DE69028309T2 - Safety lock and method of using the same - Google Patents

Description

The present invention relates to flexible tamper evident tapes where tamper evident is either transfer of a pattern to the tampered product, revealing a pattern on the backing of the closure, or tearing of the closure and/or product over a wide temperature range including temperatures on the order of -320ºF (-195ºC) where other so-called tamper evident closures do not indicate tamper evident when removed and later reapplied.

Protection against unauthorized access has been of interest in the financial and security sectors for years. However, it has gained new importance as a result of unauthorized access to food, cosmetic and pharmaceutical products.

The following patents are illustrative of the prior art, but are by no means considered to be a complete overview of the prior art.

The earliest patent, U.S. Patent No. 2,845,728 issued to Huber, discloses a self-destructing label having a pressure sensitive adhesive on one side. The main object of this invention, which is for a pressure sensitive label, can be easily applied to positions of various kinds. However, when an attempt is made to remove such labels from the article, then the label is damaged or degraded to a sufficient extent so that the condition of the label, when removed from one article and applied to another, readily and visibly serves to indicate that the label has been tampered with. Essentially, the invention consists of weakening means having either discontinuous series of cuts or substantially continuous partial cuts.

U.S. Patent No. 3,383,121 discloses a self-adhesive sample label having a laminate construction consisting of a first layer, for example a sheet of paper, a second pressure-sensitive adhesive layer preferably 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 be shock sensitive in that it carries chemicals under normally separate conditions which, after shock, mix with one another to produce a color change in the shock area in or on the third layer itself. Thus, the evidence of tampering here is a color change.

U.S. Patent No. 4,082,873 issued to Williams discloses a "laminate having a transparent or translucent outer layer having an information-containing pattern printed on the inner surface thereof, the printed inner surface being coated with a coating of pressure-sensitive film. The adhesion of the adhesive to the surface to which the laminated label is adhered and to the printed pattern is greater than the adhesion of the printed pattern to the outer layer. Once the label is applied to a substrate, when removal of the label is attempted, the layers of the label separate in such a way that the outer layer peels off and at least a portion of the adhesive layer to which at least a portion of the printed pattern is adhered adheres, remains on 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 is printed with an ink which does not dry into an inseparable film form so as to form a destructible pattern when tampered with. Thus, when the top layer is removed from the adhesive, a portion of the pigmentation of the destructible pattern adheres to both the top layer and the adhesive layer, resulting in "a reduction in the disruption of the coloration of the destructible pattern on the top layer sufficient to provide a visible indication of tampering."

U.S. Patent No. 4,184,701 issued to Franklin et al., discloses a label comprising "a laminate having a transparent or translucent outer layer having an information-containing pattern printed on the inner surface, said printed film having a non-continuous coating of a transparent plasticized organic polymeric material, said printed and coated side having a color-containing pressure-sensitive adhesive film." Upon removal, the label delaminates such that at least portions of the colored adhesive in register with the transparent non-continuous plasticized polymeric coating remain on the substrate to which the label is adhered. Thus, evidence of tampering is a visible change in at least portions of the background color.

US Patent No. 4,608,288 issued to Spindler discloses a label having a cover sheet with an adhesive layer laminated to a base sheet. The cover sheet is made of a material that is irreversibly deformable or easily broken after unauthorized access. Furthermore The cover film extends beyond the circumference of the base film, creating a safety edge that makes access to the base film difficult.

U.S. Patent No. 4,652,473 issued to Han discloses a tape with a backing having an outer and an inner layer, the outer layer having a sufficiently high tensile strength to maintain its integrity when removed. In contrast, the inner layer is thin and deformable. Consequently, evidence of tampering is provided by separating the layers. After removal of the outer layer, it separates from the inner layer, which in turn causes partial stretching of the thin inner layer. In addition, the patentee suggests the use of printed or colored layers for additional evidence.

U.S. Patent Nos. 4,721,638, 4,746,556, and 4,763,931, all issued to Matsuguchi et al., disclose a multilayer adhesive material having a variety of release forces such that when specific layers are separated, they do not reattach or cannot reattach as in their original state.

The primary disadvantage of the prior art as illustrated by the above-mentioned patents is evident at low temperatures. At a low temperature, such as that of liquid nitrogen, the adhesive layers detach from the backing, allowing reapplication without any evidence of tampering. Note that while this detachment occurs in the three patents issued to Matsuguchi et al., the label becomes evident when the material is reapplied. However, these tapes consist of a multiplicity of layers and are consequently quite expensive.

The present invention avoids the disadvantages of the prior art technology in an elegant and novel way by providing a tamper-evident lock that is effective over a wide temperature range.

In accordance with this invention, the above-mentioned disadvantages are avoided by providing a tamper-evident closure comprising a transparent backing layer and an adhesive layer for attaching the backing layer to a substrate, the transparent backing layer having surface adhesive properties that vary from location to location, characterized by a first adhesive layer whose adhesion to the backing layer varies from location to location from a first value to lower values, and a second adhesive layer for attaching the first adhesive layer and the backing layer to a substrate, the first value of the adhesion of the first adhesive layer to the backing layer being greater than the value of the adhesion of the second adhesive layer to the first adhesive layer, the arrangement being such that attempted removal of the closure from a substrate results in a visually detectable change in appearance, the closure providing tamper-evident evidence over a wide temperature range from above to below of Tg (glass transition temperature) of the adhesive layer that bonds the closure to the substrate to be protected.

The substrate can be a bag or sack.

The surface adhesion properties of the backing layer can be varied by chemical etching. Alternatively, the surface adhesion properties of the backing layer can be varied by discontinuously applying a barrier material with reduced adhesion properties, such as a silicone, to the backing layer.

The backing layer may be made of polyester, polyolefin, polycarbonate or a cellulose ester or copolymers or mixtures thereof. The barrier material may be a silicone, a Fluorocarbon or a polyoctadecyl carbonate as a discrete deposit. The first adhesive layer can be a polyester adhesive. The second adhesive layer can be a pressure sensitive acrylic adhesive.

The backing layer preferably has a thickness of 0.5 to 3 mils (0.013 to 0.075 mm). The barrier material deposits are preferably up to about 1 micron (micrometer) thick. The first adhesive layer is preferably 0.1 to 0.5 mils (0.0025 to 0.013 mm) thick. The second adhesive layer is preferably 0.1 to 0.4 mils (0.0025 to 0.01 mm) thick.

The invention may be put into practice in a variety of ways and a specific embodiment will be described by way of example with reference to the accompanying drawing which is a schematic sectional view of the novel tamper evident tape of this invention.

As mentioned above, the present invention is directed to a novel tamper evident tape for attachment over the flap or other opening of bags, sacks, envelopes or other containers for currency, security documents and the like, which tape will indicate tamper evident when the tape is removed and then reattached to gain access to the contents.

The invention is best understood by reference to the accompanying drawings.

As shown herein, the novel tamper evident closure 10 comprises a transparent backing 12 which sequentially comprises a discontinuous layer of barrier material 14, a colored laminating adhesive layer 16 and a preferably pressure sensitive adhesive layer 18 which firmly adhesively bonds to the bag, sack, envelope or other substrate. While not essential to the practice of the invention, a release layer 20 known per se is preferably provided to protect the adhesive surface from premature contact.

The backing layer 12 may be any known transparent and flexible backing or support layer, including, for example, a polyester such as polyethylene terephthalate, a polyolefin such as polyethylene or polypropylene, polycarbonate, a cellulose ester such as cellulose acetate or triacetate, etc., including copolymers or blends thereof. It may have a thickness on the order of about 0.5 to about 3.0 mils (0.013 mm to 0.075 mm), with 1.0 mils (0.025 mm) being preferred.

The barrier material 14, which is preferably applied in a pattern but may also be randomly adhered to the substrate, may be any material that will adhesively bond to the substrate 12. Examples of such materials include silicone, fluorocarbons, Quilon (a trademark of DuPont), polyoctadecyl carbonate, etc., with silicone being preferred. The function of the barrier material 14 is to eliminate or reduce adhesion of the underlying colored laminating adhesive layer 16 to the substrate 12 in the areas where it is deposited. The barrier material 14 is preferably transparent or translucent so that the underlying colored layer 16 can be seen when looking through the transparent substrate 12. The barrier material deposits may have a thickness on the order of about 1 micron. They can be provided on the inside of the base 12 by means of techniques known per se, such as gravure printing or flexible printing, application by spraying, chemical etching and the like.

The laminating adhesive layer 16 has a greater adhesion to the backing 12 than to the adhesive layer 18. Accordingly, when an attempt is made to peel the tape from the substrate, the layer 16 tends to remain on the backing 12.

The layer 16 containing a coloring material, e.g., a non-migrating ink or pigment, may comprise any of the known laminating adhesives. For example, if the backing 12 comprises a polyester, then the colored layer 16 may comprise any of the commercially available polyester laminating adhesives in which the coloring material is embedded.

The thickness of the colored layer 16 may be on the order of about 0.1 to 0.4 mils or 0.5 mils (0.0025 to 0.01 mm or 0.013 mm), with a preferred thickness being about 0.2 mils (0.0051 mm).

The adhesive layer 18 used to laminate the tape to the substrate to be sealed may comprise an acrylic pressure sensitive adhesive formulation which adheres strongly to the substrate. To improve flow and adhesion to the substrate, the adhesive preferably has an adhesion promoter such as an unsaturated fatty acid having at least 12 carbon atoms, with oleic acid being an illustrative example. Tackifiers and/or plasticizers may also be included in the acrylic adhesive to improve adhesion.

In any event, it is critical to the practice of this invention, as will be explained in detail below, that while the adhesive 18 must adhere strongly to the substrate, the bond or adhesion between the layer 18 and the overlying colored layer 16 must not be as great as the adhesion of the layer 16 to the substrate 12.

In optional embodiments, layer 18 may further contain a non-migrating coloring material that contrasts with the coloring material in overlying layer 16. It may also contain a chemical detecting agent that, upon contact with the skin of anyone attempting to remove the tape, produces a detectable reaction product in the skin and/or on layer 18 or on the bag on which it is used.

In use, the tape will of course be applied over the mouthpiece or other opening in the container or other substrate to be sealed. If the tape is removed at a temperature above the Tg of the layer 18, e.g. at ambient temperatures, so as to obtain unauthorized access to the contents, in areas where no barrier material is present, the colored layer 16 will remain on the substrate, as previously stated. However, in areas where the barrier material 14 is present, so as to preclude adhesion of the colored layer 16 to the substrate, the colored layer will be peeled away from the barrier, adhering to the adhesive layer 18 which will remain firmly adhesively bonded to the substrate. This will, in turn, provide a color pattern on the substrate in the form of adherent colorant from layer 16 and a mirror contrast image visible through the stripped backing in the form of the remaining colored layer and areas where no colorant is visible through the backing. Even if an attempt is made to reapply the tape accurately to the substrate, evidence of its removal will still be readily visible to the eye due to the distortion of the adhesive.

If the tape is removed at a temperature below the Tg of the adhesive, e.g. by first spraying liquid nitrogen and then removing the tape, evidence of tampering will also be demonstrated in one or more of the following ways.

First, when the tape is removed from the substrate, the adhesive layer 18 will separate from the colored layer 16, except where a barrier layer 14 is present. In these areas, the colored layer 16 will break away from the barrier layer 14 and peel off onto the adhesive layer 18.

A second possible evidence of unauthorized access is that the substrate tends to tear, leaving an image on the substrate along with evidence of the tearing of the substrate.

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

The invention also extends to a method of proofing unauthorized access for sealing a bag or sack against unauthorized access to the bag, which comprises the following steps:

(a) applying a closure according to the invention along one side of the opening of the bag;

(b) Closing the bag by placing both sides in side-side position and adhering one side to the other by means of the fastener.

The invention also extends to a bag or sack with a closure for detecting unauthorized access according to the present invention.

The following examples demonstrate, by way of illustration and not limitation, the novel characteristics of the present invention. example 1

* Trademark of Dupont

Example 2

Mylar film was printed with a flexible silicone layer. The printed side was then covered with the laminating layer, which in turn was covered with the adhesive layer. Finally, a cardboard release liner was applied to the adhesive side of the above film.

In each of Examples 1 and 2, the silicone layer was discontinuous, as shown schematically in the drawing.

To reiterate, the present invention provides a tamper evident closure over a temperature range from +150ºF to -320ºF (+66ºC to -195ºC). Among the many mechanisms that provide tamper evident evidence are: transfer of a color pattern to the substrate, exposure of a printed pattern on the substrate, tearing of the substrate, wrinkling of the substrate, fingerprinting, and even transfer of color to the person performing the tampering.

Claims (9)

1. A closure (10) comprising a transparent backing layer and an adhesive layer for attaching the backing layer to a substrate, the transparent backing layer (12) having surface adhesion properties that vary from location to location, characterized by a first adhesive layer (16) the adhesion strength of which to the backing layer (12) varies from location to location from a first value to lower values, and a second adhesive layer (18) for attaching the first adhesive layer (16) and the backing layer (12) to a substrate, the first value of the adhesion strength of the first adhesive layer (16) to the backing layer (12) being greater than the value of the adhesion strength of the second adhesive layer (18) to the first adhesive layer (16), the arrangement being such that attempted removal of the closure from a substrate results in a visually detectable change in appearance, the closure providing evidence of Interventions over a wide temperature range from above to below Tg (glass transition temperature) of the adhesive layer that bonds the closure to the substrate to be protected. 2. Closure according to claim 1, characterized in that the surface adhesion properties of the base layer (12) are varied by chemical etching. 3. Closure according to claim 1, characterized in that the surface adhesion properties of the backing layer are varied by discontinuously applying a barrier material (14) with reduced adhesion properties to the backing layer (12). 4. Closure according to claim 3, characterized in that the material is a silicone. 5. Closure according to one of claims 1 to 4, characterized in that the first adhesive layer (16) has a different color than the second adhesive layer (18). 6. Closure according to one of claims 1 to 51, characterized in that the second adhesive layer (18) contains a component which produces a color reaction with skin. 7. Closure according to one of claims 1 to 6, characterized in that the backing layer (12) consists of polyester, polyolefin, polycarbonate or a cellulose ester or copolymers or mixtures thereof, the barrier material (14) is a silicone, a fluorocarbon or polyoctadecyl carbonate as discrete deposits, the first adhesive layer (16) is a polyester adhesive and the second adhesive layer (18) is a pressure-sensitive acrylic adhesive. 8. A closure according to any one of claims 1 to 71, characterized in that the backing layer (12) is 0.5 to 3 mils (0.013 to 0.075 mm) thick, the deposits of barrier material (14) are up to about 1 micron (micrometer) thick, the first adhesive layer (16) is 0.1 to 0.5 mils (0.0025 to 0.013 mm) thick, and the second adhesive layer (18) is 0.1 to 0.4 mils (0.0025 to 0.01 mm) thick. 9. A security method for securing a bag, characterized in that it comprises the steps: (a) applying a closure according to any one of claims 1 to 8 along one side of the opening of the bag, (b) Closing the bag by placing both sides side by side and adhering one side to the other by means of the fastener.