AU2003205497B2

AU2003205497B2 - Security feature for value documents

Info

Publication number: AU2003205497B2
Application number: AU2003205497A
Authority: AU
Inventors: Klaus Franken; Jakob Grob; Christoph Kocher; Andreas Seyffert; Paul Smith
Original assignee: Landqart AG
Current assignee: Landqart AG
Priority date: 2002-07-19
Filing date: 2003-02-28
Publication date: 2007-07-05
Anticipated expiration: 2023-02-28
Also published as: ATE514562T1; WO2004009373A1; EP1523415B1; EP1523415A1; AU2003205497C1; AU2003205497A1

Abstract

The invention relates to a security feature for a security document, whereby the authenticity can be determined by irradiation with electromagnetic radiation (13, 18) in a spectral range outside that of the visible region. According to the invention, a simple production of security features with strong in/out effects on injection of linear polarised light and/or on observation by means of a rotating polarization filter can be achieved, whereby the security feature comprises a printing (4, 8, 9) or a coating which converts the injected electromagnetic radiation (13, 18) into visible light (15, 21), whereby said printing (4, 8, 9) is at least indirectly covered by means of a polarisation film (2, 6, 7).

Description

.WO 2004/009373 PCT/CH2003/000146

DESCRIPTION

TITLE

Security feature for documents of value 'TECHNICAL FIELD The present invention relates to a security feature for a security document in which the authenticity can be determined by means of irradiation with electromagnetic radiation in a spectral range outside the visible range.

PRIOR ART It is generally known that, in order to secure security documents or, generally, security articles such as banknotes, checks, stocks and shares, bonds, identity cards, passports, drivers' licenses, tickets, stamps, but also credit cards, bank cards and the like, it is possible to use security features in order to be able to carry out the authentication of the document. For example, nowadays, in this connection, security threads, security strips, holograms and mottled fibers are used. In this case, inter alia use is in particular also made of features which cannot be detected by eyewhen viewed in visible light but which stand out suddenly when irradiated with UV light. This can be achieved by using fluorescent dyes which absorb the incident UV light and emit it as visible light.

The dyes can in this case, for example, be contained in or respectively on the aforementioned mottled fibers or else can also be present in the form of printing on the substrate.

In connection with the present invention, inter alia WO 00/19016 appears to be relevant, which describes security features having dichroic properties. The security features are in this case applied to a security paper and exhibit either linearly polarized photoluminescence or linearly polarized absorption.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

SUMMARY OF THE INVENTION According to the present invention, there is provided a security feature for a security document in which the authenticity can be determined by means of irradiation with electromagnetic radiation in a spectral range outside the visible range, characterized in that the security feature has a print and/or a substrate and/or a coating which converts the incident electromagnetic radiation into visible light, the print or the substrate or the coating being covered, at least indirectly, by a polarization film.

Advantageously, the invention provides an alternative security feature for a security document, in which the authenticity may be determined by means of irradiation with electromagnetic radiation in a spectral range outside the visible range.

The security feature has a print or a coating or quite generally a function which converts the incident electromagnetic radiation into visible light, the print or the coating or the function being covered, at least indirectly, by a polarization film. Function means that, for example the substrate on which the security feature is applied, can also perform the function itself of converting the incident electromagnetic radiation into visible light.

The core of the invention is thus to provide on one side a feature which cannot be detected by eye when viewed under exclusively visible light but which, when irradiated with UV light or with IR light, suddenly stands out (what is known as photoluminescence). In the case of irradiation with UV light, this is what is known as a 2a Stokes process, in which electromagnetic radiation of high energy (UV) is converted into electromagnetic radiation of low energy (visible light, VIS). In the case of irradiation with IR light, this is what is known as an anti-Stokes process, in which electromagnetic radiation of low energy (IR) is converted into electromagnetic radiation of higher energy (VIS). In addition to this spectral conversion, however, polarization is simultaneously used. This is done in that a coating which fluoresces, for example, or printing which fluoresces, for example, is covered WO 2004/009373 3 PCT/CH2003/000146 !with a polarization film. In this case, the printing can be applied simply and, if appropriate, even be matched specifically to the document (for example press register). As opposed to the prior art, therefore, use is simply made in a very straightforward manner of a sandwich structure which, on the viewing side, has a polarization film above the coating or the printing or the substrate, which converts the incident electromagnetic radiation into visible light.

The security feature is a shaped, flat object which can have an extremely wide range of shapes, for example, but not only, a band, plate, disk, sheet, etc.

If the function of converting the electromagnetic radiation is performed directly by the substrate, then chemical functions which convert the incident electromagnetic radiation into visible light are preferably incorporated in this substrate. In this case, these chemical functions are preferably fluorescent and/or phosphorescent dyes incorporated in the substrate. These can either simply be inlaid in the substrate or else present in the form of fibers dyed with these dyes which are incorporated in the substrate.

According to a first preferred embodiment of the present invention, the incident electromagnetic radiation is UV radiation. In particular, the irradiation can take place in a wavelength range from 200 to 500 nm or even a range from 180 to 500 nm.

Preference is given to irradiation in the range from 200 to 400 nm or 300 to 400 nm. In a corresponding way, the print can then contain at least one fluorescent and/or phosphorescent dye which converts the UV radiation at least partly into visible light. The print can be, in particular, preferably a logo, pattern or a line of text or a combination of these elements.

If, for example, UV radiation is used for the WO 2004/009373 4 PCT/CH2003/000146 irradiation, then the verification of a security feature of this type can be carried out in that either linearly polarized UV light is used for irradiation, the polarization direction of this UV light rotating (for example by a rotating polarizer being placed immediately in front of the UV light source). When viewed in the visible range, the fluorescent symbols lying under the polarization filter then alternately appear and disappear. In other words, so to speak a light/dark or on/off effect is established. This effect can be detected very clearly and permits secure verification; on the other hand this effect can be copied only with a great deal of effort.

In particular in conjunction with this application, polarization filters are of interest in which the absorption is substantially restricted to the wavelength range of the incident excitation radiation and which substantially exhibit no absorption in the visible range, that is to say typically in a range from 400-800 nm, and therefore appear colorless.

Polarization filters with these properties permit the described effect in the sense of the present invention but without disrupting any visible printed image that may be present.

The printing preferably contains at least one photoluminescent dye and/or a photoluminescent pigment or a combination of such components. In this case, the dyes may be, for example, dyes such as Pergasol Flavin 7G, Pergasol Yellow GA, etc. or else optical brighteners such as Blankophor, Uvitex OB-One, etc. can be used. Components based on metal ions or, generally, metals are also suitable. Of course, the effect can additionally be improved by the use of different ranges with different colors.

The polarization film preferably has a thickness of in the range from 5 to 200 pm, in particular preferably .WO 2004/009373 5 PCT/CH2003/000146 ifrom 10 to 75 pm. In this case, the polarization film i should preferably have a dichroic ratio of in the i region of at least 3, in particular preferably of at least 5, in order that the light/dark effect mentioned at the beginning also stands out well.

In addition, the polarization film can be what is known as a photoluminescent polarizer in the sense of, for example, M. Eglin et al., "Ultra-high performance photoluminescent polarizers based on melt-processed polymer blends", J. Mater. Chem. 1999, vol. 9, p. 2221.

Using such a polarization film, an interesting color change effect can be achieved if the emission color of the polarization film differs from the emission color of the substrate or of the printing lying underneath.

If a feature comprising a photoluminescent substrate and a photoluminescent polarizer arranged above the latter is viewed under polarized UV light which changes its polarization axis periodically, either the emission of the polarization film or the emission of the substrate becomes alternately visible, likewise periodically. If the polarization directions of polarization film and excitation light coincide, the light energy is absorbed and is no longer available to excite the substrate, for which reason only the emission from the polarization film is visible. On the other hand, if the polarization directions of polarization film and excitation light are perpendicular to each other, no interaction with the chromophores of the polarization film takes place, for which reason the excitation energy penetrates unimpeded to the substrate and excites the latter to photoluminescence. A polarization film of this type should not absorb, that is to say should be colorless, in the visible range or at least in that range in which the substrate emits.

Another preferred embodiment of the present invention is characterized in that the security feature has WO 2004/009373 S- 6 PCT/CH2003/000146 regions of polarization film with different polarization direction arranged directly beside one another. Thus, when viewed under, for example, a rotating polarization filter, the printed characters behind these different regions also stand out in different time intervals, which produces a very interesting flickering effect. In this case, the polarization directions of mutually adjacent regions can in particular preferably be orthogonal to one another, but it is also possible, by using a plurality of strips with successively changing polarization directions, to obtain so to speak a moving subject when viewed under a rotating polarization filter.

A further preferred embodiment of the present invention is distinguished by the fact that the security feature is applied to a substrate material, the print being printed at least indirectly onto the substrate material and the polarization film being bonded to this print via an adhesion promoter. This embodiment proves to be particularly simple in production, since the substrate material simply has to be provided with photoluminescent printing in a standard process and then, for example, a polarization film provided with a contact adhesive (hot or cold) (so to speak with the effect of a Scotch Tape) has to be adhesively bonded to this printed region.

In another preferred embodiment of the present invention, on the other hand, so to speak the photoluminescent printing is applied to the polarization film. It is distinguished by the fact that the security feature is applied to a substrate material, the print being arranged on the side of the polarization film facing the substrate material, and the polarization film being applied to the substrate material via an adhesion promoter with the side facing the print, if appropriate a film being arranged between print and adhesion promoter. In other words, for WO 2004/009373 7 PCT/CH2003/000146 example in this embodiment, a polarization film provided with a photoluminescent printing and coated with a contact adhesive (printing between polarization film and contact adhesive layer) can simply be dispensed onto the substrate material.

The adhesion promoter is preferably a glue, paste, varnish, adhesive emulsion, solvent adhesive, reaction adhesive or a contact adhesive, which have adequate adhesion for the proper use of the security document.

In addition, in that embodiment in which the adhesion promoter is arranged between printing and polarization film, care should be taken that the adhesion promoter has no absorption properties in the spectral regions used (for example UV and VIS), since otherwise the effect is reduced.

The security feature can be arranged on the substrate, as described above. It is also possible to let the security feature into a depression or cutout in the substrate material, in order that a flush surface of the security document is ensured. A still further embodiment of the invention is correspondingly characterized in that the security feature is arranged in a substrate material in such a way that it can be verified from both sides of the substrate material and/or in transmitted light. In this case, the security feature can have a structure in which at least one printed layer is covered on both sides by a polarization film, it being possible for the two polarization films to have the same or different polarization directions. If there is only one printed layer between the two polarization films, and if the colors used in this printed layer are transparent in the visible range, then a structure of this type appears as a transparent window when viewed exclusively in visible light, while when irradiated with UV light, for example, a print suddenly appears. If, in this case, the two polarization films additionally do not WO 2004/009373 8 PCT/CH2003/000146 have the same polarization direction, an interesting Seffect is established which is different depending on whether viewing is carried out with irradiation from the same side of the substrate material or whether the security feature is viewed in transmitted light on the UV light source. Alternatively, it is of course also possible for two printed layers to be arranged, which are separated by a separating film. This separating film can be configured tobetransparent or translucent in the visible and/or in the UV range.

In order to protect the polarization film against external action, it may prove useful to cover the polarization film with a covering film on the side facing away from the substrate material.

Another embodiment of the present invention is distinguished by the fact that, in addition, the polarization film is also provided with a fluorescent print on the other surface, located at the top. In other words, this fluorescent print is not behind the polarization film when viewed from the same side as the irradiation and, accordingly, this print always remains visible irrespective of the position of, example, a rotating polarization filter used during the observation. This can lead to interesting contrast effects with the signals from the printing arranged behind the polarization film periodically going on/off.

Further preferred embodiments of the security feature are described in the dependent claims.

In addition, the present invention relates to a security document containing a security feature as described above. This can be a banknote, a security, a ticket, a packaging material etc. or else a credit card, bank card, etc.

WO 2004/009373 9 PCT/CH2003/000146 Moreover, the present invention relates to a method for the production of a security document, as cited in the previous paragraph. In this case, first of all the fluorescent print, in particular in the form of a logo, pattern or a line of text, is applied, in particular preferably to a substrate material, and then a polarization film provided with an adhesion promoter is adhesively bonded to the printed region. As an alternative to this, a method for the production of such a security document is proposed which is distinguished by the fact that a security feature already provided with a fluorescent print arranged between adhesion promoter and polarization film is adhesively bonded to a substrate material.

Further preferred embodiments of the method according to the invention for the production of a security document are described in the corresponding dependent claims.

Lastly, the present invention also further relates to a method for the verification of a security feature as was described at the beginning or a security document as cited above. The verification method is characterized in that either linearly polarized UV light whose polarization direction rotates is used for the irradiation or in that unpolarized UV light is used for the irradiation and the observation in the visible range is carried out through a rotating polarization filter. In the process, the light/dark or, respectively, on/off effect already mentioned appears.

The observation can in this case take place either with top light on side of the security document from which the irradiation takes place, or else observation can be carried out in transmitted light (transmission).

WO 2004/009373 10 PCT/CH2003/000146 BRIEF EXPLANATION OF THE FIGURES The invention is to be explained in more detail below using exemplary embodiments in conjunction with the drawings, in which: fig. 1 a) shows a section through a security paper with security feature, the polarizing film being applied to a fluorescent substrate; b) shows a section through a security paper with security feature, the polarizing film being applied to fluorescent printing; fig. 2 a) shows a section through a security paper with security feature, a fluorescently printed polarizing film being applied; b) as a) but, in addition, there is a further film between the fluorescently printed film and the adhesion promoter; fig. 3 a) shows a section through a security feature integrated in a security paper; b) shows a section through a security feature integrated in a security paper and transparent in the visible range; c) shows a section through a security feature integrated in a security paper, which also has printing above the polarization film; fig. 4 shows a functional mechanism under irradiation with polarized UV light, the polarization directions of UV light and polarization film a) being arranged in parallel and b) being arranged orthogonally; fig. 5 shows a functional mechanism under irradiation with unpolarized UV light, observation taking place through a polarization filter whose polarization direction a) is aligned parallel WO 2004/009373 11 PCT/CH2003/000146 with the polarization direction of the polarization film and b) is aligned orthogonally with respect to the polarization direction of the polarization film; fig. 6 shows a functional mechanism in an arrangement corresponding to fig. 5, the polarization film having regions with different polarization direction; fig. 7 shows a section through a laminated polarization fiber with polarizing sheath; and fig. 8 shows structural formulas of the dyes used in the examples.

WAYS OF IMPLEMENTING THE INVENTION Fig. 1 shows a first exemplary embodiment of the present invention. This is a section through a security document. The security document has a substrate i. Here, the substrate 1 can be a paper or plastic film or a mixed form thereof, or else a plastic wafer (cf. for example a credit card). In this exemplary embodiment, the substrate itself contains a fluorescent dye or fluorescent pigment. This fluorescent dye/pigment can, for example in the case of a paper substrate, simply be added in the papermaking process. As a variant, it is also possible to dye fibers with a fluorescent dye and then to add these fibers to the pulp during the papermaking process, so that only these dyed fibers subsequently exhibit a fluorescent effect.

In this case, suitable dyes are the familiar fluorescent dyes or fluorescent pigments; the dyes here can be of an inorganic or organic nature and, in addition, can also contain metals or metal ions.

Suitable, for example, are Uvitex OB ONE (Aldrich .WO 2004/009373 12 PCT/CH2003/000146 368590), Pergasol Yellow 8 GA (Ciba Speciality SChemicals), Tinopal ABP (Bayer), Oxonol (Aldrich 44052-3), Keystone Fluorescent colors, etc. Dyes with similar properties can be found in the range of optical brighteners, for example Blankophor (Bayer) is suitable 'for the production of blue colors.

Between substrate and polarization film there is an adhesion promoter 3, which ensures a firm connection between substrate material 1 and polarization film 2.

In this case, the adhesion promoter used should exhibit no significant absorption in any of the relevant spectral ranges.

Here, the polarization film 2 has a thickness of 10 to pm. Its level of polarization is about 18. A dichroic ratio of about 5 or higher is also possible.

Polarization filters of this type can be obtained, for example, from the Sumitomo or Polaroid companies, or can be produced in accordance with a standard polymer stretching process.

In this connection, it is important that the polarization filter actually acts in a polarizing manner in the relevant spectral ranges, specifically, for example in the case of irradiation with UV light, if possible both in the UV range and in the visible range.

Fig. Ib) shows a further exemplary embodiment, in which a photoluminescent print 4 is applied to the substrate 1. This print can be applied in a standard printing process such as inkjet, gravure printing, offset printing, etc., and can be, for example, text, images, logos, patterns or combinations of such elements, and different colors can be used beside one another. Over the print 4 there is firstly WO 2004/009373 13 PCT/CH2003/000146 A security element of this type can be produced in that, following the printing with the layer or the print 4, a polarization film 2 already provided with the adhesion promoter 3 is dispensed, for example from the roll. If the adhesion promoter is a contact adhesive, then this can be done, for example, by using a laminate in which polarization film and adhesion promoter are covered by a release film and this release film is separated from the polarization film shortly before the dispensing, in such a way that the adhesion promoter 3 remains on the polarization film 2.

A further exemplary embodiment is illustrated in fig.

2a). Here, the print 4 is not located between adhesion promoter 3 and substrate material 1 but instead between adhesion promoter 3 and polarization film 2. A security feature of this type can, for example, be dispensed onto an unprinted substrate material 1, but then the dispensed material already contains the fluorescent print 4 between adhesion promoter 3 and polarization film 2. As illustrated in fig. 2b), it is possible to arrange a film 5 between these two layers in order not to have the print 4 come into direct contact with the adhesion promoter 3.

A further exemplary embodiment is illustrated in fig.

3a). Here, the security feature is, so to speak, incorporated in the substrate material 1. The substrate material 1 has a hole in the region of the security feature. The security feature has the same thickness as the substrate material. The security feature is bounded on the upper side by an upper polarization film 6, and an upper fluorescent printed layer 8 is arranged immediately underneath this upper polarization film 6. There then follows downward, so to speak in the center of the substrate material 1, a separating film 10. This separating film can either be transparent or opaque. Toward the underside there then follows a lower fluorescent printed layer 9, and the WO 2004/009373 14 PCT/CH2003/000146 security feature is terminated toward the underside by lower polarization film 7. A security feature of Sthis type appears different, depending on the viewing side, if the two printed layers 8 and 7 are not configured in exactly the same way. If the separating film 10 is configured so as to be transparent, viewing in transmitted light is also possible.

Fig. 3b) shows an exemplary embodiment in which, once more, the security feature is arranged in the substrate material 1 in a window of this substrate material. In this case, only one fluorescent printed layer 4 is arranged between two polarization films 6 and 7. If here, for example, the fluorescent print 4 is transparent in the visible range, then the security feature appears as a transparent window under normal conditions. On the other hand, if it is irradiated, for example with UV light, and viewed under a rotating polarization filter, then the effect manifests itself in the same manner on both sides if both viewing and irradiation are carried out from the same side. If the two polarization films 6 and 7 are arranged in parallel in their polarization direction, then the security feature also appears substantially identical when viewed in transmitted light (UV light source on one side, viewing from the other side) to when irradiation and viewing are carried out from the same side.

However, if the two polarization films 6 and 7 are arranged orthogonally then, when viewed in transmitted light, the window will simplyappear dark, since two polarizers arranged orthogonally in relation to each other do not allow any light to pass through. The print 4 will not be visible in this case if the dye exhibits polarized emission in the visible range which takes place parallel to the polarization direction of the irradiation. However, if the dye exhibits unpolarized emission in the visible range under polarized irradiation (the irradiation is always polarized because of the polarization film arranged WO 2004/009373 15 PCT/CH2003/000146 above), that is to say even with polarization films arranged crosswise, the print is visible, even if in attenuated form, during such an examination.

A still more complex exemplary embodiment is illustrated in fig. 3c). This is substantially an exemplary embodiment according to fig. 3b) but, in addition, in each case a further fluorescent print 12 is arranged on the outside of the two polarization films 6 and 7. If observation and irradiation take place from the same side of the substrate material 1, this print 12 will exhibit no light/dark or, respectively, on/off effect, since the respective polarization filter is not arranged above it. However, if such a security feature is viewed in transmitted light, then these prints 12, if arranged on the side facing away from the observer, will also exhibit the on/off effect if the two polarization filters 6 and 7 are arranged in parallel.

Fig. 4 shows the method for verification of a security feature of this type, irradiation being carried out with linearly polarized UV light 13. The polarized UV light 13 has a polarization direction which is illustrated by the arrow 14. The security document in turn has a substrate material 1, on which a fluorescent print 4 is arranged behind a polarization film 2. The polarization direction of the polarization film 2 is indicated by the arrow 17. As fig. 4a) illustrates, the result, if the polarization direction 14 of the incident UV light and the polarization direction 17 of the polarization film 2 are arranged in parallel, is visibility of the printing 4 in the visible range, as indicated by the arrow 15 by the observer 16.

If, on the other hand, the polarization direction 14 of the incident UV light 13 is perpendicular to the polarization direction 17 of the polarization film 2, no visible light will be emitted by the printing 4 and WO 2004/009373 16- PCT/CH2003/000146 detectable by the observer 16. In a corresponding way, the line of text will appear and vanish again alternately if the polarization direction 14 is gradually rotated. This is possible, for example, by a polarization filter which rotates at a specific speed being connected in front of a UV light source.

Fig. 5 shows an alternative method for the verification of the security feature. Here, it is unpolarized UV light 18 which is used for the irradiation. The UV light is linearly polarized as it passes through the polarization film 2, it strikes the printing 4, is converted into visible light there and emerges in the direction of the observer, having a polarization direction which is parallel to the polarization direction of the polarization film 2. If the viewer 16 then views this signal with the aid of a polarization filter 19, and if this polarization filter 19 is aligned with its polarization direction 20 parallel to the polarization direction 17 of the polarization film 2, the observer will perceive the line of text (situation in fig. 5a). If, on the other hand, the polarization direction 20 of the polarization filter 19 and the polarization direction 17 of the polarization film 2 are arranged orthogonally, the viewer will see no signal from the line of text 4 (situation fig. Fig. 6 shows an exemplary embodiment analogous to that illustrated in fig. 5, but here the polarization film 2 has regions 2a and 2b which have different polarization directions 17a and 17b, respectively. In a corresponding way, a print 4 arranged behind this polarization film 2 will appear, depending on the relative arrangement of the polarization direction 17a or 17b of the region 2a or 2b and the polarization direction 20 of the polarization filter 19. If, as illustrated in this exemplary embodiment, the two polarization directions 17a and 17b are arranged orthogonally in relation to each other, a line of text WO 2004/009373 17 PCT/CH2003/000146 will in each case either just have vanished or just be visible, that is to say a part of the line of text will always be visible, and the line of text could likewise be easily visible in its entirety, if appropriate given an arrangement of the polarization directions 17 and in the region of 45 degrees.

The present invention can also be applied, in particular in the region of banknotes or the like, in connection with fibrous security elements (mottled fibers). For example, fig. 7 shows a section through a laminated mottled fiber 22. In this case, the fluorescent substrate used is, so to speak, the actual core 24 of the mottled fiber which, for example, can consist of a plastic or else of Lyocell or a natural fiber. The core 24 is, for example, impregnated with a dye or has a dye added to it which is capable of implementing the desired conversion of light outside the visible range into light within the visible range.

In this case, for example when a polymer material is used, the dye can be added before or after melting before the extrusion process, but it is also possible to introduce the dye following shaping.

A polarization film 23 is, so to speak, arranged around this core 24, more in the sense of a sheath. This enveloping polarization film 23 can, for example, be produced together with the core 24 in a coextrusion process, the multi-layer fiber then having to be stretched following this coextrusion process, in order that the layer 23 actually develops the desired polarizing action.

The following text indicates some experimental examples of the production of polarization films which exhibit substantially no absorption in the visible range, that is to say are substantially colorless, and which exhibit polarized absorption outside the visible spectrum, that is to say in practical terms in the WO 2004/009373 18 PCT/CH2003/000146 range of shorter wavelengths, i.e. in the UV range.

The associated structural formulas relating to the dyes specified in the examples are indicated in fig. 8.

EXAMPLE 1 A mixture of 1 g K 2 CO3 (7.2 mmol) and 5 ml dimethylformamide was stirred for 10 min at 70°C under an argon atmosphere. 933.9 mg (4.7 mmol) of p-phenylazophenol was added. 1.46 g (5.8 mmol) of 1-bromododecane was added to the stirred mixture. The mixture was stirred for 3 h at 70 0 C. The mixture was then cooled to room temperature, water was added (3 x 100 ml) and the mixture was extracted with dichloromethane (150 ml).

The organic phase was dried over MgSO 4 filtered and the solvent was rotated off under vacuum. The orange substance obtained was recrystallized from methanol.

1206.0 mg (3.3 mmol, 70%) (dodecyloxyphenyl)phenyldiazene (Ex 1) with a melting point of 77°C was obtained. By means of melt compounding at 180 0 C, a blend of linear low density polyethylene (LLDPE) with 0.2% w/w of the dye was produced, from which isotropic films of 100 pm thickness were pressed at 180 0 C. These films were stretched at temperatures of up to 120 0 C to a stretching rate 1/lo (final length/initial length) of 8. These films exhibited an absorption maximum around 351 nm and a dichroic ratio of 15.8.

The polarization film produced in this way exhibits substantially no absorption above 400 nm, that is to say exhibits virtually no absorption in the visible spectrum. Accordingly, such a film appears transparent and colorless in the visible range.

EXAMPLE 2 202.8 mg (1.03 mmol) p-phenylazoaniline was dissolved in 50 ml of acetone. 10 ml 2 M HC1 and 50 ml H 2 0 were mixed and added to this solution. The solution was WO 2004/009373 19 PCT/CH2003/000146 cooled to 5 0 C. A solution of 105.8 mg (1.5 mmol) NaNO 2 in 50 ml H 2 0 was added slowly while the Sphenylazoaniline solution was stirred, until the iodine-starch paper test indicated a slight excess of nitrous acid (following addition of of 34 g of the NaNO 2 solution). A solution of 125.6 mg (1.3 mmol) phenol in 50 ml H 2 0 and 50 ml 0.1 M NaHCO 3 was produced and cooled to 5 0 C. The solution of diazotized phenylazoaniline was added to this solution with stirring, whereupon a brown precipitate dropped out.

The pH of the mixture was kept at 7.5 by the addition of 1 M NaOH. Following the complete addition of the solution of diazotized phenylazoaniline, the precipitate formed was filtered off under vacuum and dried at 80 0 C/100 mbar. 304.0 mg (1.0 mmol, 97%) 4-(4phenylazophenylazo)phenol was obtained. 151.9 mg mmol) of this intermediate product was etherified in accordance with the method as described in example 1 with 187.3 mg (0.75 mmol) 1-bromododecane. Following recrystallization from ethanol, 199.0 mg (0.4 mmol, 84% based on 4-(4-phenylazophenylazo)phenol) of the product 4-(4-phenylazophenylazo)phenol dodecyl ether (ex 2) was obtained as a dark orange crystalline powder with a melting point of 123 0 C. Stretched films (LLDPE, 0.2% w/w, 1 1 0 8) produced in accordance with the method in example 1 exhibited an absorption maximum around 393 nm with a dichroic ratio of more than 100.

The polarization film produced in this way exhibits substantially no absorption at wavelengths above 500 nm. Accordingly, it appears transparent with a slight yellow cast.

EXAMPLE 3 A mixture of 2.53 g (18.2 mmol) p-nitrophenol and ml H 2 0 was heated to 120 0 C and 11.3 g (45.0 mmol) KOH was added. The mixture was heated to 220 0 C over a time of 30 min, whereupon a highly viscous, dark brown WO 2004/009373 20 PCT/CH2003/000146 mixture was formed with the formation of bubbles. The mixture was kept at 220°C for a further 30 min, until the gas development had decayed. The mixture was cooled to room temperature, dissolved in 150 ml H 2 0 and acidified with concentrated HCI to pH 4. The reaction products were extracted with dimethyl ether (3 x 100 ml), and the combined organic phases were dried over MgS0 4 filtered, and the solvent rotated off. The brown substance obtained was recrystallized from ethanol/H 2 0 The brown crystals obtained were dried at 80 0 C/100 mbar. 964.0 mg (4.5 mmol, 50%) 4,4'dihydroxyazobenzene were obtained. 155.5 mg (0.7 mmol) of this intermediate product were etherified with 438.5 mg (1.76 mmol) 1-bromododecane according to the method in example 1. 366 mg (0.7 mmol, 92% based on 4,4'-dihydroxyazobenzene) of the product bis-(ldodecyloxyphenyl)diazene (Ex 3) was obtained as a soft, crystalline powder with a melting point of 112°C.

Stretched films (LLDPE, 0.2% w/w, 1/0 8) produced in accordance with the method in example 1 exhibited an absorption maximum around 359 nm with a dichroic ratio of more than 100.

This film exhibits substantially no absorption above 420 nm. It appears transparent and colorless in the visible range.

EXAMPLE 4 151.4 mg (0.7 mmol) 4,4'-dihydroxyazobenzene (synthesis described in example 2) was dissolved in 10 ml waterfree pyridine. 440.0 mg (1.8 mmol) 4-hexyloxybenzyl chloride was added at room temperature with stirring.

After 2 h H 2 0 (3 x 100 ml) was added to the mixture and it was extracted with CH 2 C1 2 (150 ml). The organic phase was dried over MgSO 4 filtered, and the solvent was rotated off. The orange substance obtained was recrystallized from methanol/chloroform Following drying at 80 0 C/100 mbar, 425.0 mg (0.7 mmol, WO 2004/009373 21 PCT/CH2003/000146 168%) of the product azodi-4,1-[(hexyloxy)]phenyl Sbenzoate (Ex 4) was obtained as luminous orange crystals with a melting point of 172 0 C. Stretched films (LLDPE, 0.2% w/w, l/l0 8) produced in accordance with the method in example 1 exhibited an absorption maximum around 345 nm with a dichroic ratio of more than 100. Films based on nylon 12 with 0.2% w/w of the dye were produced in accordance with the same method at 240 0 C and stretched to a stretching level of 4 at 110 0 C. These films exhibited an absorption maximum around 365 nm with a dichroic ratio of 6.5. Films based on polyethylene terephthalate (PET) with 0.2% w/w of the dye were produced by the same method at 280 0

C

and stretched to a stretching level of 4 at 180 0

C.

These films exhibited an absorption maximum around 346 nm with a dichroic ratio of 19.

This polarization film exhibits no absorption above 400 nm and accordingly appears transparent and colorless in the visible range.

EXAMPLE 200.7 mg (0.95 mmol) 4,4'-azodianiline was reacted with hexyloxybenzoyl chloride according to the rule in example 4. Recrystallization from dimethylsulfoxide supplied 534.2 mg of the product N,N'-(azodi-4,1phenylene)bis-benzamide (Ex 5) as brownish-yellow platelets with a melting point of 313 0 C. Films based on nylon 12 with 0.2% w/w of the dye were produced in accordance with the method described in example 4 at 240 0 C and stretched to a stretching level of 4 at 110 0 C. These films exhibited an absorption maximum around 385 nm with a dichroic ratio of 17. Films based on polyethylene terephthalate (PET) with 0.2% w/w of the dye were produced by the same method at 280 0 C and stretched to a stretching level of 4 at 180 0 C. These films exhibited an absorption maximum around 385 nm with a dichroic ratio of 27.

WO 2004/009373 22 PCT/CH2003/000146 This polarization film likewise exhibits substantially no absorption above 400 nm and appears transparent and colorless in the visible range.

WO 2004/009373 23 PCT/CH2003/000146 LIST OF DESIGNATIONS 1 Substrate material, security paper 2 Polarization film 3 Adhesion promoter 4 Fluorescent print Film 6 Upper polarization film 7 Lower polarization film 8 Upper fluorescentprinted layer 9 Lower fluorescent printed layer Separating film 11 Covering film 12 Fluorescent print above polarization film 13 Incident UV light, linearly polarized 14 Polarization direction of 13 Emitted, visible light 16 Viewer 17 Polarization direction of 2 18 Incident, unpolarized light 19 Polarization filter Polarization direction of 19 21 Emitted, visible light 22 Mottled fiber 23 Enveloping polarization film 24 Core of the mottled fiber

Claims

2. The security feature as claimed in claim 1, characterized in that the security feature has a substrate in which chemical functions are incorporated which convert the incident electromagnetic radiation into visible light, these chemical functions preferably being fluorescent and/or phosphorescent dyes incorporated in the substrate, and these being in particular preferably in the form of fibers dyed with these dyes, which are incorporated in the substrate.
3. The security feature as claimed in one of the preceding claims, characterized that the incident electromagnetic radiation is UV radiation, and in that the print, the substrate and/or and the coating contains at least one fluorescent and/or phosphorescent dye and/or pigment which converts the UV radiation at least partly into visible light, the print being in particular preferably a logo, a pattern or a line of text or a combination of these elements.
4. The security feature as claimed in one of the preceding claims, characterized in that the polarization film is substantially colorless and transparent in the visible range, that is to say in particular in the range between 400 and 800 nm. The security feature as claimed in one of the preceding claims, characterized in that the printing and/or the substrate and/or the coating contains at least one photoluminescent dye or a combination of such dyes.
6. The security feature as claimed in one of the preceding claims, characterized in that the polarization film has a thickness of in the range from 5 to 200 in particular preferably from 10 to 75 lm, and/or a dichroic ratio of in the range of greater than 3, in particular preferably of greater than 5 or even 7.
7. The security feature as claimed in one of the preceding claims, characterized in that the polarization film is a photoluminescent polarization film, the emission color of the photoluminescent polarization film preferably being a different one from the emission color of the photoluminescent dye or, respectively, of the combination of such dyes, of the printing and/or of the substrate and/or of the coating.
8. The security feature as claimed in one of the preceding claims, characterized in that the security feature has regions of polarization film with different polarization direction arranged directly beside one another, the polarization directions of mutually adjacent regions in particular preferably being orthogonal to one another.
9. The security feature as claimed in one of the preceding claims, characterized in that it is applied to a substrate material, the print being printed at least indirectly onto the substrate material and the polarization film being fixed to this print via an adhesion promoter. The security feature as claimed in one of claims I to 8, characterized in that it is applied to a substrate material, the print being arranged on the side of the polarization film facing the substrate material, and the polarization film being applied to the substrate material via an adhesion promoter with the side facing the print, if appropriate a film being arranged between print and adhesion promoter.
11. The security feature as claimed in either of claims 9 and 10, characterized in that the adhesion promoter is a glue, paste, varnish, adhesive emulsion, solvent adhesive, reaction adhesive or a contact adhesive, which have adequate adhesion for the proper use of the security document.
12. The security feature as claimed in one of claims I to 8, characterized in that it is arranged in a substrate material in such a way that it can be verified from both sides of the substrate material and/or in transmitted light.
13. The security feature as claimed in claim 12, characterized in that it has a structure in which at least one printed layer is covered on both sides by a polarization film, it being possible for the two polarization films to have identical or different polarization directions.
14. The security feature as claimed in claim 12, characterized in that two printed layers are arranged, which are separated by a separating film. The security feature as claimed in one of the preceding claims, characterized in that the polarization film is covered with a covering film on the side facing away from the substrate material.
16. The security feature as claimed in one of the preceding claims, characterized in that the polarization film is also provided with a fluorescent print on the other surface.
17. The security feature as claimed in one of the preceding claims, characterized in that the substrate is a fiber with a length in the range from I to 20 mm, in particular preferably of a plastic, and in that the polarization film envelops this substrate. 15/06 '07 11:37 FAX 61282311099 FBRC O 0 F B RICE CO. 16002 o 26
18- A security document containing a security feature as claimed in one of claims 1 ;Z to 17, the security document p-referably being in particular a banknote, a security, a V) ticket or a packaging material.
19. A method for the production of a security document as claimed in claim i8, characterized in that, in the case of a printing or coating, first of all the fluorescent print Or, respectively, the coating is applied to a substrate material, in particular in the form ON of a logo, pattern or a line of text, and then a polarization film provided with an V) adhesion promoter is adhesively bonded to the printed/coated region, and in that, in the Cl case of a substrate with fluorescent components, a polarization film provided with an adhesion Promoter is adhesively bonded directly to this substrate. The method for the production of a security document as claimed in claim 18, characterized in that a security feature already provided with a fluorescent print arranged between adhesion promoter and polarization film is adhesively bonded to a substrate material.
21. A method for the verification of a security feature as claimed in one of claims J to 17 or of a security document as claimed in claim 18, characterized in that either linearly polarized UV light whose polarization direction rotates is used for the irradiation or in that unpolarized UV light is used for the irradiation and the observation in the visible range is carried out through a rotating polarization filter, the observation taking place either on the side of the security document from which the irradiation takes place, or an observation is carried out in transmission.
22. A security feature for a security document in which the authenticity can be determined by means of irradiation with electromagnetic radiation in a spectral range outside the visible range substantially as hereinibefore described with reference to the accompanying drawings. Dated this seventh day of June 2007 Landqart Patent Attorneys for the Applicant: F B RICE CO COMS ID No: SBMI-07780683 Received by IP Australia: Time 11:38 Date 2007-06-15