EP1523415B1 - Security feature for value documents - Google Patents

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

TECHNICAL AREA

The present invention relates to a security feature for a security document in which the authenticity can be determined by irradiation of electromagnetic radiation in a spectral range outside the visible range.

STATE OF THE ART

It is well known that to secure security documents or generally security articles such. For example, banknotes, checks, stocks, bonds, identity cards, passports, banknotes, tickets, tokens, as well as credit cards, bank cards and similar security features can be used to authenticate the document. So today z. B. used in this context Sicherheitsheilsfäden, security strips, holograms and mottled fibers. Among other things, particular features are used which are not recognizable when viewed in the visible light of the eye, but which emerge suddenly under the influence of UV light. This can be achieved by the use of fluorescent dyes which absorb the incident UV light and emit it as visible light. In this case, the dyes can be present, for example, in the respective mottling fibers, or they can also be present in the form of a printing on the carrier.

In connection with the present invention, inter alia, the WO 00/19016 relevant, describing soft security features with dichroic properties. The security features are applied to a security paper and show either linearly polarized photoluminescence or linearly polarized absorption.

PRESENTATION OF THE INVENTION

The invention is therefore based on the object of providing an alternative security feature for a security document in which the authenticity can be determined by irradiation of electromagnetic radiation in a spectral range outside the visible range.

The solution to this problem is achieved in that the security feature has a pressure or a coating or more generally a function that converts the radiated electromagnetic radiation into visible light, wherein the pressure resp. the coating or the function is at least indirectly covered by a polarizing film. Function means that also e.g. the carrier on which the security feature is applied can itself take over the function of converting the irradiated electromagnetic radiation into visible light.

The core of the invention is therefore to provide on the one hand a feature available, which can not be recognized by the eye when viewed under exclusively visible light, but which suddenly emerges when exposed to UV light or IR light (see above) called photoluminescence). In the case of irradiation with UV light is a so-called Stokes process in which high-energy electromagnetic radiation (UV) is converted into low-energy electromagnetic radiation (visible light, VIS). In the case of irradiation with IR light is a so-called 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 utilized at the same time. This, by a z. B. fluorescent coating or a z. B. fluorescent printing is covered with a polarizing film. The printing can be easily applied and, if necessary, even adapted to the document (eg press register). In contrast to the prior art, a sandwich structure is thus used in a very simple manner, which on the viewing side, a Polarisatiousfolie above the coating, respectively. the printing resp. of the carrier, which converts the irradiated electromagnetic radiation into visible light.

The security feature is a shaped, planar object which can identify a variety of forms, eg. B., but not only, tape, disk, disk, sheet, etc ..

If the function of converting the electromagnetic radiation is taken over directly by the carrier, preferably chemical functions are incorporated into this carrier, which convert the irradiated electromagnetic radiation into visible light. These chemical functions are preferably fluorescent and / or phosphorescent dyes incorporated in the support. These can either be incorporated simply in the carrier or else in the form of fibers dyed with these dyes which are incorporated in the carrier.

According to a first preferred embodiment of the present invention, the irradiated electromagnetic radiation is UV radiation. In particular, the irradiation may take place in a wavelength range of 200 to 500 nm or even in a range of 180 to 500 nm. Preferably, an irradiation in the range of 200 to 400 nm or 300 to 400 nm. Accordingly, then the print at least one fluorescent and / or phosphorescent dye containing at least partially converts the UV radiation into visible light. The printing may in particular preferably be a logo, a pattern, or a lettering or a combination of these elements. If, for example, UV radiation is used for the irradiation, the verification of such a security feature can be effected by irradiating either linearly polarized UV light, the polarization direction of this UV light rotating (eg by a rotating polarizer immediately in front of the UV light source is set). When viewed in the visible range, the fluorescent signs under the polarizing filter then appear and disappear in interplay. In other words, it turns out to be a light-spelled or on / off effect. This effect is very clear and allows a safe verification, on the other hand, this effect can be copied only with great effort.

Particularly in the context of this embodiment, polarizing filters are of interest, in which the absorption is limited essentially to the wavelength range of the irradiated excitation radiation and which is substantially in the visible range, i. typically in a range of 400-800 nm, have no absorption and therefore appear colorless. Polarizing filter with these properties allow the described effect in the context of the present invention, but without disturbing a possibly present visible printed image.

The printing preferably contains at least one photoluminescent dye and / or one photoluminescent pigment or a combination of such components. These may be dyes such. 13. Pergasol Flavin 7G, Pergasol Yellow GA, etc., but also optical brighteners such. Blankophor, Uvitex OB-One etc. can be used. Also on metal ions or metals generally based components come into question. Of course, the effect can be further improved by using different areas of different colors.

The polarizing film preferably has a thickness of in the range of 5 to 200 .mu.m, more preferably of 10 to 75 .mu.m. In this case, the polarizing film should preferably have a dichroic ratio of in the range of at least 3, in particular preferably of at least 5, so that the light / dark effect mentioned at the outset also emerges well.

The polarizing film may also be a so-called photoluminescent polarizer in the sense of z. BM Eglin et al., "Ultra-high performance photoluminescent polarizers based on melt-processed polymer blends," J. Mater. Chem. 1999, vol. 9, p. 2221 , act. With such a polarizing film leaves When a feature consisting of a photoluminescent substrate and an overlying photoluminescent polaristor under polarized UV light is observed, which periodically changes its polarization axis, also an interesting color-change effect will result if the emission color of the polarizing film differs from the emission color of the substrate or underlying printing periodically changing either the emission of the polarizing film or the emission of the substrate visible. If the polarization directions of the polarizing film and the excitation light coincide, the light energy is absorbed and is no longer available for exciting the substrate, so that only the emission of the polarizing film is visible. On the other hand, when the polarization directions of the polarizing film and the incident light are perpendicular to one another, there is no interaction with the chromophores of the polarizing film, which is why the excitation energy passes unhindered through the substrate and excites it to undergo pholuminescence. Such a polarization film should not absorb in the visible range, or at least in that area in which the substrate emits, ie be colorless.

Another preferred embodiment of the present invention is characterized in that the security feature has juxtaposed regions of polarization film with different polarization direction. So occur when viewed under z. B. a rotating polarization filter the printed characters behind these different areas also in different periods, which produces a very interesting flick-flare effect. In this case, the polarization directions of adjoining areas can be particularly preferably orthogonal to one another, but it is also possible to obtain a moving subject as viewed under a rotating polarization filter by using several strips with successively changing polarization direction.

A further preferred Ausrtihrungsform of the present invention is characterized in that the security feature is applied to a substrate, wherein the pressure is at least indirectly printed on the substrate, and the Polarizing film is connected via a bonding agent on this print. This embodiment proves to be particularly easy to manufacture, since the carrier material must be simply provided in a standard method with a photoluminescent printing, and then z. B. a provided with a pressure-sensitive adhesive (hot or cold) polarizing film (to some extent in the sense of a Scotch tape) must be adhered to this printing area.

In another preferred embodiment of the present invention, however, to some extent the photoluminescent printing is applied to the polarizing film. It is characterized in that the security feature is applied to a carrier material, wherein the pressure on the side facing the carrier material of the polarizing film is arranged, and wherein the polarizing film is applied to the pressure-facing side via a coupling agent on the carrier material, optionally a film is arranged between print and adhesion promoter. In other words, z. B. in this embodiment, provided with a photoluminescent printing and coated with a pressure-sensitive adhesive polarizing film (printing between polarizing film and pressure-sensitive adhesive layer) are simply applied to the carrier material.

The adhesion promoter is preferably a glue, paste, lacquer, dispersion adhesive, solvent adhesive, reaction adhesive or a contact adhesive which has an adhesion sufficient for the intended use of the security document. In addition, in the embodiment in which the adhesion promoter is arranged between printing and polarizing film, the adhesion promoter should be ensured that the adhesion promoter has no absorption properties in the spectral regions used (eg UV and VIS), since otherwise the effect is diminished ,

The security feature may be disposed on the carrier as described above. It is also possible to admit the security feature in a recess or recess of the carrier material, so that a flush surface of the security document is ensured. Yet another embodiment of the invention is accordingly characterized in that the security feature is arranged in a carrier material such that it can be verified from both sides of the carrier material and / or in a transparent view. In this case, the security feature may have a structure in which at least one. Printing layer is covered on both sides of a polarizing film, wherein the two Potarisationsfolien may have the same or different polarization direction. If there is only one printing layer between the two polarizing films, and if the colors used in this printing layer are transparent in the visible range, then such a structure appears as a transparent window only in the visible light, while on irradiation, for example. B. with UV light suddenly appears a pressure. In addition, if in this case the two polarization films do not have the same direction of polarization, an interesting effect arises, which differs depending on whether observation is made under irradiation from the same side of the substrate or if the security feature is considered in view of the UV light source , Alternatively, it is of course also possible that two printing layers are arranged, which are separated from a release film. This release film can be transparent or transparent in the visible and / or UV range.

In order to protect the polarization film from external exposure, it may prove useful to cover the polarization film on the side facing away from the carrier material with a cover film.

Another embodiment of the present invention is characterized in that, in addition, the polarizing film is also provided with a fluorescent printing on the other, uppermost surface. In other words, when viewed from the same side as the irradiation, this fluorescent pressure is not behind the polarizing film, and accordingly this pressure remains independent of the position of a z. B. always used in the observation used rotating polarizing filter. This can lead to interesting contrast effects with the periodically incoming / outgoing signals of the arranged behind the Polarisalionsfolie printing.

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

Moreover, the present invention relates to a security document containing a security feature as described above. This may be a banknote, a security, a ticket, a packaging material, etc., or even a credit card, bank card, etc.

Furthermore, the present invention relates to a method for producing a security document, as mentioned in the preceding paragraph. In this case, the fluorescent printing, in particular in the form of a logo, pattern, or lettering, is preferably applied to a carrier material first, and then a polarizing film provided with an adhesion promoter is adhered to the printed area. Alternatively, a method for adjusting such a security document is proposed which is characterized in that a security feature already provided with a fluorescent print arranged between adhesion promoter and polarization film is adhered to a carrier material.

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

Finally, the present invention also relates to a method for verifying a security feature as described above or a security document as mentioned above. The method for verification is characterized in that either linearly polarized UV light is irradiated, the polarization direction of which is rotated, or that unpolarized UV light is irradiated, and the observation in the visible range is effected by a rotating polarization filter. The already mentioned light / dark respectively on / off effect appears. The observation can take place either on the side in the incident light of the security document, from which the irradiation occurs, or it can be an observation in transmittance (transmission).

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

a) einen Schnitt durch ein Sicherheitspapier mit Sicherheitsmerkmal, wobei die polarisierende Folie auf einen fluoreszierenden Träger aufgebracht ist; b) einen Schnitt durch ein Sicherheitspapier mit Sicherheitsmerkmal, wobei die polarisierende Folie auf eine fluoreszierende Bedruckung aufgebracht ist;

Fig. 2

a) einen Schnitt durch ein Sicherheilspapier mit Sicherheitsmerkmal, wobei eine fluoreszierend bedruckte polarisierende Folie aufgebracht ist ; b) wie a), zusätzlich befindet sich aber zwischen der fluoreszierend bedruckten Folie und dem Haftvermittler eine weitere Folie.

Fig.

3 a) einen Schnitt durch ein in einem Sicherheitspapier integriertes Sicherheitsmerkmal; b) einen Schnitt durch ein in einem Sicherheitspapier integriertes, für den sichtbaren Bereich transparentes Sicherheitsmerkmal; c) einen Schnitt durch ein in einem Sielici-lleitspapier integriertes Sicherheitsmerkmal, welches auch über Bedruckung oberhalb der Polarisationsfolie verfügt;

Fig. 4

Funktionsmechanismus bei Einstrahlung mit polarisiertem UV-Licht, wobei die Polarisationsrichtungen von UV-Licht und Polarisationsfolie a) parallel und b) orthogonal angeordnet sind;

Fig. 5

Funktionsmechanismus bei Einstrahlung mit unpolarisiertem UV-Licht, wobei die Betrachtung durch einen Polarisationsfilter geschieht, dessen Polarisationsrichtung a) parallel zur Polarisationsrichtung der Polarisationsfolie und b) orthogonal zur Polarisationsrichtung der Polarisationsfolie ausgerichtet ist;

Fig. 6

Funktionsmechanismus bei einer der Fig. 5 entsprechenden Anordnung, wobei die Polarisationsfolie Bereiche mit unterschiedlicher Polarisationsrichtung aufweist;

Fig. 7

Schnitt durch eine kaschierte Polarisationsfaser mit Polarisierender Umhüllung; und

Fig. 8

Strukturformeln der in den Beispielen verwendeten Farbstoffe.

The invention will be explained in more detail with reference to embodiments in conjunction with the drawings. Show it:

Fig. 1

a) a section through a security paper with security feature, wherein the polarizing film is applied to a fluorescent support; b) a section through a security paper with security feature, wherein the polarizing film is applied to a fluorescent printing;

Fig. 2

a) a section through a security paper with security feature, wherein a fluorescently printed polarizing film is applied; b) as a), but in addition there is another film between the fluorescently printed film and the adhesion promoter.

FIG.

3 a) a section through a security feature integrated in a security paper; b) a section through an integrated in a security paper, transparent to the visible area security feature; c) a section through a safety feature integrated in a guide paper which also has printing above the polarization film;

Fig. 4

Function mechanism when irradiated with polarized UV light, the polarization directions of UV light and polarizing film a) are arranged in parallel and b) orthogonal;

Fig. 5

Function mechanism when irradiated with unpolarized UV light, wherein the observation is done by a polarizing filter whose polarization direction a) is aligned parallel to the polarization direction of the polarizing film and b) orthogonal to the polarization direction of the polarizing film;

Fig. 6

Function mechanism in one of Fig. 5 corresponding arrangement, wherein the polarizing film has regions with different polarization direction;

Fig. 7

Section through a laminated polarizing fiber with polarizing cladding; and

Fig. 8

Structural formulas of the dyes used in the examples.

WAYS FOR CARRYING OUT THE INVENTION

Fig. 1 shows a first embodiment of the present invention. It is a section through a security document. The security document has a carrier 1. The carrier 1 can be a paper or a plastic film or else a mixed form thereof, or a plastic disk (cf., for example, a credit card). The carrier itself contains a fluorescent dye or a fluorescent pigment in this embodiment. For example, this fluorescent dye / pigment can be easily added to a paper support in the papermaking process. In a variant, it is also possible to dye fibers with a fluorescent dye, and then add these fibers to the papermaking process of the pulp so that subsequently only these dyed fibers exhibit a fluorescence effect.

Suitable dyes are the common fluorescent dyes or fluorescent pigments in question, the dyes may be inorganic or organic nature, and may also contain metals or metal ions. In carrying come for example z. B. Uvitex OB ONE (Aldrich 368590), Pergasol Yellow 8 GA (Ciba Specialty Chemicals), Tinopal ABP (Bayer), Oxonol (Aldrich 44052-3), Keystone Fluorescent Colors, etc .. Dyes with similar properties may be used in the field of optical Brightener can be found, so z. B. Blankophor (Bayer) to produce blue colors.

Between carrier and polarizing film is a bonding agent 3, which ensures a firm connection between the substrate 1 and polarizing film 2. The adhesion promoter used should have no significant absorption in any of the relevant spectral regions.

The polarizing film 2 has a thickness of 10 to 30 microns. you Polarisal degree is about 18. It is also possible a dichroic ratio of about 5 or higher. Such polarization filters can, for. B. at the companies Sumitomo or Polaroid, or can be prepared by a standard polymer stretching method.

It is important in this context that the polarization filter in the relevant spectral ranges actually has a polarizing effect, namely z. B. when exposed to UV light possible both in the UV range and in the visible range.

Fig. 1b ) shows a further embodiment in which a photoluminescent pressure 4 is applied to the carrier 1. This print may be applied in a standard printing process such as ink jet, gravure, offset printing, etc., and may be typefaces, images, logos, patterns, or combinations of such elements, and different colors may be used side by side , Above the pressure 4 is initially

Such a security feature can be made by after the printing with the layer respectively the pressure 4 z. B. from a roll already provided with the bonding agent 3 polarizing film 2 is dispensed. If the adhesion promoter is a contact adhesive, this can be done, for example, by Example, using a laminate, in which polarizing film and adhesion promoter are covered with a release film, and this release film is separated just before dispensing of the polarizing film such that the bonding agent 3 remains on the polarizing film 2

Another embodiment is in Fig. 2a ). Here, the pressure is not 4 between primer 3 and substrate 1, but rather between primer 3 and polarizing film 2. Such a security feature can, for. B. aufgespendet on a blank substrate 1, but then the donor material already contains the fluorescent pressure 4 between 3 adhesion promoter and polarizing film 2. As in Fig. 2b ), it is possible, in order to prevent the pressure 4 from coming into direct contact with the adhesion promoter 3, to arrange a film 5 between these two layers.

Another embodiment is in Fig. 3a ). In this case, the security feature is incorporated into the carrier material 1 to some extent. The carrier material 1 has a hole in the area of the security feature. The security feature has the same thickness as the substrate. The security feature is limited to the top by an upper polarizing film 6, and immediately below this upper polarizing film 6, an upper fluorescent printing layer 8 is arranged. Now follows, down to a certain extent in the middle of the substrate 1, a release film 10. This release film can be either transparent or opaque. Towards the bottom, a lower fluorescent printing layer 9 follows, and the security feature is closed at the bottom by a lower polarizing film 7. Such a security feature view depending on the viewing page differently, unless the two print layers 8 and 7 are not configured exactly the same. If the release film 10 is designed to be transparent, it is also possible to see through in a transparent manner.

Fig. 3b ) shows an embodiment in which again the security feature in the substrate 1 is arranged in a window of this substrate. In this case, only one fluorescent printing layer 4 is arranged between two polarizing films 6 and 7. Is here z. For example, if the fluorescent pressure 4 is transparent in the visible range, the security feature appears as a transparent window under normal conditions. If it is, however, with z. B. irradiated UV light, and viewed under a rotating polarizing filter, the effect is shown in a similar manner on both sides, when both viewing and irradiation done from the same side. If the two polarizing films 6 and 7 are arranged in parallel in their polarization direction, the security feature also appears substantially the same when viewed in phantom (UV light source on one side, viewing from the other side), as if irradiation and viewing from the same side respectively. If the two polarizing film 6 and 7 but z. B. arranged orthogonally, the window will simply appear dark when viewed in phantom, since two orthogonal polarizers arranged to pass no light. The pressure 4 will not be visible when the dye in the visible range shows a polarized emission which parallel to Polarization direction of the irradiation takes place. However, if the dye polarized irradiation (the radiation is always polarized because of the polarizing film arranged above it) unpolarized emission in the visible range, that is even with crossed polarizing films in such a view, the pressure, although possibly weakened visible.

An even more complex embodiment is in Fig. 3c ). Essentially, this is an embodiment gem. Fig. 3b ) but in addition aussenscitig on the two polarizing films 6 and 7 each have a further fluorescent pressure 12 is arranged. This pressure 12, when observed and irradiated from the same side of the substrate 1, will show no light / dark or on / off effect, since the respective polarizing filter is not disposed above it. However, if such a security feature is viewed in phantom, then these prints 12, if arranged on the side facing away from the observer, will show the on / off effect, provided that the two polarizing films 6 and 7 are arranged in parallel.

Fig. 4 shows the method for verification of such a security feature, wherein is irradiated with linearly polarized UV light 13. The polarized UV light 13 has a polarization direction, which is shown by the arrow 14. The security document in turn has a carrier material 1, on which a fluorescent printing 4 is arranged behind a polarizing film 2. The polarization direction of the polarizing film 2 is indicated by the arrow 17. As in Fig. 4a ), when the polarization direction 14 of the irradiated UV light and the polarization direction 17 of the polarization film 2 are arranged in parallel, a visibility of the printing 4 in the visible range, as indicated by the arrow 15 in the viewer 16 results.

Conversely, if the direction of polarization 14 of the irradiated UV light 13 is perpendicular to the polarization direction 17 of the polarization film 2, no visible light is emitted from the printing 4 and can be recognized by the observer 16. Accordingly, the lettering will appear alternately and disappear again when the polarization direction 14 is successively rotated. This is z. B. possible by a UV light source is preceded by a polarizing filter which rotates at a certain speed.

Fig. 5 shows an alternative method of verification of the security feature. This is unpolarized UV light 18, which is irradiated. The UV light is linearly polarized when passing through the Polarisalionsfolie 2, hits the printing 4, where it is converted into visible light, and emerges in the direction of the viewer, wherein it has a polarization direction which is parallel to the polarization direction of the polarizing film 2. If the observer 16 now considers 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 lettering (situation in FIG Fig. 5a ). If, however, 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 of the lettering 4 (situation Fig. 5b ).

Fig. 6 shows an embodiment analogous to that in Fig. 5 illustrated, but here the polarizing film 2 has regions 2a and 2b, which have different polarization directions 17a and 17b. Correspondingly, a pressure 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 shown in this embodiment, the two polarization directions 17a and 17b are arranged orthogonal to each other, a lettering will either be either just disappeared or just be visible, ie a part of the lettering will always be visible, the lettering possibly in the arrangement of Polarization directions 17 and 20 in the range of 45 degrees as a whole could also be easily visible.

Also in connection with fibrous security elements (mottled fibers), the present invention can be applied in particular in the field of banknotes or the like. So shows, for example Fig. 7 a section through a laminated mottled fiber 22 serves as a fluorescent substrate, so to speak, the actual core 24 of the mottled fiber, which, for example, from a plastic or can also be made of Lyocell or a natural fiber. The core 24 is soaked, for example, in a dye which is capable of converting the desired conversion of light outside the visible range to light within the visible range. The dye can be added, for example, when using a polymeric material before or after melting prior to the extrusion process, but it is also possible to introduce the color after shaping.

To this core 24 is to a certain extent a polarizing film 23, more in the sense of a sheath, arranged. This enveloping polarizing film 23 can be produced, for example, together with the core 24 in a coextrusion process, after which the multilayered fiber has to be stretched after this coextrusion process so that the layer 23 actually exhibits the desired polarizing effect.

The following are some experimental examples of the preparation of polarizing films which show substantially no absorption in the visible range, ie are substantially colorless, and which outside the visible spectrum, ie specifically in the range of shorter wavelengths, ie in the UV range, a polarized absorption demonstrate. The associated structural formulas for the dyes specified in the examples are given in Fig. 8 specified.

EXAMPLE 1

A mixture of 1 g K ₂ CO ₃ (7.2 mmol) and 5 mL anhydrous dimethylformamide was stirred under argon atmosphere at 70 ° C for 10 min. 933.9 mg (4.7 mol) of p- phenylazophenol were 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 ° C. The mixture was then cooled to room temperature, water was added (3 × 100 ml) and the mixture was extracted with dichloromethane (150 ml). The organic phase was dried over MgSO4, filtered, and the solvent was rotary evaporated in vacuo. The resulting orange substance was recrystallized from methanol. There were 1206.0 mg (3.3 mmol, 70%) (4-dodecyloxy-phenyl) -phenyl diazene (Ex 1) with obtained a melting point of 77 ° C. Melt compounding at 180 ° C. produced a blend of linear low density polyethylene (LLDPE) at 0.2% w / w of the dye, from which isotropic films of 100 μm thickness were pressed at 180 ° C. These films were stretched at temperatures up to 120 ° C to a draw rate l / l ₀ (final length / initial length) of 8. These films showed an absorption maximum around 351 nm and a dichroic ratio of 15.8.

The thus prepared polarizing film shows substantially no absorption above 400 nm, i. H. in the visible spectrum it shows almost no absorption. Accordingly, such a film appears transparent and colorless in the visible range

EXAMPLE 2

202.8 mg (1.03 mmol) of p-phenylazoaniline were dissolved in 50 mL of Accton. 10 mL 2 M HCl and 50 mL H ₂ O were mixed and added to this solution. The solution was cooled to 5 ° C. A solution of 105.8 mg (1.5 mmol) NaNO ₂ in 50 mL H ₂ O was slowly added with stirring to the phenylazoaniline solution until the iodine starch assay indicated a slight excess of nitrous acid (after addition of 34 g of NaNO ₂₎ . Solution). A solution of 125.6 mg (1.3 mmol) of phenol in 50 mL H ₂ O and 50 mL of 0.1 M NaHCO ₃ was prepared and cooled to 5 ° C. To this solution was added with stirring the solution of diazotized phenylazoaniline, whereupon a brown precipitate precipitated. The pH of the mixture was maintained at 7.5 by the addition of 1 M NaOH. After complete addition of the solution of diazotized Phenylazoanilin the precipitate formed was filtered off under vacuum and dried at 80 ° C / 100 mbar. There were obtained 304.0 mg (1.0 mmol, 97%) of 4- (4-phenylazo-phenylazo) -phenol. 151.9 mg (0.5 mmol) of this intermediate was etherified by the method described in Example 1 with 187.3 mg (0.75 mmol) of 1-bromododecane. After recrystallization from ethanol, 199.0 mg (0.4 mmol, 84% based on 4- (4-phenylazo-phenylazo) -phenol) of the product 4- (4-phenylazo-phenylazo) -phenol dodecyl ether (Ex 2) as a dark orange, crystalline Powder having a melting point of 123 ° C obtained. Drawn movies (LLDPE, 0.2% w / w, l / l ₀ = 8) prepared by the method in Example 1 showed an absorption maximum around 393 nm with a dichroic ratio over 100.

The polarization film thus produced shows substantially no absorption at wavelengths above 500 nm. Accordingly, it appears transparent with a slight yellow tinge.

EXAMPLE 3

A mixture of 2.53 g (18.2 mmol) p -nitrophenol and 2.5 mL H ₂ O was heated to 120 ° C and treated with 11.3 g (45.0 mmol) of KOH. The mixture was heated to 220 ° C over a period of 30 minutes, whereupon a high viscosity, dark brown mixture formed with bubbling. The mixture was held at 220 ° C for a further 30 minutes until gas evolution subsided. The mixture was cooled to room temperature, dissolved in 150 mL H ₂ O and treated with conc. HCl acidified to pH 4. The reaction products were extracted with dimethyl ether (3x 100 mL) and the combined organic phases were dried over MgSO ₄ , filtered, and the solvent spun off. The resulting brown substance was recrystallized from ethanol / H ₂ O (1: 1). The resulting brown crystals were dried at 80 ° C / 100 mbar. 964.0 mg (4.5 mmol, 50%) of 4,4'-dihydroxyazobenzene were obtained. 155.5 mg (0.7 mmol) of this intermediate were etherified with 438.5 mg (1.76 mmol) of 1-bromododecane by the method in Example 1. 366 mg (0.7 mmol, 92% based on 4,4'-dihydroxyazobenzene) of the product bis (4-dodecyloxyphenyl) diazene (Ex 3) was obtained as a soft, crystalline powder having a melting point of 112 ° C. Stretched films (LLDPE, 0.2% w / w, l / l ₀ = 8) prepared by the method in Example 1 showed an absorption maximum around 359 nm with a dichroic ratio above 100.

This film shows essentially no absorption above 420 nm. It appears transparent and colorless in the visible area.

EXAMPLE 4

151.4 mg (0.7 mmol) of 4,4'-dihydroxyazobenzene (synthesis described in Example 2) were dissolved in 10 mL of anhydrous pyridine. 440.0 mg (1.8 mmol) of 4-hexyloxylbenzoyl chloride were added with stirring at room temperature. After 2 h, the mixture was treated with H ₂ O ( ₃ × 100 ml) and extracted with CH ₂ Cl ₂ (150 ml). The organic phase was dried over MgSO ₄ , filtered, and the solvent was spun off. The resulting orange substance was recrystallized from methanol / chloroform (1: 1). After drying at 80 ° C./100 mbar, 425.0 mg (0.7 mmol, 68%) of the product azodi-4,1- [4- (hexyloxy)] benzoic acid phenyl ester (Ex 4) were obtained as bright orange crystals with a melting point of 172 ° C received. Stretched films (LLDPE, 0.2% w / w, l / l ₀ = 8) prepared by the method in Example 1 showed an absorption maximum around 345 nm with a dichroic ratio above 100. Films based on nylon 12 with 0.2% w / w of Dye was prepared by the same method at 240 ° C and stretched at 110 ° C to a draw ratio of 4. These films showed an absorption maximum around 365 nm with a dichroic ratio of 6.5. Films based on polyethylene terephthalate (PET) at 0.2% w / w of the dye were prepared by the same method at 280 ° C and stretched to a draw ratio of 4 at 180 ° C. These films showed an absorption maximum around 346 nm with a dichroic ratio of 19.

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

EXAMPLE 5

200.7 mg (0.95 mmol) of 4,4'-azodianiline were reacted with hexyloxybenzoyl chloride according to the procedure in Example 4. Recrystallization from dimethyl sulfoxide afforded 534.2 mg (91%) of the product N, N '- (azodi-4,1-phenylene) bis-benzamide (Ex 5) as brown-yellow platelets with a melting point of 313 ° C. Films based on nylon 12 at 0.2% w / w of the dye were prepared by the method described in Example 4 at 240 ° C and stretched at 110 ° C to a draw ratio of 4. These films showed an absorption maximum around 385 nm with a dichroic ratio of 17. Films based on polyethylene terephthalate (PET) at 0.2% w / w of Dye were prepared by the same method at 280 ° C and stretched at 180 ° C to a draw ratio of 4. These films showed an absorption maximum around 335 nm with a dichroic gap of 27.

This polarizing film likewise shows essentially no absorption above 400 nm and appears transparent and colorless in the visible range.

LIST OF REFERENCE NUMBERS

1

Carrier material, security paper

2

polarizing film

3

bonding agent

4

fluorescent pressure

5

foil

6

upper polarizing film

7

lower polarizing film

8th

upper fluorescent printing layer

9

lower fluorescent printing layer

10

release film

11

Cover foil

12

fluorescent printing, above polarizing film

13

irradiated UV light, linearly polarized

14

Polarization direction of 13

15

emitted, visible light

16

observer

17

Polarization direction of 2

18

irradiated, unpolarized light

19

Polarisalionstlter

20

Polarization direction of 19

21

emitted, visible light

22

mottling

23

enveloping polarizing film

24

Core of the mica fiber

Claims (22)

1. A security feature for a security document in which the authenticity can be determined by means of irradiation with electromagnetic radiation (13, 18) in a spectral range outside the visible range, characterized in that the security feature has a print (4, 8, 9) and/or a substrate (1, 24) and/or a coating which converts the incident electromagnetic radiation (13, 18) into visible light (15, 21), the print (4, 8, 9) or the substrate (1) or the coating being covered, at least indirectly, by a polarization film (2, 6, 7, 23).
2. The security feature as claimed in claim 1, characterized in that the security feature has a substrate (1, 24) in which chemical functions are incorporated which convert the incident electromagnetic radiation (13, 18) into visible light (15, 21), these chemical functions preferably being fluorescent and/or phosphorescent dyes incorporated in the substrate (1, 24), and these being in particular preferably in the form of fibers dyed with these dyes, which are incorporated in the substrate (1, 24).
3. The security feature as claimed in one of the preceding claims, characterized that the incident electromagnetic radiation (13, 18) is UV radiation, and in that the print (4, 8, 9), the substrate (1, 24) 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 (4, 8, 9) 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 (2, 6, 7, 23) is substantially colorless and transparent in the visible range, that is to say in particular in the range between 400 and 800 nm.
5. The security feature as claimed in one of the preceding claims, characterized in that the printing (4, 8, 9) and/or the substrate (1, 24) 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 (2, 6, 7, 23) has a thickness of in the range from 5 to 200 µm, in particular preferably from 10 to 75 µm, 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 (2, 6, 7, 23) is a photoluminescent polarization film (2, 6, 7, 23), the emission color of the photoluminescent polarization film (2, 6, 7, 23) preferably being a different one from the emission color of the photoluminescent dye or, respectively, of the combination of such dyes, of the printing (4, 8, 9) and/or of the substrate (1, 24) 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 (2a, 2b) of polarization film with different polarization direction (17a, 17b) arranged directly beside one another, the polarization directions (17a, 17b) of mutually adjacent regions (2a, 2b) 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 (1), the print (4) being printed at least indirectly onto the substrate material (1) and the polarization film (2) being fixed to this print (4) via an adhesion promoter (3).
10. The security feature as claimed in one of the preceding claims, characterized in that a photoluminescent printing is applied to the polarization film.
11. The security feature as claimed in one of claims 1 to 8 or 10, characterized in that it is applied to a substrate material (1), the print (4) being arranged on the side of the polarization film (2) facing the substrate material (1), and the polarization film (2) being applied to the substrate material (1) via an adhesion promoter (3) with the side facing the print (4), if appropriate a film (5) being arranged between print (4) and adhesion promoter (3).
12. The security feature as claimed in either of claims 9 and 11, characterized in that the adhesion promoter (3) 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.
13. The security feature as claimed in one of claims 1 to 8, characterized in that it is arranged in a substrate material (1) in such a way that it can be verified from both sides of the substrate material (1) and/or in transmitted light.
14. The security feature as claimed in claim 13, characterized in that it has a structure in which at least one printed layer (4, 8, 9) is covered on both sides by a polarization film (6, 7), it being possible for the two polarization films (6, 7) to have identical or different polarization directions.
15. The security feature as claimed in claim 13, characterized in that two printed layers (8, 9) are arranged, which are separated by a separating film (10).
16. The security feature as claimed in one of the preceding claims, characterized in that the polarization film (2, 6, 7) is covered with a covering film (11) on the side facing away from the substrate material (1).
17. The security feature as claimed in one of the preceding claims, characterized in that the polarization film (2, 6, 7) is also provided with a fluorescent print (12) on the other surface.
18. The security feature as claimed in one of the preceding claims, characterized in that the substrate (24) is a fiber with a length in the range from 1 to 20 mm, in particular preferably of a plastic, and in that the polarization film (23) envelops this substrate (24).
19. A security document containing a security feature as claimed in one of claims 1 to 18, the security document preferably being in particular a banknote, a security, a ticket or a packaging material.
20. A method for the production of a security document as claimed in claim 19, characterized in that, in the case of a printing (4) or coating, first of all the fluorescent print (4) or, respectively, the coating is applied to a substrate material (1), in particular in the form of a logo, pattern or a line of text, and then a polarization film (2) provided with an adhesion promoter (3) is adhesively bonded to the printed/coated region, and in that, in the case of a substrate with fluorescent components, a polarization film (2) provided with an adhesion promoter (3) is adhesively bonded directly to this substrate.
21. The method for the production of a security document as claimed in claim 19, characterized in that a security feature already provided with a fluorescent print (4) arranged between adhesion promoter (3) and polarization film (2) is adhesively bonded to a substrate material (1).
22. A method for the verification of a security feature as claimed in one of claims 1 to 18 or of a security document as claimed in claim 19, characterized in that either linearly polarized UV light (13) whose polarization direction rotates is used for the irradiation or in that unpolarized UV light (18) is used for the irradiation and the observation in the visible range is carried out through a rotating polarization filter (19), 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.

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