Security bags and sealing means

Abstract: The invention relates to a security bag intended for carrying money or confidential documents and which if opened and re-sealed provides an indication that the bag has been tampered with. The bag (12) has an opening means (18) and sealing means (20) comprising a transparent flap adapted to fold over the opening to seal the bag by adhering the bag to an area (23) of the bag adjacent the opening. The sealing means is formed of a material whose surface has a lower co-efficient of friction or is otherwise less retentive of print than the area (23). The sealing means is printed or otherwise marked with a pattern (24) such that when the sealing means is adhered to the area (23) to seal the opening a mirror image of the pattern is transferred to the area while remaining on the sealing means. The sealing means is of a thin easily distorted material making it extremely difficult to match the original pattern once the bag has been opened and if an attempt is made to re-seal it.

Description: This invention relates to security bags, means for sealing such bags and/or sealing tapes or other members carrying adhesive and security printing. In particular, it relates to security bags (which term includes envelopes or the like) which are intended for carrying money usually bank notes or confidential documents and which if the bag is opened and re-sealed provide an indication that the bag has been tampered with. It is known, for example, from GB-A-1523933 to provide a bag with an adhesive flap for folding over the mouth of the bag to seal it. The bag is printed adjacent the mouth with security printing so that once closed the bag cannot be re-opened and the contents extracted and re-sealed without the fact being made apparent by the distortion or destruction of some of the security printing. While this bag is proof against the sealing flap being pulled open by force or after the adhesive has been loosened by heat or solvent action, it has been found that if the glue line adjacent the seal is freeze sprayed, for example to lower the temperature below minus 30°c, the adhesive becomes brittle so that the bag comes open without affecting the security printing. The bag can then be restored to ambient temperature when the adhesive will restick the flap without any indication of tampering. One object of the invention is to provide a bag with means which will indicate that the bag has been opened and re-sealed even if this is done following freeze spraying the adhesive. GB-A-2225311 describes a bag sealed by a secondary sealing means comprising a tape, which may be printed and which distorts even if opened by freeze spraying. The printing and surfaces are not such that the printing permeates to the bag surface to produce a mirror image. Document EP-A-0341699 prints a transparent adhesive masking material in a pattern to a first of two surfaces to be sealed together and places a continuous layer of colour over it. Adhesive is then applied over that to seal the first surface to a second surface with the continuous layer of colour showing through one of the surfaces. When the surfaces are separated from one another to open the package, one part of the colour sticks to one surface and the other part of the colour sticks to the other surface so that the continuous colour is broken and the two cannot be re-matched without an indication of tampering. WO-A-89/08586 describes a similar arrangement in that of EP-A-0341699 except that it is the adhesive itself (which may be coloured) and which splits between the first and second surface on opening. No pattern is visible normally but only after the two split surfaces have been put back together if the package has been tampered with. US-A-4941196 again has a continuous layer of opaque adhesive which, on opening, splits between the two separated surfaces and then the two halves cannot be re-matched. Applying adhesive or different adhesives in matched patterns can be a costly and time consuming process. In one aspect, the invention provides a bag having an opening, sealing means for sealing the opening, the sealing means comprising a transparent flap or tape adapted to fold over the opening to seal the bag by adhering the flap to an area of the bag adjacent the opening and means for providing an indication that the bag has been tampered with, characterised in that one of the sealing means and area is formed of a material whose surface is uniformly less retentive of print than the surface of the other of the sealing means and area, and which said one of the sealing means and area is printed or otherwise marked with a visible pattern on or under a layer of translucent adhesive, such that when the sealing means is adhered to said area to seal the opening a mirror image of the pattern is transferred to said other of the sealing means and area while the pattern remains marked on the said one, such that if the bag is opened without visibly distorting the adhesive and pattern, the pattern remains on both the sealing means and the area such that it is difficult to reseal the bag without misaligning the visible pattern and its mirror image, thus providing the indication that the bag has been tampered with. The surface of the bag, at least in said area, will normally have been treated with a corona discharge, in known manner, so that it will absorb and retain the printing ink and the surface of the flap will not have been so treated. The pattern will normally be repetitive and extend at multiple angles (for example stars or asterisks) across the sealing flap so that it is extremely difficult to match the original pattern with the mirror image when re-sealing. In another aspect, the invention provides a bag having an opening, a surface area of the bag adjacent the opening being of corona discharge treated material and a sealing member such as a tape or flap carrying adhesive adapted for sealing the bag by adhering to said surface area, the sealing member having a non-corona treated smooth surface beneath the adhesive and being printed on or beneath the adhesive with a detailed pattern. The surface of the sealing member is such that the printing would not be permanently retained on its surface after being jet printed (or deposited thereon by other means) but the adhesive secures the printed pattern to the sealing member until the bag is sealed at which time a mirror image of the printed pattern is transferred to the surface area but also remains on the sealing member. The pattern is sufficiently complex and difficult to match up that an intruder cannot re-match each part of the pattern on the sealing member to the surface area, and the pattern therefore appears blurred in at least some parts acting as an indication of tampering. Preferably, the sealing member is of thinner more easily distorted material than that of the bag so that it is very difficult to put it back in the same position. For example, the bag itself may be of thermoplastics material such as polyethylene of a thickness in the range 30 - 150 micron while the flap may be of polyethylene material blended with a material such as vinyl acetate to allow the material to stretch in the thickness range 20 - 60 micron. The bag may additionally incorporate known tamper resistant features such as security printing on the bag which would be destroyed by any solvents likely to be used to try to remove the mirror image pattern deposited on the surface area adjacent the opening as a result of the first sealing. One embodiment of security bag, in accordance with the invention, will now be described, by way of example only, with reference to the accompanying diagramatic drawings of which:- Figure 1 is a front view of a bag before sealing, Figure 2 is a side cross sectional view of the bag with the thicknesses of the materials exaggerated, Figure 3 shows the bag of Figure 1 in its initial sealing condition, and Figure 4 shows the bag after it has been opened and re-sealed. Referring to the drawings, a bag is generally designated 12 and intended to contain money or confidential documents. The bag is formed from a continuous web of thermoplastics film e.g. polyethylene, by folding the continuous web about a fold line 13 which constitutes the bottom of the bag. The bag has a front 14 and a back 15 with the sides of the front and back sealed together by heat sealing in known manner to provide sealed side edges 16. The surface of the bag has been treated, in known manner with a corona discharge to effectively roughen the surface so that it will receive, and permanently retain, printing. Security printing is provided at 17 along the side edges in known manner. The bag thus defines a pocket for receiving money or documents with an opening or mouth 18 at its upper end. A transparent sealing member 20 of a different, thinner, smoother and more easily distorted material for example polyethylene blended with a material which allows it to stretch is provided to seal the opening 18. The sealing member has substantially the same width as the bag and has its lower part welded to the top of the outer surface of the back 15 as indicated at 21. The upper part 22 of the sealing member forms a flap designed to fold over the opening and be secured to the area 23 of the front immediately adjacent the opening. The front surface of the flap 22 is printed, for example by jet printing with a detailed, repetitive, difficult to match pattern 24 which because of the nature of the surface of the material would not normally adhere to the surface permanently. However, the printing is covered by a layer 25 of adhesive of any type commonly used to seal such bags for example a hot melt contact adhesive. The adhesive is covered in known manner with a barrier strip 26 having a surface which releases easily from the adhesive and may therefore be stripped off immediately before the bag is sealed. As seen, the security printing comprises a series of lines made up of four asterisks or stars one beneath the other, this pattern being repetitively repeated across the width of the bag. When the bag is sealed by folding the flap down on to the area 23, which is comparatively receptive and retentive of print, the mirror image of the pattern migrates through the adhesive and is permanently deposited on the surface 23 although it also remains secured to the surface of flap 22. If the bag is opened by freeze spraying which does not otherwise distort the printing an intruder will find it impossible to exactly match the pattern along the whole width of the flap and as the flap is of transparent material, the mis-matching of the pattern can be easily seen as indicated in Figure 4. The sealing member could be a tape adhered to both sides of the top of the bag adjacent the opening, in the same manner as described above for the flap. The sides of the bag may be sealed with a skirt weld with the security printing running in the skirt or adjacent the seal on one or both sides.

Claims: A bag (12) having an opening (18), sealing means (20) for sealing the opening, the sealing means comprising a transparent flap or tape (22) adapted to fold over the opening to seal the bag by adhering the flap to an area (23) of the bag adjacent the opening and means for providing an indication that the bag has been tampered with, characterised in that one of the sealing means and area is formed of a material whose surface is uniformly less retentive of print than the surface of the other of the sealing means and area, and which said one of the sealing means and area is printed or otherwise marked with a visible pattern (24) on or under a layer of translucent adhesive (25), such that when the sealing means is adhered to said area to seal the opening a mirror image of the pattern is transferred to said other of the sealing means and area while the pattern remains marked on the said one, such that if the bag is opened without visibly distorting the adhesive and pattern, the pattern remains on both the sealing means and the area such that it is difficult to reseal the bag without misaligning the visible pattern and its mirror image, thus providing the indication that the bag has been tampered with. A bag according to Claim 1 characterised in that said other of the sealing means and area has a surface which has been altered by treatment with a corona discharge so that it will absorb and retain printing. A bag according to Claim 1 or Claim 2 characterised in that the said one is the sealing means (22) and the said other is the area (23). A bag according to any of Claims 1 to 3 characterised in that the pattern (24) is repetitve and extends at multiple angles. A bag according to any of Claims 1 to 4 characterised in that the printing (24) is initially under the adhesive but migrates therethrough. A bag according to any of Claims 1 to 5 characterised in that the bag (14, 15) and sealing member (20) are of thermoplastic film material with the sealing member thinner and more easily distorted than the material of the bag. A bag according to Claim 6 characterised in that the material of the bag has a thickness in the range 30 - 150 microns. A bag according to Claim 6 or Claim 7 characterised in that the sealing means has a thickness in the range of 20 - 60 microns. A bag according to any of Claims 1 to 8 formed from a continuous web of thermoplastic film folded and sealed along edges (16) apart from the opening, characterised in that the flap (22) is of a different material and has one edge welded (21) to one side of the opening. A bag according to any of Claims 1 to 9 characterised in that at least the area adjacent that which will be adhered to the sealing means carries additional security printing adapted to be destroyed by heat or solvents.

Inventors: DIXON DARRYL O DECOFLEX LIMITE, HAYES ANDREW DECOFLEX LIMITED, DIXON, DARRYL O., DECOFLEX LIMITED, HAYES, ANDREW, DECOFLEX LIMITED
Applicants: DECOFLEX LTD, DECOFLEX LIMITED
Application year: 1992
Main classification: B65D33
IPC codes: B65D33