652.473 issued to Han discloses a tape comprising a backing having an ou' rd inner layer, the outer layer having sufficiently high tensile strength to maintain its integrity when removed. In contrast, the inner layer is thin and deformable. Thus evidence of tampering is present by way of delamination. Upon removal of the outer layer, it delaminates from the inner layer which in turn generally causes a partial stretching out of the thin inner layer. Moreover, the patentee suggests using printed or colored layers for additional evidence.

U.S. Patents Nos. 4,721,638:-4.746.556; and 4.763.931 all issued to Matsuguchi et al disclose a multilayered adhesive material comprising various separation forces so that when particular layers are separated they cannot readhere or cannot readhere as in the original state.

The primary disadvantage of the prior art, as illustrated by the aforementioned patents, is evidenced at low temperature. At low temperatures. such as liquid nitrogen for example, the adhesive layers delaminate from the backing, thereby allowing for replacement without any evidence of tampering. Notably. while this delamination does occur in the three patents issued to Matsuguchi et al. lettering becomes evident when the material is replaced. However, these tapes comprise multiple layers and thus are quite costly.

The present invention obviates the disadvantages of the prior art in an elegant 20 and novel manner by providing for a tamper evident closure at all temperatures.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

In accord with the present invention there is provided a tamperevident adhesive tape for securing to a document container to provide evidence of tampering over a wide temperature range from above to below the Tg of the adhesive securing tape to the document container, comprising a transparent backing layer carrying on one side thereof, in order: a discontinuous layer of deposits of a transparent barrier material bonded to the backing; a coloured layer chemically bonded to the backing layer in areas where there is no barrier material deposits, the barrier material preventing 15 chemical bonding of the coloured layer to the backing layer in areas where the barrier material is present; and an acrylic pressure sensitive adhesive layer for securing the tape to the container where any evidence of tampering is desired, the chemical bond strength between the backing layer and coloured layer being greater than the adhesion strength between the coloured layer and the adhesive layer .securing the tape to the container both above and below the Tg of the adhesive layer, whereby when attempt is made to remove the tape from the container to gain access to its contents, the coloured layer will remain with the backing in areas where they are chemically bonded while in areas where the barrier material is present to prevent chemical bonding, the coloured layer will adhere to the adhesive layer to provide a coloured pattern or image evidencing tampering with the container which is visible to the eye, which evidence remains visible to the eye when an attempt is made to reapply the coloured layer and backing to the adhesive laver.

Brief Description of the Drawing The figure is a diagrammatic cross-sectional view of an embodiment of a tamper-evident tape of this invention.

Detailed Description of the Invention As heretofore mentioned, the present invention is directed to a novel tamper-evident tape for applying over the flap or other opening in pouches, bags, envelopes or other containers for currency, security documents 6/'I and the like, which tape will exhibit evidence of tamp~ering if the tape is reilovec to gain access to the content and then replaced. The tapoe will provide evidence of tampering over a, wvidle ternperature range ftfftfttf r 7 from above to below the Tg of the adhesive layer adhering the tape of the subst ate to be protected.

The invention will best be understood by reference to the accompanying drawing.

As shown therein, the novel tamper-evident disclosure 10 of this invention will comprise an adhesive tape having a transparent backing 12 carrying, in order, a discontinuous laver 14 of a barrier material, a colored laver 16 chemically bonded to backing layer 12 in areas where there is no barrier material 14 and a layer 18 of a pressure-sensitive adhesive characterized as being aggressive, i.e. possessing a high peelshear strength. for adhering the tape over the mouth or opening of the container to be secured.

Colored laver 16. which may be on the order of 0.1 to 0.6 mil thick. is characterized by possessing a covalent bond between the backing 12 which is stronger Sthan the adhesion at the interface between layer 16 and pressure-sensitive adhesive layer 18, so that any attempt to remove the tape from the container will result in separation of the backing 12 with chemically bonded layer 16 from the underlying adhesive layer, with at least a portion of colored layer 16 in areas corresponding to areas containing barrier material 14 adhering to the underlying adhesive layer 18 to reveal a pattern on the container in terms of the colored material adhering to the adhesive layer still secured over the opening of the container.

'20 The covalent bond between colored layer 16 and backing 12 will retain the preferential adherence of layer 16 to the backing even in the cold. e.g. when sprayed with liquid nitrogen to a temperature of on the order of -320°F, 8 Layer 16 is also characterized as being relatively soft and pliant so that under the force of removal it will convolute or distort, making it impossible to overlay it again on the adhesive layer precisely so that the tampering will not be visibly revealed.

Backing layer 12 will comprise a transparent polymeric material which is "compatible" with the colored underlying layer 16 in the sense that they can be chemically bonded together, as previously mentioned. The preferred compatible material for forming layers 12 and 16 will be selected from the per se known polyesters.

For example, backing layer. 12 may be on the order of from about 0.5 to about nils thick. 1,0 mil being preferred. comprised of a polyester such as "MYLAR".

trademark of E.I. Dupont de Nemours Co. for a durable, transparent. wt:er-repellant film of polyethylene terephthalate resin.

As alluded to earlier, layer 16 comprises a "compatible" material with backing 12 in the sense that it will chemically bond to the backing in areas where there is no barrier material 14. Bonding of layers 12 and 16 may be accomplished by crosslinking and where layer 12 comprises a polyester. layer 16 will also comprise a polyester, either or both layers additionally containing a crosslinking agent to provide the chemical bond between the layers. In the preferred embodiment layer 16 will contain diisocynate crosslinker in an amount sufficient to effect sufficient crosslinking to provide a covalent bond between the two layers having cohesive strength greater than the adhesion EO0 between layer 16 and the underlying adhesive layer 18.

9 The amount of crosslinker, that is. the ratio of crosslinker to crosslinkable material in layer 16 will in part be dependent upon the crosslinkable materials and is not capable of precise quantification. Accordingly, the amount to he employed will he understood by those skilled in the art as being an "effective amount". i.e. an amount effective to produce the desired chemical bond between the two layers of greater strength than the bond between layers 16 and 18, While the selection of appropriate proportions will only require routine experimentation within the expected judgment of the skilled worker in the light of the foregoing discussion, for purposes of illustration a solution of polyester and diisocyanate crosslinker may be provided in a suitable organic solvent such as ethyl acetate. the ratio by weight of polyester to crosslinker being on the order of from about 95:5 to about 60:40.

As heretofore mentioned. layer 16 will contain a suitable color-providing material. e.g. a non-migrating dye or pigment having suitable spectral absorption characteristics and density so as to he readily visible to the eve when layer 16 is viewed o through transparent backing layer 12.

A preferred polyester for layer 16 is "Pentaflex" obtained initially from Whittaker Corporation and now commercially available from Natural Starch Chemical Company, a subsidiary of Unilever United States. Inc., under the trade designation 20 6066 and which is characterized as being soft and tacky. Other useful polyesters may.

for example, be selected from those disclosed in U.S. Patents Nos. 4.581,093: 4.487.909: S' 4,486,508 and 4,419,476, all assigned initially to Whittaker Corporation and subsequently 10 to Natural Starch Chemical Company.

Suitable crosslinking agents include those disclosed, for example. in the aforementioned U.S. Patent No. 4,581.093, e.g. isocvanate crosslinkers such as toluene diisocyanate (TDI); 4,4'-methylene-bis(diphenyl diisocyanate); the 5/2 molar adduct of TDI and trimethylolpropane; the 2/1 molar adduct of TDI and diethylene glycol: 1.6hexamethylene diisocvanate, etc.

The harrier material 14. which is preferably applied in a pattern hut which may he randomly adhered to the backing. may comprise any material which bonds aggressively to backing 12. Examples of such materials include silicone. fluorocarbons.

Quilon (trademark of E.I. DuPont de Nemours polyoctadecyl carbonate, etc..

silicone being preferred. Barrier material 4, whose function is to prevent adherences of the underlying colored layer 16 to hacking 12 in areas of deposit of barrier material.

is transparent or translucent so that the underlying colored layer 16 may he seen therethrough when viewed through the transparent hacking. The harrier material 15 deposits may. for example. he on the order of about micron thick. They may be strongly secured to the inner surface of the hacking by per se known techniques such as gravure or flexible printing, spray coating, chemical etching and the like.

Adhesive layer 18 laminating the tape to the substrate may be on the order of 1.0-2.0 mils thick and may comprise any of the known acrylic pressure-sensitive adhesive formulations for strongly or aggressively adhering the tape. Tackifiers and/or plasticizers may be incorporated in the acrylic adhesive to increase adhesion.

11 As will be discussed hereinafter, rubber-based pressure-sensitive adhesives should not be employed for layer 18 in the practice of this invention.

In optional embodiments, layer 18 may further contain a non-migratory colorproviding material contrasting with the color-providing material in the overlying layer 16. It may also contain a chemical reagent which, through contact with the skin.

produces a traceable reaction product in the skin and/or a reaction product such as a fingerprint on layer 16 itself.

In use, the tape will of course be applied sealing the mouth or other opening in the container to he protected from tampering. When the tape is removed above the Tg of layer 18. e.g. at ambient temperatures or higher. so as to tamper with the contents.

in areas where no barrier material is present. the colored layer 16 will remain with the backing, as heretofore alluded to. However. in areas where barrier material 14 is present so as to preclude adhesion of colored layer 16 to the backing, the colored layer will be stripped away from the barrier, adhering to adhesive layer 18 which remains 1 15 aggressively bonded to the substrate. This will in turn provide a colored pattern or positive image on the substrate in terms of adhered colorant from layer 16 and a reverse contrast or negative image visible through the stripped-off backing in terms of the remaining colored layer and areas where there is no colorant visible through the backing. Even when an attempt is made to re-apply the tape precisely to the substrate.

evidence of its removal will still be readily visible to the eye, due to distortion or convolution of layer 16, as previously discussed.

12 When the tape is removed below the Tg of the adhesive, e.g. by first spraying with liquid nitrogen. and then removing the tape, visual evidence of the tampering will also be exhibited in one or more of the following ways.

First, when the tape is removed from the substrate, adhesive layer 18 delaminates from colored layer 16 except where barrier layer 14 is present. At these areas, colored layer 16 breaks from barrier layer 14 and transfers with adhesive layer 18. It is important to note, that if a rubber-based adhesive were to he employed for layer 18. the rubber-based adhesive laver will dclaminate from colored laver 16 in the cold without breaking layer 16 as herein contemplated.

A second possible evidence of tampering, is that the backing is liable to tear.

leaving an image on the substrate along with the evidence of tearing of the backing.

A third evidence which may occur is a noticeable wrinkling or distortion of the substrate.

The following example shows by way of illustration and not by way of limitation the practice of this invention.

EXAMPLE

On a MYLAR backing approximately 1.0 mil thick a discontinuous layer of silicone approximately 1.0 micron thick was flexible printed in a pattern (layer 14) repeatedly spelling out "OPENED". A solution comprising 43.0 gms of ethyl acetate, O 43.0 gms of Pentaflex 56066 (now commercially available from Natural Starch Chemical Company under the trade designation 30-600r)), 3.0 gms of the isocyanate 13 crosslinker, TDI from Natural Starch Chemical Company under the trade designation 30-6806, and 9.0 gms of copper phthalocyanine. a blue pigment was then coated thereover to provide a layer (16) about 0.2-0.3 mil thick.

After drying to remove the solvent, an ethyl acetate-based acrylic pressuresensitive adhesive was then coated over the blue layer (16) to provide an adhesive layer approx. 1.5 mils thick. Finally, after drying to remove the coating solvent, a standard mils high density polyethylene release liner was applied to cover the adhesive layer.

From the foregoing descriFpion. including the drawing and illustrative example.

it will thus be seen that the present invention provides an elegant security closure which will provide visible evidence of tampering over a wide temperature range from hot to cold, e.g. from 150°F to -320°F. Evidence of tampering may be readily observed by one or more of the following mechanisms provided by the closure: transfer of a o colored pattern to the container or other substrate: revealing a printed pattern on the backing: tearing of the backing: color change: wrinkling: and finger 15 prints.

It will be appreciated that various changes may he made without departing from the scope of the invention herein contemplated. Accordingly. it is intended that all matter contained in the forgoing description and accompanying drawing shall he taken as illustrative and not in a limiting sense.

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Claims (7)

1. 2. A tamper-evident tape as defined in Claim 1 wherein the chemical bond between the backing and colored layer is a covalent bond obtained by crosslinking the colored layer to the backing.
2. 3. A tamper-evident tape as defined in Claim 2 wherein the backing layer and colored layer each comprise a layer of a polyester material.
3. 4. A tamper-evident taje as defined in Claim 3 wherein the discontinuous layer of barrier material comprises a patternwise deposition of the barrier material.
4. 5. A tamper-evident tape as defined in Claim 4 wherein the barrier material comprises silicone.
5. 6. A tamper-evident tape as defined in Claim 3 wherein the colored layer *,,.consists essentially of a color-providing material and polyester characterized as being relatively soft and pliant so that under force of removal it will convolute or distort so 15 that it cannot later be overlaved on the adhesive laver without evidence of its removal being visibly revealed.
6. 7. A tamper-evident method for revealing tampering of a container having an opening for access to insert or to remove an article within the container, comprising the steps of: 20 inserting an article through the opening and into the container; and thereafter sealing the opening closed by applying over the opening a tamper-evident tape as defined in Claim 1. 16
7. 8. A container having an opening for inserting or removal of an article, an article disposed within the container, and a tamper-evident tape as defined in Claim I adhered across the opening of the container to seal the opening closed. Dated this 10th day of March 1994. THE KENDALL COMPANY By: Patent Attorneys for the Applicant F. B. RICE CO. l **ae ABSTRACT Disclosed is a tamper-evident tape for applying over the flap or other opening in pouches. bags, envelopes and the like. which tape will provide evidence of tampering over a wide temperature range from above to below the Tg of the adhesive layer adhering the tape to the substrate.o be protected from tampering. 0 ft a 0o*0 o* e b *eb 0