EP2084016B1 - Security element - Google Patents

Abstract

The safety unit has a substrate (1) with a recess (3), and an imprint (4) provided on the substrate and adjacent to the recess. A foil (5) covers the recess and forms a search window in the substrate. A visually inspectable safety feature (6) is provided on the film and places an automatically reversible color imprint relative to information pattern, such that the information pattern is disguised without external stimulus and visible recognizability of the pattern is facilitated by the effect of the external stimulus. An independent claim is also included for a method of manufacturing a safety unit.

Description

The invention relates to a security element for product security, for example in the form of a label, seal, packaging or other product security element, but especially for use in security documents, such as banknotes, stocks, certificates, stamps, checks, check cards, credit cards, ID cards, passports, Tickets, tickets, tickets and the like. As such, the security element may be integrated with the security document or applied to the security document in the form of a patch or security strip.

In particular, the invention relates to such security elements or security documents which have a see-through window. A see-through window is formed by an opening penetrating the substrate material, which is closed by means of a transparent film. In the WO 2006/018171 A2 Such a security element is described in connection with a banknote. On the banknote substrate, which usually consists of paper, but can also consist of plastic, an information-conveying imprint is applied. The recess penetrating the substrate is restricted to portions of the information-conveying imprint. Since the background of the imprint is bright, usually white, the information is difficult to recognize when the bill is viewed against a light background. Only against a dark background do the recessed areas appear dark and complement each other with the non-recessed areas of the information processing print, so that the information is generally visible. An inverse effect is achievable if the information-providing imprint is printed with a light color on a dark background. Then, the total information becomes clearly recognizable when the bill is viewed against a bright background.

In the WO 2006/018171 A2 Further, it is proposed to cover the entire print including the recesses with a transparent film provided with a liquid crystal layer. The liquid crystal layer is transparent in transmitted light and substantially colorless. However, it appears above the dark print in a characteristic dark color, while appearing transparent against the light background. Looking at the document against a dark background, the dark color is also visible in the area of the recesses and thus the information as a whole. Alternatively, a partial region of the information adjacent to the recess can also be realized as a dark imprint with a liquid crystal layer printed thereover, and the other subregion of the information as a liquid crystal layer on the foil covering the recess. When viewed against a dark background, both parts then complement each other again to the overall information and show the characteristic of liquid crystals dark colors.

The above-described security element allows an authenticity check by being viewed first in transmitted light and then against a dark background. It is imitable only at great expense, since various technical challenges have to be overcome, such as manufacturing tolerances of the recesses relative to the information-conveying imprint and register-accurate positioning of the film strip relative to the information-conveying imprint and the like. The security element is thus easily verifiable and difficult to imitate.

Object of the present invention is to further improve the security element in terms of verifiability and imitation security. This problem is solved according to the invention by a security element having the features of claim 1 and by a security document provided with such a security element. In dependent claims advantageous developments and refinements of the invention are given. In addition, an inventive method for producing the security element is also specified.

According to the invention, the combinatory effect between the imprint and the recess (which can also be a plurality of recesses), which complement or at least contribute to an information-conveying character or pattern, for example a code, is combined with another security feature, which exerts an additional decisive influence on the recognizability of the information.

Specifically, by means of the further security feature, the information-conveying character or pattern is obscured so that it is not, not completely, or at least not readily recognizable. The further security feature is characterized in that it imparts a color impression which is variable by an external stimulus, so that only by means of the stimulus the simple visual recognizability of the information-conveying character or pattern is made possible or at least facilitated.

The external stimulus is the temperature, and the security feature, as a thermochromic material, comprises an encapsulated thermochromic polymer solution that decays temperature-dependently into a polymer-rich and a polymer-poor solution phase, moving from a transparent to a grape state.

The term "stimulus" is used synonymously with the term "stimulus", as is also known from the free encyclopedia Wikipedia (http://en.wikipedia.org/wiki/Reiz). Stimulus is primarily used in this application physical stimuli, such as temperature, pressure, light, sound, magnetism, electrical voltage, etc. It goes without saying that, for example, the stimulus "temperature" physically considered a heat transfer to the security feature or a withdrawal of heat from the security feature means. Accordingly, the stimulus "light" is physically understood to mean the action of electromagnetic radiation of the visible and non-visible wavelength range on the security feature. In addition to the physical stimuli, it is basically also conceivable that chemical stimuli changes the color impression of the security feature. For example, the color impression can be effected by the moisture acting on the security element in the form of water or other liquids or by any chemical compounds in the gaseous state of matter. In the following, a chemical stimulus is thus generally understood to mean the action of liquid, gaseous or solid chemical compounds on the security element.

The mediated by the security feature color impression is independently reversible, d. h., in the absence of the external stimulus, the security feature changes color until it recovers the color before the stimulus is applied, thus re-creating the original color impression on the viewer. According to the invention, the independent reversibility applies to all forms of stimuli, in particular physical and chemical stimuli.

Depending on the material used for the security feature, the external stimulus other than temperature may also be pressure, electrical voltage, light (electromagnetic radiation), sound and / or magnetism, the safety feature being thermochromic, piezochromic, electrochromic, photochromic, sound waves and / or magnetism color changeable material. It will be appreciated that the color of a deployed security feature may also be altered by different stimuli. For example, it is known to the person skilled in the art that certain piezochromes Compounds also have thermochromic properties simultaneously. For chemical stimuli a suitable material is used in a similar manner, ie z. B. a hygrochrome compound.

The further security feature can be combinatorially combined in a variety of ways with the information-conveying characters or patterns formed by the imprint and the recess. In a further development of the embodiment described above from the WO 2006/018171 A2 , in which the information-conveying characters including their recesses are covered by a liquid crystal-coated film, z. B. the Flüssigkrista1Ibeschichtung be replaced by a thermochromic layer, which is transparent at normal operating temperature, usually ambient temperature, opaque and temperature increase or possibly also in temperature reduction. The information-conveying characters or patterns are then recognizable only if, at the same time, the necessary temperature increase or decrease has taken place to render the security feature transparent, and the security element is viewed against a suitable background in which the imprint becomes visible with the background visible through the recesses added to the information-conveying signs or patterns. It is therefore advantageous if the color impression of the security feature changes from opaque to transparent under the influence of the stimulus.

The liquid crystal coating known from the prior art may itself have thermochromic properties in that the liquid-crystalline material is in the liquid state at normal operating temperature and therefore transparent, and at a correspondingly reduced temperature passes into the liquid-crystalline state and that for the respective liquid crystalline material gives characteristic color impression. In this variant, the information-conveying characters or patterns are only completely recognizable with the typical color impression if both the temperature reduction has taken place and a viewing takes place against a suitable background.

The "obfuscation" of the information-conveying characters or patterns by the security feature in the absence of the stimulus does not necessarily require complete coverage of the characters or patterns by the security feature. It may also be covered only by a part of the recess and / or a contribution to the information conveying part of the imprint of the variable security feature.

It is even possible that neither the recess nor the imprint are covered by the security feature. For example, the security feature directly adjoin the information-conveying imprint and z. B. at the usual operating temperature give the same color impression as the imprint itself, for example, black or any other color. Under the influence of the external stimulus, the color impression of the security feature then changes from black to z. B. white or from a first color to a second color such that the information-conveying imprint of contrasting stands out and, if the security element is then viewed against a suitable background, the now no longer veiled imprint with the background color visible through the recess supplemented for full information.

As a "color impression" within the meaning of the invention accordingly not only genuine, ie pure colors, but also black and white and transparent to understand. Even a change from dull to clear can serve the obfuscation and is therefore to be understood in the context of the invention as a changing color impression.

According to one variant, (only) the part of the imprint which contributes to the information transfer can have a negative edge contour line, that is to say for example a bright contour line in an otherwise dark environment. Then, the information-conveying characters or patterns are difficult to see when viewing the security element against a dark background, as the dark background visible through the recess does not stand out clearly enough from the dark environment of the information-conveying character or pattern. However, in front of a light background, the clear-edged recess then complements the bright edge contour line of the part of the imprint that contributes to the transmission of information to the overall information.

In addition, if also the recess has a bright edge contour line, the complete information is visible both against light and against a dark background, in the case of a dark background as a complete dark character or pattern with a completely bright negative edge contour line.

The imprint is preferably for security documents such as bank notes, typical offset printing or nyloprint. This allows you to print one-colored or multi-colored filigree guilloche patterns.

As a substrate material is mainly paper, especially cotton vellum paper, use. Of course, paper can also be used which contains a proportion x polymeric material in the range of 0 <x <100 wt .-%.

Furthermore, it is conceivable that the substrate material is a plastic film, for. B. a polyester film is. The film may also be monoaxially or biaxially stretched. The stretching of the film, inter alia, leads to it receiving polarizing properties that can be used as another security feature. The tools required for exploiting these properties, such as polarization filters, are known to the person skilled in the art.

It may also be expedient if the substrate material is a multilayer composite which has at least one layer of paper or a paper-like material. Such a composite is characterized by an extremely high stability, which is for the durability of the security feature of great advantage and also increases the security against counterfeiting.

It is also conceivable, however, to use a multilayer, paper-free composite material as the substrate material. These materials can also be used to advantage in certain climatic regions of the world.

All materials used as substrate material can have additives which serve as authenticity features. It is primarily to think of luminescent, which are preferably transparent in the visible wavelength range and in the non-visible wavelength range by a suitable tool, for. B. a UV or IR radiation emitting radiation source can be excited to produce a visible or at least detectable with auxiliary luminescence. Others too Security features can be used to advantage if they do not affect the viewing of the imprint or only slightly.

The film may be formed as a patch covering a partial surface of the substrate or as a strip extending over the entire length or width of the security document. As materials for the film are primarily plastics, in particular PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate), PP (Polyproyplen), PA (polyamide), PE (polyethylene), into consideration. The film may also be monoaxially or biaxially stretched.

The recess can be formed both during and after the production of the substrate. In the first case, another security feature is created due to the irregularly protruding into the recess fibers, as described in more detail in the WO 03/054297 A2 is described. In that regard, the disclosure of the WO 03/054297 A2 included in the present application. In the second case, the recess after the production of the substrate, for. B. by punching or laser beam cutting generated. The person skilled in the art for this purpose, suitable tools, such as punching and cutting devices and lasers, basically known.

The application of the security feature to the film takes place before or preferably after the application of the film to the substrate. In the latter variant, the security feature advantageously extends beyond the film to the substrate. This complicates the imitation, since the adhesion of the ink on a film on the one hand and a preferably paper-based substrate on the other hand is different and not every color composition is suitable.

Preferably, the security feature is at least partially on the film. It is particularly preferred if the security feature is printed by intaglio printing on the film and possibly also on the adjacent substrate. First, tactile structures characteristic of intaglio printing can thereby be produced, which on the one hand stem from the pasty inks used, which are applied to the printed substrate and project tangibly from the substrate surface. On the other hand, the tactile structures are due to the fact that the printed substrate is pressed in the printing process in the filled with the ink wells of the intaglio printing plate used for printing and thereby "embossed". Secondly, the printing of films in intaglio printing, in particular to avoid cracks in the film by the action of the engraving pressure plate, considerable technical expertise and therefore provides additional protection against counterfeiting.

The contributing to the information transfer part of the imprint can be applied either on both sides of the substrate either congruent or each other in the transmitted light complementary. In both cases you need a simultaneous printing machine to achieve the desired level of coverage. This additionally protects the security element against counterfeiting.

The film may include further layers. Thus, the security feature and a transparent or semitransparent effect layer can at least partially cover each other, in order to integrate in this way a supplementary security feature in the security element. The effect layer may comprise thin-film pigments with interference effects, such as the so-called IRIODIN® from Merck. But other optically variable security features are conceivable, such as transparent and / or nontransparent holographic elements, diffractive structures, and the like.

Furthermore, the film may be partially metallized, wherein the metallization is aligned when applying the film to the substrate accurately to the imprint or to a separate background printing. This measure also makes forgery more difficult, since it requires the precise application of such a security strip particularly accurate machines. The registration accuracy of the film relative to the imprint is preferably 0.3 mm to 0.5 mm or less.

The formation of the recess accurately relative to the imprint is of particular importance, since even small tolerances in conjunction with the contributing to the information sharing part of the imprint attract attention to the viewer. If the recess is punched, with a punch width of preferably at least 2 mm to about 3 mm, the fit accuracy of the recess relative to the imprint should be less than 0.2 mm.

The security element according to the invention can be used independently, for example as label, seal, packaging or other product securing element. However, it is particularly suitable for covering a through-hole in a security document.

In particular banknotes, but also shares, certificates, stamps, checks, check cards, credit cards, ID cards, passports, entrance tickets, tickets, air tickets and the like come into consideration as security documents.

Instead of applying the security element as a separate element to the security document, it can also be integrated in a security document, wherein the substrate of the security element is then formed by the security document material and the recess of the security element is realized as a through hole in the security document.

Fig.1

eine Banknote mit einem Sicherheitsmerkmal gemäß einem ersten Ausführungsbeispiel,

Fig. 2

die Banknote aus Fig.1 im Querschnitt,

Fig. 3

eine Banknote mit einem Sicherheitselement gemäß einem zweiten Ausführungsbeispiel,

Fig. 4

eine Banknote mit einem Sicherheitselement gemäß einem dritten Ausführungsbeispiel,

Fig. 5

eine Banknote mit einem Sicherheitselement gemäß einem vierten Ausführungsbeispiel,

Fig. 6

die Banknote aus Fig. 5 im Querschnitt, und

Fig. 7

eine Banknote mit einem Sicherheitselement gemäß einem fünften Ausführungsbeispiel.

The invention will be described by way of example with reference to the accompanying drawings. Show:

Fig.1

a banknote with a security feature according to a first embodiment,

Fig. 2

the banknote Fig.1 in cross section,

Fig. 3

a banknote with a security element according to a second embodiment,

Fig. 4

a banknote with a security element according to a third embodiment,

Fig. 5

a banknote with a security element according to a fourth embodiment,

Fig. 6

the banknote Fig. 5 in cross-section, and

Fig. 7

a banknote with a security element according to a fifth embodiment.

Fig.1 shows a security document, here using the example of a banknote, which is equipped with a security element 2. It is understood that the security documents described below, in addition to the security element 2 further security elements or features, not shown, such. As security prints, color-changing coatings, holograms, diffraction structures, see-through register, etc. The security element 2 of Fig.1 is integrated into the banknote insofar as a through-hole 3 in the substrate of the banknote is a component of the security element 2. The through hole 3 constitutes a see-through area in the document. The security element 2 further comprises a print 4 on the banknote substrate 1, a film 5 completely covering the through-hole 3 and the print 4, and a coating 6 which is a special one Security feature forms by their color impression is reversibly variable by an external stimulus.

First, the imprint 4 is printed on the substrate 1 with a contrasting color to the substrate 1, for example with black printing ink. For this purpose, a usual in banknote printing printing method, such. B. offset printing or Nyloprint serve. Subsequently, the through-hole 3 (in this case several) is punched out of the substrate 1 with an exact fit to the imprint 4, so that the corresponding recesses, together with the imprint 4, convey the information "20". Of course, it is also conceivable in principle to form the recess before applying the imprint, namely z. B. in the sense of WO 03/054297 A2 during the production of the substrate, e.g. As the papermaking, or after the preparation of the substrate, but before printing the substrate with the imprint. In addition, a transparent film 5 is applied, so that the information "20" is particularly evident when looking at the banknote against a dark background.

The transparent film 5 is expediently already coated at the time of its application to the substrate 1 with the security feature 6 in the illustrated embodiment. However, the coating can also be applied only in a subsequent step, for. B. are printed, and can then extend beyond the film 5 in addition to the substrate 1 in particular. The security feature 6 can also be limited to one or more portions of the film 5 beyond. It is also conceivable that the security feature, at least in some areas, has information that individualizes the security element or security document in the form of an alphanumeric character, barcodes, pattern, microprint, etc. Such information is not shown here for reasons of clarity.

The security feature 6 has at least thermochromic and, in addition, optionally piezochromic, electrochromic, photochromic, hygrochrome, color-changeable properties responsive to sound waves and / or magnetism, namely such that it is opaque or opaque in normal use and the view of the underlying information "20" impeded, and that it releases the view of the information "20" in the stimulated state. However, the information "20" becomes optimally recognizable only when the banknote is viewed in front of a correspondingly dark background, so that the see-through areas 3 with the imprint 4 complete the overall information "20".

Hereinafter, variants of the security feature 6 are explained, which, however, are not all according to the invention in the specific concretely described embodiment.

Microencapsulated, organic, thermochromic three-component dye system

As a first example of a thermochromic material of the security feature 6, with which the film 5 may be printed or coated, is a microencapsulated, three-component organic dye system. The dye system comprises an electron-rich organic dye, the "Color Former", also referred to as "Electron Donor", a "Color Developer", also referred to as "Electron Acceptor", and a suitable solvent. These three components are microencapsulated, typically in gelatin. As an electron donor so-called leuco dyes are used, in particular spirolactones, fluorans, spiropyrans or fulgides. The electron acceptor used is a weak acid, for example bisphenol A (4,4'-methylethylidene bisphenol), alkyl p-hydroxybenzoates, 1,2,3-triazoles or 4-hydroxycoumarin. The solvent used is a polar solvent, for example alcohols, ketones, esters or ethers. These three component blends are typically colored or opaque at lower temperatures and colorless at higher temperatures. The turnover temperature can be adjusted by modifying the components. Preferably, the turnover temperature of the microencapsulated three-component mixture is in the range of -10 ° C to 60 ° C, more preferably in the range of 25 ° C to 60 ° C. It is ideal if the transfer temperature between a conventional ambient temperature of z. B. 25 ° C to 30 ° C and the body temperature of 37 ° C, so that the color change can be achieved by transferring body heat. The above-described organic thermochromic mixtures are described in more detail with reference to further literature in White / LeBlanc "Thermochromism in Commercial Products", Journal of Chemical Education, 1999, page 1202.

The microencapsulated three-component mixture can be contained in ink adapted to the intaglio printing process in order to produce security-relevant gravure printing products. In intaglio produced print images can be characterized in particular by tactility. Furthermore, very fine line structures or microfills can be realized by intaglio printing, which are not possible in screen printing.

The ink is comparatively viscous and "stands" on the printed substrate surface, i. H. tangibly protrudes from the substrate surface. In order to achieve this, in addition to the microencapsulated three-component mixture, the printing ink comprises a suitable binder, if appropriate, further fillers, dryers, varnishes and thinners. The proportion of the microencapsulated three-component mixture in the printing ink is 10% by weight to 40% by weight, preferably 25% by weight to 35% by weight, the weight ratio of the three-component mixture to the binder being in the range of 1 to 1 6 to 2 to 1 lies. Suitable binders are rosin resins and oils.

As a dryer, a mixture of Mn / Co-octoates, as a thinner high-boiling mineral oils and as a varnish, overgrown resins can be used. Suitable fillers are CaCO ₃ , BaSO ₄ and TiO ₂ . To produce the intaglio printing ink, the microencapsulated three-component mixture is mixed as a pigment directly or as an aqueous suspension with a suitable binder and optionally additives, such as fillers, solvents, varnish, thinner, dryer, etc. The weight ratio of colored pigments to the three-component mixture may be in the range of 1 to 40 to 1 to 1, and the weight ratio of effect pigments to the three-component mixture may be in the range of 1 to 40 to 1 to 2.

Thus, for example, with a yellow colored pigment and a three-component mixture which changes color from blue to colorless when the temperature increases, an ink is obtained which appears green below the transition temperature and yellow above the transposition temperature. This may be particularly suitable for an embodiment to be described in more detail below.

In order to be suitable for the intaglio printing process, the printing ink according to the invention has a pasty consistency and accordingly has high viscosity values of preferably 100 Pa.s to 600 Pa.s at 20 ° C. and a shear rate of 4 s ^-1 , particularly preferably of 200 Pa · S up to 500 Pa · s at 20 ° C and a shear rate of 4 s ^-1 .

The printed image produced in intaglio printing is preferably full-surface or is characterized by very fine lines. Suitable printing plates for the production of full-surface, produced in intaglio printing process printed images are in the EP 1117 537 B1 and in the EP 1119 457 B1 described.

In addition, two concrete embodiments of the stitch ink are cited.

Embodiment 1

The starting substance is the microencapsulated three-component mixture Matsui 25 Fast Black. This is a slurry of 70% by weight of pigment in 30% by weight of water. This is concentrated so that the pigment is present. 23 wt .-% of the dried pigment are ground with 62.5 wt .-% transparent white (binder with filler, No. 9 SL 0700 Fa. SICPA). This mixture was further treated with 2.3 wt .-% a Mn / co-octoate mixture (dryer, No. 870950, Fa. SICPA), with 9.3 wt .-% HT varnish (Varnish, No. 850090, Fa. SICPA) and 2.9 wt .-% high-boiling mineral oils (thinner, No. 859041, Fa. SICPA) mixed.

Embodiment 2

32.5 wt .-% of the microencapsulated three-component mixture Matsui 25 Fast Black are mixed with the following components: 39.2 wt .-% transparent white (binder with filler, No. 9 SL 0700 Fa. SICPA), 2.3 wt. % of a Mn / co-octoate mixture (dryer, No. 870950, SICPA), 23.2% by weight of HT-Vamisch (Varnish, No. 850090, from SICPA), 2.8% by weight high-boiling mineral oils (thinner, No. 859041, Fa. SICPA).

Further details of the used for the security element of the invention Stichdruckfarben can the unpublished German patent application DE 10 2006 016118.1 are removed, the disclosure content of which is included in the present application in this respect.

Thermochromic liquid crystalline materials

As a second example, the color variable security feature by the external stimulus comprises a microencapsulated thermochromic cholesteric liquid crystalline substance. Cholesteric liquid crystals are offered, for example, by the manufacturers Merck and TMC. In cholesteric liquid crystals, the molecules are oriented in preferred directions, the preferred directions changing periodically over the layer thickness. The distance of these differently oriented layers changes with the temperature and thus changes their color effect, which changes with the temperature course over red, orange, yellow, green, blue, violet.

For use in inks, the liquid crystals are microencapsulated in gelatin or other encapsulating media. In White / LeBlanc "Thermochromism in Commercial Products", Journal of Chemical Education 1999, 1201 ff , Cholesteric liquid crystals are explained in more detail with reference to further literature. Most often they include a nematic host with chiral dopant. The rainbow-like color gradient becomes visible only when heated and usually only when viewed against a dark background. At normal temperature, the material is colorless. Upon further increase in temperature, when the material changes from the liquid-crystalline state into the liquid state, the material which has been colored in the liquid-crystalline state becomes transparent again.

Thermochromic turbid-clear polymers

As a third example, polymer solutions may serve as the material for the security feature. A polymer solution breaks down into a polymer-rich and a polymer-poor solution phase if a critical value X _{k is} exceeded or undershot. The value of X _k depends on the degree of polymerization, on the temperature and of course on the system. As systems can be exemplified the solution of poly (N-acryloyl-pyrrolidine) in water and polystyrene in cyclohexane. As a rule, the value X _k decreases with increasing temperature, ie the polymer solubility increases. From a critical temperature Tucsr (English: Upper Critical Solution Temperature) changes the appearance of the polymer solution from cloudy to clear. But it is also possible that the value X increases with increasing temperature or initially decreases with increasing temperature and then rises again. The temperature at which the value X reaches the critical limit X _k for the second time is referred to as the lower critical solution temperature T _LCST (English: Lower Critical Solution Temperature). In the temperature interval between T _UCST and T _LCST , the polymer is completely soluble and therefore clear. If the temperature drops below the value T _UCST or _exceeds the value T _LCST , the polymer precipitates and the polymer solution becomes cloudy. This phenomenon is also referred to as temperature-induced segregation. The temperature interval in which the polymer is completely soluble, the larger, the smaller the molecular weight.

By a suitable choice of the polymer solution system, the molecular weight and the mixing ratio, the turnover temperature and the temperature interval can be adjusted. By encapsulation of these systems z. B. in gelatin they can be mixed inks. Printed via a window, the window can be switched by changing the temperature either transparent and cloudy. Similarly, information previously deposited on the window or on the substrate may be exposed by temperature change. The physical relationships of thermochromic turbid-clear polymers are in Lechner / Gehrke / Nordmeier "Macromolecular Chemistry" 2nd ed., Page 183 ff , described.

Piezochrome and thermochromic metal complexes

As a fourth example, compounds which change their hue on pressure ("piezo") can also be used. As piezochrome materials, metal complexes present in a solvent are known. A slight increase in the dielectric constant of the solvent by pressurization affects the energy distribution within the metal complexes. Due to the pressure, the metal complexes assume a different electronic state (from "high spin" to "low spin" and vice versa). This causes a noticeable color change. This is for example in Takagi / Noda / Itoh / Iwatsuki "Piezochromism and Related Phenomena Exhibited by Palladium Complexes "in Platinum Metals Revision, 2004,117 ff , Physically explained by means of palladium complexes. Other known complexes are iron or nickel complexes.

The effect of the spin transition is a reversible electron-dynamical phenomenon that can be observed on numerous coordination compounds of first-transition-metal elements with 4 to 7 electrons in the valence shell (configurations d ⁴ to d ⁷ ). This phenomenon is particularly common in iron (II) coordination compounds. However, the spin transition is not only pressure dependent, but may also be caused by a change in temperature such that these materials have both thermochromic and piezochromic properties. In addition, the spin transition simultaneously leads to a drastic change in the magnetic properties of the coordination compounds involved. While the color change is visible to the naked eye, the spin transition can therefore also be detected by measuring the magnetism. Since the spin transition is completely reversible and the color of the complex compounds is based on the absorption of light by the valence electrodes of their metallic central atom, the substances remain lightfast and colourfast even with long-term use.

In the DE 103 07 513 A1 various iron (II) coordination compounds with different ligands are described. The color change in iron (II) complexes with tetrazole, triazole, and oxazole ligands associated with the spin transition is accompanied by an easily recognizable color change from white to red to violet.

The thermochromic properties of the metal complexes can be observed without the metal complexes having to be in solution. However, the piezochromic properties require the presence of a solvent. In this case, a microencapsulation of the metal complex solution z. As required in gelatin.

Piezochrome polymers

As a fifth example, piezochromic polymers may be mentioned. For polymers whose molecules have a certain order and orientation, the color impression of the polymer compound can be changed by pressure. For example, liquid crystals rearrange under pressure. This can be observed by the well-known effect that occurs when pressing on an LC display. The orientation of the molecules can be designed in such a way that interferences are generated which show a visually perceptible change by pressure. Suitable classes of materials are, for example, thermotropic and lyotropic liquid crystal systems.

Electrochromic compounds

In principle, as a sixth example, electrochromic compounds can also be used as a security feature in connection with the present invention. Electrochromic compounds are known in connection with so-called intelligent windows and automatically dimming rear-view mirrors. The glass in these cases is coated with electrochromic compounds which are capable of changing color or transparency at an applied voltage. To check the security feature, therefore, the application of electrical voltage is a prerequisite. It is therefore particularly suitable as a machine-readable authenticity feature.

The security feature in this case has a multilayer structure, wherein the electrochromic material is arranged adjacent to an electrolyte layer between two electrodes. The electrolyte is required for charge mobility. When a voltage is applied to the electrodes, ions migrate from the electrolyte layer into the electrochromic material or vice versa. As a result, the electrochromic material is reduced or oxidized, which simultaneously changes the color.

The most popular electrochroic material is WO ₃ , which is uncharged colorless and oxidized blue colored. Also, inorganic complex compounds and also a variety of organic, conductive polymers are electrochromic, such as polyaniline, polypyrrole, polythiophenes and their derivatives. PEDOT from Bayer (Baytron®) is also electrochromic. Likewise, organic materials such as so-called viologens (Bipyridiunnsalze) are electrochromic.

Photochromic compounds

Finally, the seventh example photochromic compounds may be mentioned, such as fulgides, Fulgidimide, spiro-dihydroindolizines and more. Such compounds are for example in the EP 0 327 788 B1 described for use in printing inks. The photochromic property (phototropism) is based on a change in the absorption behavior of visible light when the compound is exposed to electromagnetic radiation of predetermined wavelength. For example, systems that change color when irradiated with ultraviolet light are known. The original absorption spectrum will either re-establish itself after a certain time, especially in the dark, or can be restored by heating. The material is microencapsulated or microparticles from 1 μm to Broken 20 microns. It is suitable for most printing processes, including intaglio printing.

Hereinafter, further embodiments of the invention will be described. They merely represent a small portion of the possible combinations which result from the fact that the aforementioned materials suitable for the security feature can be combined with one another, for example by mixing them in printing ink or printing them on top of one another and / or side by side. Furthermore, combination possibilities result from the fact that the materials are provided wholly or partly over the recess contributing to the information-conveying character or pattern and / or completely or partially over the imprinting information or merely adjacent to the recess and / or the imprint can. In addition, the multiplicity of possible combinations increases as a result of the fact that the safety feature formed from the above-described materials can change from opaque / opaque to colorless or from colorless to opaque / opaque or from one color to another color, depending on the application.

Fig. 3 shows an embodiment similar Fig.1 and Fig. 2 However, the transparent film 5 is provided only in partial areas with the security feature 6, so that portions of the see-through areas 3 remain visible in any case. The visible subregions of the see-through areas 3 represent a first easy-to-check security feature. By means of the external stimulus, the obfuscation of the information "20" can be temporarily canceled, whereby this information becomes well recognizable only against a dark background.

Fig. 4 shows a further embodiment in which the security feature 6 immediately adjacent to the imprint 4 and the recesses 3, which together form the information-conveying character "20", is arranged. The color impression of the security feature 6 is in the non-activated state, ie without the external stimulus, identical or nearly identical to the color impression of the imprint 4, for example green, so that a viewer normally only recognizes the see-through windows 3. However, the security feature 6 could additionally cover the see-through windows. Now, if the color impression of the security feature 6 is changed by an external stimulus, for example, from green to yellow, or in the event that the window areas 3 are covered by the security feature 6, after transparent, initially the imprint 4 is contrasted by the security feature. 6 from. The complete information "20" is then again clearly visible in front of a correspondingly colored or dark background.

The security feature 6 can be applied to the film 5 before or after the film 5 is applied to the substrate 1. In the case where it is previously applied, it may be on the final product between the substrate 1 and the film 5 so that it is protected by the film 5, or it may be on the outer side of the film 5. This also applies to the embodiments described above and below. In the latter case, it may be expedient to cover the security feature 6 with an outer protective layer (not shown), for example a lacquer layer or a laminated film. It is also possible to laminate or print on further effect layers (not shown) which contain, for example, interference-layer pigments or other optically variable constituents.

Preferably, the security feature 6 is printed on the outside of the film by intaglio printing, so that the feel of the intaglio printing is perceptible as an additional security feature.

Disguising the information "20" can also be realized by means of a security feature 6, which is transparent in the non-activated state and can be switched to opaque or opaque by means of the external stimulus. This is exemplary in Fig. 5 and Fig. 6 shown, where Fig. 6 a cross-section of the banknote Fig. 5 shows. There, the polychrome security element 6 is provided exactly and exclusively over the see-through areas 3. In the non-activated state, the security feature is transparent, so that the total information "20" formed by the see-through windows 3 and the imprint 4 becomes recognizable only against a dark background. Alternatively, when the imprint 4 is printed light on a dark background or in a dark environment, the information "20" is completely visible when viewing the bill against a light background (not shown). The security element 6 now makes it possible to make the obscured information "20" completely visible regardless of a particular background by switching the transparent appearance of the security feature 6 to cloudy or opaque by means of the external stimulus.

Fig. 7 shows a further embodiment of the invention. In this case, on the substrate 1 of the banknote, the film 5 is applied not as a patch but as a film strip extending over the entire banknote width. Printed on the substrate is again the imprint 4, which contributes to the information "20" with individual components and, moreover, completely encloses the information "20". Not printed is an area 4 'immediately adjacent to the information "20". This area 4 'forms thereby a kind of negative contour to the information "20". The information "20" is in turn completed by the see-through areas 3 in the substrate 1.

Due to the negative contour 4 ', the information "20" can be recognized independently of whether the banknote is viewed against a dark or a light background. However, against a dark background, the information "20" becomes even clearer, because the negative contour 4 'thereby contrasts sharply. If the negative contour 4 'is limited only to the part of the imprint 4 which contributes to the information transmission, ie does not extend along the transparent areas 3 (not shown separately), the complete information "20" is difficult to perceive when the banknote is viewed against a dark background , However, it is clearly perceptible against a lighter background since the negative contour 4 'then complements the window areas 3 for information.

The security element 6 is in turn applied over the information and obfuscates the information in the non-stimulated state. In this case, the security feature 6 extends partially over the imprint 4, partially over the see-through areas 3, and also extends beyond the film 5 to the substrate 1. The security feature 6 can in turn be advantageously realized as intaglio.

The substrate 1 further has a background printing 7, which is indicated here by five arcuate lines and is typically realized as an entangled line pattern ("guilloche pattern"). The imprint 4 and the background printing 7 can be produced in the same operation, for example in offset printing or Nyloprint. The foil 5 may in turn have line patterns 8 corresponding to the background printing 7.

It is then to ensure a register-accurate application of the film 5 on the substrate 1, so that the patterns 7 and 8 complement each other and / or cover each other congruent. This further increases the security against forgery of the document. The line patterns 8 of the film 5 are preferably designed as a metallization, which on the one hand, the complexity and thus the security against counterfeiting is increased and on the other hand, a simple visual inspection of the precise application of the film strip 5 is facilitated by the untrained user. The patterns 7 and / or 8 can also be realized advantageously in the other embodiments.

When the film 5 is applied to the substrate 1 over the window areas 3, it is important to ensure that, as far as the adhesive layer also covers the viewing areas 3, an adhesive is used whose adhesive capacity in the area of the see-through areas 3 already decreases after a very short time, thus during stacking documents are prevented from sticking together adjacent sheets during production. The person skilled in the art suitable adhesives are known.

In a further embodiment of the embodiments, the imprint 4 may be printed on both sides of the substrate 1, either congruent to each other or each other in transmitted light complementary. This represents another security feature which can only be imitated with particular technical effort and which can be realized in technically complex simultaneous printing.

In addition, the security feature 6 or components of the information "20" with transparent or semi-transparent effect pigments, such. B. with interference layer pigments, IRIODIN®, Colorcrypt etc. overprinted.

Furthermore, the security feature 6 can advantageously be covered with a protective layer, in particular by means of a clearcoat layer or a laminated transparent film, in order to protect the color-changeable security feature against environmental influences. The protective lacquer layer can be applied over the entire surface or in partial areas. In the paint system z. B. UV coatings, hybrid coatings, oil-based or dispersion coatings of one or two component type can be used. The protective lacquer layer is preferably printed, for. B. by flexographic or offset printing.

Claims (16)

1. A security element (2), comprising

   - a substrate (1) having a print (4), the print (4) comprising at least a part of an information-conveying sign or pattern,

   - a gap (3) penetrating the substrate, the gap (3) being restricted to a part of the information-conveying sign or pattern,

   - a foil (5) covering at least the gap (3) and forming with the gap (3) a see-through window in the substrate (1), and

   - a visually checkable security feature (6),

   characterized in that the security feature (6) conveys an independently reversible color impression changeable by an external stimulus and is arranged such that the information-conveying sign or pattern is veiled without the external stimulus, and the visual recognizability of the information-conveying sign or pattern is facilitated under the action of the external stimulus, the security feature (6) comprising micro-encapsulated thermochromic material and the external stimulus being temperature, the thermochromic material comprising an encapsulated thermochromic polyester solution which breaks down temperature-dependently into a polymer-rich and a polymer-poor solution phase and thereby passes from a transparent to a cloudy state.
2. The security element according to claim 1, characterized in that the color impression of the security feature is changeable by means of the stimulus from opaque to transparent.
3. The security element according to claim 1 or 2, characterized in that the security feature immediately adjoins the information-conveying sign or pattern upon viewing in plan.
4. The security element according to claim 1 or 2, characterized in that the security feature covers the gap at least partly, preferably completely, and/or that the security feature covers at least a part of the print contributing to information conveyance.
5. The security element according to any of claims 1 to 4, characterized in that at least the part of the print contributing to information conveyance has a negative edge contour line and/or that the gap has an edge contour line.
6. The security element according to any of claims 1 to 5, characterized in that the security feature is applied as an intaglio print and/or that the security feature and a transparent or semitransparent effect layer cover each other at least partly.
7. The security element according to any of claims 1 to 6, characterized in that the print is an offset print or Nyloprint and/or that the print is applied to both sides of the substrate congruently or complementing each other in transmitted light.
8. The security element according to any of claims 1 to 7, characterized in that the foil is partially metallized and placed on the substrate such that the metallization is aligned in an accurate fit with the print and/or a background print, the accurately fitting alignment of the foil with the print and/or background print preferably being 0.3 mm to 0.5 mm or therebelow.
9. The security element according to any of claims 1 to 8, characterized in that the gap is aligned relative to the print with a fit factor of less than 0.2 mm, in particular 0.1 mm.
10. The security element according to any of claims 1 to 9, characterized in that the security element is selected from the group of: label, seal, package or other product securing element.
11. A security document, characterized in that it has a security element according to any of claims 1 to 10, wherein preferably the substrate of the security element is formed by the security-document material and the gap of the security element is realized as a through hole in the security document.
12. The security document according to claim 11, characterized in that the foil extends as a strip over the total length or width of the security document.
13. The security document according to claim 11 or 12, characterized in that the foil is applied as a patch over the through hole of the security document.
14. The security document according to any of claims 11 to 13, characterized in that the security document is selected from the group of: bank note, share, deed, postage stamp, check, check card, credit card, identity card, passport, admission ticket, transport ticket, air ticket.
15. A method for producing a security element (2) according to any of claims 1 to 10 or a security document according to any of claims 11 to 14, comprising the steps of:

    - printing a substrate (1) with a print (4) comprising at least a part of an information-conveying sign or pattern,

    - forming at least one gap (3) penetrating the substrate (1), the gap being restricted to a partial area of the information-conveying sign or pattern,

    - applying a foil (5) so that the foil covers at least the gap (3), and

    - applying a security feature (6) before or after the step of applying the foil (5),

    characterized in that the security feature (6) conveys an independently reversible color impression changeable by an external stimulus and is arranged upon application such that the information-conveying sign or pattern is veiled without the external stimulus, and the visual recognizability of the information-conveying sign or pattern is facilitated under the action of the external stimulus, the security feature (6) comprising micro-encapsulated thermochromic material and the external stimulus being temperature, the thermochromic material comprising an encapsulated thermochromic polymer solution which breaks down temperature-dependently into a polymer-rich and a polymer-poor solution phase and thereby passes from a transparent to a cloudy state.
16. The method according to claim 15, characterized in that the at least one gap is effected after production of the substrate, in particular by punching or cutting, particularly preferably by laser beam cutting, and/or that the printing of the substrate is effected before the forming of the at least one gap, and/or that the the application of the foil is effected before the application of the security feature.

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