The invention relates to an anti-counterfeit security object, i.e. an object that is difficult to counterfeit, with a volume hologram.
Security objects of this type may e.g. be bank notes, passports, credit cards, identity cards, packages or tags for valuable goods, data carriers, letterheads, etc. Such objects are often equipped with security features with the purpose to make counterfeiting difficult.
Security features based on holograms are widely known. While most of these features are using surface holograms (i.e. surface diffraction gratings having a depth in the order of only one or a few wavelengths), “volume holograms” have also been proposed for such applications, see e.g. EP 1 091 267. Volume holograms have gratings of a depth that is much larger than the wavelength of visible light, e.g. a depth of at least 10 μm, advantageously at least 50 μm. They can have high diffraction efficiencies, generate powerful images and have well-defined diffraction angles and wavelengths.
With the increasing skill of counterfeiters, a further improvement of such security objects is desired. Also, it is desired that the security objects have characteristics that makes them easy to be verified.
Hence, it is a general object of the invention to provide a security object that provides strong anti-counterfeiting protection and/or that is easy to verify.
Now, in order to implement these and still further objects of the invention, a security object according to the independent claims is provided.
Such a security object contains a first visible motif stored in the volume hologram and a second visible motif stored outside the hologram.
A “motif” in this context designates any kind of symbol, pattern, character or similar that is visible to the unaided eye or to machinery.
“Stored outside the hologram” designates any kind of motif that is not encoded in the refractive index or absorption gratings of the volume hologram, such as a print on the substrate, or a non-holographic coloring of the matrix containing the volume hologram.
The first and the second motif are arranged in alignment, i.e. they are mutually aligned in a defined way. For example, an edge or line formed by the first motif may coincide with, be collinear with or be parallel with an edge or line formed by the second motif.
The first motif is visible under a given viewing condition only, as it is typical for motifs stored in a hologram. For example, it may only be visible when viewing the volume hologram from a first given angular range while illuminating the hologram from a second given angular range with light in a given spectral range. Hence, by deviating from the viewing condition, the first motif may partially or completely disappear or may change its shape or color.
When viewing the first motif under the viewing condition, it combines with the second motif to a third motif.
This kind of arrangement not only allows to check the presence of the first motif but also to compare its relation to the second motif, which provides a further parameter for checking a document's authenticity.
In a particularly advantageous embodiment, the second motif is formed at least in part by an optically variable device (OVD), such as a surface hologram, an optically variable pigment (OVP) that changes its color depending on the viewing direction, or microscopic holes, i.e. a feature that looks different under different angles. This combination allows to provide a very distinctive behavior of the motifs that makes them easy to detect. This is in particular true if the second motif becomes at least partially visible under the viewing condition of the first motif or if the second motif becomes at least partially invisible under the viewing condition of the first motif, because (in both cases) the two motifs seem to interact or to “belong together”.
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:
In the present embodiment, security feature 5 comprises visible motifs. The first motif 6, represented in the figure by a hatched pattern, forms the lower halves of the letters ‘100’, while the second motif 7, represented in the figure by a dotted pattern, forms the upper halves of the letters ‘100’. The first and the second motif are mutually aligned to form, in combination, the letters ‘100’.
The first motif 6 is formed by the diffraction grating of a volume hologram 8, as it is shown by the embodiment of
Volume hologram 8 is structured to form the first motif 6, e.g. by cutting the matrix 9 to have the shape of the lower halves of the letters ‘100’ while the volume hologram 8 extends over the whole matrix 9, or limiting the extension of the volume hologram 8 to the shape of the lower halves of the letters ‘100’ while the matrix 9 may have larger size.
Suitable materials and methods for preparing a volume hologram are known to the person skilled in the art and are e.g. described in WO 03/036389 by Xetos AG, Germany.
Typically, the first motif 6 is visible under a certain viewing condition only, because the diffraction condition of the hologram's diffraction grating must be fulfilled. For example, with diffuse white light illumination, the first motif may be visible by eye as a colored image under a viewing angle α between 40° and 100° and be substantially invisible from directions outside that viewing angle.
In the example of
The document of
As can be seen from
The dye 10 may be a conventional, anisotrodic dye that has the same color from all viewing angles. However, it may advantageously comprise a optically variable pigment (OVP), as it is e.g. described in WO 02/073250. Such an OVP (also called “optically variable ink”, OVI) changes color depending on viewing angle. In an advantageous embodiment, volume hologram 7 and dye 10 are chosen such that, under the viewing condition of the volume hologram 8, both motifs have substantially the same color or complementary-colors. This, and the interaction between the first and the second motifs, adds a further security feature to the document.
A second embodiment of the invention is shown in
The volume hologram 8 and the optically variable device 12, 13 of
A further embodiment of the invention is disclosed in
Volume hologram 8 and surface grating 15 of
Hologram 8 and surface grating 15 may lie beside each other (as shown in
The Fabry-Perot filter 18 is structured, e.g. by being cut in the shape of half-letters, to form the second motif 7.
Again, the comparison of the optical properties of the two motifs 6, 7 of the embodiment of
The motifs 6, 7 of the embodiment of
Another advantageous embodiment is shown in
Advantageously, the holes 20, 21 are shaped to exhibit the second motif 7 only when viewed under an oblique angle, and the viewing condition for volume hologram 3 is such that the first motif 6 is also visible under such the same oblique angle, which gives a user a very strong indication of the validity of a document.
In general, the holes 20, 21 are advantageously shaped and positioned to exhibit the second motif 7 only under a given viewing angle range, over at least part of which viewing angle range the first motif 6 is visible as well.
As is shown in
Yet a further advantageous embodiment is shown in
In the embodiments shown so far, the first and the second motif 6, 7 each represent the lower or upper half, respectively, of the legible text ‘100’.
In combined motif 31, the first and second motifs 6, 7 again combine to form legible text, namely the text “valid”. The first motif 6 forms the even characters, while the second motif 7 forms the odd characters of the text.
In combined motif 32, the first and second motifs each form line segments, both type of lire segments being arranged collinearly to form a substantially continuous line when viewed under the viewing condition.
In combined motif 33, the first motif 6 forms a square while the second motif 7 forms two lines aligned to the edges of the square.
All these examples illustrate how the first and second motifs 6, 7 combine to a third motif that can be recognized easily.
As mentioned above, the present invention can be used as a security feature on a wide range of objects, such as banknotes, checks or other documents of value, or on passport, credit cards, id cards, but also on quality office paper or any other object where counterfeiting is to be made difficult.
While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CH2004/000541 | 8/27/2004 | WO | 00 | 9/24/2007 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/021102 | 3/2/2006 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4124947 | Kuhl et al. | Nov 1978 | A |
4705356 | Berning et al. | Nov 1987 | A |
4856857 | Takeuchi et al. | Aug 1989 | A |
5142383 | Mallik | Aug 1992 | A |
5310222 | Chatwin et al. | May 1994 | A |
5648165 | Phillips et al. | Jul 1997 | A |
5801857 | Heckenkamp et al. | Sep 1998 | A |
6089614 | Howland et al. | Jul 2000 | A |
6369947 | Staub et al. | Apr 2002 | B1 |
20060181077 | Kaule et al. | Aug 2006 | A1 |
Number | Date | Country |
---|---|---|
39 32 505 | Apr 1991 | DE |
0 304 194 | Feb 1989 | EP |
1 091 267 | Apr 2001 | EP |
02073250 | Sep 2002 | WO |
03031198 | Apr 2003 | WO |
2004011274 | Feb 2004 | WO |
Number | Date | Country | |
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20080164690 A1 | Jul 2008 | US |