DE102006062281A1 - Substrate for use with safety feature, has pigments of optically variable color of safety features that are irreversibly changed in partition by electromagnetic radiation - Google Patents

Abstract

The substrate (1) has an optically variable color (3) with pigments (4). The individual pigments have an interference-capable, multi-layered configuration. The pigments of the optically variable color of the safety features are irreversibly changed in a partition (6) by an electromagnetic radiation (5). The interference effect is visually or automatically changed in the partition. The internal reflection layer consists of aluminum. One of the dielectric layers has silicon dioxide. The outer partially transmitting layers have chromium and/or nickel. An independent claim is also included for a method for producing a substrate with a safety feature.

Description

The The invention relates to a substrate having a security element that has at least one optically variable color with pigments. The individual pigments in this case consist of at least one interference-capable, multi-layered Construction.

To the Protection against imitation, especially with color copiers or others Reproduction methods, become data carriers, such as banknotes or cards, equipped with optically variable security elements. The counterfeit protection is based Make sure that the visually and easily and clearly recognizable optically variable effect of the above reproductive devices not or only insufficient is reproduced.

optical variable security elements are, for example, thin-film elements, consisting of a reflector layer, a dielectric and an absorber layer consist. Does the security element from the absorber side viewed, the viewer perceives a particular color, the with change of the viewing angle changes.

reason the color shift is an interference effect between the light rays, from the surface the outer partially permeable layer (absorber layer) be reflected, and the light rays passing through the outer semi-permeable and the passing through the middle dielectric layer and from the inner dielectric layer Reflected metal reflector layer back to the partially transmissive layer become. At the partially permeable Layer, the light beams are then either transmitted to the outside or reflected again, so in this case the light rays several times between the reflective layer and the partially transparent layer be reflected back and forth. Thus, the light rays, the through the thin film layer are passed through, a longer Way back than the ones on the surface the thin film layer reflected light rays so that they are out of phase with respect to these, if they interfere with them.

To meet on the thin film layer incident light rays with different angles of incidence on the thin film layer on, is in the thin film layer covered Path of light rays of different lengths. This difference results from the path difference changed by the angle of incidence of the multiple within the thin film layer reflected rays. Therefore, the phase angle of the interfering Light rays vary depending on the angle of incidence, so that depending on the angle of incidence different colors or shades of the resulting, revealed by the observer perceived light beam.

Such thin film elements can be used in the form of films, such as. In WO 2005/108110 described. Out WO 2005/108110 a security element with a thin film layer is known in which the individual layers are arranged over the entire area on the security element. Markings in the form of patterns, letters, numbers or images are introduced into the layer sequence by the action of laser radiation. For this purpose, the layer sequence contains a marking layer composed of a color mixture which has a mixture component which absorbs the laser radiation and a mixture component transparent to the laser radiation. The markings are visually and / or mechanically recognizable due to an irreversible change in the optical properties of the paint mixture caused by the action of the laser radiation.

Similarly, pigmented thin-film elements are known, which are mixed into an ink. The EP 0 227 423 B1 describes thin-film elements with a symmetrical structure to ensure that the pigment looks the same from every side. Each of the thin film elements is composed of a five-layered thin film composed of an inner metal reflector layer, a lower and upper dielectric layer having a refractive index of 1.65 or less, and an outer semi-opaque layer, respectively. The five-layer thin film causes on the side facing the observer a color shift, ie a change between two different colors or shades at a first and a second viewing angle. For example, the optically variable color appears magenta from a given viewing angle and green from a different viewing angle. If a viewer tilts a data medium onto which such an optically variable ink has been applied, it perceives a color change from magenta to green or vice versa.

Of the Invention is based on the object with a security element capable of generating interference Anti-counterfeiting pigments embody.

These The object is solved by the features of the independent claims. Further developments of Invention are the subject of the dependent claims.

The invention in this case comprises both a substrate with a security element and a data carrier with a substrate with a security element. The data carrier here is in particular a value document, such as a banknote, a security, a credit or identity card, a passport, a document and the like, a la a packaging or other element for product safety.

According to the invention Pigments of the optically variable color of the security element by means of an electromagnetic radiation in at least a portion irreversibly changed, in this subarea, the interference effect is visually and / or machine clearly noticeably changed or completely canceled is.

The irreversible change a pigment occurs on the one hand by the change in the optical properties at least one layer of the pigment, d. H. in particular transparency, the reflectivity, the polarization direction and the color or hue of the pigment. On the other hand, the irreversible change of a pigment takes place an at least partial displacement of at least one layer of the pigment. In this case, a layer of the pigment is not removed, evaporated or converted, but at least partially from his original Position within the layer structure removed and to a new Position shifted within the layer structure. This will be for example by reducing the thickness of a layer in one place at the same time Increase the Thickness of one layer on another, especially the adjacent one Reached.

• – für die mittlere Reflexionsschicht alle reflektierenden Substanzen, insbesondere Metalle, wie Aluminium oder Kupfer,
• – für die dielektrischen Schichten SiO₂ (Silizium-Dioxid), ZrO₂ (Zirkon-Dioxid) oder TiO₂ (Titan-Dioxid) oder andere transparente Stoffe,
• – für die teildurchlässigen Schichten Chrom und/oder Nickel.

The pigments or the pigmented thin-film elements are preferably five-layered. They consist of a central reflective layer, two dielectric layers surrounding the central reflective layer on each side, and two outer partially transparent layers. As materials for these layers are used in particular:

• For the middle reflection layer, all reflective substances, in particular metals, such as aluminum or copper,
• For the dielectric layers SiO ₂ (silicon dioxide), ZrO ₂ (zirconium dioxide) or TiO ₂ (titanium dioxide) or other transparent substances,
• For the semitransparent layers chromium and / or nickel.

One Pigment thus consists of a lower partially permeable layer chromium and / or nickel followed by a dielectric layer made of silicon dioxide, a medium reflective layer of aluminum, to be on the opposite Side again a dielectric layer of silicon dioxide connects, as well finally from an upper semi-permeable Layer of chromium and / or nickel. Light on the top or Part of the pigment impinges partially on the partially permeable layer reflected and partially transmitted. The latter part occurs through the dielectric layer, which has a different refractive index as the semi-permeable Layer, and is reflected back from the reflective layer and after passing through the dielectric layer back into one transmitted and split a reflected portion.

The However, the invention is not limited only to five-layered pigments, but applicable to all single or multi-layer pigments, the one produce optically variable effect. In particular, are out of the state the technique known optically variable layers, starting from the reflection layer in the direction of the viewer more than two layers exhibit. Also on pigments that are made of such optically variable Layers are made and thus have more than five layers is the Invention applicable.

The at least one modified layer by the electromagnetic radiation is advantageously the outermost layer of the pigment facing the direction of irradiation. For pigments with five-layered Build up the semitransparent layer, after the irradiation no longer partially permeable, but preferably transparent is.

A Influencing an interference-capable layer structure always succeeds when the reflection minimum of the interference-capable layer structure with the wavelength the electromagnetic radiation is largely identical. This can either the angle of incidence or the wavelength of the electromagnetic Radiation to the reflection minimum of the interference-capable layer structure be adjusted. By the change of the angle of incidence, the reflection minima are known to shift to shorter ones Wavelengths, so that almost always a suitable angle can be found, in which an influence on the structure takes place.

Becomes while the irradiation with electromagnetic energy at the same time Energy modulated by electromagnetic radiation is particularly evident advantageously a gradient of the interference effect, d. H. lie in different places or at different depths of the Substrate different color gradients before.

According to the invention, it is not only possible to apply a single pigment color to the substrate, but also to apply a mixture of at least two pigment colors or several interference layers one above the other onto the security element, of which only one has a suitable reflection minimum and thus only one pigment color can be selectively changed. Alternatively, it is further possible to use a mixture of at least one pigment color and at least one printing ink or another effect color, such as, for example, a color based on cholesteric liquid crystals, or thermal inks on the security element apply. In this case, the further effect color can also be applied over the pigment color, as long as it is transparent to the laser wavelength and at least in parts of the visible spectrum.

Should the substrate with a security element against mechanical damage, such as As scratches, protected It is advantageous, the pigment colors within two films a multilayer film body to arrange. Such a multilayer film body is For example, a credit or identity card, wherein the security element according to the invention inside the film body is located and covered by a transparent film. Of course it is it also possible an inventive security element a security such. B. a banknote, through a transparent Cover film.

In a further advantageous embodiment of the invention is Substrate printed on the front and / or the back and the printing in Transmitted light visible. This has the advantage that different Information in transmitted light and reflected light are recognizable.

A Reflection in incident light is a lighting in the sense of this invention an object from one side and a viewing of the object from the same side. A reflection in reflected light is thus for example then before, when the front of the object is illuminated and also is looked at.

A Transmission in the context of this invention is illumination an object from one side and a view of the object from another side, especially the opposite side. A consideration in transmitted light is thus for example, if the back illuminated the object and viewed the front of the object becomes. The light thus shines through the object.

According to one Another advantageous embodiment of the invention is the security element at least partially made of a transparent film that matches the pigment colors is printed. In this case, advantageously, the irradiation with electromagnetic Radiation on the top of the print or on the bottom through the transparent film. Alternatively or additionally the irradiation with electromagnetic energy also on both Pages of the film done. In reflected light is only through the irradiation on the respective side caused change visible, in transmitted light however, no information is visible anymore.

In a further advantageous embodiment of the invention the pigments are ablated by the electromagnetic radiation or carbonized. In combination with the change described above of the pigment, this gives rise to further design options for a Safety element. For the ablation or carbonization are significantly higher energy densities necessary as for the destruction a pigment layer.

The source of the electromagnetic radiation laser sources are preferably used. In particular, pulsed Nd: YAG lasers, Nd: YVO ₄ lasers, CO ₂ lasers or other laser types in the wavelength range from UV to far-infrared are suitable, the lasers often also having advantageous frequency multiplication with an average light power between 0.5 W and 2 W work, thus preferably with a pulse energy between 10 .mu.J and 100 .mu.J. Laser sources in the near infrared are used with particular advantage, since this wavelength range fits well with the absorption properties of the substrates and printing inks used for value documents. For example, it is easy to specify for this range printing inks which are transparent to the laser radiation but opaque and colored in the visible spectral range for the human observer. With particular advantage, infrared lasers in the wavelength range of 0.8 .mu.m to 3 .mu.m, in particular Nd: YAG laser or Nd: YVO ₄ laser, ver used. If lasers with higher power are used, the pulse energy can be reduced to the necessary level by fading, beam splitting, absorption filters, defocusing or similar known methods. Alternatively, the laser frequency can be increased accordingly.

With For example, an Nd: YAG marker laser (λ = 1.064 μm) may be used Vectors are inscribed in the layer sequence, which is above all else for fast Labels is beneficial. This can be done with a Nd: YAG laser Pulse frequency of, for example, 20 kHz, a power between 0.5 W and 2 W, and a diameter of the focus of the laser between 70 μm to 300 μm, particularly advantageous 100 microns up to 200 μm operate. The working distance between lens and substrate will be slightly lower than for Optimal focusing is required to achieve a slight defocus to reach the laser spot. If the focus diameter becomes larger than chosen the favorable attitude, can with even energy distribution in the beam (top has) and correspondingly higher pulse energy with a Pulse also changed larger areas and so that the labeling speed can be increased at the expense of the resolution.

If the laser is chosen to be energetically modulatable from pulse to pulse, a color gradient of the interference effect can be achieved. In this case, different color gradients are present at different locations or at different depths of the substrate in front. In addition, with appropriate energy control without any effort, the pigment or absorbing color components can be completely or partially ablated / carbonized

The Substrate with the security element according to the invention serves in particular to increase the counterfeit protection of value documents, such as banknotes, checks, shares, ID cards, tickets, tickets, certificates, credit cards, Check cards and the like.

The Substrate with the security element according to the invention is in particular within a value document with any other security feature combined. So can the substrate with the security element according to the invention, for example, over a Security thread may be appropriate with a hologram or diffractive structures combined or alongside or overlapping with others visually be arranged variable structures.

Based The following examples and additional figures are the Advantages of the invention and various preferred embodiments of the invention explained. In detail, show schematically:

1 Substrate with a security element according to the invention of an optically variable color with pigments, in side view;

2 Layer structure of a single pigment in side view and here

2a before irradiation with electromagnetic energy and

2 B after irradiation with electromagnetic energy;

3 Substrate with a security element according to the invention in supervision and in this case 3a in incident light and 3b in transmitted light.

Of the better understandability because of the embodiments described in the following examples reduced to the essential core information as well as the representations in the figures highly schematized and do not reflect the real Conditions. Above all, those shown in the figures correspond Proportions do not match the reality of reality and serve exclusively to improve the clarity. In the practical implementation can much more complex patterns or images in single or multi-color printing come as a coating for use. The in the following examples information can be displayed also by any complicated Image or text information to be replaced.

The Examples are preferred embodiments to which, however the invention should not be limited in any way. Especially are the different embodiments also not limited to use in the form described, but can to increase the effects are also combined with each other.

In a preferred embodiment is according to 1 a security element 2 on a surface of a substrate 1 arranged. The security element 2 consists of a visually variable color 3 , in the pigments 4 are embedded. A subarea 6 the optically variable color 3 is due to electromagnetic energy, eg. B. in the form of a laser beam 5 , irradiated.

As optically variable color 3 For example, the color OVI ^® 9Z 3050A of Messrs. Sicpa with pigments of Fa. Flex is used with a color change from magenta to green or the corresponding color OVI ^® 9Z 1050 having a color change from gold to green.

In 2 is a lateral cross section through a pigment 4 shown. That of the laser beam 5 still unaffected pigment 4 exists according to 2a from a middle reflection layer 7 , a dielectric layer 81 on its underside, a dielectric layer 82 on its upper side and a partially permeable layer 91 on the dielectric layer 81 and a partially transparent layer 92 on the dielectric layer 82 , The partially permeable layer 92 lies on the laser beam 5 facing side of the pigment 4 whereas the partially permeable layer 91 through the reflection layer 7 is covered. Now hits a laser beam 5 on the pigment 4 , according to 2 B at a suitable irradiance and wavelength of the light of the laser beam 5 only the partially permeable layer 92 affected. In particular, in this case, the optical properties of the partially transparent layer 92 changed, so that, for example, the transmissivity of the partially permeable layer 92 is increased, ie the color change is changed. The partially permeable layer is preferred 92 almost completely transparent, so that the viewer only the color of the reflective layer 7 perceives. If this is metallic or silvery matt or shiny, the pigment appears 4 silvery for the observer.

The laser beam 5 thus changes the partially permeable layer 92 the optically variable color 3 , As a result, a change in the color change is achieved, for example, in the Silvery, depending on the irradiance of the laser beam 5 a part of the optically variable effect is retained. The lower the irradiance of the laser beam 5 is, the more the optically variable effect is retained.

The of the laser beam 5 influenced place is according to 3a clearly visible when viewed in reflected light, z. B. as a silvery spot with a changed color change or as an exclusively silvery spot without further color change. The adjacent areas of optically variable color 3 not from the laser beam 5 On the other hand, in reflected light they still show a color change. This results in a contrast between areas with changed and areas with unchanged color change.

Will the optically variable color 3 printed on a partially or completely transparent substrate appears according to 3b the optically variable color when viewed in transmitted light both in the laser beam 5 influenced as well as in the uninfluenced areas in a nearly uniform hue, z. B. uniformly gray. The of the laser beam 5 Thus influenced spot does not stand out in transmitted light with respect to the uninfluenced areas because of the laser beam 5 Pigments were only affected in single layers whereas the nearly opaque reflection layer 7 has remained unaffected. Thus, the overall transmittance and the optical density of the pigments were not changed.

Claims (41)

Substrate ( 1 ) with a security element ( 2 ) containing at least one optically variable color ( 3 ) with pigments ( 4 ), wherein the individual pigments ( 4 ) have at least one interference-capable, multilayer structure, characterized in that the pigments ( 4 ) of the optically variable color of the security element ( 2 ) in at least one subarea ( 6 ) by means of electromagnetic radiation ( 5 ) are irreversibly changed so that in this subarea ( 6 ) the interference effect is changed visually and / or mechanically clearly recognizable. Substrate ( 1 ) with a security element ( 2 ) according to claim 1, characterized in that the irreversible change of a pigment ( 4 ) by changing the optical properties of the pigment ( 4 ) he follows. Substrate ( 1 ) with a security element ( 2 ) according to claim 2, characterized in that the irreversible change of a pigment ( 4 ) in at least one layer of the pigment ( 4 ) he follows. Substrate ( 1 ) with a security element ( 2 ) according to claim 3, characterized in that the at least one modified layer is the outermost layer of the pigment ( 4 ) facing the direction of irradiation. Substrate ( 1 ) with a security element ( 2 ) according to claim 1, characterized in that the irreversible change of a pigment ( 4 ) by an at least partial displacement of at least one layer of the pigment ( 4 ) he follows. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the pigments ( 4 ) are five-layered and from a central reflective layer ( 7 ), two the middle reflection layer ( 7 ) surrounding dielectric layers on each side ( 81 . 82 ) and two outer partially transparent layers ( 91 . 92 ) consist. Substrate ( 1 ) with a security element ( 2 ) according to claim 6, characterized in that the inner reflection layer ( 7 ) consists of aluminum. Substrate ( 1 ) with a security element ( 2 ) according to claim 6 or 7, characterized in that at least one of the dielectric layers ( 81 . 82 ) consists of silicon dioxide. Substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 6 to 8, characterized in that the outer partially permeable layers ( 91 . 92 ) consist of at least chromium and / or nickel. Substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 6 to 9, characterized in that the electromagnetic radiation ( 5 ) at least the partially permeable layer ( 92 ) of a pigment ( 4 ) irreversibly changed. Substrate ( 1 ) with a security element ( 2 ) according to claim 10, characterized in that the electromagnetic radiation ( 5 ) the transparency of the partially transparent layer ( 92 ) irreversibly changed. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the reflection minimum of the interference-capable layer structure with the wavelength of the electromagnetic radiation ( 5 ) is largely consistent. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the pigment color consists of a mixture of at least two pigment colors, of which only one has a suitable reflection minimum and thus only one pigment color is selectively changeable. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the pigment inks are arranged within two sheets of a multilayer film body. Substrate ( 1 ) with a security element ( 2 ) according to claim 14, characterized in that the multilayer film body is a credit or ID card or a passport. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that a plurality of optically variable colors are arranged one above the other. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the optically variable color consists of a mixture of at least one pigment color and at least one printing ink or effect color. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the substrate is printed on the front and / or the back and the printing is visible in transmitted light. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that the security element ( 2 ) consists at least partially of a transparent film. Substrate ( 1 ) with a security element ( 2 ) according to at least one of the preceding claims, characterized in that a laser is the electromagnetic radiation ( 5 ). Substrate ( 1 ) with a security element ( 2 ) according to claim 20, characterized in that the diameter of the focus of the laser is 70 microns to 300 microns. Substrate ( 1 ) with a security element ( 2 ) according to claim 21, characterized in that the diameter of the focus of the laser is 100 microns to 200 microns. Substrate ( 1 ) with a security element ( 2 ) according to one of claims 20 to 22, characterized in that the laser is a pulsed Nd: Yag or Nd: YVO ₄ laser. Substrate ( 1 ) with a security element ( 2 ) according to one of claims 20 to 23, characterized in that the laser has a Lichtleis device between 0.5 W and 2 W and a pulse energy between 10 μJ and 100 μJ. Substrate ( 1 ) with a security element ( 2 ) according to one of claims 20 to 24, characterized in that the energy density of the laser is reduced by weakening or defocusing a laser with a power between 0.5 W and 2 W to the desired power. Substrate ( 1 ) with a security element ( 2 ) according to one of claims 20 to 25, characterized in that the laser is frequency-multiplied. Substrate ( 1 ) with a security element ( 2 ) according to one of claims 20 to 26, characterized in that the laser is energy modulated. Disk with a substrate ( 1 ) with a security element ( 2 ) according to one of claims 1 to 27. disk according to claim 28, characterized in that the data carrier a Value document, in particular a banknote or a card. Use of a substrate ( 1 ) with a security element ( 2 ) according to one of claims 1 to 27 or a data carrier according to claim 28 or 29 for product safety. Method for producing a substrate ( 1 ) with a security element ( 2 ), to which at least one optically variable color ( 3 ) with pigments ( 4 ), the individual pigments ( 4 ) are formed from at least one interference-capable, multi-layered structure, characterized in that the pigments ( 4 ) of the optically variable color of the security element ( 2 ) in at least one subarea ( 6 ) by means of electromagnetic radiation ( 5 ) are irreversibly changed so that in this subarea ( 6 ) the interference effect is changed visibly and / or mechanically clearly recognizable. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to claim 31, characterized in that the wavelength of the electromagnetic radiation ( 5 ) is adapted to the reflection minimum of the interference-capable layer structure. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to claim 31, characterized in that the reflection minimum of the interference-capable layer structure by the angle of incidence to the wavelength of the electromagnetic radiation ( 5 ) is adjusted. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to claim 31, characterized in that the wavelength of the electromagnetic radiation ( 5 ) is adapted to the reflection minimum of the interference-capable layer structure. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 31 to 34, characterized in that by a modulation of the energy of the electromagnetic radiation ( 5 ) a grayscale modulated image is generated. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 31 to 35, characterized in that a mixture of at least two pigment inks on the security element ( 2 ) is applied and only one pigment color is selectively changed. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 31 to 36, characterized in that the substrate is printed on the front and / or the back and the printing is visible in transmitted light. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 31 to 37, characterized in that the security element ( 2 ) is at least partially formed by a transparent film. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to claim 38, characterized in that the upper side of the printing or the lower side passes through the transparent film with electromagnetic radiation ( 5 ) is irradiated. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 37 to 39, characterized in that both sides are exposed to electromagnetic radiation ( 5 ) are irradiated. Method for producing a substrate ( 1 ) with a security element ( 2 ) according to at least one of claims 31 to 40, characterized in that the pigments ( 4 ) by the electromagnetic radiation ( 5 ) are ablated or carbonized.