GB2327933A

GB2327933A - A tamper evident closure

Info

Publication number: GB2327933A
Application number: GB9816771A
Authority: GB
Inventors: David Tinkler; Peter John West
Original assignee: BRITTON SECURITY PRODUCTS
Current assignee: BRITTON SECURITY PRODUCTS
Priority date: 1997-08-05
Filing date: 1998-07-31
Publication date: 1999-02-10
Anticipated expiration: 2018-07-31
Also published as: GB2327933B; GB9816771D0

Abstract

A tamper evident closure, for sealing bags or the like, comprises a base material 2 with, on one side, a first layer 4 comprising a clear pattern of a high release substance, a plurality of coatings (e.g. 8 and 10) and a layer of adhesive 12 over the coatings. A layer 16, forms the outside of the seal in use and carries a pigmented layer which provides strongly contrasting visible areas when damaged. The base material 2, which may be the flap of a bag or a separate tape, distorts if heat is applied to it and the coatings are adapted to be differently affected by the application of heat or cold (e.g. coatings that are made of or contain ink with a high concentration of wax, metal, thermochromic material, solvent or water sensitive material, perforations or lines of weakness or material which has low adhesion at low temperatures). Preferably, a release cover 14 protects the adhesive layer 12 before use.

Description

Tamper Evident Closure" This invention relates to tamper evident closures, and particularly to a self-seal bag having a closure flap or tape which is adapted to provide an indication of any illicit attempt to open and re-close the bag.

Hereinafter, the term "closure" will be used generically to refer to a flap which is integral with a security bag, or a closure which comprises a separate tape which can be applied to a security bag or other container.

For example it may be applied to transit luggage for airlines, parcels, boxes or for Customs and Excise sealing, Duty Free packages etc.

Preferably, the closure is adapted to provide detection of various different methods of attack, such as heating, cooling or freezing, or any combination of such methods. For example, one common method of attacking such closures is to apply a freezing spray to the closure, in an attempt to cause the adhesive to become solid or brittle, so that it cannot resist finger pressure.

Accordingly, the present invention provides a tamper evident closure including a base material carrying on one side, a first layer comprising a clear pattern of a high release substance, a plurality of coatings which are adapted to be differently affected by the application of heat cold, and a layer of adhesive over the coatings; the other side, which forms the outside, in use, carrying a pigmented layer having good display characteristics, i.e., one which provides strongly contrasting visible areas when damaged.

Preferably, the adhesive side includes a heat detecting coating comprising an ink with a high concentration of wax, so that heating causes the ink to liquefy and thereby show clear distortion. In addition, a concentrated metallic coating may be provided, which acts to highlight surface damage caused by physical attack. In addition there may be a "thermochromic" coating which changes colour upon heating or cooling, preferably on the outside of the closure. For example, this coating may be of the type described in British Patent No. 2270857, which on heating, displays a permanent message or shape in a bold, permanent colour.

Preferably, the base material of the closure is also formed in such a way, for example with unrelieved stress patterns, that the application of any significant amount of heat will cause it to shrink, buckle or distort, and thereby provide a further indication of tampering.

Preferably, means are also provided for detecting solvent attack or the effect of pre-moistening the adhesive layer, for example by means of solvent detecting inks or resins which change colour or dissolve.

Preferably, the closure is also provided with perforations or other lines of weakening, which are adapted to tear if an attempt is made to peel it from the bag.

In addition, the pigmented coating on the outside of the closure may be formed from a material which has low adhesion at low temperatures, and is therefore easily dislodged by the application of a jet of gas, for example from an aerosol.

Some embodiments of the invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a cross-section through a tamper evident closure in accordance with the invention; Figure 2 is a plan view of the closure; Figure 3 is a front view of a bag having a closure in accordance with Figures 1 and 2; and Figure 4 is a cross-section on the line IV-IV of Figure 3.

As illustrated, the closure comprises a base material 2, which may be the flap of a bag, or may be a separate tape, which is formed from a material such as polyethylene which is formulated so as to distort or buckle, if any significant amount of heat is applied to it. As illustrated in the drawing, it will be appreciated that the upper side of the base material 2 is the side which carries the adhesive, whilst the lower side forms the "outside" of the closure when it is in a closed position.

In the example shown, a first layer 4, closest to the base material, comprises an "invisible" coat, which may for example be a standard printing ink formulation but without pigmentation, and comprises selective printing of a pattern which is revealed in use, by the effects of tampering as described below. After printing, this layer is subjected to corona discharge at 36-42 dynes, forming a "capture layer" 6. It will be appreciated that this is not drawn to scale and is in fact, discontinuous since the treatment will only affect the unprinted parts of the pattern. A pigmented coating 8 is then applied over the treated layer, and only adheres strongly in the areas affected by the treatment.

This pigmented coating may comprise an ink with a very high wax content, for example, of the order of 60% or more as opposed to the normal 20% or so, so that if heat is applied to the closure, the ink will be liquefied, and thus any printed message or shape formed in this layer will become obviously distorted. Similarly, any physical attack will of course selectively dislodge the areas of pigmented coating which did not adhere strongly due to the ink pattern.

A further layer 10 superimposed on the layer 8 comprises a concentrated metallic coating, which has a highlighting effect when damaged, and finally, a release cover 14, which protects the adhesive layer 12 before use, is superimposed over the whole multilayer structure, and will of course be removed in use to uncover the adhesive layer 12.

On the other side of the base material 2, a low key coat 16 is applied, and this is preferably formed from a white or other coloured pigment, which is such as to contrast strongly with the underlying layers. This coating is so formed that it is very sensitive to mechanical disruption, and may, for example, be dislodged by the application of a high velocity spray from a freezer aerosol.

In addition to this coating, further heat detecting or cold detecting layers, as described above, may also be applied on this obverse side of the tape, using corona discharge to prepare the surface if necessary.

As shown in Fig. 2, which is a plan view of the closure of Fig. 1, the base material 2 may also be provided with lines of perforations 18 and 20, along its length, so that any attempt to peel the edges will result in the material breaking along the lines of perforation. In addition, the base material is preferably one having a characteristic that it will severely distort on the application of heat, so that any attempt to loosen the adhesive by applying heat will result in severe malformation of the base material itself.

Figures 3 and 4 illustrate a typical construction of tamper evident bag incorporating the seal of Figures 1 and 2. The bag comprises a folded-over strip 22 of plastics material, the fold being offset from the centre line of the strip so that one end 24 extends beyond the other to form a closure flap. The side edges 26 of the overlapped part of the folded strip are heat sealed together, and the flap is formed with lines of perforations 18 and 20 and carries the seal, covered by the protective release cover 14, as explained above.

As an alternative to the "integral" construction of Figure 3 and 4, the tamper evident closure flap may be formed in a separate strip of material which is attached (e.g. by heat sealing) onto the flap 24 during manufacture.

Claims

1. A tamper evident closure including a base material carrying on one side, a first layer comprising a clear pattern of a high release substance, a plurality of coatings which are adapted to be differently affected by the application of heat or cold, and a layer of adhesive over the coatings; the other side, which forms the outside, in use, carrying a pigmented layer which provides strongly contrasting visible areas when damaged.

2. A tamper evident closure according to claim 1 in which the adhesive side includes a heat detecting coating comprising an ink with a high concentration of wax, so that heating causes the ink to liquefy and thereby show clear distortion.

3. A tamper evident closure according to claim 1 or claim 2 in which the closure also comprises a concentrated metallic coating which is adapted to highlight the effects of surface damage.

4. A tamper evident closure according to any preceding claim further comprising a thermochromic layer which changes colour upon heating or cooling.

5. A tamper evident closure according to any preceding claim in which the base material is formed into unrelieved stress patterns so that the application of any significant amount of heat will cause it to shrink, buckle or distort, and thereby provide a further indication of tampering.

6. A tamper evident closure according to any preceding claim further comprising solvent or water soluble layers or ink or resin which change colour or dissolve in response to the application of solvent or moisture.

7. A tamper evident closure according to any preceding claim further comprising perforations or lines of weakening so that it tears if an attempt is made to peel it open.

8. A tamper evident closure according to any preceding claim in which the pigmented coating on the outside of the closure is formed from a material which has low adhesion at low temperatures so that it is easily dislodged by the application of a jet of cold gas.

9. A security bag having a closure according to any preceding claim.

10. A security bag substantially as herein described with reference to Figures 3 and 4 of the accompanying drawings.

11. A tamper evident closure substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.