Title of Invention	A SECURITY ELEMENT FOR DOCUMENTS AND A METHOD FOR ITS FABRICATION
Abstract	A security element for a document with a substrate characterized in that the security element comprises a volume hologram into which a kinetic effect has been introduced This invention also relates to a method for fabrication of the above security element for a document.

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- 1A- The invention relates to a document with a substrate and a security element which comprises an optical grating and to a security element for such a document. The invention further relates to a method for the fabrication of such a document or security element. With documents of the most varied type, for example with bank notes, securities or similar documents, a security element is often required which is intended to provide protection against copying. Security elements of this type which comprise an optical grating are already known. In the solutions previously known, optical gratings are used which as designed as surface reliefs. However, the copy protection obtained in this way is not sufficient in all cases. On this basis, it is the object of the invention to improve the copy protection in documents with a security element. This object is solved in accordance with the invention by the optical grating being a volume hologram into which a kinetic effect has been introduced. In this way, a substantially greater copy protection can be achieved. -2- In the fabrication of a volume hologram, a film or another grain-free, translucent, photosensitive medium is irradiated with coherent light, in particular with laser light. Due to the interference in the film material, Bragg network planes are created which embody the information written in the hologram. One advantageous embodiment is characterised in that the volume hologram has been fabricated with two or more different wavelengths. In this way, a controlled multicolour effect can be achieved. The controlled multi-colour effect can be obtained with the use of only two different wavelengths. When at least three different wavelengths are used which correspond to the colours in the colour triangle,a controlled fast-colour effect can be achieved. This cannot be obtained with the previously known surface relief structures as the colour dispersion is fixed by the physical principles of the diffraction grating. With a surface relief, therefore, a rainbow colour spectrum is always generated in the reconstruction with white light. In accordance with the advantageous embodiment of the method in accordance with the invention, in contrast, controlled colour effects are possible. The document or security element can be fabricated in that a volume hologram is fabricated from a surface relief by means of an optical copying process. The surface relief is used as the so-called master. The volume hologram is fabricated from this by means of an optical copying process. But it is also possible to fabricate the volume hologram by means of direct irradiation. The improved copy protection of volume holograms is based on the one hand by such volume holograms being able to be reconstructed only in monochrome form. If, therefore, an attempt is made to copy a volume hologram, this can only be successful if exactly the same wavelength of coherent light or laser light is used as in the recording of the volume hologram. Even then, the copying process will only be successful if there is no topical shrinking or swelling in the film material after the recording of the volume hologram. Based on this, an additional copy protection can be -3- obtained by topical regions of the volume hologram which are otherwise not recognisable being shrunk and/or swollen after the recording of the volume hologram so that the Bragg network planes in these regions change correspondingly. A copy of such a volume hologram could only be made with holographic means by an adaptation of the wavelength, but this is not possible as the topical regions in which the Bragg network planes have been changed are not recognisable to the outside. This means that with an only topical or inhomogeneous shrinking or swelling of the layers (network planes), the volume hologram can only be copied point by point or pixel by pixel; but this requires such a great effort that it is no longer interesting for economic reasons. On the other hand, the increased copy protection is achieved by the diffraction gratings being very angle-selective in the volume holograms. This means that the volume hologram can only be copied if exactly the same irradiation angle is used as in the recording. Even then, the volume hologram can only be copied with the greatest difficulty - if at all - if it has been applied to a surface which is not exactly smooth; if, for example, it has been applied to a document made from paper or to any other not exactly smooth surface. In this way, topical partial regions of the surface possess angles which differ slightly from one another with only small angle differences being sufficient to make copying impossible. Due to the angle differences which are created by the surface roughness, the whole hologram cannot be reconstructed with a plane wave. In the event of attempted copying, this has the result that only parts of the volume hologram are copied and that at those points where no reconstruction of the volume hologram was performed the copied hologram remains un-irradiated or that at least a clear colour difference or variation in brightness occurs. A kinetic or kinematographic effect is introduced or written into the volume hologram. To generate such kinetic effects, the diffraction structure in the volume hologram is such that patterns which occur at a given direction of illumination and observation move with regard to a coordinate system in a fixed connection with the substrate along a pre-determined path at a pre-determined speed when the substrate is moved -4- preferably in its plane, for example is turned in a certain direction of rotation and at a certain speed. By the introduction of such kinetic effects into volume holograms, the copying of these holograms can be made more difficult. Furthermore, in this way a greater recognition value can be provided. In addition, by means of different single irradiations, individual data can be irradiated into the volume hologram as well whereby the security value of the security element is enhanced even further. To explain the invention Fig. 1 shows a hologram designed as a surface relief; and Fig. 2 shows a section through a volume hologram. The surface relief shown in Fig. 1 can be applied to a document as a security element. The information in the hologram is stored in the surface structure. Fig. 2 shows a document with a substrate 1 onto which a volume hologram 2 has been applied. By means of the irradiation, there are created in the film material Bragg network planes nl, n2, etc., which are located at a distance of #d/2 (where #d is the wavelength of the light used) and whichcontain the holographic information. -5-WE CLAIM i. A security element for a document with a substrate, characterized in that, the security element comprises a volume hologram into with a kinetic effect has been introduced. 2. A security element as claimed in claim 1,wherein the volume hologram has been fabricated with two or more different wavelengths. 3. A method for the fabrication of a security element for a document with a substrate as claimed in claims 1 or 2, wherein a volume hologram is fabricated from a surface relief by means of an optical copying process. 4. A method for the fabrication of a security element as claimed in either of claims 1 or 2, wherein the volume hologram is fabricated by means of direct irradiation. 5. A method as claimed in claim 6, wherein the volume hologram is fabricated by direct irradiation with two or more wavelengths. A security element for a document with a substrate characterized in that the security element comprises a volume hologram into which a kinetic effect has been introduced This invention also relates to a method for fabrication of the above security element for a document.

Documents:

01479-cal-1998-abstract.pdf

01479-cal-1998-assignment.pdf

01479-cal-1998-claims.pdf

01479-cal-1998-correspondence-1.1.pdf

01479-cal-1998-correspondence-1.2.pdf

01479-cal-1998-correspondence.pdf

01479-cal-1998-description(complete).pdf

01479-cal-1998-drawings.pdf

01479-cal-1998-form-1.pdf

01479-cal-1998-form-2.pdf

01479-cal-1998-form-3.pdf

01479-cal-1998-form-5.pdf

01479-cal-1998-pa.pdf

01479-cal-1998-priority document.pdf

1479-CAL-1998-CORRESPONDENCE-1.3.pdf

1479-CAL-1998-FORM 15.pdf

1479-CAL-1998-PA.pdf