Europaisches Patentamt (19) European Patent Office Office europeenpeen des brevets EP 0 530 267 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention (51) intci.6: G09F 3/02, B65D 33/34, of the grant of the patent: B65D 27/30 16.10.1996 Bulletin 1996/42 (86) International application number: (21) Application number: 91909909.3 PCT/GB91/00809 Date of 22.05.1991 (22) filing: (87) International publication number: WO 91/18377 (28.11.1991 Gazette 1991/27)

(54) TAMPER RESISTING SECURITY SEAL ORIGINALITATSSICHERHEITSSIEGEL CACHET DE SECURITE ANTI-SPOLIATION

(84) Designated Contracting States: (74) Representative: AT BE CH DE DK ES FR GR IT LI LU NL SE Skone James, Robert Edmund et al GILL JENNINGS & EVERY (30) Priority: 22.05.1990 GB 9011457 Broadgate House 7 Eldon Street (43) Date of publication of application: London EC2M 7LH (GB) 10.03.1993 Bulletin 1993/10 (56) References cited: (73) Proprietor: DE LA RUE HOLOGRAPHICS LIMITED WO-A-89/08586 FR-A- 1 151 039 London WC2N 4DE (GB) FR-A- 2 445 568 GB-A-2 211 760 US-A- 4 834 552 (72) Inventors: • KAY, Ralph 15 Juniper Drive Ray Park Road • Patent Abstracts of Japan, volume 12, no. 354, Berkshire SL6 8RE (GB) (P-761)[3201] 22 September 1988; & JP A 63 • JONES, Keith, Alan 106780 (TOPPAN CO.) 11 May 1988 Berkshire TW19 5EW (GB) • SILK, Adam, Justin 88 Brookhouse Road Cove Hants G414 0BT (GB)

DO Is- CO CM

CO lO Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice the Patent Office of the Notice of shall be filed in o to European opposition to European patent granted. opposition a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. a. 99(1) European Patent Convention). LU

Printed by Jouve, 75001 PARIS (FR) 1 EP 0 530 267 B1 2

Description the holographic impression is supplemented by a partial appearance of the underlying surface which may be a The invention relates to a tamper resistant security photograph. seal, for example for sealing such as security Makowka (US-A-4834552) describes making pouches and the like which are used for conveying items s tamper-evident seals for plastic . The seal is of value such as banknotes, letters of credit and the like. double sided requiring two and is concealed It is extremely important that any such pouches pos- undertheflap in use. Inspection of tamper evidence can sess tamperproof or tamper-evident seals. Various at- only be by folding back the flap and looking at the edges. tempts have been made in the past to make such seals. or cloth having a porous structure is used to pro- Generally these seals are backed tape 10 tect against low temperature attack. constructions which are applied under or over the edge The use of holographic effects for security purposes of the pouch flap so that the flap is held in place against is thus well known. The fineness of optical embossing the body of the pouch in a firm and tamperproof manner. and the nature of the holographic image make it very They can also be in the form of . difficult to alter such devices or manufacture them In recent years the use of metallised films has been 15 afresh. replaced by the use of optically embossed metallised The term "counterfeiting" may be taken to mean the films, which have a holographic or diffractive image. copying of an article by fresh but fraudulent manufac- Such a construction was recently described by Ad- ture. vanced Holographies in GB-A-2211760. The advantage Holographic devices are counterfeit resistant and of using holographic films is that their counterfeiting is 20 may be counterfeit indicating. It is relatively difficult to extremely difficult. The construction of the general pur- construct an holographic image by "copying" it on a ho- pose tape is similar to tapes used for hot stamping, for lographic table even if one were available. Slight varia- example as described in GB-A-21 29739. tions in image quality would also be readily detected in Very generally these tapes consist of a supporting any copy because of the fineness of the surface relief film, a wax release layer, and a of an embossa- 25 structures employed. The counterfeiter would need to ble thermoplastic polymer which has been subsequently have access to holographic equipment, embossing diffractively embossed. Vapour deposited aluminium is equipment and metallising equipment to manufacture then applied with an optional protective layer. The ad- copies, in practice this would be very difficult. hesive is then applied from a coating solution. WO-A- Holographic seals are also forgery resistant by 88/05728 introduces the general concept of a holo- 30 which is meant alteration resistant. They are also readily graphic protective film having a wax interlayer. Then a alteration indicating, as it is very difficult for a forger to general purpose pressure sensitive adhesive layer is replace accurately any cut away or altered area: the applied which is in turn protected by a peelable release fineness of optical relief embossing acts as a consider- paper. In use, the tape is fixed to a substrate using the able deterrent. adhesive. It is difficult to copy or alter. 35 Despite many holographic seal variants disclosed JP-A-631 06780 also describes another general in the art, these all being directed towards enhancing in purpose holographic tape. The tape is designed with various ways the anti-counterfeiting properties and/or weaker bonding between a protective layer over the ho- anti-forgery properties, the importance of providing sub- lographic layer and an adhesive layer than between a stitution resistance, which is the third form of attack transparent film on which the tape is formed and the ho- 40 which a criminal may make, has not hitherto been max- lographic layer. imised. Similar constructions are known for covering large The prior art recognises that holographic seals areas of, say, card in which an holographic trans- should not be readily detachable from the substrate to fer foil is rolled onto the card to produce a card having which the seals are attached. Thus for example it is rec- a diffractive metallic appearance. Such transfer foils are 45 ognised in GB-B-21 36352 that the holographic layer not known to have been used for security pouch seals. should be weak so that attempted removal of the carrier However, they are of similar structure to the tapes men- will destroy the holographic embossing. tioned above except that instead of a wax release layer Similarly in GB-A-2211760 the removal of the car- the embossable layer is chosen to have release prop- rier film (aided by the strength of the wax it is assumed) erties from the carrier film. so will cause damage to the holographic layers. Searle (GB-B-21 36352) discloses holographic While such structures have been used previously, seals in which locally embossed areas of thermoplastic they are unlikely to have provided substitution preven- polymer are covered by a which is then tion ortamper prevention and possibly tamper indicating demetallised. This leaves areas which are unprotected properties for example when such substitution or tam- by the holographic image which is undesirable in 55 pering is undertaken at extremes of ambient tempera- forgery is attempted. ture during freezing or heating. Neither is there any in- Dai Nippon Insatsu in US-A-4856857 discloses dication in the prior art as to how a superior holographic transparent embossed holographic structures in which tape possessing such properties may be made.

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By substitution is meant the detachment of all or scale using conventional production equipment. part of the seal allowing its replacement without giving These new security seals, which are resistant to a evidence of that having happened. For example if a seal wide range of criminal challenges, may be made with a on a security pouch could be temporarily detached and structure which is so fragile that it will very readily fail. then resealed without trace, this would be particularly 5 We have realised that it is important to make an im- undesirable. Yet many of the prior art seals are suscep- proved seal which has high resistance to counterfeiting, tible to such action. forgery and substitution, yet which will degrade irrevers- By tampering is meant unauthorised interference ibly and readily under many conditions to which the crim- with the seal whether for the purposes of counterfeiting, inal may subject it. forgery or substitution. 10 We have devised a new type of tamper resistant se- In this specification, by printing is meant the appli- curity seal which is capable of resisting not only a high cation of readable markings of dyes and/or pigments temperature challenge but also a challenge at low tem- such as those delivered during printing operations, es- perature. Such a challenge could result in complete de- pecially thin ink film printing operations such as occur in struction of the optical pattern defining layer, a variation lithographic, flexographic and gravure printing. The is in that optical pattern, or a variation in the laminate struc- marking may be employed under electronic control such ture such that any attempt to remove the seal from a as during laser printing of toners, ink jet printing, thermal substrate will cause the optical pattern to be varied or transfer printing, impact ribbon printing and the like. destroyed. Preferably, the laminate is constructed so as Markings may take the form of fine line security indicia, to withstand a challenge at -50°C. such as alpha numerical characters, symbols, geomet- 20 The film forming carrier layer may comprise a Sun, rical designs, obliterating and the like. Ault and Wiborg VHL16157 lacquer. This is preferably Markings may also be made caused by printing applied at 2 to 4 microns thickness from a first solvent/ small shapes which pattern the embossed surface be- reverse roll using a coater. The composition may be a fore or after metallisation or by gross embossing number polyvinyl butyral and polyacrylate mixture in solvent. shapes. The printed markings may take the form of sin- 25 The film forming carrier layer has much more cohesive gle images which may require registration for labels, or strength than the subsequently applied optical pattern the printed markings may take the form of multiple rep- defining layer and provides surface protection to a linear etitions of a particular design in the form of an endless extent when there is no support. Additionally, the carrier pattern. Serial or batch numbering may be used to iden- is selected to bond securely to the subsequent coating tify individual seals. 30 and it contracts proportionally much more than the other In accordance with a first aspect of the present in- layers on prolonged freezing to low temperatures such vention a tamper resistant assembly comprises a sup- as by liquid nitrogen. port layer; and a laminate on the support layer including The optical pattern defining layer comprises a trans- a transparent carrier layer, a polymeric optical, diffrac- parent film forming polymeric coating and a metallic lay- tion pattern defining layer, and an adhesive layer for ad- 35 er provided on the surface of the polymeric coating re- hering the seal to a substrate, wherein an optical pattern mote from the carrier layer. The pattern comprises a defined by the optical, diffraction pattern defining layer transmission hologram or diffraction pattern which is is visible from outside the laminate, and wherein the op- viewed by reflection against a metallic surface. tical, diffraction pattern defining layer is permanently To provide resistance to heat attack, the polymeric bonded, directly or indirectly, to the transparent carrier 40 coating, such as an embossable lacquer, will typically layer, such that any attempt to delaminate the carrier have a Tg of below the boiling point of water but above from the optical, diffraction pattern defining layer will ir- ambient transporting conditions ie in the range 50 to reversibly damage the optical pattern and is character- 90°C preferably 60 to 80°C. Embossing may occur at ised in that the assembly is a security seal; in that the temperatures of 20°C degrees above the Tg of the given adhesive is a pressure sensitive adhesive; in that the 45 lacquer. laminate is non-self supporting; and in that the carrier For example, the optical pattern defining layer may layer contracts more than the other layers on freezing be applied to the carrier layer at 4 to 12 microns dry so that a reduction in temperature below 0°C will cause thickness and comprise Holden's 31 90 lacquer. The op- an irreversible, detectable change in the optical pattern. tical pattern defining layer will be thermoplastic and may The permanent bond between the carrier and opti- so have some elastomeric properties. Chemically it may be cal pattern defining layer allows the layers to be kept a polyurethane or a which when applied to the very thin. Thus, any attempt to peel the layers apart will carrier layer will exhibit significantly greater adhesion cause the optical pattern defining layer to fragment de- than that between the carrier layer and additional sup- stroying the optical pattern. port layer. The invention provides a security seal which exhib- 55 The exposed side of this optical pattern defining lay- its a high degree of deterrence to each of counterfeiting, er is preferably embossed against a nickel or similar forgery and substitution attempts within an integrated master shim, in order to impart optically diffracting char- structure which is suitable for manufacture on a large acteristics.

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A surface of the carrier layer or optical pattern de- least compatibility, or there may be included very low fining layer may be printed or otherwise marked. The molecular weight polymers. metallic layer is applied generally completely to the em- The pressure sensitive adhesives will generally be bossed surface, such that substantially all the em- acrylic polmers and the like. Many examples may be bossed diffracting pattern is covered, and this layer may 5 found in the art. be of aluminium and for example be 20 nm thick. The The pressure sensitive adhesive should be chosen metallic layer is preferably continuous but may alterna- to maintain its tackiness for prolonged periods at the tively be partial for example in a halftone pattern which specified minimum operative temperature for a given may in turn depict larger shapes, the embossing nor- application. mally covering the complete area of the seal. It is pref- 10 The support layer may comprise a transparent film, erable that the embossed area extends over the com- for example biaxially orientated polyester film of the ICI plete surface without interruption. pic "Melinex" type. Its thickness will be typically 23 mi- At least one of the materials of the carrier and em- crons or 50 microns but could be very thin such as 12 bossing layers is preferably susceptible to common sol- microns. Generally the polyester will be colourless al- vents such that it will swell or dissolve on solvent chal- 15 though it may be tinted. It may carry or lenge, often causing irreversable change to the delicate other markings on either surface if the support layer is holographic layer. The use of alkali is likely to affect any intended to remain on the affixed seal. In other embod- aluminium reflector. The structure is preferably acid and iments however the support layer may be stripped off water resistant. from the remainder of the seal after it has been affixed The pressure sensitive transfer adhesive may com- 20 to the pouch. The remaining layers are however usually prise a National Adhesive Company pressure sensitive too fragile to withstand much handling and usually the transfer adhesive. The adhesive must be a pressure support layer is left in place. Its removal does not destroy sensitive adhesive preferably protected by a siliconised the holographic layer in this embodiment. It must be left release paper, applied by transfer i.e. after drying it is in place during affixing. rolled at ambient temperature under mild pressure 25 In accordance with a second aspect of the present against the remainder of the construction. The use of invention a method of manufacturing security com- solvent borne pressure sensitive adhesives coated onto prises providing a length of tamper resistant security the metal is impossible because of solvent sensitivity of seal according to the first aspect of the invention, the the embossable layer. Hot stamping adhesives cannot seal including a releasable, film forming protective layer be used because of the inbuilt temperature sensitivity. 30 over the adhesive layer, wherein the releasable, protec- The release paper may be continuous, but is pref- tive layer is releasable in more than one section, folding erably releasable in more than one section. Generally a length of security material to form a bag with an the pressure sensitive adhesive is chosen to retain its opening, removing one section of the protective layer, adhesive properties over a temperature range of -1 0°C and affixing the length of security seal to one edge of to +60°C, preferably the range is from -50°C to +60°C, 35 the opening via the portion of the adhesive layer thereby and to have a Tg from 50°C to 150°C. It is well known exposed. that general purpose pressure sensitive adhesives will This is a particularly important aspect of the inven- harden during chilling, causing them to adopt a glassy tion enabling security bags to be mass produced, as ex- state exhibiting no adhesion. Thus by providing an ad- plained below. hesive which retains its tack at low temperatures, freez- 40 Preferably, the adhesive layer defines a pattern of ing delamination can be avoided. Similarly adhesives areas with and without adhesive. may soften and thus be susceptible to heat delamination The security seal is visible at all times, as distinct and become peelable. from being concealed under a flap or the like, to enable Such adhesives may be obtained commercially easier detection of tampering, and either remains intact from adhesive suppliers and suitability for particular ap- 45 or rapidly degrades on being subjected to a variety of plications may be tested experimentally so as to ensure attacks. a high degree of adhesion at the lowest temperatures A new method of manufacturing such extremely del- to the substrate and to the metallic layer. icate structures and methods of application have been The pressure sensitive adhesives are generally devised such that the tape can be made using relatively made from polymers which have a high surface energy. so conventional manufacturing equipment. Relatively inex- While relatively pure polymers having a low Tg may be pensive security products which incorporate the seals employed and the Tg may equate approximately to the of the invention may also be made. change between tackiness and the non-tacky -like An example of a seal and its use in the manufacture state, it will often be found that plasticising or tackifying of security bags according to the present invention will agents may be incorporated with the polymer to render 55 now be described with reference to the accompanying it tacky at temperatures below the Tg of the polymer. drawings in which:- Sucktackifying agents may be non-volatile organic mol- ecules having structual similarity to the polymer, or at Figure 1 is a schematic, cross-section not to scale

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of one embodiment of the seal; corona discharge. Wax is not used as the bonding be- Figure 2 illustrates manufacture of security bags in- tween the support 1 and the carrier 2 can be more easily corporating the seal of Figure 1 ; and cost effectively controlled to make it release easily Figure 3 is a schematic cross-section of a second or not at all, depending on the corona setting. This of embodiment of the seal; and, s course is readily controllable. Figure 4 illustrates a patterned adhesive for use The embossable lacquer 3 is applied to the carrier with the seal of Figure 1 or Figure 3. 2. The surface of this embossable lacquer 3 remote from the carrier 2 is embossed to define a diffraction pattern The seal shown in Figure 1 comprises a smooth such as a hologram. transparent support 1 formed by a polyester film, biaxi- 10 The dry thickness of the embossable lacquer 3 is ally orientated for strength, with a thickness in the range from 4 to 12 urn and preferably 6 to 8 urn It is thermo- 12-50 microns. Typically 19 or 23 micron polyester film plastic and cuttable with a hot wire. Thermoset, highly is used. This support 1 provides support for the remain- crosslinked coatings are not used as they are too tough. ing layers and can be removed. This removal can be Typically a non-crosslinkable polyurethane or polyester done without damage to a holographic image embossed 15 is chosen. Solvent soluble polymers are employed as on a subsequent layer. The removal of the support 1 they cannot withstand solvent attack later. would be done only after the seal was affixed to its rest- The embossable lacquer 3 is generally selected to ing place as the construction is not otherwise self sup- have a Tg between 50°C and 90°C. The lower limit is porting. The support could be left in place and indeed rather too low for hot countries but generally allows the would be left in place for many applications because it 20 embossable lacquer not to "melt" under normal working imparts scuff resistance to the seal. In its absence the conditions. The higher limit is selected to be low enough holographic image could be irreversibly damaged dur- to cause deterioration of the holograhic embossing pat- ing normal handling. The use of corona discharge treat- tern on hot air (hair drier) or steam challenge. If subject- ment provides fine control of the bonding characteristics ed to these temperatures the embossable lacquer 3 to a degree greater than wax could provide, so that a 25 would relax and the holographic quality would deterio- balance of properties may be achieved. rate to a noticeable extent, providing tamper evidence. Instead of biaxially orientated tereph- Embossing takes place at a temperature such that thalate (polyester) the support 1 may be made of a ther- the lacquer 3 permanently accepts the embossing pat- moplastic film material which has a lower Tg e.g. an eth- tern. On solvent attack the embossable lacquer 3 which ylenic polymer such as . Polypropylene 30 is soft and solvent soluble is quickly irreversibly dam- has the advantage that it is easier to cut with a hot wire aged resulting in loss of holographic image quality. If than paper or polyester. The support 1 may have printing heated with hot air or steam to a temperature above the on one or both surfaces or be tinted. Polymer surfaced softening point of the embossable lacquer (50°C to paper may be used as a support provided its surface is 90°C) the embossable lacquer 3 relaxes and the holo- relatively smooth: this would be subsequently removed. 35 graphic properties degrade irreversibly. levels of 50 dynes per cm of polyester The embossable lacquer 3 is embossed at a tem- film will give a useful degree of releasable bonding to perature as described above and under pressure and the preferred lacquer which is used, while balancing then metallised with a thin metallic film 4 of aluminium handling and security requirements. or other metal typically 20 urn thick. The embossable A smooth transparent carrier film forming polymer 40 lacquer 3 may be metallised then embossed but this is 2 is coated on the support 1 . The carrier 2 has interme- not usually done in practice. diate release properties relative to the support 1 such The holographic layers 3,4 are very thin and fragile. that the support may be removed later without delami- The seal can be handled well at room temperature pro- nating any of the layers in the construction. vided that it is on its support 1 . This is very important for The carrier 2 is coated very thinly indeed. The dry 45 automatic application of lengths of tape. thickness limits, which are critical, are between 2 and 6 The embossable lacquer 3 may be metallised par- microns, preferably between 2 and 4. The carrier 2 is tially, balancing holographic reflectance and see- tougher than the embossable lacquer 3, which is useful through transmission in this use. Transmissions of 75 to for scuff resistance, but the carrier is less tough than the 80% are typical. support 1 . The carrier 2 can be cut with a hot wire as it so The embossed diffraction patterns can include holo- is thermoplastic. The material is generally not as sus- grams of objects, two dimensional graphical diffraction ceptible to attack from solvent as the embossable lac- patterns (which give the perception of none or one or quer 3 but the combined differential solubility of the two more layers of depth to the viewer), stereoholograms, layers provides a useful defence against solvent assist- kinoforms, diffractive mosaic patterns including compu- ed tampering. 55 ter generated diffracting patterns and the like alone or The relative adhesion between the carrier 2 and the in any combination. The images are preferably white support 1 is controlled by selection of the materials and light viewable. The images may be individual perhaps also surface treatment of the support 1 , such as with a surrounded by plain metal or continuously repeating in

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register in an overall geometric design. The holographic breakdown can be enhanced by providing some irregu- features may alternatively be viewable only on mono- larity in the flap of a bag being sealed, e.g. by serrating chromatic light including visible and infrared light. Ma- the edge of the flap. Regular failure to a geometric de- chine readable and verifiable diffraction patterns may be sign is attractive but security can be enhanced by pro- included in the holographic embossing. 5 viding greater degrees of irregularity than simply by ser- A protective polymeric coating (not shown) may be rations. This can be achieved by placing a pattern of ad- applied to the metallic film 4 before applying a pressure hesive using patterned adhesive printing rollers. Either sensitive transfer adhesive 6. The adhesive is not coat- the adhesive is laminated in place rather than coated or ed on as its solvent or drying would possibly attack the the bond between the continuous adhesive and the met- carrier 2 or embossable lacquer 3. Rather the adhesive 10 al is broken by printing a release coating onto the metal is transferred already releasably adhered to a release in a patterned form. paper (or film) 7, and the two surfaces are brought to- Figure 4 illustrates a patterned adhesive for use on gether under mild pressure of rollers to bond the pres- a seal, the adhesive layer being arranged with adhesive sure sensitive adhesive 6 firmly and irreversibly to the areas 20 and non-adhesive areas 21 . Two longitudinally metallic film 4. is uninterrupted tracks of adhesive 22 and 23 are provided The bond strength between the pressure sensitive where the tape is to be slit along lines 24-25 and 26-27 adhesive and the release paper 7 is less than that be- so as to prevent the soft coatings prematurely detach- tween the support 1 and the carrier 2. This allows the ing. release paper 7 to be stripped away and the seal to be The net effect is that when the support is peeled adhered in place. The support 1 may then be removed 20 away those areas with adhesive are kept affixed to the as the bond to the carrier 2 is weaker than the bonding substrate whilst those areas which are adhesive free are among the carrier 2, embossable lacquer 3, metallic film pulled by the carrier. The weak layers are therefore sub- 4 and pressure sensitive adhesive 6 (otherwise the tape jected to contrary forces and as the adhesion to adhe- would split apart). sive and adhesion to the carrier are greater than the co- The support 1 must be kept in place while the seal 25 hesion and adhesion of the carrier and embossable lay- is being affixed because it is too soft to remain intact ers, these layers tear irregularly and cannot be reinstat- while being peeled from the release paper 7 over the ed. pressure sensitive adhesive 6 without the support. The adhesive pattern also causes local variation in After removal of the support 1 the holographic layer the thickness of the seal and this effect manifests itself is so weak that it rips apart on attempted peeling. The 30 in the holographic layer. This is otherwise completely flat support 1 can be detached without pulling off the holo- but it is tilted by the adhesive. graphic layers. Overall the construction is very thin, typ- Thus, patterned adhesives may be used where ex- ically the carrier and embossable layers taking up about tra breakdown and tamper evidence is required. Solvent 8-10 urn. readily wicks under the coatings where there is no ad- The release paper 7 could be siliconised paper, sil- 35 hesive and because of the differential thermal conduc- iconised plastic, or releasable plastic such as polyester tivity of the structure, rapid cooling and heating might (if necessary surface treated), polythylene, polypropyl- result in additional visible changes to the holographic ene or the like. Plastic is useful since it allows the com- image. pleted seal to be cut with a hot wire during plastic secu- Another adaptation is to print a security bag with a rity bag manufacture. The Tg of the thermoplastic re- 40 patterned releasable flexographic ink where the seal is lease layer will not usually be greater than 1 80°C to al- to be sealed. The pattern is applied by standard printing low hot wire cutting. The completed material can then techniques and when the seal is peeled away by trying be cut into reels or sheets for use as tape or individual to lift it, for example with adhesive tape, the holographic labels. The release paper 7 may be partially slit. layer tears in the pattern of the ink. The ink may be made As a variant the adhesive can be supplied in a pat- 45 to have release properties by including wax or other terned format, covering at least half of the available sur- compatible low surface energy material. face. The advantage of this is that tearing attempts will In a further variant the corona field intensity may be encounter differential adhesion. It is however somewhat varied across the web so as to provide differential ad- of a disadvantage as the adhesive pattern can be seen hesion. against the holographic layer where the level changes. so On freezing in a freezer at -10°C or lower temper- If patterned adhesive is to be used then the adhesive ature, according to the adhesive's properties the adhe- has to be placed in tramline fashion to span where the sive 6 will not debond from the substrates which have slitting knives will cut, otherwise the seal will destruct on been used because of the choice of adhesive. The ad- slitting. In between the tramline's partial coverage a se- hesive 6 has a low hardening temperature. On regaining ries of small blocks may be used. 55 room temperature no deterioration of holographic qual- The patterned adhesive gives differential failure ity need be evident. On prolonged freezing or on very variation of the seal. The seal described above breaks low temperature challenge such as at liquid nitrogen down readily on tampering, especially peeling. This temperatures the hologram will irreversably deteriorate

6 11 EP 0 530 267 B1 12 as thermal stresses develop between the securely and could be signed. bonded layers. Additionally it is thought that the pres- The seal is designed to be resistant to freezing and ence of ice crystals forming within the holographic struc- high temperature attack as well as solvent or chemical ture contribute to the effect. The aluminium layer ap- eg alkali solution attack The seal if peeled causes irre- pears to lose reflectance and this is readily noticeable. 5 versible irregular splitting of the soft holographic layers. The seal, which may be a continuous tape or com- An example of a higher strength seal for use with prise individual labels, is applied to a flat surface for ex- security bags is shown in Figure 3. A transparent biax- ample to protect an underlying feature, over the joint be- ially orientated polyester film 2, which may be between tween two flat overlapping surfaces such as a bag flap 19 urn and 50 um thick, in this case 23 microns, was or flap, or over a short gap in a surface. The 10 corona treated at approximately 50 dynes per centime- pressure sensitive adhesive will be varied depending on tre to provide a surface on which the subsequent coating the end use. would exhibit clinging engagement. The seal may be used as an edge seal for example To the corona treated surface of the carrier 2 a spanning part of one edge of a photograph or visa af- transparent coating of embossable lacquer 3 of the fixed to a passport page or to seal a gap completely, for is aforementioned type is then applied at for example 8 example security bag flaps. microns dry thickness and gently dried. The lacquer may The fragility of the holographic layers means that be applied from a volatile solvent which is subsequently the seal does not provide a significant degree of strength removed, at a thickness of between 7 um and 12 um. to the area being sealed. Thus in security bags which A holographic pattern is then imparted to the sur- have a flap which is folded and sealed against the body 20 face of this lacquer 3, the holographic pattern compris- of the bag, there is generally a separate adhesive strip ing a series of abutting individual images separated by which provides a strong bond. This adhesive may be a small plain margins. The surface of the lacquer 3 may double sided adhesive strip protected by a removable be printed with a thin ink layer in a fine pattern. Emboss- release layer. After the flap is sealed in position the ad- ing is undertaken under heat and pressure against a hesive strip will not normally be visible even though it 25 nickel shim which holds the holographic pattern on its may have a tamper indicating construction. surface at a temperature about 20 °C degrees above Although the seal is weak when the support 1 is left the Tg of the lacquer, approximately 80°C to 110°C. in position as will commonly be the case, the support 1 The embossed composite film is then metallised ei- adds to the stress resistance of the holographic layer so ther completely or partially (to allow transparency), with that the seal is able to withstand minor flexing without 30 aluminium under vacuum to deposit a layer of metal 4 damage. The support 1 also provides scuff resistance. approximately 20 nm thick. If the support 1 is removed the carrier 2, which is tougher To the surface of a roll of corona treated polypropyl- than the embossable lacquer, will provide limited impact ene film 7 is applied National Adhesives acrylic pressure protection. sensitive adhesive Type 380-281 9 or 1 825 at a dry thick- A stronger version of security seal can be made for 35 ness of approximately 12 microns. This is dried to form example for use for or sealing in place of the pressure sensitive adhesive layer 6 which is then passport photographs. This requires that there is a per- rolled against the metallised composite film under mild manent backing which is not releasable. In practice this pressure to provide the final seal. This is then slit into is done by using polyester as the carrier, which has been rolls and at the same time the release layer covering the surface treated with a corona discharge so that it bonds 40 adhesive is provided with a longitudinal tearing line to strongly to the coating. The soft embossable lacquer 3 allow part of the adhesive to be made available for af- is then between the strong pressure sensitive adhesive fixing the seal to a security bag. 6 and the carrier 2. On peeling there will be metal 4 to The adhesion between this surface of the carrier 2 embossable lacquer 3 failure or cohesive failure of the and the embossable lacquer 3 being sufficient to allow embossable lacquer 3. 45 for manufacturing and automated seal affixing stresses. While complete metallisation can be used for this The adhesion between the carrier 2, embossable lac- seal for some purposes, partial metallisation has to be quer 3, metal layer 4 and the adhesive 6 is greater than used for the passport photograph overlaminate applica- that between the pressure sensitive adhesive 6 and its tion to allow the photograph to be seen. release paper 7. The seal can be affixed to a substrate The passport overlaminate application has anti- so by removing the pressure sensitive adhesive's release counterfeit and antiforgery properties. It possesses paper 7. strong bonding with clear tamper resistance. This seal may then be affixed in a continuous secu- The seal may be supplied in lengths so that it can rity bag manufacturing line to the surface of a thermo- be bound into a passport book, next to the photograph plastic security bag. Individual bags are cut from the page. The release paper which is not be stitched would 55 continuous strip by means of a hot wire or gullotine be peeled off to reveal the adhesive which would then which cuts and seals the bag edges and simultaneously be smoothed over the page holding the holder's photo- cuts the security seal. graph. The seal may be used to seal the edge of a visa Figure 2 illustrates a continuous series of security

7 13 EP 0 530 267 B1 14 bags bearing the seal of the invention, the bags having failure of the diffraction image. The construction exem- been vertically edge sealed by a hot wire which has cut plified with the materials above has not only withstood through the thermoplastic bag material as well as the freezing to -50°C with f reon spray but has also withstood structural adhesive and the holographic . integral peeling after exposure to liquid nitrogen. We A roll of heat sealable 8 such as opaque 5 have found that with the above construction the polyvi- polypropylene, suitable for making security pouches, nyl butyral layer seems to contract much faster than the longitudinally printed on the outside with the agent's optical layers to which is firmly adhered with the result name, is folded longitudinally on film transporters such that the holographic seal visibly fragments. that an edge 9 of an upper surface 10 does not extend The seal was also found to be resistant to removal as far as another edge 1 1 of a lower surface 1 2. The flap 10 or failed irreversably on exposure to cold water, hot wa- portion comprises a numbered section (the number is ter, steam, aqueous alkali, aqueous acid, common sol- on the other side of the flap) detachable along a perfo- vents such as methylated spirits, acetone, petroleum rated line 1 3 when the bag is about to be holographically spirit, ethylacetate, peeling, bending. The seal was dif- sealed. The flap has a series of perforations 1 4 to cause ficult to copy or alter. tearing on tampering. 15is This improvement is very significant indeed in main- Individual bag shapes are then prepared by cutting taining the integrity of pouches or at least showing that lengths of this continuous assembly with a heated plas- a tamper condition has arisen. tic wire (orthogonal to the direction of the seal). This will Different grades of seal are suitable for different ap- also have the effect of sealing the edges of the bag. Al- plications. A normal grade may be used for light duty ternatively, the edges of the bag may be heat sealed 20 labels (including crack back release), or tape for bags, together to provide edge bands which are then cut in the envelopes, cassettes, small seals, or passport stickers. middle of the bands with a hot wire or knife. The heavier duty seal with lower temperature resistance The bag, any detachable flap and optionally the seal is suitable for strips, tapes, and labels where more load may be numbered, for example by ink jet printing, to pro- resistance is required such as the passport photograph vide individuality to the bags. 25 overlaminate which is partially metallised. The light duty In use the numbered section is detached and the patterned adhesive may be used for applications where flap is folded at line 9 and affixed to the surface 10 with extra breakdown and tamper evidence is needed. A a strong double sided adhesive strip 1 5 bearing its ther- heavy duty patterned adhesive may be used for strip moplastic release layer. Holographic security seal 16 of seals, labels, bags envelopes, and containers. the type described above is affixed to the bag by the 30 The term "crack back" is used to indicate a method adhesive on one half 17 of the seal (following removal of applying labels in which the release paper fixed to the of half the protective layer). The other half 1 8 of the seal adhesive is sharply folded over a right angle causing the still bears its protective layer so that the edge 13 may front of the to project with its adhesive surface ex- be sealed when the flap extends to its limit 19. posed. The adhesive engages substrate and the sub- Security envelopes are used for the secure trans- 35 strate then pulls the label off the release paper. Crack port and storage of valuable items. By providing a holo- back is necessary for automated label applications. Ad- graphic seal which is difficult for the criminal to repro- ditional transparent layers having a thickness of less duce and which cannot be substituted or broken and than 1 2 microns may be added within the laminate. The sealed, they are made more visibly tamper evident. The seal of the invention may be used on envelopes which seal supplied may be 25 mm wide and the release paper 40to are designed to hold computer discs such as 13.3 cm or film has a longitudinal tearing line so that one side (5/4") or 8.9 cm (314") floppy discs. The seals may be can be stripped off. The seal may be applied to the bags numbered individually or in batches to provide en- during their in-line manufacture. hanced levels of security. The seals may also be used In order to test the laminate shown in the drawing, to secure containing magnetic recording media delaminating tests have been carried out at several tem- 45 which are provided in reel form such as magnetic tape peratures on the type of seal which has a removable cartridges for use as computer storage media, video re- support (Figure 1). These are 70 degrees Celsius, am- cording tapes, audio tapes and the like. bient temperature of about 20°C, -50°C and -180°C. The test seal is applied to a polypropylene or other plastic pouch surface and picking off intact is attempted. 50 Claims While the support may be able to be removed without destruction of the optical layer, the seal could not be re- 1 . A tamper resistant assembly comprising a support moved intact at any of these temperatures. On exposure layer (1 ); and a laminate on the support layer includ- to the high or very low temperature the optical structure ing a transparent carrier layer (2); a polymeric opti- was irreversibly deformed. This may occur because of cal, diffraction pattern defining layer (3); and an ad- the differential stresses inside the structure so that on hesive layer (6) for adhering the seal to a substrate, freezing, say, the carrier contracts more than the other wherein an optical pattern defined by the optical, dif- layers with the result that the internal stresses cause fraction pattern defining layer (3) is visible from out-

8 15 EP 0 530 267 B1 16

side the laminate, and wherein the optical, diffrac- 11. An assembly according to claim 10, wherein the tion pattern defining layer is permanently bonded, transparent coating of the optical pattern defining directly or indirectly, to the transparent carrier layer, layer (3) has a dry thickness in the range 7-12 um. such that any attempt to delaminate the carrier from the optical, diffraction pattern defining layer will ir- 5 12. An assembly according to claim 10 or claim 11, reversibly damage the optical pattern; character- wherein the metallic layer has a thickness of about ised in that the assembly is a security seal; in that 20 nm. the adhesive is a pressure sensitive adhesive; in that the laminate is non-self supporting; and in that 13. An assembly according to any of the preceding the carrier layer (2) contracts more than the other 10 claims, wherein the optical pattern defining layer (3) layers on freezing so that a reduction in temperature has a thickness of 4-12 um. below 0°C will cause an irreversible, detectable change in the optical pattern. 14. An assembly according to any preceding claim, wherein the optical pattern defining layer (3) has a 2. An assembly according to claim 1 , wherein the pol- is Tg in the range 50°C to 90°C. ymeric optical, diffraction pattern defining layer (3) has a Tg such that when heated the optical pattern 15. An assembly according to claim 14, wherein the op- undergoes an irreversible change. tical pattern defining layer (3) has a Tg in the range 60°C to 80°C. 3. An assembly according to claim 1 or claim 2, where- 20 in the laminate is constructed so as to withstand a 16. An assembly according to any of the preceding challenge at or less than -50°C. claims, wherein the material of the optical, diffrac- tion pattern defining layer (3) is susceptible to sol- 4. An assembly according to any preceding claim vents for weakening the adhesive layer or delami- wherein the transparent carrier layer (2) comprises 25 nating the tape, so as to cause an irreversible a thermoplastic which is soluble in an inorganic sol- change in the optical pattern. vent. 17. An assembly according to any of the preceding 5. An assembly according to any preceding claim, claims, further comprising an additional, protective wherein the transparent carrier layer (2) has a thick- 30 polymeric coating applied to the optical pattern de- ness in the range 2-4 microns. fining layer (3) between that layer and the adhesive layer (6). 6. An assembly according to any preceding claim, wherein the support layer (1) is removably bonded 18. An assembly according to any of the preceding to the transparent carrier layer (2). 35 claims, having a thickness of 8-1 0 um excluding the support layer (1 ). 7. An assembly according to claim 6, wherein the sur- face of the support layer (1 ) has been corona treat- 19. An assembly according to any of the preceding ed to assist adhesion between itself and the trans- claims, further comprising a releasable, film forming parent carrier layer. 40 protective layer (7) over the adhesive layer (6).

8. An assembly according to claim 6 or claim 7, where- 20. An assembly according to claim 19, wherein the in the combined thickness of the transparent carrier protective layer (7) is a plastics material. layer (2) and the support layer (1) is in the range 8 um to 12 um. 45 21. An assembly according to claim 20, wherein the re- leasable protective layer (7) on the pressure sensi- 9. An assembly according to any of claims 6 to 8, tive adhesive (6) comprises a thermoplastic having wherein the support layer (1 ) comprises a transpar- a Tg of from 50°C to 150°C. ent film, for example biaxially orientated polyester film. so 22. An assembly according to any of claims 19 to 21, wherein the releasable, protective layer (7) is re- 10. An assembly according to any one of the preceding leasable in more than one section. claims, wherein the optical diffraction pattern defin- ing layer (3) comprises a transparent film forming 23. An assembly according to any preceding claim polymeric coating and a metallic layer provided on 55 wherein the pressure sensitive adhesive (6) retains the surface of the coating remote from the carrier its adhesive properties over a temperature range of layer (2). -50°C to +60°C.

9 17 EP 0 530 267 B1 18

24. An assembly according to claim 23, wherein the gerschicht (2) sich beim Gefrieren starker zusam- pressure sensitive adhesive (6) retains its adhesive menzieht als die anderen Schichten, so dal3 eine properties over a temperature range of -30°C to Verringerung der Temperatur unter 0°C eine irre- +60°C. versible, feststellbare Anderung in dem optischen 5 Muster bewirkt. 25. An assembly according to claim 24 wherein the pressure sensitive adhesive (6) retains its adhesive 2. Anordnung nach Anspruch 1 , bei der die polymere, properties over a temperature range of -20°C to optische, ein Beugungsmuster begrenzende +60°C. Schicht (3) eine solche Tg hat, dal3 das optische Mu- 10 ster bei Erhitzung einer irreversiblen Anderung un- 26. An assembly according to claim 25, wherein the terliegt. pressure sensitive adhesive (6) retains its adhesive properties over a temperature range of -10°C to 3. Anordnung nach Anspruch 1 oder Anspruch 2, bei +60°C. der das Laminat so aufgebaut ist, dal3 es einem An- 15 schlag bei einer Temperatur von -50°C oder darun- 27. An assembly according to any of the preceding ter standhalt. claims, wherein the optical pattern defining layer (3) is directly bonded to the carrier layer (2). 4. Anordnung nach einem der vorstehenden Anspru- che, bei der die transparente Tragerschicht (2) ein 28. A method of manufacturing security bags, the meth- 20 thermoplastisches Material aufweist, das in einem od comprising providing a length of tamper resistant anorganischen Losungsmittel loslich ist. security seal in accordance with at least claim 22, folding a length of security bag material (8) to form 5. Anordnung nach einem der vorstehenden Anspru- a bag with an opening, removing one section of the che, bei der die transparente Tragerschicht (2) eine protective layer (7), and affixing the length of secu- 25 im Bereich von 2 bis 4 Mikrometer liegende Dicke rity seal to one edge of the opening via the portion aufweist. of the adhesive layer thereby exposed. 6. Anordnung nach einem der vorstehenden Anspru- 29. A method according to claim 28, further comprising che, bei der die Stutzschicht (1) losbarmit dertrans- dividing the composite bag/seal construction into a 30 parenten Tragerschicht (2) verbunden ist. number of smaller bags. 7. Anordnung nach Anspruch 6, bei der die Oberfla- 30. An assembly according to any of claims 1 to 17, che der Stutzschicht (1) coronabehandelt ist, um wherein the adhesive layer (6) defines a pattern of die Adhasion zwischen sich und der transparenten areas with (20) and without (21) adhesive. 35 Tragerschicht zu unterstutzen.

Anordnung nach Anspruch 6 oder Anspruch 7, bei Patentanspriiche der die Gesamtdicke der transparenten Trager- schicht (2) und der Stutzschicht (1) im Bereich von 1. Manipulationssichere Anordnung mit einer Stutz- 40 8 um bis 12 um liegt. schicht (1 ) und einem Laminat auf der Stutzschicht, das eine transparente Tragerschicht (2), eine poly- 9. Anordnung nach einem der Anspruche 6 bis 8, bei mere, optische, ein Beugungsmuster begrenzende der die Stutzschicht (1 ) eine transparente Folie auf- Schicht (3) und eine Klebstoffschicht (6) zum An- weist, z.B. eine biaxial orientierte Polyesterfolie. kleben des Siegels an einem Substrat aufweist, wo- 45 bei ein optisches Muster, das durch die optische ein 10 Anordnung nach einem der vorstehenden Anspru- Beugungsmuster begrenzende Schicht (3) be- che, bei der die das optische Beugungsmuster be- grenzt ist, von auBerhalb des Laminats sichtbar ist, grenzende Schicht (3) einen eine transparente Fo- und wobei die optische, das Beugungsmuster be- lie bildenden polymeren Uberzug und eine metalli- grenzende Schicht permanent, direkt oder indirekt, so sche Schicht aufweist, die auf der der Tragerschicht mit der transparenten Tragerschicht verbunden ist, (2) abgekehrten Oberflache des Uberzugs vorge- so dal3 jeder Versuch, den Trager von der opti- sehen ist. schen, das Beugungsmuster begrenzenden Schicht zu delaminieren, das optische Muster irre- 11. Anordnung nach Anspruch 1 0, bei der der transpa- versibel beschadigt, dadurch gekennzeichnet, dal3 55 rente Uberzug der das optische Muster begrenzen- die Anordnung ein Sicherheitssiegel ist, dal3 der den Schicht (3) eine Trockendicke im Bereich von Klebstoff ein druckempfindlicher Klebstoff ist, dal3 7 bis 12 um hat. das Laminat nicht selbsttragend ist und da!3 die Tra-

10 19 EP 0 530 267 B1 20

12. Anordnung nach Anspruch 10 oder Anspruch 11, empfindliche Klebstoff (6) seine Klebfahigkeit in ei- bei der die metallische Schicht eine Dicke von etwa nem Temperaturbereich von -30°C bis +60°C bei- 20 nm hat. behalt.

13. Anordnung nach einem der vorstehenden Anspru- 5 25. Anordnung nach Anspruch 24, bei der der druck- che, bei der die das optische Muster begrenzende empfindliche Klebstoff (6) seine Klebfahigkeit in ei- Schicht (3) eine Dicke von 4 bis 12 um hat. nem Temperaturbereich von -20°C bis +60°C bei- behalt. 14. Anordnung nach einem der vorstehenden Anspru- che, bei der die das optische Muster begrenzende 10 26. Anordnung nach Anspruch 25, bei der der druck- Schicht (3) eine Tg im Bereich von 50°C bis 90°C empfindliche Klebstoff (6) seine Klebfahigkeit in ei- hat. nem Temperaturbereich von -10°C bis +60°C bei- behalt. 15. Anordnung nach Anspruch 14, bei der die das op- tische Muster begrenzende Schicht (3) eine Tg im is 27. Anordnung nach einem der vorstehenden Anspru- Bereich von 60°C bis 80°C hat. che, bei der die das optische Muster begrenzende Schicht (3) direkt mit der Tragerschicht (2) verbun- 16. Anordnung nach einem der vorstehenden Anspru- den ist. che, bei der das Material der das optische Beu- gungsmuster begrenzenden Schicht (3) empfind- 20 28. Verfahren zum Herstellen von Sicherheitsbeuteln, lich auf Losungsmittel zur Schwachung der Kleb- bei dem ein langgestrecktes manipulationssicheres stoffschicht oderzum Delaminieren des Bandes ist, Siegel nach wenigstens Anspruch 22 gebildet wird, um eine irreversible Anderung des optischen Mu- ein langgestrecktes Sicherheitsbeutelmaterial (8) sters zu bewirken. zur Bildung eines Beutels mit einer Offnung gefaltet 25 wird, ein Abschnitt der Schutzschicht (7) entfernt 17. Anordnung nach einem der vorstehenden Anspru- wird und das langgestreckte Sicherheitssiegel an che, die einen zusatzlichen polymeren Schutzuber- dem einen Rand der Offnung iiber den dadurch frei- zug auf der das optische Muster begrenzenden gelegten Teil der Klebstoffschicht befestigt wird. Schicht (3) zwischen dieser Schicht und der Kleb- stoffschicht (6) aufweist. 30 29. Verfahren nach Anspruch 28, bei dem die zusam- mengesetzte Beutel/Siegel-Konstruktion in mehre- 18. Anordnung nach einem der vorstehenden Anspru- re kleinere Beutel unterteilt wird. che, die eine Dicke von 8 bis 1 0 um ohne die Stutz- schicht (1) aufweist. 30. Anordnung nach einem der Anspruche 1 bis 1 7, bei 35 der die Klebstoffschicht (6) ein Muster aus Flachen 19. Anordnung nach einem der vorstehenden Anspru- mit (20) und ohne (21) Klebstoff begrenzt. che, mit einer ablosbaren, eine Folie bildenden Schutzschicht (7) iiber der Klebstoffschicht (6). Revendications 20. Anordnung nach Anspruch 19, bei der die Schutz- 40 schicht (7) aus einem thermoplastischen Kunststoff 1 . Assemblage antispoliation comprenant une couche besteht. d'appui (1 ); et un stratifie sur la couche d'appui com- prenant une couche de support transparente (2) ; 21 . Anordnung nach Anspruch 20, bei der die ablosba- une couche definissant une configuration de diffrac- re Schutzschicht (7) auf dem druckempfindlichen ts tion optique polymere (3) ; et une couche adhesive Klebstoff (6) einen Thermoplasten mit einer Tg von (6) pour faire adherer le cachet sur un appui, dans 50°C bis 150°C aufweist. lequel une configuration optique definie par la cou- che definissant la configuration de diffraction opti- 22. Anordnung nach einem Anspruche 19 bis 21, bei que (3) est visible de I'exterieur du stratifie et dans der die ablosbare Schutzschicht (7) in mehr als ei- so lequel la couche definissant la configuration de dif- nem Abschnitt ablosbar ist. fraction optique est Nee en permanence, directe- ment ou indirectement a la couche de support trans- 23. Anordnung nach einem der vorstehenden Anspru- parente, de sorte que toute tentative pour delaminer che, bei der der druckempfindliche Klebstoff (6) sei- le support de la couche definissant la configuration ne Klebfahigkeit in einem Temperaturbereich von 55 de diffraction optique deteriore irreversiblement la -50°C bis +60°C beibehalt. configuration optique ; caracterise en ce que I'as- semblage est un cachet de securite; en ce que I'ad- 24. Anordnung nach Anspruch 23, bei der der druck- hesif est un adhesif sensible a la pression ; en ce

11 21 EP 0 530 267 B1 22

que le stratifie n'est pas autoporteur; et en ce que 11. Assemblage selon la revendication 10, dans lequel la couche de support (2) se contracte plus que les le revetement transparent de la couche definissant autres couches lors de la congelation, de sorte la configuration optique (3) presente une epaisseur qu'une reduction de temperature en dessous de seche dans I'intervalle de 7-12 um. 0°C provoque une modification detectable, irrever- 5 sible dans la configuration optique. 12. Assemblage selon la revendication 10 ou la reven- dication 11, dans lequel la couche metallique pre- 2. Assemblage selon la revendication 1, dans lequel sente une epaisseur d'environ 20 nm. la couche definissant la configuration de diffraction optique polymere (3) presente une Tg telle que lors- 10 13. Assemblage selon I'une quelconque des revendica- qu'elle est chauffee, la configuration optique est tions precedentes, dans lequel la couche definis- soumise a une modification irreversible. sant la configuration optique (3) presente une epaisseur de 4-12 um. 3. Assemblage selon la revendication 1 ou la revendi- cation 2, dans lequel le stratifie est construit afin de is 14. Assemblage selon I'une quelconque des revendica- resister a une contrainte de ou inferieure a -50°C. tions precedentes, dans lequel la couche definis- sant la configuration optique (3) presente une Tg 4. Assemblage selon I'une quelconque des revendica- dans I'intervalle de 50°C a 90°C. tions precedentes, dans lequel la couche de sup- port transparente (2) comprend une matiere ther- 20 15. Assemblage selon la revendication 14, dans lequel moplastique qui est soluble dans un solvant inorga- la couche definissant la configuration optique (3) nique. presente une Tg dans I'intervalle de 60°C a 80°C.

5. Assemblage selon I'une quelconque des revendica- 1 6. Assemblage selon I'une quelconque des revendica- tions precedentes, dans lequel la couche de sup- 25 tions precedentes, dans lequel le materiau de la port transparente (2) presente une epaisseur dans couche definissant la configuration de diffraction I'intervalle de 2-4 um. optique (3) est sensible aux solvants pour fragiliser la couche adhesive ou delaminer le ruban afin de 6. Assemblage selon I'une quelconque des revendica- provoquer une modification irreversible de la confi- tions precedentes, dans lequel la couche d'appui 30 guration optique. (1) est Nee de maniere detachable a la couche de support transparente (2). 1 7. Assemblage selon I'une quelconque des revendica- tions precedentes. comDrenant en outre un revete- 7. Assemblage selon la revendication 6, dans lequel ment polymere protecteur supplemental applique la surface de la couche d'appui (1 ) a ete traitee par 35 sur la couche definissant la configuration optique decharge lumineuse pour contribuer a I'adhesion (3) entre cette couche et la couche adhesive (6). entre elle-meme et la couche de support transpa- rente. 1 8. Assemblage selon I'une quelconque des revendica- tions precedentes, presentant une epaisseur de 8. Assemblage selon la revendication 6 ou la revendi- 40 8-1 0 um a I'exclusion de la couche d'appui (1 ). cation 7, dans lequel I'epaisseur combinee de la couche de support transparente (2) et de la couche 1 9. Assemblage selon I'une quelconque des revendica- d'appui (1) se trouve dans I'intervalle de 8 um a 12 tions precedentes, comprenant en outre une cou- um. che detachable, protectrice, formant un film (7) sur 45 la couche adhesive (6). 9. Assemblage selon I'une quelconque des revendica- tions 6 a 8, dans lequel la couche d'appui (1 ) com- 20. Assemblage selon la revendication 19, dans lequel prend un film transparent, par exemple un film de la couche protectrice (7) est une matiere plastique. polyester biaxialement oriente. so 21. Assemblage selon la revendication 20, dans lequel 10. Assemblage selon I'une quelconque des revendica- la couche protectrice detachable (7) sur I'adhesif tions precedentes, dans lequel la couche definis- sensible a la pression (6) comprend une matiere sant la configuration de diffraction optique (3) com- thermoplastique presentant une Tg de 50°C a prend un revetement polymere formant un film 150°C. transparent et une couche metallique fournie sur la 55 surface du revetement eloignee de la couche de 22. Assemblage selon I'une quelconque des revendica- support (2). tions 1 9 a 21 , dans lequel la couche protectrice de- tachable (7) est detachable dans plus qu'une sec-

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tion.

23. Assemblage selon I'une quelconque des revendica- tions precedentes, dans lequel I'adhesif sensible a la pression (6) conserve ses proprietes adhesives s sur un intervalle de temperature de -50°C a +60°C.

24. Assemblage selon la revendication 23, dans lequel I'adhesif sensible a la pression (6) conserve ses proprietes adhesives sur un intervalle de tempera- 10 ture de -30°C a +60°C.

25. Assemblage selon la revendication 24, dans lequel I'adhesif sensible a la pression (6) conserve ses proprietes adhesives sur un intervalle de tempera- 15 ture de -20°C a +60°C.

26. Assemblage selon la revendication 25, dans lequel I'adhesif sensible a la pression (6) conserve ses proprietes adhesives sur un intervalle de tempera- 20 ture de -10°C a +60°C.

27. Assemblage selon I'une quelconque des revendica- tions precedentes, dans lequel la couche definis- sant la configuration optique (3) est directement Nee 25 a la couche de support (2).

28. Procede de fabrication de sacs de securite, le pro- cede consistant a fournir une longueur de cachet de securite antispoliation selon au moins la reven- 30 dication 22, a plier une longueur du materiau de sac de securite (8) pour former un sac presentant une ouverture, a eliminer une section de la couche pro- tectrice (7) et a apposer la longueur du cachet de securite sur un bord de I'ouverture par I'intermediai- 35 re de la partie de la couche adhesive exposee par celle-ci.

29. Procede selon la revendication 28, consistant en outre a diviser la construction composite sac/cachet 40 en un nombre de sacs plus petits.

30. Assemblage selon I'une quelconque des revendica- tions 1 a 1 7, dans lequel la couche adhesive (6) de- finie une configuration de zones avec (20) et sans 45 (21) adhesif.

50

55

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