FR2888025A1 - FILM MATERIAL FOR DETECTION OF INTRUSION, AND SECURE CONTAINER INCORPORATING SUCH MATERIAL - Google Patents

Abstract

The anti-intrusion film material comprises a plastic substrate (1), a first electrically conductive track (2) applied to a first face of the substrate, and a second electrically conductive track (3) applied to a second face of the opposed substrate. on the first side. The two tracks are arranged in respective patterns misaligned.

Description

FILM MATERIAL FOR DETECTION OF INTRUSION,

  The present invention relates to intrusion detection systems inside certain enclosures. BACKGROUND OF THE INVENTION

  The speakers to be secured can perform various functions. In a representative example, the enclosure belongs to a transport bag. Such a suitcase has a security system that causes the destruction or smudging of the funds transported (diffusion of an ink or etching solution on the notes) in the event of detection of an intrusion, in order to dissuade robbers. The invention is also applicable to securing containers such as bank terminal boxes, payment, gaming, etc., so that these boxes react to intrusion attempts ("tamper responsive" housing), or protection cryptographic resources.

  It is known to coat a wall of a secure container with a film material carrying an electrically conductive track extending over most of its surface (see for example US-A-5,049,704). An electrical circuit detects any breakage of the conductive track, caused in particular by the penetration of an object through the film material, to trigger an intrusion alarm.

  The conductive track of such a material generally follows a path composed of parallel segments which are connected in series at their ends. If these segments have a width d and are separated by intervals of width e, the penetration of any object of transverse dimension greater than 2d + e is detected. It is possible, however, that an object of size up to 2d + e passes through the film material without breaking the conductive track. It is particularly possible that a fraudster uses a thin blade to cut the film material between two adjacent segments and thus access the interior of the enclosure without triggering an alarm.

  The 2d + e dimension can be decreased by using an advanced method of the kind employed in microelectronic or micromechanical techniques. But this is very unfavorable to the production cost of the film material. It would be preferable to be able to use a more conventional and less expensive method, such as the serigraphy of conductive inks, which makes it possible to reach the order of magnitude where the dimensions d and e are of a few tenths of a millimeter.

  An object of the present invention is to provide a new type of film material that enhances intrusion detection capabilities.

  The invention thus provides a film material for intrusion detection, comprising a plastic substrate, a first electrically conductive track applied to a first face of the substrate, and a second electrically conductive track applied to a second face of the opposite substrate. on the first side. The first and second tracks are arranged in respective patterns misaligned.

  The two faces of the substrate are thus used by depositing respectively two conductive tracks in mutilated patterns. This arrangement greatly reduces the probability that an object will cross the material without breaking a track. In addition, a significant sensitivity gain results from the fact that if a fraudster pushes a metal object through the material, it will generally cause a short circuit between the two tracks, which the electrical circuit will detect easily.

  In a preferred embodiment, the patterns of the first and second tracks are mutually crossed. The substrate may thus have at least one region where the first track is in the form of segments extending in a first direction between two opposite edges of said region and wherein the second track is in the form of segments extending between two opposite edges. of said region, in a second direction forming an angle with said first direction. It then becomes almost impossible to cut this region of the substrate parallel to the direction of the segments of a track without triggering an alarm. In addition, the angle formed between the segments makes it possible to dispense with accurate relative positioning between the masks used to form the conductive patterns on both sides of the substrate. The penetration of the material will be very difficult to achieve by a fraudster if the characteristic dimension of the tracks is of the order of 0.5 mm, as is easily achieved with a screen printing technique. The preferred angle between the first and second directions is about 90.

  Another aspect of the present invention relates to a secure container, comprising a wall internally coated with a film material as defined above, and a detection circuit connected to the first and second tracks of the film material to detect a breaking of electrical continuity of any of the first and second tracks and a short circuit between the first and second tracks.

  In a typical embodiment, the container wall has a bottom member and a cover member hinged together and each coated with a film material as defined above, the detection circuit being connected to the first and second leads of the container. each of the film materials of the bottom member and the cover member.

  According to another advantageous characteristic, the film material of one of the two elements has one of its first and second tracks interrupted in at least one zone, and this zone is covered with a conductive member adapted to come into contact with the track in response to a transverse force to the substrate of said film material to restore the electrical continuity of the interrupted track. The other of the two elements is provided with a support member opposite said zone to exert the transverse force in a closed position of the wall and to release this transverse force in an open position of the wall.

  Thus, the electrical continuity of the conductive tracks testifies not only to the absence of intrusion, but also to the fact that the wall is closed. The opening detection function is combined with the intrusion detection function.

  The conductive member is advantageously in the form of an elastic dome fixed at its periphery to the substrate of the film material in at least one point of contact with the interrupted track, the dome having a central portion in front of a second point of contact with the interrupted track, a deflection of the elastic dome bringing its central portion against the second point of contact to restore the electrical continuity of the interrupted track. Preferably, the support member is mounted on said other element by means of an elastic suspension having a stiffness greater than that of the elastic dome.

  This minimizes the risk of false aperture detection.

  In a particular arrangement, the elastic suspension comprises a part of the movable bottom element parallel to a closing movement between the elements, a housing formed in said part opposite the dome to receive the support member, a sliding piston relative to the support member and out at the bottom of the housing, and a spring placed between the piston and the support member. The closure between the elements compresses the spring to push the support member against the dome and then to push the piston towards the support member.

  Other features and advantages of the present invention will appear in the following description of nonlimiting exemplary embodiments, with reference to the accompanying drawings, in which: - Figure 1 is a schematic exploded perspective view of a material in film according to the invention; FIG. 2 is a cross-sectional diagram of the film material of FIG. 1; FIG. 3 is a diagram illustrating the difficulty of penetrating through such a film material; FIG. 4 is a schematic view from above of a variant of film material according to the invention; FIG. 5 is a cross-sectional diagram of a secure container according to the invention; - Figures 6 to 8 are schematic sectional views showing a container opening detector in different operating positions; FIG. 9 is a plan view of a metal dome belonging to the opening detector; and FIG. 10 shows a section of the dome taken along the X-X plane indicated in FIG. 9.

  With reference to FIG. 1, the film material according to the invention comprises a plastic substrate 1, the two faces of which are respectively coated with electrically conductive tracks 2, 3.

  The substrate 1 is cut in a shape adapted so that the film material comes to line the inside of the wall of a part of an enclosure. In the example shown, the film material is intended to be applied to the inner face of the lid of the enclosure, its edges being folded in the broken lines shown on the substrate 1 to cover the edges of the lid.

  As can be seen in FIG. 1, the two conductive tracks 2, 3 are not aligned with each other on the two substrate faces 1. The track 2 situated on the upper face of the substrate consists of parallel segments at the smaller sides of the substrate, the adjacent segments being interconnected along the longer sides of the substrate so as to form a continuous track. Similarly, the track 3 located on the underside of the substrate 1 consists of segments parallel to the longer sides of the substrate, the adjacent segments being interconnected along the smaller sides of the substrate so as to form a continuous track. On both sides of the substrate 1, the conductive tracks 2, 3 are covered with an insulating protective varnish 4 (Figure 2).

  Substrate 1 is preferably a polyester such as polyethylene terephthalate (PET). Its thickness is typically a few tens of microns. Tracks 2, 3 may consist of silkscreen inks made of silver. Their thickness is for example of the order of 10 m, and their width d of the order of 0.5 mm. The interval e between two segments of the same track may also be of the order of 0.5 mm.

  The two ends of each track 2, 3 form a pair of terminals 5, 6 disposed near a corner of the film material (Figure 1). These terminals can be connected to a detection circuit 27 placed inside the enclosure, capable of detecting any of the following conditions: - breaking of the electrical continuity of one or the other of the tracks 2, 3; and - short circuit between the two tracks 2, 3.

  The detection of one of these conditions triggers an alarm by the circuit 27.

  Thus, it is extremely difficult to penetrate through the film material without being detected since, as illustrated in FIG. 3, this can only be achieved with a very thin object 10, the maximum dimensions of which are, in one case ideal, 2d + e in one direction, and e in the other perpendicular direction. A larger conductor object will necessarily cause a break in one of the tracks or a short circuit between the two tracks.

  The use of a polyester substrate is advantageous to facilitate the detection of the possible introduction of a non-conductive hot object, which melts the silver track. This material is also advantageous by its resistance to solvents or chemicals that could be used by an attacker to seek to destroy the structure of the intrusion detection material.

  The fact that the two tracks 2, 3 are arranged at right angles to each other maximizes the probability of intrusion detection, and facilitates the production of the film material, since it is not necessary to perform a precise alignment of the screen-printing masks on both sides of the substrate. It will be observed that an angle other than 90 could also be adopted between the two tracks.

  On the other hand, very varied patterns can be adopted to form the conductive tracks 2, 3. In the variant shown in FIG. 4, the substrate 1 has not only one, but three regions 7, 8, 9 in which the upper track 2 'is in the form of parallel segments interconnected at their ends. In the central region 7, the segments of the track 2 'are parallel to the narrow sides of the substrate 1, while in the two lateral regions 8, 9 located on either side of the central region 7, the segments of the screw upper 2 'are parallel to the long sides of the substrate.

  Naturally, without this being shown in FIG. 4 for ease of reading, the lower track 3 then comprises homologous regions in which the segments of the tracks are always perpendicular to those of the upper track 2 '. It will be understood that, in the context of the invention, the designer of a particular film material may, according to his needs, use screen printed patterns of very varied shapes.

  FIG. 5 schematically shows a transport bag constituting a secure container according to the invention.

  The bag has an outer enclosure comprising a bottom 20 and a cover 21 hinged together by hinges 22. Two film materials 23, 24 of the type described above are placed against the inner faces of the walls of the bottom 20 and the cover 21, respectively .

  Along its periphery, the cover 21 has flanges forming a skirt whose inner face is covered by the edges of the film material 24 as indicated above. This skirt covers the portion of the bottom 20 having the film material 23, which forms baffles ensuring the continuity of the intrusion detection material around the volume of the outer enclosure.

  An inner chamber 25 is housed inside the enclosure 20, 21 to receive the tickets to be transported. The outer enclosure 20, 21 also contains, next to the enclosure 25, the electronic circuits 27 ensuring the appropriate responses in case of detection of an intrusion with the materials 23, 24 to which they are connected. These responses include in particular the dispersion of a destructive solution in the inner enclosure 25.

  In a preferred version of the secure container according to the invention, one of the film materials 23, 24 providing the intrusion detection is also equipped with switches participating in the opening detection function of the outer enclosure 20, 21 In the example shown, it is the film material 24 placed on the wall of the cover 21. These switches cooperate with bearing elements 26 belonging to the bottom 20 and shown schematically in FIG.

  By way of example, the film material 24 of the cover may be provided with four switches arranged at the locations indicated by dashed circles in FIG. 4, i.e., a switch approximately in the middle of each edge of the container.

  The aforementioned switches are advantageously made in the form of metal domes 30 placed on the face of the substrate 1 directed toward the bottom 20. In front of each dome location, the bottom 20 comprises a support member 31 placed in a housing 32 provided in a portion 33 of the bottom 20. The housing 32 is open at its base to let a piston 34. A spring 35 working in compression is mounted between the support member 31 and the piston 34 and tends to move mutually. End stops limit the spacing between the support member 31 and the piston 34, as well as the sliding of the support member 31 towards the inside of the housing 32 (position illustrated in FIG. 6) .

  In this position illustrated in FIG. 6, the cover 21 comes into contact with the bottom 20, the elastic dome 30 remaining in its relaxed position. From this position, when the user pushes the lid towards the closed position, the portion 33 descends towards the rest of the bottom 20, until the piston 34 bears against the bottom 20. The spring 35 is sized to have a stiffness greater than that of the elastic dome 30, so that it is crushed against the film material 24 when the closing movement continues (position shown in Figure 7), which closes the switch. The additional pressure applied by the user increases the compression of the spring 35, which pushes the piston 34 inside the bearing member 31, as shown in FIG.

  This mechanical arrangement is advantageous in that it avoids the risk of inadvertent opening of the opening detection switch in response to vibrations that may occur while the case is closed.

  In the position shown in FIG. 8, the movement likely to be generated by such vibrations will be essentially a downward movement of the piston 34 with respect to the support member 31, the elastic dome 30 remaining crushed against the material movie 24.

  The resilient domes 30 may be of the same kind as those commonly used to form the keys of certain keyboards. Figures 9 to 10 show an illustration.

  In this example, the dome 30 rests on the substrate 1 of the film material by means of four feet 41-44 arranged at 90. One of these feet 41 is welded to one end of a portion of conductive track 2A adjacent to an interrupted area of this track. On the other side of the interrupted zone, the end of the track portion 2B is under the center of the dome 30. This portion of the track 2B passes between one of the four arches defined between the feet 43, 44 of the dome . The dome 30 may have a slight depression 45 at its center to facilitate contact with the track portion 2B.

  In the relaxed state of the dome (FIG. 10), its central portion 45 is separated from the track portion 2B, and the switch is open. When the support member 31 crushes the dome 30 in response to the closure of the bag, its central portion 45 comes into contact with the track portion 2B, which closes the switch and restores the electrical continuity of the track 2.

  Thus, the observation of the same physical phenomenon (loss of electrical continuity of the track 2) is attributable either to an attempt to intrude through the film material 24, or to an opening of the outer enclosure 20, 21. Each of these two events is in principle allowed only after receipt of a validation signal by the control electronics 27 of the bag. If it is detected at an unexpected time, the contents of the internal speaker are destroyed or smudged.

2888025 -10-

Claims (14)

  A film material for intrusion detection, comprising a plastic substrate (1) and a first electrically conductive track (2, 2 ') applied to a first face of the substrate, characterized in that it further comprises a second electrically conductive track (3) applied to a second face of the substrate opposite to the first face, and in that the first and second tracks are arranged in respective misaligned patterns.   Film material according to claim 1, wherein the patterns of the first and second electrically conductive tracks (2, 3) are mutually crossed.   A film material according to claim 2, wherein the substrate (1) has at least one region where the first track (2, 2 ') is in the form of segments extending in a first direction between two opposite edges of said region and wherein the second track (3) is in the form of segments extending between two opposite edges of said region, in a second direction forming an angle with said first direction.   The film material of claim 3, wherein said angle is substantially 90.   Film material according to any one of the preceding claims, wherein the plastic material of the substrate (1) is a polyester.   A film material according to any one of the preceding claims, wherein one of the first and second tracks (2) is interrupted in at least one area and said area is covered with a conductive member (30) adapted to come in contact with the track in response to a force transverse to the substrate (1) to restore the electrical continuity of said track.   The film material according to claim 6, wherein said conductive member is in the form of an elastic dome (30) fixed at its periphery to the substrate at at least one point of contact with the interrupted track (2A), the dome having a portion central (45) facing a second point of contact with the interrupted track (2B), a deflection of the elastic dome bringing its central portion against the second point of contact to restore the electrical continuity of the interrupted track.   8. Film material according to any one of the preceding claims, wherein the electrically conductive tracks (2, 3) are screen printed on the substrate (1).   A secure container, comprising a wall (20, 21) internally coated with a film material (23, 24) according to any one of the preceding claims, and a detection circuit (27) connected to the first and second tracks ( 2, 3) of the film material to detect a break in electrical continuity of any of the first and second tracks as well as a short circuit between the first and second tracks.   The secure container according to claim 9, wherein the wall has a bottom member (20) and a cover member (21) hinged together and each coated with a film material (23, 24) in accordance with one of any one of claims 1 to 7, the detection circuit (27) being connected to the first and second tracks (2, 3) of each of the film materials of the bottom member and the cover member.   The secure container according to claim 10, wherein the film material (24) of one of the elements (21) has one of its first and second tracks (2) interrupted in at least one area, said area being covered with a conductive member (30) adapted to engage the track in response to a force transverse to the substrate (1) of said film material to restore electrical continuity of the interrupted track, and wherein the other elements (20) is provided with a support member (31) facing said zone for exerting said transverse force in a closed position of the wall and for releasing said transverse force in an open position of the wall.   The secure container of claim 11, wherein said conductive member is resilient dome-shaped (30) secured at its periphery to the substrate (1) of said film material (24) at at least one point of contact with the interrupted track. (2A), the dome having a central portion (45) opposite a second point of contact with the interrupted track (2B), a deflection of the elastic dome bringing its central portion against the second point of contact to restore electrical continuity of the interrupted track.   13. Secure container according to claim 12, wherein the support member (31) is mounted on said other element (20) via an elastic suspension (32-35) having a stiffness greater than that of the elastic dome (30).   14. Secure container according to claim 13, wherein the elastic suspension comprises a portion (33) of the bottom member (20) movable parallel to a closing movement between the elements, a housing (32) formed in said portion face of the dome to receive the support member (31), a piston (34) sliding relative to the support member and leaving the bottom of the housing (32), and a spring (35) placed between the piston and the support member, the closure between the elements (20, 21) compressing the spring to push the support member (31) against the dome (30) and then to press the piston (34) towards the member support.