DE102019110747B4 - Method of modifying a hologram - Google Patents

Abstract

Method for modifying a hologram contained in a hologram layer (3), in which first a layered composite is produced with an upper side, an underside and with the hologram layer (3) as an inner layer of the layered composite, with a relief (4th ) is pressed into the layered composite, characterized in that the relief (4) is pressed into the layered composite in the pressing step under increased pressure and temperature in such a way that the hologram layer (3) is deformed in such a way that the relief (4) contained Information is transferred as holographic 3D information into the hologram layer (3), so that the hologram contained in the hologram layer (3) is subsequently reconstructed in three dimensions with the holographic 3D information, the hologram layer (3) being sandwiched between two elastic layers (5) of the Layered composite is embedded, wherein the elastic layers (5) have a modulus of elasticity between 20 MPa and 500 MPa, the layered composite having a carrier layer (1) and a cover layer (2), the elastic layers (5) being intermediate layers between the carrier layer (1) and the hologram layer (3) and between the hologram layer (3 ) and the cover layer (2), the cover layer (2) consisting of a thermoplastic material, the relief (4) being applied to the cover layer (2) before the pressing step by applying a curable transparent lacquer in relief to the cover layer (2 ) is applied and cured, and wherein the relief (4) is pressed into the top layer (2) on the upper side of the layered composite in the pressing step.

Description

The present invention relates to a method for modifying a hologram contained in a hologram layer according to the preamble of independent claim 1.

In such a method, a layered composite is first produced with an upper side, an underside and with the hologram layer as an inner layer of the layered composite, as is known, for example, from the German Offenlegungsschrift DE 10 2008 007 620 A1 is known. The layered composite here consists of a plastic document, for example an ID document, as a carrier layer, a volume hologram laminated thereon and a final protective surface coating or a protective film laminated on to increase the scratch resistance and the chemical stability of the holographic surface.

Holograms are used, for example, to ensure that certain documents are protected against forgery, in particular that personal documents are protected against forgery. Various methods are known from the prior art for providing documents of this type with corresponding hologram layers. Methods are also known which allow the hologram contained in the hologram layer to be modified or individualized during the document production process. For example, describes the international patent application WO 2007131496A2 a process in which a light-curable, monomer-containing swelling agent is used to individualize a hologram. The swelling agent is applied to the hologram layer by means of screen printing, partially diffuses into the hologram layer and is then cured under light. The diffusion of the swelling agent into the hologram layer causes a color shift. Multicolored holograms can be produced in this way by staggered curing.

In the case of the already mentioned German Offenlegungsschrift DE 10 2008 007 620 A1 known methods, the modification is carried out in that the desired additional information is applied to the document surface by printing or embossing with a relief character, with a liquid monomer-containing adhesive then being applied over the entire surface of the document surface, with the volume hologram film then being laminated on and the adhesive curing after a dwell time . Here, too, the individualization of the hologram takes place through the use of a swelling agent. The customization of the hologram is limited to color changes.

Out US20130229697A1 a method according to the preamble of independent claim 1 is known. The hologram is modified here by pressing on a stamp provided with a relief. Other related prior art is out JP 2015060001A , EP 1765600 B2 , EP 1091267 A2 and DE 102004012787 A1 known.

The object of the present invention is to specify a method for modifying a hologram, with which the protection against forgery of a personal document can be further improved. Furthermore, the modification or individualization of the hologram should be possible without great effort and in a simple manner, for example by the issuing authority.

The object is solved by the features of independent claim 1.

The method according to the invention allows holographic 3-D information to be subsequently introduced into a 2-dimensionally reconstructing starting hologram in a simple manner. The initial hologram into which the information is introduced by the method according to the invention can either contain no information or image information at all, or it can already have holographic information, in particular of a 2-dimensional or also 3-dimensional type. After the method according to the invention has been carried out, when the viewing angle changes, both the position and the brightness of the holographic information change according to the incidence of light, and a three-dimensional impression is created. In comparison to the known methods described above for modifying a hologram, the method according to the invention offers hitherto unimagined possibilities for subsequent individualization of a hologram, as a result of which the security against forgery is significantly increased. In addition, the method according to the invention can be carried out in a simple manner and without great effort. In particular, issuing authorities can use this to create forgery-proof ID documents quickly and on site.

The relief is pressed into the layered composite on top of the layered composite. The relief becomes part of the layered composite through the pressing process.

So that the information introduced can be easily recognized, both the hologram layer and the layers of the layered composite lying above it are preferably transparent.

The method according to the invention is particularly suitable for adding additional 3-D information into a hologram of a card in ID-1 format. The initial hologram can, for example, have been recorded with a laser with a wavelength of 532 nm, so that it is reconstructed in green color under white light.

According to the invention, the hologram layer is embedded between two elastic layers of the layered composite, with the elastic layers having a modulus of elasticity between 20 MPa and 500 MPa. It has been shown that this is of particular advantage or even necessary in order to be able to introduce 3D information into the hologram. The modulus of elasticity of the elastic layers is preferably in the range between 100 MPa and 400 MPa. A particularly preferred value for the modulus of elasticity of the elastic layers is 300 MPa. The layer thickness of the elastic layers is more preferably at least 5 μm and more preferably not more than 30 μm.

According to the invention, the layered composite has a carrier layer and a cover layer, with the elastic layers forming intermediate layers between the carrier layer and the hologram layer and between the hologram layer and the cover layer, with the cover layer consisting of a thermoplastic material, and with the relief in the pressing step on the upper side of the layered composite is pressed into the top layer. The carrier layer either forms the underside of the layered composite or it is arranged at least below the hologram layer. The cover layer either forms the top or it is at least arranged over the hologram layer. The top layer is preferably made of polycarbonate or polyethylene terephthalate. The carrier layer also preferably consists of a thermoplastic material. The use of polycarbonate or polyethylene terephthalate is also particularly preferred here. The carrier layer can in particular be a card in ID-1 format, the thickness of which is more preferably between 0.5 mm and 1 mm.

According to the invention, the relief is applied to the top layer before the pressing step, in that a curable transparent lacquer is applied in relief to the top layer and cured. The relief thus becomes part of the composite layer. The hardenable paint can be applied to the top layer particularly easily and quickly, for example using the inkjet method. The lacquer used is more preferably radiation-curable. It is particularly preferably a UV lacquer. More preferably, the paint is an acrylate-based paint.

Further advantageous embodiments of the method according to the invention are the subject matter of the dependent claims.

In a preferred embodiment of the present invention, the curable paint has a maximum modulus of elasticity of 1600 MPa in the cured state.

According to a further preferred embodiment of the present invention, the relief is pressed into the top layer in the pressing step in such a way that the upper side is then flat. During the pressing step, the material in the top layer flows, as a result of which the relief valleys are filled or backfilled from below. In this embodiment, the relief whose information is imaged onto the hologram layer by the method according to the invention can no longer be seen on the upper side of the layered composite. If the material of the cover layer and the material used for the relief have different refractive indices, the information originally imaged in the relief can only still be recognized in the glancing angle on the upper side of the layered composite. This applies, for example, when polycarbonate with a refractive index of 1.64 is used for the cover layer and an acrylate-based UV lacquer with a refractive index of 1.5 is used for the relief.

According to a further preferred embodiment of the present invention, the relief has a maximum thickness of at least 10 μm before the pressing step. The maximum thickness is preferably 10 to 30 μm, more preferably 15 to 25 μm, and particularly preferably about 20 μm. It is of particular advantage if the relief has a minimum thickness of at least 1 μm, the difference between the maximum thickness and the minimum thickness of the relief being at least 10 μm. If, for example, a hardenable lacquer is used to create the relief on the upper side of the layered composite in the printing process, the upper side is covered with the lacquer in the entire printed area before the pressing step, with a minimum thickness of 1 µm. As a result, the information contained in the relief is no longer recognizable in the specular angle after the pressing step. The information is then only visible in the hologram. More preferably, the minimum thickness of the relief is at least 4 μm. The difference between the maximum thickness and the minimum thickness is more preferably at least 15 μm.

According to a further preferred embodiment of the present invention, the layer thickness of the cover layer is at least 30 μm. More preferably, the layer thickness of the top layer is in the range between 40 μm and 100 μm. The value for the layer thickness of the top layer is particularly preferably around 50 μm.

According to a further preferred embodiment of the method according to the invention, the hologram layer is first applied to the carrier layer, with the cover layer being a film which is laminated onto the hologram layer applied to the carrier layer. This embodiment contributes to the simple feasibility of the method according to the invention. The film is preferably a polycarbonate film or a polyethylene terephthalate film. The film is more preferably heat laminated.

According to a further preferred embodiment of the present invention, the elastic intermediate layers consist of a heat-reactive adhesive. For example, the hologram layer can be coated with the heat-reactive adhesive and then laminated onto the carrier layer. The same applies to the top layer. The cover layer is preferably coated with a heat-reactive adhesive and then laminated onto the carrier layer or the hologram layer. The adhesive is preferably a polyurethane-based adhesive.

According to a further preferred embodiment of the present invention, the hologram layer is formed by a volume reflection hologram. The layer thickness of the hologram layer is preferably at least 5 μm, more preferably 5 to 20 μm, more preferably 8 to 20 μm, more preferably 10 to 20 μm and particularly preferably about 10 μm. If a transparent holographic hot stamping film with a layer thickness of less than 1 μm is used instead of a volume reflection hologram, the method according to the invention does not lead to a satisfactory result. The hologram layer is further preferably produced on a photopolymer basis.

The pressure, temperature and duration of the pressing step are preferably selected in such a way that the cover layer melts or partially melts, but the length and width of the layer composite remain unchanged. For example, the ID-1 format of a personal document should not change when the method according to the invention is carried out.

Thus, according to a further preferred embodiment of the present invention, the pressing step takes place at a surface pressure of at least 2 bar. More preferably, the pressure is in the range between 2.0 bar and 6 bar. More preferably, the pressure is at least 3 bar, particularly preferably at least 4 bar.

More preferably, the pressing step takes place at a temperature equal to or higher than the melting temperature of the top layer. Thus, considering the preferred materials for the top layer, the pressing step preferably takes place at a temperature of at least 110°C. The temperature during the pressing step is more preferably in the range between 110°C and 160°C. The temperature is more preferably at least 130.degree. C., particularly preferably at least 140.degree. The temperature information preferably relates to the temperature of the press plates of the press used.

More preferably, the pressing step lasts between 15 and 60 seconds.

Compliance with the above-mentioned ranges or key values for pressure, temperature and the duration of the pressing step guarantees that the information contained in the relief is transferred correctly as holographic 3D information into the hologram layer without the hologram being destroyed. If the specified ranges or key values are observed, it is also avoided that only a color shift and no transmission of three-dimensional holographic information takes place.

In a particularly preferred embodiment of the present invention, a press with flat press plates is used to carry out the pressing step.

The invention also provides a laminate having a hologram layer as an inner layer of the laminate modified by the method of the invention.

As a result of the lacquer relief applied to the document surface, pressure differences are generated during the method step according to the invention, which cause a three-dimensional deformation of the embedded hologram. Another advantage is that a flat document surface is also achieved. This ensures that the generated holographic 3D information can be easily recognized, as well as high mechanical stability and longevity of the document surface. In this way, individual three-dimensional holographic personal data can be generated by means of digital printing processes, which represent increased protection against counterfeiting.

Exemplary embodiments of the method according to the invention are explained in more detail below with reference to drawings.

• 1: das Auflaminieren einer Hologrammschicht auf eine Trägerschicht in einem ersten Schritt des erfindungsgemäßen Verfahrens,
• 2: das Auflaminieren einer Deckschicht auf den Schichtenverbund aus 1,
• 3: den Schichtenverbund aus 2 mit aufgedrucktem Relief auf der Oberseite der Deckschicht, sowie das Verpressen des entstandenen Schichtenverbunds,
• 4: den Schichtenverbund aus 3 nach dem Pressschritt,
• 5: den Schichtenverbund aus 3 mit einem alternativ aufgebrachten Relief, und
• 6: den Schichtenverbund aus 5 nach dem Pressschritt.

Show it:

• 1 : the laminating of a hologram layer onto a carrier layer in a first step of the method according to the invention,
• 2 : the lamination of a cover layer on the layered composite 1 ,
• 3 : the layer composite 2 with a printed relief on the upper side of the top layer, as well as the pressing of the resulting layered composite,
• 4 : the layer composite 3 after the pressing step,
• 5 : the layer composite 3 with an alternative applied relief, and
• 6 : the layer composite 5 after the pressing step.

For the following explanations, the same parts are denoted by the same reference symbols. If a figure contains reference symbols that are not discussed in more detail in the associated description of the figures, reference is made to the preceding or following descriptions of the figures.

1 shows a first step of the method according to the invention, in which a hologram layer 3 coated with a heat-reactive adhesive 5 is laminated onto a carrier layer 1 made of polycarbonate. The carrier layer 1 can be, for example, a card in ID-1 format, in particular an identification document or the like.

As 2 shows, in a subsequent step, a polycarbonate film 2 is also coated with a heat-reactive adhesive 5 and laminated as a protective cover layer onto the layer composite formed in the first step.

The top of the cover layer 2 is then printed with the desired information, for example with an image, using the inkjet method. A transparent UV lacquer is used as a medium, which is then cured under UV light, so that on the upper side of the cover layer 2 the in 3 Relief shown 4 arises. As in 3 is indicated, the resulting composite layer is then pressed between two flat press plates 6 at a pressure of about 4 bar and an elevated temperature of about 130 ° for 30 seconds. The material from the top layer flows into the valleys of the relief 4, so that a flat surface is ultimately created, as shown in 4 is shown. During the pressing process, not only the cover layer but also the underlying hologram layer 3 is deformed in such a way that the information previously contained in the relief, for example in the form of an image, is transferred as three-dimensional information into the volume reflection hologram of the hologram layer 3. A certain elasticity of the adhesive intermediate layers 5 plays a very important role in this. They should have a modulus of elasticity in the range between 20 MPa and 500 MPa, preferably between 100 MPa and 400 MPa.

Due to the different refractive indices of the UV coating and the top layer, the information contained in the relief is also visible on the upper side of the composite layer in the specular angle. In order to avoid this, the UV lacquer can be applied to the entire printed area with a minimum thickness of at least 1 μm, so that the lacquer also covers the surface of the cover layer 2 in the area of the relief valleys. After the process according to the invention has been carried out, in this case the upper side of the layered composite is not only flat but also has a uniform refractive index, so that the information contained in the relief is no longer visible in the glancing angle, but is visible in the hologram.

Reference List

1

backing layer

2

top layer

3

hologram layer

4

relief

5

elastic intermediate layer

6

press plate

Claims (12)

Method for modifying a hologram contained in a hologram layer (3), in which first a layered composite is produced with an upper side, an underside and with the hologram layer (3) as an inner layer of the layered composite, with a relief (4th ) is pressed into the layered composite, characterized in that the relief (4) is pressed into the layered composite in the pressing step under increased pressure and temperature in such a way that the hologram layer (3) is deformed in such a way that the relief (4) contained Information is transferred as holographic 3D information into the hologram layer (3), so that the hologram contained in the hologram layer (3) is subsequently reconstructed in three dimensions with the holographic 3D information, the hologram layer (3) being sandwiched between two elastic layers (5) of the Layered composite is embedded, wherein the elastic layers (5) have a modulus between 20 MPa and 500 MPa, the layered composite having a carrier layer (1) and a cover layer (2). has, wherein the elastic layers (5) form intermediate layers between the carrier layer (1) and the hologram layer (3) and between the hologram layer (3) and the cover layer (2), wherein the cover layer (2) consists of a thermoplastic material, wherein the relief (4) is applied to the top layer (2) before the pressing step, by applying a curable transparent paint in relief to the top layer (2) and curing it, and the relief (4) in the pressing step on the upper side of the layered composite in the cover layer (2) is pressed in. procedure after claim 1 , characterized in that the hardenable lacquer is an acrylate-based UV lacquer which is applied to the cover layer (2) using the inkjet method. procedure after claim 1 or 2 , characterized in that the hardenable paint has a modulus of elasticity of at most 1600 MPa. Procedure according to one of Claims 1 until 3 , characterized in that the relief (4) is pressed into the cover layer (2) in the pressing step in such a way that the upper side is then flat. Procedure according to one of Claims 1 until 4 , characterized in that the relief (4) has a maximum thickness of at least 10 µm before the pressing step. procedure after claim 5 , characterized in that the relief (4) has a minimum thickness of at least 1 µm, the difference between the maximum thickness and minimum thickness of the relief (4) being at least 10 µm. Procedure according to one of Claims 1 until 6 , characterized in that the cover layer (2) has a layer thickness of 40-100 µm. Procedure according to one of Claims 1 until 7 , characterized in that the hologram layer (3) is first applied to the carrier layer (1), the cover layer (2) being a polycarbonate film or a polyethylene terephthalate film which is laminated onto the hologram layer (3) applied to the carrier layer (1). Procedure according to one of Claims 1 until 8th , characterized in that the elastic intermediate layers (5) consist of a heat-reactive adhesive. Procedure according to one of Claims 1 until 9 , characterized in that the hologram layer (3) is formed by a volume reflection hologram and has a layer thickness of 5-20 µm. Procedure according to one of Claims 1 until 10 , characterized in that the pressing step is carried out at a temperature of between 110°C and 160°C and at a pressure of between 2 and 6 bars. Layer composite with a hologram layer (3) as an inner layer of the layer composite, modified according to the method according to any one of Claims 1 until 11 .

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