EP1827864A1

EP1827864A1 - Safety element provided with an optically-variable layer and method for the production thereof

Info

Publication number: EP1827864A1
Application number: EP05798822A
Authority: EP
Inventors: Manfred Heim; Friedrich Kretschmar
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2004-10-07
Filing date: 2005-10-06
Publication date: 2007-09-05
Anticipated expiration: 2025-10-06
Also published as: PL1827864T3; ATE405434T1; DE102004049118A1; CN101035685B; EP1827864B1; US20070241553A1; PT1827864E; RU2386540C2; CA2579470A1; SI1827864T1; CN101035685A; RU2007117933A; WO2006040069A1; US8276945B2; DE502005005150D1; HK1106934A1; ES2313427T3; CA2579470C

Abstract

The present invention relates to a security element for securing valuable articles, having an optically variable layer (20) that imparts different color impressions at different viewing angles. According to the present invention, in a covering area (32), a semi-transparent ink layer (34) is disposed on top of the optically variable layer (20), the color impression of the optically variable layer (20) being coordinated with the color impression of the semi-transparent ink layer (34) in the covering area (32) when viewed under predefined viewing conditions.

Description

SECURITY ELEMENT WITH AN OPTICAL VARIABLE LAYER AND METHOD FOR THE PRODUCTION THEREOF

The invention relates to a security element for safeguarding objects of value with an optically variable layer which imparts different color impressions at different viewing angles. The invention further relates to a method for producing such a security element, a transfer element, a security paper and a value object with such a security element.

Valuables, such as branded goods or documents of value, are often provided with security elements for the purpose of protection, which allow verification of the authenticity of the object of value and at the same time serve as protection against unauthorized reproduction. Valuable items in the sense of the present invention are, in particular, bank notes, shares, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other papers susceptible to counterfeiting, such as passports and other identity documents, as well as product security elements, such as labels, seals, packaging and the same. In the following, the term "valuable item" includes all such items, documents and product securing means. The term "security paper" is understood to mean the item of value that can not be processed yet.

The security elements can be embodied, for example, in the form of a security thread embedded in a banknote, an applied security strip or a self-supporting transfer element, such as a patch or a label, which is applied to a value document after its manufacture.

In order to prevent the adjustment of the security elements even with high-quality color copying machines, the security elements often have a visual appearance variable elements that give the viewer a different image impression under different viewing angles and show, for example, a different color impression or different graphic motives.

In this context, it is known to use security elements with multi-layered thin-film elements in which the color impression for the viewer changes with the viewing angle and, for example, changes from green to blue, blue to magenta or magenta to green when the security feature is tilted. Such color changes when tilting a security element are referred to below as a color-shift effect or a color-shift effect.

The document US Pat. No. 3,858,977 describes such optical interference coatings with color shift effect in connection with security elements. Depending on the type and number of layers in the layer structure, two or more different color effects depending on the viewing angle may occur.

The document WO 03/068525 A1 discloses a security element for insertion into or application to a security document. The security element has a substrate with a reflection layer and an interference element with a color shift effect on each side of the reflection layer. In addition, the security element may have diffractive structures and / or areas with negative writing.

A value document with an optically variable material in the security element is also described in document WO 00/50249 A1. Here lies the optically variable material in the form of interference layer material or of liquid-crystalline material, which also conveys different color impressions at different viewing angles. An embodiment is described in which two liquid-crystalline materials with thermochromic properties are used in adjoining areas, which have the same appearance under normal ambient conditions, but show a color change to different colors when heated.

If an area of a security element merely has a simple color-tilting effect, then this is often only slightly noticeable and is easily overlooked as an authenticity feature. Two adjacent areas, each showing a color shift effect with a different color change, are indeed more conspicuous, but are often perceived by observers as confusing.

Based on this, the object of the invention is to specify a generic security element with high counterfeit security, which avoids the disadvantages of the prior art.

This object is achieved by the security element having the features of the main claim. A production method for the security element, a transfer element, a security paper and a valuable article with such a security element are specified in the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, a semitransparent ink layer is arranged over the optically variable layer in an overlapping area, wherein the color impression of the optically variable layer is, when viewed under preferential conditions, If viewing conditions are adapted to the color impression of the semitransparent ink layer in the covering area. The invention is based on the idea of employing a combination of two color areas which have a very similar effect from a certain viewing direction and in which the color impression of one of the areas changes during tilting, but the other area remains color-constant. Such a combination looks visually attractive, is self-explanatory for the user and also has a high security against counterfeiting.

The immediate vicinity of color variable and constant color area enhances the optical conspicuousness and thus draws the attention of the observer to the security element. The color-constant region simultaneously forms a visually stationary pole and a comparison point for the color-variable region in the authenticity test. The combination of the two color effects in the immediate vicinity makes it difficult to adjust the security element since freely available colors or foils with color-tilting effects can no longer be used directly.

The use of a semitransparent ink layer causes, in comparison to the use of opaque ink layers, a much greater approximation of the color impressions of the optically variable layer and of the coverage area under the predetermined viewing conditions. In particular, as explained in detail below, unavoidable color fluctuations of the optically variable layer within a production series can be captured and the brilliance and gloss in the coverage area can be matched to the high values typical of optically variable layers.

In a preferred embodiment, the semitransparent ink layer in a spectral range in which the color impression of the optically variable Layer is adapted to the color impression of the semitransparent ink layer, a light transmission between 60% and 100%, more preferably between 80% and 100%.

The semitransparent ink layer can be applied in various ways, with advantage it is printed on the optically variable layer, for example in screen printing, gravure printing, flexographic printing, or another suitable printing process.

In order to introduce additional features into the security element, the semitransparent color layer is present in preferred embodiments in the form of characters, patterns or codes. The semitransparent ink layer can also have recesses in the form of characters, patterns or codings.

A particularly appealing effect can be achieved if the optically variable layer and the semitransparent color layer are matched to one another such that, when the security element is viewed vertically, the color impression of the optically variable layer outside the coverage area essentially corresponds to the color impression of the semitransparent color ¬ layer corresponds to the coverage area. When viewed vertically, which often results in the first perception of a security element applied to a valuable item, the color-variable and the color-constant range initially impart substantially the same color impression. When the security element is tilted, the color impression changes in the color-variable range, while it remains unchanged in the color-constant coverage area. Instead of having a semi-transparent ink layer, the fiction, contemporary security element can also be equipped with a screened ink layer. As a result, the color impressions of the optically variable layer and of the overlapping area under the predetermined viewing conditions are likewise brought about in comparison with the use of full-surface opaque color layers. With the aid of the screening, a type of semi-transparency of the color layer is thus produced, so that opaque color layers in the color-constant coverage area can also be used. In preferred embodiments, the screened color layer is present as a negative grid, a positive grid or a bar screen.

The optically variable layer can consist of a single layer, but as a rule it is formed to achieve particularly attractive, optically variable effects of several partial layers.

In a preferred variant of the invention, the optically variable layer is formed by a thin-film element with color-shift effect, which preferably contains a reflection layer, an absorber layer and a dielectric spacer layer arranged between the reflection layer and the absorber layer. The color shift effect in such thin-film elements is based on viewing angle-dependent interference effects due to multiple reflections in the different sub-layers of the element. The path difference of the light reflected at the different layers depends on the one hand on the optical thickness of the dielectric spacer layer, which determines the distance between the absorber layer and reflection layer, and on the other hand varies with the respective viewing angle.

Since the path difference lies in the order of magnitude of the wavelength of the visible light, the result of cancellation and amplification is wavelengths with an angle-dependent color impression for the observer. By a suitable choice of material and thickness of the dielectric spacer layer, a plurality of different Farbkippeff ekte be taltet ges, for example, tilting effects in which the color impression changes with the viewing angle of green to blue, from blue to magenta or from magenta to green.

Alternatively, the thin-film element may have a layer structure which, in addition to a reflective layer, comprises a dielectric spacer layer that is partially absorbent. An additional absorber layer can be omitted in this case.

The reflection layer of the thin-film element is preferably formed by an opaque or by a semitransparent metal layer. As a reflection layer, an at least partially magnetic layer can be used, so that a further authenticity feature can be integrated without requiring an additional layer in the layer structure.

The reflective layer may also have recesses in the form of patterns, characters or codes that form transparent or semi-transparent regions in the thin-film element. In the transparent or semi-transparent recess areas, the viewer is presented with a striking contrast to the surrounding color shift effect. In particular, the patterns, characters or codes in transmitted light can light up brightly when the thin-film element is applied to a transparent carrier.

The thin-film element can also be formed by superimposed absorber layers and dielectric spacer layers, wherein a plurality of absorber and spacer layers alternately overlap one another. orders can be. Instead of alternating absorber layers and dielectric spacer layers, it is also possible to provide exclusively dielectric spacer layers, wherein adjoining layers have very different refractive indices so that a color shift effect is produced. The refractive indices of the adjoining dielectric spacers differ expediently by at least 0.03.

The dielectric spacer layer is preferably formed by a print layer or by an ultrathin film, in particular a stretched polyester film.

As an alternative or in addition to recesses in the reflection layer, the absorber layer and / or the spacer layer may also have recesses in the form of patterns, characters or codes. In the recessed areas of the absorber layer or the spacer layer, no color-tilting effect occurs.

The thin-layer element formed from partial layers can also be in the form of pigments or particles with a suitable particle size, distribution and

Form factor present, the other materials, in particular a Druckfar¬ be admixed.

In another, likewise preferred variant of the invention, the optically variable layer contains one or more layers of liquid-crystalline material, in particular of cholesteric liquid-crystalline material. The liquid-crystalline material is expediently present as a liquid-crystalline polymer material or in the form of pigments embedded in a binder matrix. In a further equally advantageous variant of the invention, the optically variable layer is formed by a diffractive diffraction structure. In this variant, the diffractive diffraction structure and the semitransparent color layer are advantageously matched to one another in such a way that they produce substantially the same color impression when viewed at a predetermined, non-perpendicular viewing angle. The safety element according to the invention then shows the observer, when viewed vertically, first of all two different color impressions which equalize during tilting until the color impressions of the color-variable and the color-constant region coincide in the predetermined viewing direction.

In an advantageous embodiment, the diffractive diffraction pattern forms a grating image for displaying a true color image, which has a plurality of true color areas which illuminate in a desired true color when the grating image is illuminated.

Lattice patterns with a given lattice constant only diffract light of a certain wavelength into the viewing direction, so that the lattice fields occupied with a uniform lattice pattern always shine in one of the spectral colors. To the naturally occurring colors, the so-called

These true colors are represented as a mixture of certain basic colors since the human eye has three different pin systems with overlapping sensitivity ranges in the red, green and blue parts of the visible spectrum In the real color areas of a grid image, small subregions are then defined in which, for example, three different gratings are introduced which bend red, green and blue light in the desired viewing direction The ones with the grid patterns Occupied area proportions are chosen according to the red, green and blue portions of the respective true colors.

In a development of the invention, the security element contains at least one further layer provided with a security feature. The at least one further layer may advantageously comprise an optically effective microstructure which is arranged below the layer structure of optically variable layer and semitransparent ink layer. In particular, the optically effective microstructure can be designed as a diffractive diffraction structure. Thus, for example, color shift holograms can be realized in which the Farbkippeff effect of the optically variable layer is combined with a holographic effect. Alternatively, the optically effective microstructure may also be a matt structure which, when viewed, exhibits no diffractive effects, but merely has a scattering effect. In a further advantageous embodiment, the optically effective microstructure may be formed by an arrangement of micromirrors, microlenses or the like.

In order to enable an automatic authenticity check and optionally a more extensive sensory detection and processing of the valuables equipped with the security element, the at least one further layer can also contain machine-readable feature substances, in particular magnetic, electrically conductive, phosphorescent, fluorescent or other luminescent substances.

In an advantageous embodiment, the security element has a substrate on which the optically variable layer and the semitransparent color layer are arranged. This substrate may in particular be formed by a plastic film. The security element is preferably a security thread, a security band, a security strip, a patch or a label for application to a security paper, value document or the like.

The invention also includes a method for producing a security element of the type described above, in which a semi-transparent color layer is arranged in an overlapping region via an optically variable layer, which conveys different color impressions at different viewing angles. The color impression of the optically variable layer when viewed under predetermined viewing conditions is adapted to the color impression of the semitransparent ink layer in the coverage area.

The semitransparent ink layer is advantageously printed on the optically variable layer in the process according to the invention. It is advisable to apply the optically variable layer itself to a substrate, in particular to print it on. When using a transparent substrate, it is also possible first to print it with the semitransparent ink layer, onto which in turn the optically variable layer can be applied, in particular printed.

In advantageous developments, the optically variable layer and / or the semitransparent ink layer are provided with recesses in the form of patterns, symbols or codes.

The invention further comprises a transfer element for application to a security paper, document of value or the like, which is equipped with a security element of the type described above. The transfer element preferably has a carrier film on which the security device element in the reverse order, as it later comes to rest on the Sicherheitspa¬ pier or the object of value, prepared and subsequently ßend by means of an adhesive layer, for. As adhesive or paint layer is transferred in a hot embossing process in the desired outline contours on the security paper or the valuable item. It therefore makes sense to initially apply the semitransparent ink layer to the carrier film, in particular to print it on. The optically variable layer is then advantageously printed on the semi-transparent ink layer. Alternatively, the optically variable layer can also be vapor-deposited or applied in another suitable manner. The separate carrier film can then be removed after transfer from the layer structure of the security element. Alternatively, the carrier film can remain as a protective layer as an integral part of the security element on the layer structure. Optionally, between the security element and the carrier film, a release or release layer, for. As a wax may be provided.

A security paper for the production of security documents, such as banknotes, identity cards or the like, is preferably equipped with a security element of the type described above. In particular, the security paper can comprise a carrier substrate made of paper or plastic.

The invention also includes a valuable article such as a brand name article, a value document or the like provided with a security element described above. The valuable item may be, in particular, a security paper, a value document or a product packaging.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a bar and proportions true reproduction was omitted in order to increase the An¬ vividness.

Show it:

1 shows a schematic representation of a banknote with a embedded security thread and a glued transfer element, in each case according to an exemplary embodiment of the invention,

2 is a plan view of a portion of the security thread of

Fig- X

3 shows a cross section through the security thread of FIG. 2 along the line III-III, FIG.

4 shows a diagram which shows the reflection spectra of a thin-film element alone and after printing of a semitransparent ink layer in the wavelength range λ from 300 nm to 2000 nm,

5 shows a cross section through a transfer material according to the invention,

6 is a more detailed view of the transfer element of FIG. 1 in plan view,

7 shows a hologram security thread according to another exemplary embodiment of the invention in cross section, 8 shows the layer structure of a security element according to the invention with a liquid crystal structure as optically variable layer, and FIG

9 the layer structure of a security element according to the invention with a diffractive diffraction structure as optically variable layer,

10 is a diagram showing the transmission spectrum of a transparent printed with a semi-transparent ink layer

Plastic film in the wavelength range λ from 300 ran to 750 nm shows.

The invention will now be explained in more detail using the example of a banknote. 1 shows a schematic representation of a banknote 10 with two security elements 12 and 16, each formed according to an embodiment of the invention. The first security element represents a security thread 12, which protrudes at certain window areas 14 on the surface of the banknote 10, while it is embedded in the intervening areas in the interior of the banknote 10. The second security element is formed by a glued transfer element 16 of any shape.

The structure of the security thread 12 will now be explained in more detail with reference to Figures 2 and 3. FIG. 2 shows a plan view of a partial area of the security thread 12, FIG. 3 shows a cross section through the security thread along the line III-III of FIG. 2.

The security thread 12 contains a thin-film element 20 with Farbkipp- eff ect, which is applied to a transparent carrier film 22. The optical Variable thin-film element 20 comprises a reflection layer 24 formed by an opaque aluminum layer, an ultrathin spacer layer 26 applied to the reflection layer, and a partially transparent absorber layer 28, eg of chromium. As explained above, the color shift effect of the thin-film element 20 is based on interference effects due to multiple reflections in the different sub-layers 24, 26, 28 of the element.

One half of the security thread 12 forms a covering area 32, in which a semi-transparent ink layer 34 is printed on the thin-film element 20. In the immediately adjacent, uncovered region 36, the optically variable layer 20 is present without a printed ink layer. The thin-film element 20 and the color layer 34 are matched to one another in such a way that they produce substantially the same color impression at a perpendicular viewing angle. The color impression of the thin-layer element 20 at a normal viewing angle is also referred to below as a vertical tilting color.

When tilting the security thread 12, the color impression of the thin-film element 20 changes in the uncovered region 36, while the color impression in the covering region 32 remains virtually unchanged. Such a combination of a color-variable range with a color-constant range in the immediate vicinity of the visual conspicuity of Farbkippeff ect is still significantly enhanced because the human eye reacts to the color differences occurring more than on the color change itself. The observer's attention is therefore drawn even more to the safety feature. Moreover, the mode of operation of the security element is self-explanatory, so that it can easily be checked for authenticity by anyone. The combination of a color-calm element with a color-tilting element is generally perceived as visually very appealing. For potential counterfeiters, the combination of the two color effects in the immediate vicinity signi? Cantly complicates the adjustment since freely available colors or foils with color-tilting effects can no longer be used directly.

The use according to the invention of a semi-transparent ink layer 34 has several advantages which will be explained in detail below.

The use of a semitransparent ink layer 34 leads to an additional matching of the color impression of the thin-film element 20 in the uncovered region 36 and the color impression of the semitransparent ink layer 34 in the overlap region 32. While the color location of the printed semitransparent ink layer 34 can be set very accurately and reproducibly If the vertical tilting color in which the thin-film element appears at a normal viewing angle varies, as a rule, something may vary from security element to security element as a result of manufacturing variations. These color variations, which are due to the extremely high sensitivity of the color visible at a normal angle to the layer thickness of the dielectric spacer layer, are small, but quite perceptible to the naked eye.

If the color layer 34 is semitransparent according to the invention, the vertical tilt color of the thin-film element 20 partially shines through the color layer 34 and contributes to the overall color impression of the security element in the overlap area 32 when viewed perpendicularly. Now varies the vertical tilt color of the thin-film element 20 in the uncovered region 36 of security element to security element Something, the color impression in the covering area 32 changes accordingly due to the translucent component. The Gesamtfarbein¬ pressure in the overlap region 32 adapts to the color impression in the uncovered region 36.

The contribution of the vertical tilting color to the overall color impression is illustrated in the diagram of FIG. 4, which shows the reflection spectrum 40 of the thin-film element 20 in the uncovered region 36 at a perpendicular viewing angle. Also shown is the reflection spectrum 42 of the combination of thin-film element 20 and semitransparent color layer 34 in the overlapping area 32. It can clearly be seen that the color impression of the thin-film element 20 remains visible through the semitransparent color layer 34 and amounts to the overall color impression. For vertical viewing, in spite of the unavoidable small thickness fluctuations of the spacer layer, an excellent correspondence of the color impressions in the two areas can thus be achieved.

The semitransparent ink layer 34, however, is highly translucent only at an almost perpendicular viewing angle. At an oblique viewing angle, it reflects significantly more light compared to perpendicular viewing so that the light portion of the underlying thin film element 20 is forced into the background.

Overall, when viewed vertically, the translucent color contribution of the thin-film element 20 in the overlapping region 32 contributes to the equalization of the color impressions of the two adjacent regions. At an oblique angle Be¬ the translucent color contribution occurs in the background, so that then the color constant contribution of the semi-transparent ink layer 34 dominates the overall impression of the coverage area 32. The color contribution of the semitransparent ink layer will now be explained in more detail with reference to a transmission spectrum 46 of a color-printed, transparent plastic film illustrated in FIG. The semitransparent color layer, in the example a red printing ink, has a very good transparency in the red spectral range (about 90%), while it is e.g. B. in the green Spektral¬ range at a wavelength of about 550 ran only a Lichtdurchläs¬ sigkeit of about 15%. The effect according to the invention becomes effective precisely due to this different spectral transmission. In particular, the color impression of the semitransparent ink layer in the covering area of an underlying tilting color, which appears magenta, for example, at a perpendicular viewing angle, fits well, since the semi-transparent ink layer is almost transparent in the relevant spectral range. If, however, the security element is viewed at a different tilt angle, the color impression of the tilting color changes, for example, from magenta to green. The semitransparent color layer has a much lower transparency in this wavelength range, so that the translucent color contribution of the tilting color passes into the background and instead the color-constant contribution of the overlying color layer dominates.

A further advantage of the use of semitransparent color layers is the equalization of the brilliance of the two partial areas 32 and 36. The reflection layer 24 of the thin-film element 20 is usually designed such that it reflects about 90% of the incident light and the color-shift effect occurs in the uncovered area 36 therefore very bright and with high brilliance in appearance. The luminance value or the L value in the CIELab color space, which essentially indicates the proportion of the reflected light, is therefore very high in the uncovered area 36. Conventional printing inks do not achieve such high brilliance and such high L values. When an opaque printing ink is used for covering, the color impression of the vertical tilting ink and the printing ink will therefore be different, even if the color loci (expressed by the red-green color information a and the blue-yellow color information b in CIELab System) are almost the same. When using a semi-transparent ink layer, an additional light contribution of the thin-film element 20 is obtained in the overlapping region 32, so that its brilliance is increased and thus further approximated to the color impression of the uncovered region 36.

Moreover, the interference layer structure of the thin film element 20 is extremely flat, so that the uncovered region 36 also has a high gloss and acts almost like a colored mirror. The gloss of printing inks is much lower in comparison. For opaque inks, this difference in glossiness is evident to a viewer, even if the color loci (again expressed by a and b in the CIELab system) are nearly identical. The use of a transparent layer of color 34 increases the gloss in the covering area 32, thanks to the translucent high-gloss thin-film element 20, so that the visual impression for the viewer is matched to the impression of the uncovered area 36.

In the reflection layer 24 of the thin-film element 20, in the exemplary embodiment of FIGS. 2 and 3, recesses 30 are introduced which, for example, can form a negative writing. In the region of these recesses 30, the thin-film element 20 is transparent, so that in addition to the described effects, a striking contrast effect in the transmitted light results.

If a security element, such as the transfer element 16 of FIG. 1, is applied in the form of a patch or strip to the valuable article to be secured. brought, so it is useful initially prepared in the form of label material or transfer material, triggered in the desired shape and then transferred to the object to be protected. An example of such a transfer material is shown in cross-section in FIG. 5, the released transfer element 16 glued onto a valuable article is shown in plan view in FIG.

The transfer material 50 contains a carrier layer 52, in particular a plastic film, onto which the layer structure 54 of optically variable layer and semitransparent color layer is applied. It may be advantageous to provide a separating layer 56 between the layer structure 54 and the carrier layer 52. An adhesive layer 58, for example a hot-melt adhesive layer, is provided on the layer structure 54 of the transfer material, with which the security element can be fastened on the object to be protected.

For transfer, the transfer material 50 is placed on the article and the adhesive layer 58 activated, for example by heat. Subsequently, the carrier layer 52 is removed from the object, so that only the glued-on layer structure 54 remains on the object to be protected. The layer sequence of the layer structure 54 is reversed by adhering to the object to be protected in relation to the layer in the transfer material 50, so that the semitransparent ink layer on top of the article is applied to the carrier layer 52 before the optically variable layer in the production of the transfer material must become.

Fig. 6 shows the triggered and glued transfer element 16 in plan view. Like the security thread of FIGS. 2 and 3, the transfer element contains an optically variable thin-film element 60 with a color-shift effect and a in regions above the thin-film element 60 arranged semitranspa¬ rente color layer 62nd

In the exemplary embodiment, the thin-film element 60 and the color layer 62 are formed by concentric circular disks, the semitransparent ink layer 62 covering only the central, inner region of the thin-film element 60. In the outer, uncovered region 64, in which the thin-film element 60 is present without covering by a colored layer, recesses 66 in the form of the lettering "PL 2004" are introduced into the reflection layer of the thin-film element 60, which appear bright in transmitted light.

The thin-film element 60 and the semitransparent ink layer 62 are coordinated with one another in this exemplary embodiment in such a way that they produce essentially the same color print at a perpendicular viewing angle. The entire circular disk of the thin-film element 60 thus appears with a uniform color impression when viewed vertically. When the transfer element 16 is tilted, the color impression of the outer, non-covered ring 64 changes due to the color-shift effect of the thin-film element 60, while the inner disk, overprinted with the semitransparent ink layer 62, remains color-constant.

The security element of the exemplary embodiment shown in FIG. 7 represents a hologram security thread 70 in which an optically variable layer with color-shift effect is additionally provided with a flat optical microstructure. This microstructure may be, for example, a diffraction structure 74. For this purpose, an embossing lacquer layer 78 is applied to a carrier film 76, into which the desired diffraction structure 74 is embossed. The thin-film element 72, whose layer structure may be formed, for example, as in FIG. 3, is applied to the embossing lacquer layer 78.

A semitransparent ink layer 80 is applied to a partial region of the hologram security fabric 70, and the semitransparent ink layer 80 and the thin-film element 72 are matched to one another in such a way that they produce substantially the same color impression at a perpendicular viewing angle. In addition to the effects described in connection with FIGS. 2 and 3, the hologram security thread 70 exhibits a holographic effect combined with the color-shift effect.

In the embodiments described so far, the optically variable layer is always formed by a thin-film element with a color-shift effect. However, the combination of optically variable layer and semi-transparent color layer according to the invention is not limited to such embodiments, but can also be used for all other types of optically variable layers, as follows using the example of a liquid crystal structure (FIG. 8) and FIG Diffractive diffraction structure (Fig. 9).

8 shows the basic layer structure of a security element 90 according to the invention, in which the optically variable layer contains one or more layers of liquid-crystalline material. For this purpose, a smooth film 92, for example a PET film of good surface quality, is provided with an absorbing, dark background layer 94. One or more layers 96-1, 96-2,... 96-n of a cholesteric liquid-crystalline material are / is applied to this background layer 94. Alignment layers and / or adhesive layers 98 can be provided between the liquid-crystal layers, which serve to align the liquid crystals in the liquid crystal layers or the connection of the individual liquid-crystalline layers and to compensate for unevenness in the substrate. A portion of the security element 90 is provided with a semi-transparent ink layer 100. The semitransparent ink layer and the liquid crystal structure are matched to one another in such a way that they produce substantially the same color impression at a perpendicular viewing angle. When tilting the security element 90, the liquid crystal structure offers the viewer a changing color impression, while the color impression of the area provided with the color layer 100 remains substantially constant.

In the security element 110 of FIG. 9, the optically variable layer is formed by a diffractive diffraction structure which, when observed under predetermined viewing conditions, provides a certain color impression to which the semitransparent color layer is tuned.

The security element 110 contains a base film 112 and a printed, embossed and cured UV lacquer layer 114. The relief structure of the lacquer layer 114 is provided with a thin reflective metal layer 116 or a dielectric layer in a subsequent vapor deposition step, so that depending on the embossing a diffractive Diffraction structure with the desired properties arises. For example, the diffraction structure in diffuse illumination can diffract red light into a predetermined viewing direction 120. For illustration, an oblique viewing direction 120 is shown in the figure with a viewing angle of 60 ° to the vertical.

In a subarea, the diffractive diffraction structure is provided with a semi-transparent color layer 118, wherein the semitransparent color layer 118 and the diffraction structure are matched to one another in such a way that, viewed from the predetermined viewing direction 120, considerably cause the same color impression. In the exemplary embodiment, the semitransparent ink layer 118 is selected such that it also reflects red light in the viewing direction 120 in the case of diffuse illumination.

The security element 110 of FIG. 9 initially shows the observer two different color impressions when viewed vertically. When the security element is tilted, the color impressions of the area covered with the color layer and the area uncovered equalize until they practically coincide from the predetermined viewing direction 120. By means of a suitable design of the diffractive diffraction structure, it is possible to set a very narrow angle range for the agreement of the color impressions, so that a characteristic color effect which is difficult to imitate arises.

Of course, in addition to the layers described in the above exemplary embodiments, further layers may be present, which have been omitted here for reasons of clarity. Thus, the above layered structures may have protective layers which are formed, for example, by a plastic layer or film. In addition, the individual layers of the security elements, in particular the optically variable layer and the semitransparent ink layer, can be spaced apart by further transparent layers or be present on different sides of a transparent carrier film.

Claims

Patent claims

1. Security element for securing valuables with an optically variable layer, which gives different color impressions at different viewing angles, characterized in that a semi¬ transparent ink layer is arranged in a covering area over the optically variable layer, and that the color impression of the optically variable Layer is adapted to the color impression of the semitransparent ink layer in the coverage area under predetermined viewing conditions.

2. A security element according to claim 1, characterized in that the semitransparent color layer in a spectral range in which the Farb¬ impression of the optically variable layer is adapted to the color impression of the semitransparent layer, a light transmission between 60% and 100%, preferably between 80% and 100%.

3. Security element according to claim 1 or 2, characterized in that the semi-transparent ink layer is printed on the optically variable layer.

4. Security element according to at least one of claims 1 to 3, da¬ characterized in that the semi-transparent ink layer is in the form of characters, patterns or codes.

5. Security element according to at least one of claims 1 to 4, da¬ characterized in that the semitransparent color layer Aussparun¬ conditions in the form of characters, patterns or codes has.

6. Security element according to at least one of claims 1 to 5, da¬ characterized in that when viewed perpendicularly the Sicherheitssele¬ ment the color impression of the optically variable layer outside the Überde¬ ckungsbereich substantially corresponds to the color impression of the semitransparent ink layer in the coverage area.

7. security element for hedging valuables with an optically variable layer, which gives different color impressions at different viewing angles, characterized in that in a coverage area above the optically variable layer a raster¬ te color layer is arranged, and that the color impression of optically variab¬ len Layer is adapted when viewed under predetermined viewing conditions to the color impression of the screened color layer in the coverage area.

8. Security element according to claim 7, characterized in that the screened ink layer has a negative grid, a positive grid or a bar screen.

9. Security element according to at least one of claims 1 to 8, da¬ characterized in that the optically variable layer is formed of several Teil¬ layers.

10. The security element according to claim 1, characterized in that the optically variable layer is formed by a thin-layer element with a color shift effect.

11. The security element according to claim 10, characterized in that the thin-film element is a reflection layer, an absorber layer and includes a dielectric spacer layer disposed between the reflective layer and the absorber layer.

12. The security element according to claim 10, characterized in that the thin-film element contains a reflection layer and a dielectric spacer layer, wherein the dielectric spacer layer is formed partially absorptive.

13. The security element according to claim 11 or 12, characterized marked, that the reflection layer by an opaque or semi-transparent

Metal layer is formed.

14. A security element according to at least one of claims 11 to 13, characterized in that the reflection layer is at least partially present as a magnetic layer.

15. The security element according to claim 10, characterized in that the thin-film element contains at least one absorber layer and at least one dielectric spacer layer, wherein the absorber layers and the dielectric spacer layers are arranged alternately one above the other.

16. The security element according to claim 10, characterized in that the thin-film element contains a plurality of dielectric spacer layers, wherein adjoining layers of the dielectric spacer layers have strongly different refractive indices.

17. The security element according to claim 16, characterized in that the refractive indices of the adjacent dielectric spacer layers differ by at least 0.03.

18. A security element according to at least one of claims 11 to 17, characterized in that the dielectric spacer layer is formed by a pressure layer.

19. The security element according to at least one of claims 11 to 18, characterized in that the dielectric spacer layer is formed by an ultrathin film, in particular a stretched polyester film.

20. A security element according to at least one of claims 11 to 14, characterized in that the reflection layer has recesses in the form of patterns, characters or codes that form transparent or semitransparent areas in the thin-film element.

21. The security element according to claim 11, characterized in that the absorber layer and / or the spacer layer has recesses in the form of patterns, characters or codes in which no color-shift effect can be recognized.

22. A security element according to at least one of claims 11 to 19, characterized in that the thin-film element is present in the form of pigments or particles of suitable size and form factor.

23. A security element according to at least one of claims 1 to 9, da¬ characterized in that the optically variable layer one or more Layers of liquid-crystalline material, in particular of cholesteric liquid-crystalline material containing.

24. The security element according to claim 23, characterized in that the liquid-crystalline material is present as a liquid-crystalline polymer material or in the form of pigments embedded in a binder matrix.

25. The security element according to claim 1, characterized in that the optically variable layer is formed by a diffractive diffraction structure.

26. The security element according to claim 25, characterized in that the diffractive diffraction structure forms a grating image for representing a real image image, which has a plurality of true color areas which illuminate the illumination of the grating image in a desired true color.

27. Security element according to at least one of claims 1 to 26, characterized in that the security element contains at least one weite¬ re provided with a security feature layer.

28. A security element according to claim 27, characterized in that the at least one further layer comprises an optically effective microstructure, which is arranged below the layer structure of optically variable layer and a transparent layer of color.

29. The security element according to claim 28, characterized in that the optically effective microstructure is a diffractive diffraction structure, a matt structure or an optically effective microstructure produced by micromirrors or microlenses.

30. The security element according to claim 27, characterized in that the at least one further layer contains maschi¬ nenlesbare feature substances, in particular magnetic, electrically conductive, phosphorescent, fluorescent or other luminescent substances.

31. The security element according to at least one of claims 1 to 30, characterized in that the security element has a substrate on which the optically variable layer and the semitransparent color layer are arranged.

32. The security element according to claim 31, characterized in that the substrate is formed by a plastic film.

33. Security element according to at least one of claims 1 to 32, characterized in that the security element is a security thread, a security tape, a security strip, a patch or a label for application to a security paper, document of value or the like.

34. A method for producing a security element according to claim 1, wherein a semitransparent color layer is arranged in an overlapping region via an optically variable layer, which conveys different color impressions at different viewing angles, wherein the color impression of the optically variable layer is adapted to the color impression of the semitransparent ink layer in Überüberungsbe¬ area under consideration under predetermined viewing conditions rich.

35. The method according to claim 34, characterized in that the semi-transparent color layer is printed on the optically variable layer.

36. The method of claim 34 or 35, characterized in that the optically variable layer is applied to a substrate, in particular auf¬ printed.

37. The method according to at least one of claims 34 to 36, characterized in that the optically variable layer and / or the semitransparent color layer are provided with recesses in the form of patterns, characters or codes.

38. Transfer element for application to a security paper, Wertdo¬ document or the like, with a security element according to at least one of claims 1 to 37.

39. Transfer element according to claim 38, characterized in that the transfer element comprises a carrier film.

40. Security paper for the production of security or Wertdo¬ documents, such as Bänknoten, checks, ID cards, certificates or derglei¬ chen, the che with a security element according to at least one of Ansprü¬ 1 to 37 or a transfer element according to claim 38 or 39 out ¬ tattet.

41. Security paper according to claim 40, characterized in that the security paper comprises a carrier substrate made of paper or plastic.

42. Valuable item, such as branded article, valuable document or the like, with a security element according to at least one of claims 1 to 37 or a transfer element according to claim 38 or 39.

43. The object of value according to claim 42, characterized in that the object of value is a security paper, a document of value or a product packaging.