DE102017003281A1 - Security element with relief structure and manufacturing method therefor - Google Patents

Abstract

In a security element (S) for producing value documents, such as banknotes, checks or the like, which shows a motif in front of a background, which has a relief structure (7, 10, 12-14, 16, 17) which has a motif area (1, 4) of the security element (S) and there provides the subject and a background area (2) of the security element (S) covered and there provides the background, an outline (3) is provided, which delimits the subject against the background, which also by the relief structure is formed, wherein the relief structure (12, 14, 17) of the outline differs from the relief structure (10, 13, 16a) of the motif area and the relief structure (7, 16b) of the background area (2), so that a brightness and / or color contrast between the outline (3) on the one hand and the subject area (1, 4) and background area (2) on the other.

Description

The invention relates to a security element for the production of value documents, such as banknotes, checks or the like, which shows a motif against a background, wherein the security element has a relief structure which covers a motif area of the security element and provides the motif there and a background area of the security element covered and there provides the background.

The invention further relates to a value document with a security element.

Finally, the invention also relates to a production method for a security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, wherein a relief structure is produced, which covers a motif area of the security element and provides the motif there and covers a background area of the security element and provides the background there.

Security features for banknotes contain motifs, such as symbols, images or true color images, which are to achieve a particularly good visibility and anti-counterfeiting security. Such motifs are known, for example, from the following publications: H. Lochbihler, "Colored images generated by metallic sub-wavelength gratings", Opt. Express, Vol. 17, pages 12189-12196, 2009; WO 2012/156049 A1 ; EP 1434695 B1 ; EP 2453269 A1 ; WO 2013/091858 A9 ; US 9188716 B2 and DE 102014011425 A1 ,

Motifs with such security elements, however, are in need of improvement in terms of visibility in low light conditions.

The invention is therefore based on the object to improve a security element, a value document and a manufacturing method of the type mentioned so that the recognizability is increased. At the same time a simple production should be possible.

The invention is defined in claims 1, 10 and 11.

The security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, has a relief structure which covers a motif area of the security element and provides the motif there and covers a background area of the security element and provides the background there; In addition, an outline area is provided which delimits the motif area from the background area and which is likewise formed by the relief structure, wherein the relief structure of the contour line area differs from the relief structure of the motif area and that of the background area, such that a brightness and / or color contrast between the outline area on the one hand and the motif area and background area on the other.

In the manufacturing process for a security element for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, a relief structure is created, which covers a motif area of the security element and provides the motif there and covers a background area of the security element and there Background and a contour area is provided which delimits the motif area against the background area and which is also formed by the relief structure, wherein the relief structure of the contour area differs from the relief structure of the motif area and the background area, so that a brightness and / or color contrast between the outline area on the one hand and the subject area and the background area on the other hand.

The invention is based on the recognition that the motif is easier to recognize when it is delimited from the background by a high-contrast outline. In order to achieve a particularly good contrast and to facilitate the manufacturability, the outline is also defined by the relief structure, which differs in the outline area from the subject area and the background area, so that a brightness and / or color contrast between the outline area on the one hand and the subject area and the background area, on the other hand. This approach circumvents registration requirements that would arise, for example, in the conventional printing of a contour line with high-contrast color. At the same time, the outline can be designed to achieve the maximum contrast to the subject as well as the background, i. For example, a bright outline is easily possible. The invention thus significantly increases the perceptibility of the subject for a viewer.

The contrast between outline area and motif area and background area can be achieved, for example, by appropriate selection of the profile geometry of the relief structure. The relief structures are usually coated, for example metallic, high-refractive index or with a color-effect-producing layer composite, such as, for example, from WO 2008/080499 A1 For generating motifs, various relief structures are known from the prior art, ie with these Relief structures, a contrast between the subject area on the one hand and background area on the other hand can be achieved. For example, relief structures with micromirrors are known from the prior art (cf. DE 102010049617 A1 ). These micromirrors can be arranged in pixels, each having identically oriented micromirrors. Furthermore, Fresnel structures (cf. EP 1562758 B1 ) or combined with micromirrors. For micromirrors, relief heights of 1 μm to a maximum of 100 μm are known and lateral dimensions of less than 10 μm to less than 100 μm. Another known relief structure for generating a motif are hologram gratings in the form of relief holograms. They consist of metallized relief structures with grating periods of 500 nm to 2 μm and are arranged so that a viewer perceives a motif or a true color image in the first diffraction order. The US 9188716 B1 uses relief structures in the form of retroreflective structures to create colored motifs. For generating a motif or the background, further one- or two-dimensional subwavelength gratings are known, for example from the publication H. Lochbihler, "Colored images generated by metallic sub-wavelength gratings", Opt. Express, Vol. 17, pages 12189-12196, 2009 , or the WO 2012/156049 , By pixel-wise arrangement of relief structures with different profile parameters, true color images can be generated in the zeroth diffraction order, which can also be used to create a motif against a background. It is also possible, with the juxtaposition of certain relief structures, for example microstructures, to cause motion effects in an image (cf. DE 102010047250 A1 ). All of these different relief structures can be used and combined in the context of the present invention for generating the motif and the background, ie in the motif area and the background area and for generating the outline. Of course, a different relief structure can be used for the background area and the motif area and the outline. The decisive factor is that there is a visually perceptible contrast between the outline area and the motif area as well as between the outline area and the background area with the unaided eye. Another example of sub-wavelength structures are so-called moth-eye structures (cf. WO 2006/026975 A2 and EP 2453269 A1 ). The creation of colored motifs can be done by staining a relief structure.

In a development, the contour area can be provided with a structuring by the relief structure is designed accordingly. The structuring may mean an interruption of the contour area and / or micro-text or information that is invisible to the naked eye.

The outline area may also be a contour line within a complex subject. A complex motif consists of several motif components, whereby one of the motif components in the optical perception is to be understood as background, so that the contour area delimits the background area, ie a motif area of the complex motif, against another area of the complex subject. The contour area may also be unstructured in specific embodiments.

• 1 eine Draufsicht auf ein Sicherheitselement mit mehreren Motiven vor einem Hintergrund, wobei Umrisslinien die Motive gegen den Hintergrund abgrenzen,
• 2 eine schematische Schnittdarstellung durch das Sicherheitselement S mit drei Bereichen I bis III entsprechend dem Motivbereich, dem Umrisslinienbereich und dem Hintergrundbereich des Sicherheitselementes der 1,
• 3 eine Darstellung ähnlich der 2, wobei andere Reliefstrukturen für Motivbereich, Hintergrundbereich und Umrisslinienbereich verwendet werden, und
• 4 eine Darstellung ähnlich der 2 und 3, wobei wiederum andere Reliefstrukturen für Motivbereich, Hintergrundbereich und Umrisslinienbereich zum Einsatz kommen.

The invention will be explained in more detail with reference to the figures by way of example, which also show features essential to the invention. In the drawings shows:

• 1 a top view of a security element with several motifs against a background, with outlines delineating the motifs against the background,
• 2 a schematic sectional view through the security element S with three areas I to III corresponding to the subject area, the contour line area and the background area of the security element of 1 .
• 3 a representation similar to the 2 , where other relief structures are used for the motif area, the background area and the outline area, and
• 4 a representation similar to the 2 and 3 In turn, other relief structures for motif area, background area and outline area are used.

1 shows a security element S representing a hummingbird with a date in front of a textured background as a motif. A motif area 1 and a background area 2 are formed by different relief structures, which form an optical contrast in reflection, so that the subject can be perceived with the unaided eye. The motif is delimited by a narrow outline from the background. The year is also separated from the background by an outline. The outlines in outline areas 3 are also created by relief structures which are designed to provide contrast both to the subject area 1 . 4 as well as to the background area 2 form. For a viewer, this significantly increases the perceptibility of the motifs. The subject area 1, 4 and the background area 2 are formed by relief structures, which are metallized, for example, and embedded in a dielectric. The same applies to the outline 3 , Of the Contrast between the different areas is created by appropriate selection of the profile geometry of the relief structure.

2 schematically shows a sectional view of examples of such relief structures. The area I corresponds to the motif area 1 or 4 , the area II the background area 2 and the area III the outline area 3. The security element S is on a substrate film 5 formed on which an embossing lacquer layer 6 was applied, in which the relief structure was introduced, which was then metallized. A topcoat layer 8 and a cover sheet 9 complete the security element S which can span, for example, a window area of a banknote.

Both the region I and the region II are formed in the embodiment of the hologram gratings 7, 10 with a sinusoidal profile. The hologram gratings 7 and 10 differ in their design with respect to the image generated by them. The contrasting outline area 3 is through a subwavelength grid 12 realized in area III. The sub-wavelength grating 12 may be one or two-dimensionally periodic. It creates a contrast both with respect to the hologram grid 7 as well as towards the hologram grid 10 and thus highlights as an outline the motif that passes through the subject area 1 . 4 is formed, against the background, which through the background area 2 is formed out.

3 shows a further embodiment to illustrate that the relief structures in the areas I, II and III are freely selectable in large areas as long as there is a contrast between the areas I and II and a contrast between the area III and the areas I and II given is. In the embodiment of the 3 is the background area 2 designed differently. It is on the one hand, ie in some sections, formed by the hologram grid 7 and on the other, ie in other sections, by a smooth surface 15 , The motif area is realized by a micromirror arrangement 13. The contour regions are filled with light-absorbing moth-eye structures 14 in regions III.

4 shows an embodiment in which the contour line area realizes a bright border. The areas I and II are here designed with transmissive hologram gratings, as for example from the DE 102014011425 A1 are known. You have next to the zeroth order of diffraction 0 , O. and the first diffraction order 1 , O. also in addition an effect in transmission, ie incident radiation e is not only reflected as reflected radiation R, as in the embodiments of 2 and 3 the case was, but also as transmitted radiation T partially transmitted. In this way, a transmitted light motif is possible. In area III, this is combined with a conventional hologram grid, which is opaque after metallization. In this way, in plan view, a delineation of the subject area 1 . 4 against the background area 2 achieved, which causes a bright outline. The structure of 4 also shows a motif in transmission. In this perspective, the outline, ie the area III appears dark and enhances the recognizability of this motif. These contrast changes in transmission can generally be realized by opaque outlines. For this purpose, relief structures are the metallized and have a profile, which have an aspect ratio, ie a ratio of depth to period of less than 0.4. Particular examples are smooth metallized surfaces, micromirror arrangements, matt structures or conventional holographic structures, etc. Transmissive structures can be, in particular, those described in the initially cited publication by Lochbihler, Opt. Express, or from US Pat WO 2012/156049 are known. Such transmissive structures generally appear darker in reflection than opaque metallic structures with a low aspect ratio because the transmitted light decreases reflection. Therefore, these flat structures as bright outlines clearly enhance the perception of the subject in reflection.

The embodiments of the 2 to 4 Of course, by way of example only, the lateral arrangement of different relief structures in the areas I to III. Equally, other combinations of micromirror arrangements, fresnel-like structures, μ-lenses, hologram gratings, retroreflective structures, one- or two-dimensional subwavelength gratings or moth-eye structures and microcavities are possible, which provide a brightness and / or color contrast between the respective areas for a viewer.

It is also possible to provide dark structures in the outline areas. Such appear dark from different, preferably all viewing directions. For this are particularly suitable in 3 used moth-eye structures 14 , From the literature various possibilities are known, such Moth eye structures 14 to create. Exemplary is on the already mentioned WO 2006/026975 A2 or the EP 1434695 B1 directed. These publications describe metallically vapor-deposited random surfaces which form a refractive index gradient layer and have a good absorption effect. In this case, the structure depth is preferably more than 50 nm and the mean distance between adjacent elevations is less than 500 nm, hence the name sub-wavelength structures. Such random surfaces can be produced from plastic substrates, eg PMMA, with a plasma etching process. Alternatively, too Periodically arranged moth eye structures are used. Furthermore, it is known that moth-eye structures which are coated with a multilayer, for example a so-called color-shift coating, provide high-contrast dark colors (cf. EP 2453269 A1 ). Even structures which have a mean distance greater than 500 nm can show a high absorption effect after metallization. Such so-called microcavities preferably have a hemispherical recess with a ratio of depth to aperture width greater than 0.5 and are arranged, for example, hexagonal or orthogonal next to one another. From the EP 1434695 B1 For example, a moth-eye structure is known which is formed by a metallized cross-grating with a period of less than 420 nm. Also, a two-dimensionally periodic sub-wavelength grating can be used for light absorption, as for example in the WO 2012/156049 A1 is described. This grid is also suitable for color filtering. The geometry parameters of the grating can be chosen so that maximum light absorption occurs and the average reflection is less than 20%, preferably less than 10%.

The delimitation between the background area, the motif area and the outline area can be achieved by such structures acting as color filters. These do not necessarily have to be black, but may also appear in a different color, e.g. Red or blue. Dark colors, however, are advantageous for the recognizability of the subject. These named metallic subwavelength structures show an increased light absorption in the visible spectral range, partly due to a resonant absorption of light, which leads to a colourfulness of the reflection. A high contrast between the contour area and the subject area or background area is ensured since the average absorption in the visible wavelength range is always higher than that of mirror-smooth surfaces, such as e.g. Micromirrors. Alternatively, these structures may not be dark even from some directions. For example, the outline area can also be filled by micromirrors, which are all the same orientation and then light up brightly only at one angle. Although this has the disadvantage that the areas III then light up at a certain angle (undesired) brightly, the contour line area does not cause the demarcation between the motif and the background under certain angles under certain circumstances, however, a technically particularly easy realization is obtained for this disadvantage because no further structures have to be produced in addition to micromirrors, in particular no nanostructures. It is then possible to carry out the relief structures for background area, contour line area and motif area exclusively by micromirrors, wherein only the orientation of the micromirrors between the individual areas changes. Advantageously, one chooses the angle of unwanted illumination of these areas so that it is as little as possible, for example, in this area, all mirrors are maximally oriented downwards, so that occurs only at very oblique insight of the lighting effect. Alternatively, a tilt in east / west direction can be selected with extremely far oriented, for example, east-oriented alignment of the micromirrors.

To form bright outlines, relief structures with a low aspect ratio are suitable. After metallization, such structures are largely opaque in transmission and appear bright to a viewer in reflection. Micromirrors, hologram gratings, retroreflective structures, and planar surfaces are particularly suitable for this purpose.

When using color shift coating, the relief structure can change the color shift color in the outline area to effect the demarcation.

For good visibility, the average brightness of the outline area is less than 50% of the average brightness of the subject area as well as the background area in reflection and optionally also in transmission. Alternatively, the average brightness of the contour line area is more than 20% higher than that of the motif area and the background area in reflection and optionally also in transmission.

Micromirrors, hologram gratings and / or sawtooth gratings are preferably used in the motif area and the background area, sub-wavelength structures (in particular color-filtering or moth-like eyes), hologram gratings and / or matt structures in the contour line area.

The relief structure is preferably produced by lithographic methods, for example an e-beam system or a laser writing system which operates, for example, with a two-photon absorption process. Alternatively, it can be produced in a two-step lithographic process. In a first step, a nanostructuring is carried out. This is done, for example, by an electron beam lithographic process. Alternatively, laser beam interference methods come into question. Aperiodic moth-eye structures can also be generated by plasma etching or by structuring with ultrashort laser pulses. In a subsequent step, such an original or a copy thereof is leveled with photoresist. Particularly suitable for this purpose are spin coating or dip coating processes. Then the relief structure is written in a photolithographic step in the photoresist and the desired areas of the structures are free-scanned. This process can be done with the help of a laserwriter using the direct exposure method. The resulting original can subsequently electroplated or copied using photopolymers (eg Ormocere). The surface structure of a stamp produced in this way can now be multiplied by a step-and-repeat method on a larger area side by side. By galvanic impression of this replicated on the surface of the original of an embossing cylinder can be made. Finally, the structure can be embossed on a film in a continuous roll-to-roll process. In this case, nanoimprint processes such as hot stamping or embossing in UV-curable materials come into question. Finally, the embossed film is metallized metallically. The usual vapor deposition methods are electron beam vapor deposition, thermal evaporation or sputtering. The metallic material used may be metals such as aluminum, silver, copper, palladium, gold, chromium, nickel, iron, cobalt and / or tungsten and their alloys. After vapor deposition, the structure is optionally laminated and protected with the cover film 9. Instead of a simple metal coating, the relief structure can also be coated with a multiple layer. For this purpose, in particular so-called color-shift coatings come into question, which consist of a semi-transparent metal layer, a dielectric spacer layer and an underlying metallic mirror layer. Suitable dielectrics are in particular SiO ₂ , MgF ₂ , Ta ₂ O ₅ , ZnS and polymers. Another alternative is a dielectric coating with a high refractive index material. In addition, if demetallized areas on the film element are required, wash ink is printed on the desired areas before steaming and then removed after evaporation. Alternatively, these areas may also be generated by laser demetallization or wet chemical etching techniques.

In a further embodiment, a motif (eg in the form of a cord) is provided with a movement effect. The motif area 1 . 4 is produced by a juxtaposition of micromirrors and has a "rolling bar" effect, as z. B. off DE 102010047250 A1 are known in which light bars move up and down when tilted. The movements of several bars can be the same or in opposite directions. Such motifs are clearly better to recognize with outlines, as a viewer would see otherwise only a "confusion" of bright light reflections. The outline area makes the actual shape clearly visible to a viewer. He can z. B. color-filtering sub-wavelength structures or - if a dark contour is desired - be realized by moth eye structures. In particularly advantageous variants, the micromirrors can be provided with a color-shifting coating (eg triple-layer structure with the sequence absorber, dielectric, reflector). Particularly advantageous change the relief structures in the outline area the color impression of this coating, z. By suitable subwavelength structures. Thus, not only light or dark outlines, but also outlines with a different color than the color within the motion effects can be generated.

Another effect, which can be generated in particular with subwavelength structures in the contour line region, is a higher transmission. Metallic sub-wavelength gratings, which have a pronounced transmission, show a clear contrast to flat surfaces, hologram gratings or micromirror structures. Particularly in the use of moth eye structures in the outline area this appears in supervision dark and in review (eg when used in a banknote window) bright. In color-tilting coatings (especially for example with two thin absorber layers, so the structure absorber, dielectric, absorber) and / or Using color-filtering subwavelength structures in the outline area, the color of the outline area may be different from the color of the area of the subject with a moving effect of viewing and reviewing. Even the outline area itself can show different colors in reflected and transmitted light.

LIST OF REFERENCE NUMBERS

1, 4

Basic Zone

2

Background area

3

Outline area

5

substrate film

6

Embossing lacquer layer

7

hologram structure

8th

topcoat

9

cover sheet

10

hologram structure

12

subwavelength

13

Micromirror structure

14

Moth-eye structure

15

smooth area

16

transmissive hologram grid

17

opaque hologram grid

S

security element

e

incident radiation

R

reflected radiation

T

transmitted radiation

0. O.

Zero order

1. O.

First order

I-III

Area

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2012/156049 A1 [0004, 0021]
• EP 1434695 B1 [0004, 0021]
• EP 2453269 A1 [0004, 0011, 0021]
• WO 2013/091858 A9 [0004]
• US 9188716 B2 [0004]
• DE 102014011425 A1 [0004, 0019]
• WO 2008/080499 A1 [0011]
• DE 102010049617 A1 [0011]
• EP 1562758 B1 [0011]
• US 9188716 B1 [0011]
• WO 2012/156049 [0011, 0019]
• DE 102010047250 A1 [0011, 0028]
• WO 2006/026975 A2 [0011, 0021]

Claims (15)

Security element for producing documents of value, such as banknotes, checks or the like, which shows a motif in front of a background, wherein the security element (S) has a relief structure (7, 10, 12, 13, 14, 16, 17) which has a motif area ( 1, 4) of the security element (S) and provides the motif there and covers a background region (2) of the security element (S) and provides the background there, characterized in that an outline region (3) is provided which covers the motif region (3). 1, 4) delimits against the background area (2) and which is likewise formed by the relief structure, the relief structure (12, 14, 17) of the contour line area extending from the relief structure (12, 13, 16a) of the motif area (1, 4) and the relief structure (7, 16) of the background area (2) differs, so that a brightness and / or color contrast between the outline area (3) on the one hand and the motif area (1, 4) and background area (2) on the other s exists. Security element after Claim 1 , characterized in that the relief structure (12, 14) of the contour line region (3) has a sub-wavelength grating. Security element after Claim 2 , characterized in that the motif area (1, 4) and background area (2) are otherwise free of sub-wave gratings. Security element after Claim 2 or 3 , characterized in that the relief structure of the contour line region (3) has a moth eye structure (14). Security element after Claim 4 , characterized in that motif area (1, 4) and background area (2) are otherwise free of moth eye structures. Security element according to one of Claims 1 to 5 , characterized in that the relief structure (12, 14) of the contour line region (3) microcavities. Security element according to one of Claims 1 to 6 , characterized in that the relief structure of the contour line region (3) has a micromirror structure. Security element according to one of Claims 1 to 7 , characterized in that the relief structure of the contour line region (3) has a hologram structure. Security element according to one of Claims 1 to 8th , characterized in that the relief structure of the contour line region (3) has retroreflective structures. Security element according to one of Claims 1 to 9 , characterized in that the relief structure of the contour line region (3) is coated metallically, with high refractive index or with a color-effect-producing layer composite. Security element according to one of Claims 1 to 10 , characterized in that the relief structure forms the contour line region (3) with a structuring of the contour line region (3). Security element after one Claim 11 , characterized in that the structuring of the contour line region (3) comprises interruptions of the contour line region (3) and / or microtext or information that is not recognizable or resolvable with the naked eye. Value document with a security element according to one of Claims 1 to 12 , Manufacturing method for a security element (S) for producing value documents, such as banknotes, checks or the like, which shows a motif against a background, wherein a relief structure (7, 10, 12, 13, 14, 16, 17) is produced, comprising a Subject area (1, 4) of the security element (S) covered and there provides the subject and a background area (2) of the security element (S) covered and there provides the background, characterized in that an outline area (3) is provided, which is the subject area (1, 4) delimits against the background area (2) and which is likewise formed by the relief structure, the relief structure (12, 14, 17) of the contour line area (3) extending from the relief structure (10, 13, 16a) of the motif area (FIG. 1, 4) and the relief structure (7, 16b) of the background area (2) differs, so that a brightness and / or color contrast between contour line area (3) on the one hand and the motif area and background area (2) ande on the other hand. Production method according to Claim 14 , characterized in that the security element according to one of Claims 1 to 12 will be produced.

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