AU695459B2

AU695459B2 - A laminar compound for transferring optically variable single elements to objects to be protected

Info

Publication number: AU695459B2
Application number: AU16135/95A
Authority: AU
Inventors: Wittich Kaule
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 1994-03-31
Filing date: 1995-03-28
Publication date: 1998-08-13
Anticipated expiration: 2015-03-28
Also published as: EP0675006A1; ATE193249T1; DE4411404A1; DE4411404B4; EP0675006B1; FI951518A0; DE59508367D1; PT675006E; FI118041B; ES2145856T3; FI951518A; AU1613595A

Abstract

The layer (6) possessing the diffraction structures has the shape of the outline of the element being transferred (2) and rests on the substrate (3) only in parts. The reflecting layer is positioned solely near the diffraction structures and in the form of a metal layer (5) in which are cavities in the form of signs or patterns. The join between layers, between the substrate and the layer possessing the diffraction structures, has a wax-like dividing layer. The layer possessing the diffraction structures is a reaction coating layer of a thermoplastic layer. <IMAGE>

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 'tlt

'II.

i 0 44 Invention Title: A LAMINAR COMPOUND FOR TRANSFERRING OPTICALLY VARIABLE SINGLE ELEMENTS TO OBJECTS TO BE PROTECTED The following statement is a full description of this invention, including the best method of performing it known to us: i GH&CO REF: P23770-A:CAS:RK -1A_ A laminar compound for transferring optically variable single elements to objects to be protected This invention relates to a laminar compound for transferring optically variable elements to objects to be protected, particularly security documents such as bank notes or identity cards, comprising a substrate having a layer in which diffraction structures are incorporated in the form of a relief and which is combined with a reflecting layer.

Optically variable elements, such as holograms or interference layer elements, are gaining increasing importance in many areas for various reasons. As a rule these elements show different colors dependent on the viewing angle. However they can also contain different information which is S: recognizable solely at certain viewing angles. In the area I of protection of a great variety of objects against forgery, falsification or other kinds of manipulation, holograms and similar diffraction structures have been applied in many ways, since the angle-dependent effects can be imitated only L Q with disproportionately high effort. On the other hand, optically variable elements permit a fast visual check and offer good copy protection since the angle-dependent effects cannot be reproduced by a copying machine.

For the protection of security documents such as identity cards or bank notes, reflection holograms are fre- Squently used. They are usually produced by means of special matrices which have a surface relief corresponding to the diffraction pattern of the hologram by embossing the surface relief in a layer of lacquer, subsequently metalizing it and providing a protective layer. The metalizing ensures the brilliance of the hologram so that it is well recognizable visually.

Various possibilities have been proposed for applying such holograms to security documents in a locally limited F, 4 -2form. One of the most proven techniques is to prepare a separate, continuous transfer band from which the hologram is transferred to the document well-placed in the desired contour (DE-A1 33 08 831). The layers to be transferred are applied all over to a substrate provided with an easily detachable separation layer in the reverse order to the one in which they are to exist later on the document. The uppermost layer is an adhesive layer, for example a hot-sealing adhesive layer. Via this adhesive layer the hot stamping band and the document are interconnected under the influence of heat and pressure (hot stamping). The substrate of the transfer band can subsequently be removed effortlessly because of the separation layer. The definition of the surface areas to be transferred can take place either via the adhesive layer, which is printed on in a certain pattern so that the layer structure to be transferred adheres to the document only in some places, or via the pressure stamp used during lamination, which in this case has a contour shape corresponding to the shape to be transferred, so that even if hot-sealing adhesive is applied over a large surface only those areas of the adhesive layer are activated on which the punch exerts pressure and heat (DE-Al 33 08 831). During the following removal of the transfer band the hologram layer structure comes off the transfer band in the area of the activated adhesive layer and adheres to the document. This presupposes, however, that the hologram layer structure is of very thin and relatively unstable design to guarantee a clean separation of the element from the continuous coating of the transfer band. This requirement conflicts with the general striving to make holograms as durable and resistant as possible.

To also do justice to the demand that the hologram be resistant to mechanical or other influences it was proposed in the past to provide in the layer structure of the transfer band a thin resistant film layer which serves as a protective layer for the hologram after transfer to the final -3substrate (EP-A2 466 118). This guarantees sufficient protection of the hologram against mechanical and other loads, but the transfer of this layer structure to a substrate requires additional method steps since the stable protective layer does not tear in the edge area of the activated adhesive layer upon removal of the transfer band and thus prevents extraction of the element. It is thus necessary to prestamr the contour of the desired surface element in the protective film before applying the hologram, so that it is possible to extract the hologram from the surrounding material during transfer.

An alternative possibility of transferring relatively durable hologram labels to documents by a modified transfer method is described in DE-Al 41 30 896. Here the carrier film first receives a cold adhesive layer over which the usual hologram layer structure is finally disposed in the order in which it is to exist on the document later, folt lowed by a stable protective layer. To produce defined single elements the layer structure is stamped without damaging the carrier film. The superfluous part of the laminar compound (grid) is removed from the carrier film so that only the spaced apart single labels are present on the carrier film. During transfer the carrier film is removed and the label fastened to the document by means of the cold adhesive layer. Since the adhesive layer is covered by the carrier film, automated transfer of these labels is complicated and requires additional apparatus components which further increase the already high production costs of hologram elements.

The invention is thus based on the problem of producing a laminar compound from durable and tear-resistant layers which contains diffraction structures and permits wellplaced single elements to be applied to objects to be protected by the transfer method in a simple and cost-effective way.

i

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4 In a first aspect, the present invention provides a laminar compound for transferring optically variable elements to an object to be protected, the laminar compound comprising a substrate and at least one diffraction layer in which diffraction structures are incorporated in the form of a relief and which is combined with a reflecting layer, the diffraction layer having the contour shape of the element to be transferred and being present on the substrate only in sections.

In a second aspect, the present invention provides a method for producing a laminar compound according to the first aspect of the present invention, the method comprising forming the diffraction layer in sections on the substrate in the contour shape of the element to be transferred.

In a third aspect, the present invention provides a method for applying optically variable elementz to an object to be protected, the method comprising bringing a ft elaminar compound according to the first aspect of the present invention in contact with the object to be protected in the area of the diffraction structures over an adhesive layer and removing the substrate.

In a fourth aspect, the present invention provides an object having an optically variable element, the 25 optically variable element having been applied to the object by a method according to the third aspect of the present invention.

2 i S:23770AI700 4a The invention is based on the "fundamental idea of already considering the contour shapes of the single element to be transferred during production of the element layer structure on a substrate or carrier film, i.e. the single elements are produced directly on the carrier film of the laminar compound. They have the sequence of layers typical of transfer elements, in which the adhesive layer forms the outermost layer, unless it is applied to the document beforehand. However, this sequence of layers is disposed on f. the carrier band in spaced apart areas.

The inventive solution has the advantage that virtually t any materials can be selected for the layer structure of the single elements, solely according to their expediency for the element to be produced. Furthermore, when transferring the elements one requires no additional apparatus or measures which make the transfer of these elements more elabot e" rate and thus ultimately raise the price of the final product. Since the later geometric extension of the element on the object to be protected is already considered during production of the element layer structure on a carrier substrate, there is no need for the layer structure to tear at the edges of a hot stamping die, as is used in the conventional hot stamping method. One can thus of course also dispense with the use of a specially formed hot stamping die. If hot-melt adhesives are used it thus suffices to ensure a sufficient supply of heat which activates the adhesive.

The apparatus necessary in the prior art for prestamping any tear-resistant layers present in the element layer structure are likewise no longer required for transferring the inventive elements. A further advantage is to be seen in the fact that practically no surplus layer material is produced. With conventional hot stamping filns, which are provided all over with the layer structure to be transferred, -cU:Cif c W1~PIC*I I~ 5 the elements are stamped out according to the desired contour shape via the hot stamping die so that the surplus always remains on the carrier substrate. According to the invention, however, only so much layer material is applied to the carrier substrate as is subsequently required for transfer. After the elements are transferred to the document material the carrier substrate is practically free from any element layer material and can possibly be reused for the production of single elements.

According to a preferred embodiment the laminar compounds comprises a carrier film to which a reaction lacquer is applied in the form of the later element in spaced apart areas. This layer of lacquer contains the diffraction structures in the form of an embossed relief structure which is provided with a thin reflecting layer, pref-rably a metal hrrK layer. The well-placed application of the metalizing prefrerably takes place via masking by means of chemically soluble inks. The carrier film provided with the embossed lacquer areas is printed with a soluble ink in the later metal-free areas and subsequently metalized all over e.g. in a vacuum evaporation unit. In a solution bath the ink is washed off along with the parts of the metal layer directly t thereabove. The metalized embossing remains on the carrier film. During application to an object to be protected, e.g.

a security document or product packaging, the object is preferably provided with an adhesive layer whose extension is larger than the element to be placed, with consideration of tolerances.

To guarantee easy detachment of the element layer structure from the carrier film, it can be provided with a separation layer. This is preferably a cold-detaching reaction lacquer as is known from P 44 04 128.4.

Further embodiments of the invention as well as its advantages will be explained with reference to the figures.

For more clarity, the individual layers of the layer struc- -6tures shown in the figures are shown with exaggerated thickness and not true to scale.

Fig. 1 shows a security document with a well-placed single hologram Fig. 2 shows a laminar compound according to the invention Figs. 3a to 3f show the production of the inventive laminar compound and the transfer of a single element to an object to be protected Fig. 4 shows a further embodiment of the inventive laminar compound Fig. 5 shows the transfer of a single element to an object to be protected Fig. 1 shows bank note 1 with optically variable element 2 according to the present invention. optically variable element 2 is preferably a reflection hologram, which was transferred to document 1 as a well-placed single t-lement by the transfer method.

Fig. 2 show inventive laminar compound 10 which comprises substrate 3 on which holographic single elements 2 are disposed in spaced apart areas. Elements 2 shown here ~are composed of embossed lacquer layer 6, metal. layer covering the embossing as well as further lacquer layer 4 which serves as a protective layer. The protective layer preferably likewise comprises a layer of reaction lacquer.

Since elements 2 are produced on the carrier substrate as isolated single elements, the layer structure can also be composed of any other layer materials. For example, stable thermoplastic layers as are described e.g. in EP A2 0 466 118 can be used instead of lacquer layer 6. It is likewise possible for example to use instead of metal layer 5 a dielectric layer with an accordingly adapted refractive index.

As substrate 3 one can use any material which fulfills the desired demands for tear resistance and adhesive characteri sti_ 1 but- preferably a n 1 astic film is used.

i -7- With reference to Fig. 3 the production method as well as the transfer of single element 2 to an object to be protected will be described in the following. In a first step carrier band 3 is printed at preferably regular intervals with lacquer layer 6 in the size and shape of the hologram to be placed. As shown schematically in Fig. 3a, this can be done in halftone photogravure printing unit 15. But any other coating and/or printing method screen printing) is also conceivable.

Printed lacquer layer 6 can be a layer of reaction lacquer, e.g. a UV or blue light hardenable or UV initiatable lacquer, as are described in German patent application P 4404128.4, which is explicitly referred to here.

Subsequently this printed carrier film 3 is provided in the area of lacquer coating 6 with diffraction structure 9 by bringing die 7 bearing relief structure 9 to be transferred in contact with lacquer layer 6 and simultaneously oI' hardening lacquer layer 6 (Fig. 3b).

According to Fig. 3c the carrier film is printed in the next process step with chemically soluble ink 8 in the areas which are to bear no metalizing in the finished laminar compound. Since the surface extent of lacquer layer area 6 is larger than actual embossed area 9 to permit compensation of tolerances in register, the edge areas of lacquer layer 6 are also printed with soluble ink 8 so that essentially only embossed structure 9 remains unprinted. Carrier film 3 prepared in this way subsequently receives all-over metalizing that covers both ink areas 8 and embossed structure 9 (Fig. 3d). The metalizing can be done by one of the standard methods, e.g. vacuum evaporation. In the following step soluble ink 8 and the part of metal layer 5 located thereabove are removed in a suitable solution bath. As shown in Fig. 3e, only embossed lacquer areas 6 and metal layer covering embossing 9 remain on carrier film 3. Instead of masking by a chemically soluble ink as described above, one I 8 can of course also use any other masking method to metalize the embossing.

The metalizing can now be optionally covered with protective layer 4, as shown in Fig. 2. For transferring element 2 to an object to be protected, either the object or element area 2 of carrier film 3 is provided with adhesive layer 11, preferably a reaction adhesive, whereby adhesive 11, in view of possible tolerance problems, occupies a larger surface than element 2 actually to be transferred.

Finally, laminar compound 10 is brought in contact with the ,0 predetermined place in the bank note substrate in the area of element 2, and adhesive 11 hardened. In a last step carrier band 3 is removed (Fig. 3f).

o. The well-placed hologram now comprises an embossed, metalized inner area and a transparent, narrow edge area in which lacquer layer and adhesive layer overlap and which not only absorbs the manufacturing tolerances but also seals the metal layer, thereby protecting it from harmful environmental influences.

To facilitate detachment of the elements from the carrier film, the film can be printed with a waxy separation layer, e.g. an easily detached layer of reaction lacquer, before being coated with the islandlike lacquer areas.

Since antifalsification papers have a relatively rough surface to be able to take up steel intaglio ink, and this roughness might possibly disturb the visual impression of the diffraction structures, it is frequently advantageous to smooth the area of the paper intended for receiving the security element before transfer. This can be done by compressing the paper and/or by applying a smoothing primer layer.

In a variant of the above-described embodiment, additional optical effects can be produced by partly printing the embossed area or not printing the edge area of lacquer layer 6 with ink 8 (see Fig. 3c). By additionally printing the embossed area in the form of characters, patterns or the Spaesot -9like, one can thus produce a further maetal-free area within hologram embossing 9 which represents e.g. readable inf ortj mation.

K The application of the described method is of course I not limited to transferring holograms to bank notes. Interference layer elements or other layer structures with optical effects dependent on the viewing angle can also be pro-- K duced well-placed on the carrier film and transferred to any objects to be protected, such as product packaging, the products themselves or identity cards, analogously to the method described above f or holograms.

However, the inventive method can also be used advantageously for conventional thermoplastic hologram layers, .~.since they need no longer be tearable but can be as stable as possible. In this case carrier film 3 is printed in a ft first step with e.g. waxy separation layer 16 all over or likewise in well-placed fashion. The carrier film is then printed with thermoplastic lacquer 17, as shown in Fig. 3a.

The following production steps proceed analogously to those shown in Figs. 3b to 3e. In a last step adhesive layer 18 is C applied to the element layer structure, whereby this layer should also be of somewhat larger diLmensions than embossed lacquer layer 17 to compensate tolerances and to seal the j metal layer. Fig. 4 shows the layer structure of lamina~r compound 20. Adhesive layer 18 can be cither one of the abovementioned reaction lacquers or a hot-melt adhesive.

Thus prepared single elements 2 are transferred with 2 the help of heated die 19, which activates hot-melt adhesive 18 and fixes element layer structure 2 to subst:rate 1 (Fig.

Finally, carrier film 3 is removed in a last step.

Claims

1. A laminar compound for transferring optically variable elements to an object to be protected, the laminar compound comprising a substrate and at least one diffraction layer in which diffraction structures are incorporated in the form of a relief and which is combined with a reflecting layer, the diffraction layer having the contour s-ape of the element to be transferred and being present on the substrate only in sections.

2. A laminar comoound as claimed in claim 1 wherein the diffraction structures are present in an inner area of the diffraction layer.

3. A laminar compound as claimed in claim 1 or claim 2 wherein the reflecting layer is provided only in the area of the diffraction structures.

4. A laminar compound as claimed in any one of the preceding claims wherein the reflecting layer is a metal layer.

A laminar compound as claimed in any one of the preceding claims wherein the diffraction layer is a layer of reaction lacquer or a thermoplastic layer.

6. A laminar compound a, claimed in any one of the preceding clai.ns further comprising an adhesive layer for fixing the elements to the object. 25

7. A laminar compound as claimed In claim 6 wherein .4 4 the adhesive layer is a layer of reaction adhesive or layer of hot-melt adhesive.

8. A laminar compound as claimed in any one of the preceding claims wherein the reflecting layer has gaps in the form of characters or patterns.

9. A laminar compound as claimed in any one of the preceding claims further comprising a waxy separation layer between the substrate and the diffraction layer. A laminar compound for transferring optically variable elements to an object, the laminar compound being substantially as herein described with reference to O AL the accompanying drawings.

LU SOyo I i m Il-r~e *na~ 11

11. A method for producing a laminar compound as claimed in claim 1, the method comprising forming the diffraction layer in sections on the substrate in the contour shape of the element to be transferred.

12. A method as claimed in claim 11 comprising the steps of: providing a plastic film, partially coating at least one surface of the plastic film with an embossable layer, incorporating the diffraction structures in the embossable layer, and metallising the diffraction structures.

13. A method as claimed in claim 12 wherein the metallising of the diffraction structures in step is performed by a masking method using chemically soluble inks.

14. A method as claimed in claim 13 further comprising the steps of: printing the areas of the plastic film not to be metallised with a chemically soluble ink, metallising the surface of the plastic film all over, detaching the soluble ink and the metallising located thereabove so that the metall.ising remains solely 25 in the ink-free areas of the plastic film.

A method as claimed in claim 14 wherein the metallising in step is performed' by vacuum evaporation.

16. A method as claimed in any one of claims 12-15 30 wherein the plastic film is printed before step at least partially with a waxy separation layer.

17. A method as claimed in any one of claims 12-16 wherein, in step a reaction lacquer or thermoplastic lacquer is printed.

18. A method as claimed in any one of claims 12-17 wherein gaps are produced in the metallising in the form of characters or patterns. :23770A/700 12 r i 44t ~r

19. A method for producing a laminar compound for transferring optically variable elements to an object to be protected, the method being substantially as herein described with reference to the accompanying drawings.

20. A method for applying optically variable elements to an object to be protected, the method comprising bringing a laminar compound as claimed in any one of claims 1-10 in contact with the object to be protected in the area of the diffraction structures over an adhesive layer and removing the substrate.

21. A method as claimed in claim 20 wherein the adhesive layer is applied to the object to be protected, the surface extension of the adhesive layer being larger than that of the ciffraction layer.

22. A method as claimed in claim 20 or claim 21 wherein the adhesive layer is a layer of reaction adhesive which is hardened during the contact between the laminar compound and the object to be protected.

23. A method as claimed in claim 20 or claim 21 wherein the adhesive layer is a layer of hot-melt adhesive which is activated with heat and hardened between contacting the object to be protected and the laminar compound and removing the substrate.

24. A method as claimed in any one of claims 20-23 wherein the object to be protected is an antifalsification paper and the antifalsification paper is smoothed in the area to which the element is to be applied.

An object having an optically variable element, the optically variable element having been applied to the object by a method as claimed in any one of claims 20-23.

26. An object as claimed in claim 25 wherein the object is a security document.

27. An object as claimed in claim 26 wherein the security document is a bank note or an identity card. I N -13 DATED this 22nd day of June 1998 C4IESECKE DEVPJENT GmnbH By its Patent Attorneys GRIFFITH HACK L4 Abstract The invention relates to a laminar compound for trans- ferring optically variable elements to objects to be pro- tected, particularly security documents such as bank notes or identity cards. This laminar compound comprises a sub- strate on which the optically variable elements are produced as single elements in spaced apart areas. on *r t 9 4I 4 t 1 I I I 4* 1( 94 44 S I *4 4 *4 9* 9 4. 4.4 A