EP1395881A1

EP1395881A1 - Optical element and method for the production thereof

Info

Publication number: EP1395881A1
Application number: EP02774033A
Authority: EP
Inventors: Irina Menz; Günther Dausmann
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2001-05-30
Filing date: 2002-05-29
Publication date: 2004-03-10
Also published as: UA77418C2; WO2002097537A1; US20040207892A1; US20060228471A1; DE10126342C1; US7420720B2; RU2003136081A; RU2280885C2; CZ20033257A3; US7149013B2

Abstract

The invention relates to a method for producing an optical element, preferably a security feature, according to which a film with a first embossed hologram is provided in an embossed layer, and a second embossed hologram is embossed into the same embossed layer whereby the first embossed hologram is partially replaced by the second embossed hologram. The invention also relates to a method for producing an optical element according to which a film, which is capable of being embossed and which is provided with an embossed hologram, is at least partially filled out with a printing varnish. The invention additionally relates to a method for producing an optical element according to which the hologram embossing is prevented by a prior partial imprinting of the embossed film with curable printing varnish. The invention finally relates to optical features, which can be produced by using the inventive methods, to valuable documents containing the inventive optical feature, and to a numbering embossing unit for use in an inventive production method.

Description

Optical element and method for its production

The invention relates to methods for producing an optical element, optical elements that can be produced with these methods, documents of value with such optical elements and a numbering embossing unit for use in a method according to the invention.

Documents, certificates, banknotes, ID cards, plastic cards etc. can be reproduced true to detail and true to color with the help of modern high-resolution color scanners and with the help of color laser printers or thermal sublimation printers. The general availability of color copiers has also made it considerably easier to produce high-quality counterfeits.

There is therefore a need to make documents, ID cards, banknotes, securities, plastic cards etc. tamper-proof by means of additional security features. Security features of this type can at least cause the production of a high-quality counterfeit to be made more difficult and more expensive. Security features include watermarks, silk threads, intertwined line structures and the use of special paper known. The application of metallized embossed holograms to banknotes, credit cards and Euro check cards has also become generally accepted. Due to the holographic effect, such embossed holograms can also be used for the special aesthetic design of such documents or other objects.

Such embossed holograms are e.g. B. produced by mass-embossing holographic image reliefs in an embossable film. An adhesive layer is applied to the embossed film. A further design is therefore no longer possible. With the adhesive layer, the stamping foil z. B. applied as a security feature.

Such simple embossed holograms also offer only limited protection against counterfeiting. The increasing spread of appropriate technology already makes it possible to reproduce corresponding embossed holograms.

It would therefore be desirable if there were methods available with which optical elements can be produced, whose counterfeiting is further complicated, and which allow simple individualization. It is the object of the present invention to provide corresponding methods for the production of optical elements, optical elements which are difficult to forge, documents of value with such optical elements and an embossing tool for use in a production method.

This object is achieved with a method with the features of claim 1, an optical element with the features of claim 23 and a numbering embossing device with the features of claim 22.

In a first method according to the invention, an embossable film or substrate surface is first provided with a first embossing hologram. This embossed hologram may have been embossed in a known manner as a holographic image relief in an embossable film. In this respect, the first embossing holo Gram can be mass-produced in the embossed layer of this film. In the method according to the invention, a second embossing hologram is embossed in the same embossing layer in which the first embossing hologram has already been introduced. According to the invention, the second embossed hologram partially replaces the first embossed hologram.

With the method according to the invention, two embossed holograms are thus embossed into one another. The second embossed hologram can be selected such that it holographically reconstructs a different image than the first embossed hologram when illuminated. If the second embossed hologram is viewed, a different optical effect arises than if the surfaces that carry the first embossed hologram are considered. The optical structures, e.g. B. diffraction grating of embossed holograms, have typical orders of magnitude and distances of a few 100 nm and are therefore not visible to the naked eye. The holographically stored information is only visible when illuminated with the appropriate reconstruction light and viewed under the holographic reconstruction angle. Different than when e.g. B. two adhesive holograms would be glued on top of one another, so when looking at them with the naked eye, it is generally not possible to see that two embossed hologram structures are present in one embossing layer. Illumination with reconstruction light and viewing at the appropriate reconstruction angle make the double structure recognizable.

The method according to the invention can thus be used to produce an optical element which, on the one hand, produces a special optical and possibly particularly aesthetic effect. In addition, the structure with several different embossing holograms in an embossing layer is more difficult to imitate. The result is a higher recognition value, which can be easily checked even without special equipment.

The embossing of the second embossed hologram structure in the same embossed layer as the first embossed hologram structure enables simple production. To have to different layers are not glued or bonded together.

Of course, further embossing steps can be provided for further embossing holograms, which partially replace the first and / or the embossed holograms embossed beforehand.

The second embossed hologram structure can have the same external shape for all optical elements. However, there is a significant increase in counterfeit security and / or the area of application if the second embossed hologram is different for each optical element. In this way, the optical element can be individualized as a security feature, e.g. B. in the form of a consecutive registration number.

In advantageous embodiments, the first and the second embossed hologram have either different reconstruction angles and / or different reconstruction wavelengths.

Additional information can be displayed if the external shape of the second embossed hologram can also convey information. The first embossed hologram is then replaced by the latter in the form of the outer shape of the second embossed hologram. When viewing the optical element, depending on the viewing angle or viewing light, the information stored in the first embossed hologram or the information stored in the second embossed hologram becomes visible. The outer shape of the second embossed hologram can also be seen. For example, the second embossed hologram can have the outer form of a number. This number can e.g. B. correspond to the serial number of a value document.

While the first embossing hologram can be introduced in bulk into the embossing layer of the film, the second embossing hologram can be individually embossed in the form of a different number for each individual optical feature become. In this way, the optical features can be customized very well.

The method according to the invention can be carried out particularly easily using a numbering embossing tool, which advantageously comprises metallic positive or negative numbers produced by etching or engraving, to which a holographic relief is applied in each case. If the numbers of the numbering embossing unit already have the holographic relief for the second embossing hologram on the embossing surface, the numbering process for producing the respective second embossing hologram can be carried out in the same way as in a normal numbering embossing process. While a first embossing hologram is brought into the embossing position for the second embossing hologram, the numbering tool switches to the desired number. The second embossing hologram is embossed in the outer form of the desired number in the embossing layer of the first embossing hologram layer. Then z. B. applied an adhesive layer on the back and the optical feature on the object to be secured, for. B. a value document stuck on. Another first embossed hologram is in the. Position for embossing the second embossing hologram while the numbering embossing tool advances by one number. Now the process is repeated accordingly.

As a holographic relief on the embossing surface of the numbering tool, e.g. B. a corresponding nickel matrix can be provided, which carries the embossing structure of the second embossing hologram in metallic form.

In another advantageous embodiment, a nickel tape with a holographic relief is placed over the number ring of an embossing numbering unit. The embossing surfaces of the numbering unit do not have to be provided with the holographic relief. In the embossing process for the second embossing hologram, the embossing surface of the respective number of the numbering embossing press presses the nickel tape with the holographic relief into the embossing layer of the first embossing hologram. In the outer form of the respective number of the numbering die In this way, the holographic relief structure of the nickel band is stamped into the embossing layer of the first embossing hologram.

An optical element according to the invention, which can be used particularly advantageously as a security feature for documents of value, comprises a first embossed hologram in an embossed layer and a second embossed hologram in the same embossed layer. The second embossed hologram is arranged within the outer outline of the first embossed hologram.

The object is also achieved with a method with the features of one of claims 11 or 13 or an optical element with the features of one of claims 26 or 27.

In such a method according to the invention, an embossable film or substrate surface is partially printed with a curable printing varnish. This printing varnish is then cured. In a further process step, an embossing hologram is embossed on the substrate which has been partially printed in this way, the hardened printing varnish preventing the embossing in the printed partial areas. With such a method according to the invention, the representation of information is also possible through the outer shape of the surface printed with the hardened printing varnish. The image, which is holographically reconstructed when the embossed hologram is illuminated, saves the printed sub-areas. In this way, the information z. B. is shown in the outer shape of the printed areas, visible.

In a further method according to the invention, an embossable film or substrate surface is first provided with an embossed hologram. In some areas, a printing varnish is applied to this embossed hologram, which fills the embossed relief structure of the hologram. If necessary, the printing varnish is then cured. In this method according to the invention, too, an optical element is thus produced, the embossed hologram of which is left out in partial areas. Again, the partial areas can have an external form of information have, e.g. B. a number. When the embossed hologram is illuminated, the filled-in partial areas do not reconstruct the image stored in the hologram, so that the information stored by the external shape can be recognized.

In the latter method according to the invention, it is thus possible in a simple manner to display additional information which goes beyond what is holographically reconstructed by the embossing hologram. The application of the printing varnish is possible in a simple manner and, if necessary, individually for each individual optical element. This ensures a high level of security against counterfeiting.

In these methods according to the invention, in which printing varnish is used, the outer shape of the printed partial areas can correspond to an individual number, in order, for. B. to enable continuous registration of optical elements or the security features or value documents provided with them.

The printing varnish can be applied to the embossing film in various ways. Application is particularly simple and reliable using a jet printer, similar to an inkjet printer, which applies the printing varnish in the desired outer shape. Application with a laser printer also enables simple and reliable design.

It is particularly advantageous if the printing varnish is transparent or colored transparent. Such an embodiment increases the security against forgery of the finished optical element, since the surface in the partial areas does not differ from the surrounding embossed hologram areas by a completely different color or permeability.

The optical element produced by a method according to the invention can be used in various ways, e.g. B. can be used and secured as a security element. It is particularly simple and therefore advantageous if only after Carrying out all the embossing processes, an adhesive layer is applied to the non-embossed side in order to attach the optical element to the object to be secured. An adhesive layer that is only stuck on after all embossing processes have been carried out does not hinder the embossing processes.

An adhesive coating in the form of a hot-melt adhesive coating which can be treated thermally is particularly advantageous.

In all of the methods according to the invention, a metallization or coating with a highly refractive material is advantageously carried out at least at the end of all the embossing processes in order to protect the structure or to make the holographic effect easy to display.

Embossable substrate surfaces, in particular and particularly advantageously hot stamping foils, sticker stamping foils, paper coated with thermal lacquer or substrate surfaces coated with UV lacquer, can be used for the method according to the invention.

An optical element according to the invention of another embodiment, which can also be used particularly advantageously as a security feature for a value document, comprises an embossed hologram in an embossed layer, at least a partial area of the relief embossed in the embossed layer being filled in, so that no holographic reconstruction can take place in the partial area ,

In an optical element according to the invention of a further embodiment, which can also be used particularly advantageously as a security feature for documents of value, an embossed hologram is provided in an embossed layer, the relief being left out in at least one partial area in the embossed layer. The methods according to the invention and the optical elements according to the invention can be used particularly advantageously for documents of value, eg. B. as a security feature, as is the subject of claims 28 and 29, respectively.

The invention is explained in detail below on the basis of preferred embodiments and refinements. The figures show examples of configurations according to the invention in a schematic representation. It shows

FIG. 1 shows a document of value according to the invention with an optical feature according to the invention,

FIG. 2 shows an optical element according to the invention,

FIG. 3 shows another embodiment of an optical element according to the invention,

FIG. 4 shows an embossing stamp of a numbering embossing tool according to the invention,

5 shows the top view of an optical element according to the invention in accordance with a further embodiment, and

FIG. 6 shows a cross section along the line A-A of FIG. 5.

Figure 1 shows a schematic representation of z. B. a banknote 1. On this banknote information is known in a known manner. B. the value and image information applied, which are of no further interest here and are accordingly not included in the figure. Banknote 1 may contain various security features, such as. B. watermarks or guioches, which are also not shown here. 3 denotes a security feature according to the invention on the banknote 1 according to the invention. Among other things, the security feature 3 according to the invention comprises a number 5, in the example shown the number “123”.

Figure 2 shows the security feature of this embodiment according to the invention in an enlarged view. It comprises a first embossed hologram 30, which is only shown schematically in the form of lines. This first embossed hologram can be a diffraction grating. The distance between the individual grating strips is typically a few 100 nm in order to be able to produce interference effects in visible light in a known manner. Of course, the invention is not limited to such stripe-shaped holograms, but can have any embossed hologram shapes that represent other information holographically, e.g. B. the image of a three-dimensional object.

In the same layer of the first embossing hologram 30 there is a second embossing hologram, the embossed structure 50 of which is again only drawn in the form of lines in a highly schematic representation. A possible embodiment again comprises a diffraction grating similar to diffraction grating 30. However, the spacing of the individual grating strips is different, so that a different wavelength interferes in this diffraction grating than in the first embossed hologram. The second embossed hologram 50 reconstructs in a different direction, which is to be indicated schematically by the other hatching direction in FIG. 2. Of course, it also applies to the second embossed hologram 50 that any other holographic information can be stored, e.g. B. the three-dimensional holographic image of an object.

The outer shape of the second embossed hologram 50 shows the number “123” in the example shown.

FIG. 3 shows an embodiment in which the second embossed hologram 51, again indicated very schematically only as hatching, has cutouts in the form of numbers. The first embossing hologram 30 is in these recesses 31 visible. In this respect, the numbers of the number "123" shown as an example are surrounded by the second embossed hologram 51.

FIG. 4 shows the embossing stamp of an embodiment of a numbering embossing work according to the invention. The embossing stamp 7 for a structure 9, here the number “1”, is shown. On the embossing side 13, the number “1” is raised in an inverted representation. The embossed structure 11 for an embossed hologram is applied to the embossed surface of the raised digit as a nickel matrix. Of course, here too, the representation is only indicated very schematically as hatching.

Optical elements according to the invention can be produced as follows using a method according to the invention.

First of all, a first embossing hologram 30 is introduced into an embossable foil, which is either completely formed as an embossing layer or comprises an embossing layer, in the conventional way. For example, the embossing layer can be a thermal lacquer layer in which a hologram is hot-embossed in a known manner. To do this, the desired embossed hologram structure is embossed using a hot stamp. This process can happen in mass production. For example, the first embossed hologram structure can be embossed onto a larger film unit and cut later.

The film produced in this way with the first embossing hologram 30 in the embossing layer is fed to a numbering tool which is suitable for embossing consecutive numbers. With this embossing tool, a number is embossed in the same embossing layer in which the first embossing hologram 30 is located and in this way replaces the embossed structure of the first embossing hologram in the outer shape of the embossing surface of the embossing stamp of the numbering tool. The second embossing hologram 50, 51 is thus embossed into the first embossing hologram structure 30 in the outer form of the numbers of the numbering tool. Different shapes for the numbers are conceivable. For example, the numbers of the second embossed hologram structure can positively represent a number as shown in FIG. B. in Figure 3, appear in negative form as a border.

In Figure 4 z. For example, the embossing stamp 7 is shown for a positive number “1”. The second embossing hologram structure is located, for example, as a nickel die on the embossing surface 11 of an embossing stamp of the numbering tool. In an alternative embodiment, a nickel strip is placed around the number ring of the numbering embossing tool The structure of the nickel strip is shaped into the embossing layer of the first embossing hologram with the aid of the numbering tool, without the embossing surfaces of the numbering ring itself having to be structured.

FIG. 5 shows a further security feature 3 according to the invention, which can be provided on a bank note 1. As shown in FIG. 1, the security feature according to this embodiment again comprises a number 5, in the example shown the number “123”.

The security feature of this embodiment according to the invention comprises an embossed hologram 63, which in turn is only shown schematically in the form of lines. This embossed hologram can also be a diffraction grating, the grating spacing of which is typically a few 100 nm, in order to be able to produce interference effects of visible light in a known manner. Of course, here too the embossed hologram is not limited to such strip-shaped holograms, but can have any embossed hologram that represents other information holographically, e.g. B. the image of a three-dimensional object.

Within the contours of the embossing hologram 63 are areas 61 which do not have an embossing structure, such as the surrounding embossing hologram 63. This can be achieved in various ways, which are described below. No holographic reconstruction takes place in the areas 61 when illuminated, so that the holographic effect is left out in these areas. The entire security feature 3 thus shows a holographic effect, e.g. B the representation of a three-dimensional object. Only the partial areas 61 in the outer shape of the number "123" do not holographically reconstruct an image, so that they become recognizable and the information about their outer shape is visible.

Such an optical feature according to the invention can be produced as follows. An embossing hologram 63 is introduced into an embossable foil, which is either completely embodied as an embossing foil or comprises an embossing layer. It can be in the embossing z. B. can be a thermal lacquer layer in which a hologram is hot-stamped in a known manner. For this purpose, the desired embossed hologram structure is also embossed using a hot embossing stamp. This process can be done in mass production. B. can be embossed on a larger film unit and cut later.

With a laser printer or a jet printer, similar to an inkjet printer, printing varnish 61 is applied to the embossed hologram structure 63 in the desired outer shape, here the number “123”, in order to fill up the relief of the embossed hologram structure. This is visible in section in FIG. In the areas filled with printing varnish 61, the embossed hologram layer 63 no longer holographically reconstructs when illuminated with reconstruction light.

In another method according to the invention, prior to embossing the embossing hologram with a laser printer or a jet printer, similar to an inkjet printer, printing varnish 61 is applied to an embossable film in a desired outer shape, e.g. B. in the form of the number "123". After a hardening step for the printing varnish, the film thus partially provided with printing varnish is embossed in a manner known for embossing holograms, so that embossing hologram 63 is produced. Embossing is carried out in the areas printed with printing varnish 61 currency prevented by the embossing step, so that no holographic reconstruction can take place in the finished optical element.

In all the described embodiments, a hot-melt adhesive layer is applied to the back of the optical element 3 only after all the necessary embossing processes have been carried out, with the aid of which the optical element can be attached to the value document 1. Since this adhesive layer is only carried out after all stamping processes, it cannot interfere with the previous process steps.

In all of the embodiments according to the invention, hot stamping foil, sticker stamping foil, paper coated with thermal lacquer or substrate surfaces coated with UV lacquer can be used as the embossable substrate surface. The invention is not limited to a single number 5. The method and the optical features are particularly advantageous if the outer shape of the differently reconstructing holographic area 50, 31 or of the non-holographically reconstructing area 61 is a consecutive number that is assigned individually for each optical element. In this way, individualization of the respective optical element is possible, e.g. B. in the manner of a registration number for a value document.

Claims

claims

1. A method for producing an optical element, preferably a security feature, with the following steps

a ¹ ) providing an embossable film or substrate surface with a first embossing hologram (30, 31) in an embossing layer, and

b ¹ ) embossing at least one second embossing hologram (50, 51) in the same embossing layer such that the first embossing hologram (30, 31) is partially replaced by the second embossing hologram (50, 51).

2. The method according to claim 1, wherein with step b ¹ ) the optical element (3) is individualized.

3. The method according to claim 2, in which step b ¹ ) is carried out with an individualized embossing stamp.

4. The method according to any one of claims 1 to 3, wherein the first embossing hologram (30, 31) and the second embossing hologram (50, 51) have different reconstruction angles and / or different reconstruction wavelengths.

5. The method according to any one of claims 1 to 4, in which step b ¹ ) is carried out using an embossing tool with at least one embossing surface (11) in the form of the desired outer shape of the second embossing hologram (50, 51).

6. The method of claim 5, wherein step b ¹ ) comprises embossing a second embossing hologram with the outer shape of an individual number.

7. The method according to claim 6, in which step b ¹ ) comprises the use of a numbering embossing tool which comprises positive or negative numbers (9) on its embossing stamps (7) to which a holographic relief (11) is applied.

8. The method according to claim 7, wherein the positive or negative numbers (9) comprise etched or engraved metallic numbers.

9. The method according to claim 7, in which a nickel matrix is used as the holographic relief (11).

10. The method according to claim 6, in which a nickel strip with a holographic relief is placed over the numbers of a number ring of an embossing numbering unit to carry out step b ¹ ).

11. Method for producing an optical element, preferably a security feature, with the following steps: a ² ) printing partial areas of an embossable film or substrate surface with a curable printing varnish (61), curing the printing varnish, and

b ² ) embossing an embossing hologram (63) on the printed substrate, the hardened printing varnish (61) preventing the embossing in the printed partial areas.

12. The method according to any one of claims 1 to 11, with the following additional step:

c) Metallization or coating with a highly refractive material on the embossed side of the optical element (3).

13. A method for producing an optical element, preferably a security feature, with the following steps:

a ³ ) providing an embossable film or substrate surface with an embossing hologram (63) in an embossing layer,

b ³ ) applying a printing varnish (61) in partial areas of the embossed hologram structure (63) such that the relief structure of the embossed hologram structure (63) is filled with printing varnish (61) in the partial areas, and

c ³ ) Metallization or coating with a highly refractive material on the embossed side of the optical element.

14. The method according to any one of claims 11, 12, insofar as it is dependent on claim 11, or 13, in which in step b ² ) or b ³ ) the printing varnish (61) is applied in an outer form which represents information ,

15. The method according to any one of claims 11 to 14, in which step b ² ) or b ³ ) is carried out for individualizing the optical element.

16. The method according to claim 15, in which in step b ² ) or b ³ ) the printing varnish (61) is applied in an outer shape which has an individual outer shape for individual optical elements (3).

17. The method of claim 16, wherein the outer shape comprises the shape of an individual number (5).

18. The method according to any one of claims 11 to 17, wherein the printing varnish (61) is applied with a jet printer or a laser printer with the desired outer shape.

19. The method according to any one of claims 11 to 18, wherein the printing varnish (61) is transparent or colored-transparent.

20. The method according to any one of claims 1 to 19, in which after step b ¹ ), b ² ) bbzzww .. bb ³³ )) aauuif the non-embossed side of the film, an adhesive coating is applied.

21. The method according to any one of claims 1 to 20, in which in step a ¹ ), a ² ) or a ³ ) embossable substrate surfaces, in particular hot embossing foils, sticker embossing foils, paper coated with thermal lacquer or substrate surfaces coated with UV lacquer are used ,

22. Numbering embossing unit for use in a method according to one of claims 1 to 10, the embossing surfaces of which are each provided with a holographic relief (11), the external shape of the embossing surfaces corresponding either positively or negatively to the external shape of the number to be embossed.

23. Optical element, in particular a security feature for documents of value, with a first embossed hologram (30, 31) in an embossed layer and a second embossed hologram (50, 51) in the same embossed layer, the second embossed hologram being arranged within the outer outline of the first embossed hologram.

24. The optical element according to claim 23, wherein the first embossed hologram (30, 31) and the second embossed hologram (50, 51) have different reconstruction angles and / or different reconstruction wavelengths.

25. Optical element according to one of claims 23 or 24, wherein the second embossed hologram (50, 51) comprises an individual outer shape, in particular the shape of a number (5) either in a positive or in a negative representation.

26. Optical element, in particular a security feature for documents of value, with an embossed hologram structure (63) in an embossed layer and at least one partial area (61) in the embossed layer in which the embossed relief is filled.

27. Optical element, in particular a security feature for documents of value, with an embossed hologram (63) in an embossed layer and at least one partial area (61) in the embossed layer in which the relief of the embossed hologram structure is left out.

28. Optical element according to one of claims 26 or 27, wherein the at least one partial area (61) comprises an individual external shape, in particular the shape of a number, either in a positive or negative representation.

29. Optical element according to one of claims 23 to 28, wherein the film is provided on the non-embossed side with an adhesive layer.

30. document of value with an optical element according to one of claims 23 to 29.

31. Document of value with an optical feature produced by a method according to one of claims 1 to 21.