EP1924446B1 - Certificate of authenticity with micro-refraction image - Google Patents

Description

The invention relates to a certificate of authenticity with a micro-refraction image.

Refraction images consist of a periodic line pattern applied to a substrate and a lens pattern covering the line pattern of cylindrical lenses parallel to the lines of the lens pattern. Depending on the viewing angle under which the periodic line pattern is seen through the lens structure, in each period of the line pattern, different lines are visible, which together give the perceived image. By designing the line pattern, various optical effects can be achieved by which the viewer perceives different image contents at different viewing angles. The viewing angle dependent effects may be a color change, a shape change, or a combination of color change and shape change.

Conventional refraction images can be used as security features in certificates of authenticity or securities. However, they are not particularly tamper-proof because they have a relatively coarse structure. For the optical effect of a refraction image, it is in fact necessary for the lens structure to be applied exactly congruent or at least parallel and with a constant offset over the periods of the line pattern. In the prior art, the lens structures are made by extruding transparent plastic or by mechanical deformation. With such a manufacturing method, lens structures in which the lens width can hardly be less than several 1/10 mm can be obtained. Accordingly coarse is the underlying line pattern.

By the US Pat. No. 3,576,689 A A method for producing a stereoscopic image with a lenticular screen is known, comprising applying a clay-like coating layer to a base film, printing specific linear or dotted images on the coated base film, applying an adhesive layer to the printed base film, adhering the film to the base film Back of the lenticular screen and peeling the film from the coating layer, wherein the coating layer properties of peelability and printability, and the printed images produce stereoscopic views when viewed through the lenticular screen.

By the WO 03/079092 A1 For example, a tamper resistant structure is known, comprising: an information containing structure; and a transparent structure comprising a first lens element and a second lens element both formed on an outer surface of the transparent structure, the first lens element constructed and arranged to have at least one of (i) non-parallel, (ii (iii) is unevenly shaped, (iv) is irregular in width, and (v) is dimensioned nonuniformly in height with respect to the second lens element, and wherein the information containing structure contains information obtained by looking through the transparent structure see is.

By the DE 85 29 297 U1 an identification card is known in which information is introduced by means of a laser beam in an inner layer area, which are visible in the form of changes in the optical properties of the layer material due to an irreversible, caused by the laser beam material change, the identification card consists of at least one transparent plastic layer, which is provided at least in a partial area with a surface relief in the form of a plurality of cylindrical lenses, wherein at least a part of the introduced by the laser beam information is introduced through these cylindrical lenses and wherein the visible material changes in the inner layer region to one, based on the width of the cylindrical lenses to narrow the narrow range.

By the US 5 851 615 A there is known a heat-shrinkable packaging material comprising a heat shrinkable film and a tamper evident security device, the security device having a substrate having a surface relief structure causing an optically variable effect, each surface of the substrate carrying an adhesive layer, abutting the device through one of the adhesive layers the film is attached and each adhesive layer has a strength such that the substrate, after it is adhered to a surface, can not be removed without damaging the optically variable effect.

The invention provides a certificate of authenticity with a micro-refraction image having all the features of claim 1, which makes counterfeiting almost impossible due to the high fineness of its line pattern.

The micro-refraction image according to the invention consists of a substrate, a periodic line pattern printed on the substrate and a periodic lens structure covering the line pattern from the lenses of the line pattern parallel cylindrical lenses. The period of the cylindrical lenses coincides with the period of the line pattern. The lenses are preferably, but not necessarily, aligned with the lines of the line pattern. The lines consist of orbits of elementary pressure points or pixels (pixels). The number of tracks of elementary printing dots in a period approximately between 4 and 16. The height of the cylindrical lenses at the vertex is in a range of half the width of one period and about the width of one period of the line pattern. With advanced offset printing methods, which are used for example in security printing (eg for banknotes), a printing accuracy of about 4 microns is achieved. It is preferable to select the elementary pressure points only slightly greater than the achievable printing accuracy. Realistic are elementary printing points of an approximately square shape with a side length of 4-8 .mu.m, in particular 6 μ m or slightly more. With minimal requirements for the design options for the line pattern, two lines per period are sufficient. Each line should consist of at least two orbits of elementary pressure points. This corresponds to a period width of about 40 microns. In the matching lens structure, the individual cylindrical lenses have a height at the apex of preferably slightly more than half the period width. Such fine lens structures can be produced by printing a transparent mass with an Intaglio printing process or by embossing the transparent mass with an Intaglio gravure plate.

For high demands on the design possibilities for the refraction image, the periodic line pattern contains a maximum number of lines, which is determined by the possibilities of the Intaglio method for producing the lens structure. For a good refraction effect, the cylindrical lenses must be square or square in size for semicircular or parabolic cross-sectional shape (ie their height at the apex is at least equal to half the period width). With the Intaglio technique structures of relief height up to about 100 μ m or can be generated. As a result, taking into account a small distance between adjacent lenses and depending on the cross-sectional shape of the lenses, a period width of the line pattern of up to about 220 μ m. Very diverse design possibilities arise in a line pattern with seven lines per Period, where each line consists of two tracks of pressure points. With the same period width, two lines each consisting of seven lanes or even fourteen lines of only one lane each are possible.

The invention thus combines two printing techniques, each of which is used on the edge of its possibilities: on the one hand, the cost-offset printing method whose printing accuracy is fully exploited, and on the other hand, the also inexpensive Intaglioverfahren, because of the limited relief heights generated to create the appropriate Lens structures can only be used because the line pattern generated with the described high-precision offset printing an extremely fine structure, and thus a correspondingly small period width, have.

For colored refraction effects, the lines within a period of the line pattern have different colors. For the printing of different colored lines with high dimensional accuracy, the simultaneous offset printing is suitable.

If an optical effect with a sudden change of the image content is desired with a small change in the viewing angle, cylindrical lenses with a prismatic cross-sectional shape are used.

Novel optical refraction image effects are possible if the line patterns and the lens structure have congruent surface areas in which the course of the lines or lenses is different from the course direction in at least one other area area.

In a method of producing a micro-refraction image, a periodic line pattern is printed on a substrate with precision offset printing. Then, over the line pattern, a lens structure in a transparent mass is applied by intaglio printing or embossing of the transparent mass with an Intaglio engraving plate. The combination of simultaneous offset printing, which makes full use of printing accuracy, with the Intaglio technique of applying the lens pattern over the line pattern allows for extremely complex and high quality produce resolution refraction images with a variety of optical effects at low cost.

For the perfect optical function, it is necessary that the cylindrical lenses of the lens structure are largely congruent over the periods of the line pattern or at least have a constant over the entire extent of the refraction image offset. Although various printing methods are used for the application of the line pattern and the generation of the lens structure, it is possible to achieve the required dimensional stability between line structure and lens structure. For this purpose, in particular for the production of the printing plate for the precision offset printing and for the production of Intaglio engraving plate, the same Maßbasis used. In both cases laser technology is used. For the production of the printing plate for offset printing, a laser exposure method is used. For the production of the Intaglio engraving plate, a laser process with ablation, in particular by evaporation, is applied directly to the surface of the printing plate.

According to the invention, the substrate consists of a transparent material. The lens structure is arranged on one side and the line structure on the surface of the substrate facing away therefrom. The distance between the line pattern and the lens structure due to the thickness of the substrate favors the achievable optical effects.

A certificate of authenticity is provided with at least one security element, which is applied to a substrate and has a periodic line structure, and with a periodic lens structure comprising parallel cylindrical lenses covering the security element. The period of the lens structure coincides with the period of the line structure, respectively, and the lenses are aligned with the periodic line structure of the security element. Further, the height of the cylindrical lenses above the security element at the apex is at least half the width of one period and at most the width of one period. The certificate of authenticity according to the invention is so complex that counterfeiting is hardly possible. Any counterfeits are visually easily recognizable without technical aids.

In a certificate of authenticity according to the invention, two security elements are arranged on the same substrate. These are connected in a transition zone by overlay, so that a visually verifiable linkage of the two security elements is produced. The link can e.g. be that when changing the viewing angle a color highlighted strip or the like from the one security element continuously migrates through the transition zone into the other security element. The security elements may be the described micro-refraction images, but also other types of security elements such as holograms, colorgrams or kinigrams. One of the security elements may be determined by one product vendor and the other by a certification authority issuing the certificate of authenticity.

A certificate of authenticity according to the invention consists in that it is made up of several layers, one of which is provided with adhesive properties against a product to be protected and at least one more whose removal destroys the certificate is pre-perforated or pre-punched along predetermined tear lines. Such a certificate of authenticity has the function of a seal.

• Fig. 1 eine perspektivische Illustration der Variationen eines Mikro-Refraktionsbildes unter verschiedenen Betrachtungswinkeln;
• Fig. 2 eine Draufsicht eines Mikro-Refraktionsbildes;
• Fig. 2a eine stark vergrößerte Detailansicht des Mikro-Refraktionsbildes von Fig. 2;
• Fig. 3 eine stark vergrößerte Schnittansicht einer Linsenstruktur von parallelen Zylinderlinsen in Zuordnung zu einem periodischen Linienmuster von relativ großer Periodenbreite;
• Fig. 4 eine stark vergrößerte Schnittansicht einer Linsenstruktur von parallelen Zylinderlinsen in Zuordnung zu einem periodischen Linienmuster von relativ kleinen Periodenbreite;
• Fig. 5a bis 5g vergrößerte Schnittansichten einer Linsenstruktur von parallelen Zylinderlinsen verschiedener Querschnittsformen;
• Fig. 6a bis 6e Draufsichten verschiedener Ausführungen von Linsenstrukturen mit parallelen Zylinderlinsen;
• Fig. 7 eine Draufsicht eines Echtheitszertifikats mit zwei Sicherheitselementen und einem diese verknüpfenden Übergangsbereich;
• Fig. 8 eine Draufsicht eines Echtheitssiegels mit vorperforierten oder vorgestanzten Aufreißlinien;
• Fig. 9a und Fig. 9b schematische Schnittansichten zur Darstellung einer Ausführungsform und ihrer Herstellung.

Further advantages and features of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. In the drawings show:

• Fig. 1 a perspective illustration of the variations of a micro-refraction image under different viewing angles;
• Fig. 2 a plan view of a micro-refraction image;
• Fig. 2a a greatly enlarged detail view of the micro refraction image of Fig. 2 ;
• Fig. 3 a greatly enlarged sectional view of a lens structure of parallel cylindrical lenses in association with a periodic line pattern of relative large period width;
• Fig. 4 a greatly enlarged sectional view of a lens structure of parallel cylindrical lenses in association with a periodic line pattern of relatively small period width;
• Fig. 5a to 5g enlarged sectional views of a lens structure of parallel cylindrical lenses of different cross-sectional shapes;
• Fig. 6a to 6e Top views of various embodiments of lens structures with parallel cylindrical lenses;
• Fig. 7 a top view of a certificate of authenticity with two security elements and a transition area linking them;
• Fig. 8 a plan view of a seal of authenticity with pre-perforated or pre-punched tear lines;
• Fig. 9a and Fig. 9b schematic sectional views illustrating an embodiment and its preparation.

In Fig. 1 10a shows a perspective view of a greatly enlarged section of a micro-refraction image at a certain viewing angle. The same section of the micro-refraction image is in Fig. 1 with 10b next to it under a rotated by approximately 90 ° viewing angle. Below are in Fig. 1 Figures 12a, 12b and 12c show three manifestations of the micro-refraction image as presented to the viewer when the viewing angle is changed from the situation shown at 10a to that shown at 10b. The appearance indicated by 12a is a combination of a letter "S" with the numeral "1". The appearance indicated by 12c is a combination of a letter "H" with the numeral "1". The intermediate appearance 12b is a transient state between the appearances 12a and 12c, the transitions being fluid.

Refraction images of this kind are known in principle. They consist of a periodic line pattern applied to a substrate and a lens structure covering it of cylindrical lenses parallel to the lines of the line pattern, the width of which coincides with the period width of the line pattern.

As from the in Fig. 2 shown vertical top view of the exemplary micro-refraction image and more particularly from the detailed view in Fig. 2a is apparent, this consists of a plurality of parallel line sections of different lengths, wherein in each period of the line pattern, the lines may have different colors, such as the colors red, green and blue in a line pattern with three colors.

One of the peculiarities of the invention lies in the extraordinary fineness of the line pattern and the lens structure. According to the invention, two per se known printing methods are used to realize such high-resolution micro-refraction images, but each on its own edge. The line pattern is printed with offset printing, with a realistic printing accuracy of about 4 μ m on a substrate. If the lines are to have different colors in each period, simultaneous offset printing is used. In addition, the lens structure is printed with intaglio printing from a transparent mass.

For the desired refraction effect, the cylindrical lenses must have a peak height above the line pattern, which corresponds approximately to half the period width of the line pattern or is preferably slightly larger. However, the structure heights possible with intaglio printing are limited. The maximum possible period width of the line pattern is therefore determined by the possibilities of Intagliodrucks, while the fineness of the line pattern is limited by the possibilities of offset printing. This situation will be described below on the basis of Fig. 3 and 4 be explained in more detail. Therein, "BP" designates an elementary pixel which is assumed to be ideally square with a side length of little more than the achievable printing accuracy of approximately 4 μm , for example a side length of slightly more than 6 μm .

In the Fig. 3 and 4 is a first dotted line 14 schematically illustrates a limit of intailible with intaglio structures. she has a Structure height of about 12 pixels BP and a feature width of about 14 pixels BP. A second dotted line 16 schematically shows a limit of the fineness of a line pattern that can be achieved with offset printing. Within these boundary lines, a method for producing a micro-refraction image is optimally executable. In Fig. 4 however, it is assumed that each period of the line pattern includes three lines and each line has a width of two pixels BP. If one accepts a line pattern with only two lines per period, the boundary line 16 reduces to only four pixels BP. Furthermore, results in Fig. 3 the feature width of fourteen pixels at a maximum feature height of twelve pixels BP from the requirement for an over-square cross-sectional shape of the cylindrical lenses (ie, the peak height is greater than half the feature width). On the other hand, if a square cross-sectional shape of the cylindrical lenses is also accepted, the corresponding structure width of the line pattern is sixteen instead of fourteen pixels BP.

It is understood that these values require available printing techniques. With increasing possibilities of offset printing, the line patterns can be even finer and the lens structures even higher.

In Fig. 3 the cross section of a lens structure is shown over a line pattern consisting of fourteen parallel and contiguous printing webs of a width of one pressure point BP. If each line of the line pattern consists of two such print paths, each period of the line pattern contains seven lines which may have different colors. Alternatively, each line of the line pattern, for example, consists of only two lines, each consisting of seven printing lines of a width of one BP, or any combination of printing webs.

Furthermore, in Fig. 3 various possible cross-sectional shapes of the cylindrical lenses drawn. For optimum refraction effect, the cross-sectional shape should be "over-square", ie the peak height is greater than half the period width. However, since the possibilities of Intagliodrucks are limited in terms of structure height, a compromise of about 5/8 of the period width is regarded as the peak height (corresponding to 8.75 pixels) as particularly favorable. This cross-sectional shape is solid line in Fig. 3 located. With broken lines are less ideal cross-sectional shapes in Fig. 3 located. The period width of the lens structure results from the width of the lenses and the width of the small distance between adjacent lenses. This is advantageous for two reasons: on the one hand, such sharp edges on the Intaglio engraving plate are avoided, which could cut into the substrate; On the other hand, the Intaglio pressure favors the wiping process with which the transparent mass is wiped off its raised surfaces after its application to the gravure plate. The distance between adjacent lenses is only about one pixel or only a few pixels.

At the in Fig. 3 assumed period width of the line pattern of fourteen pixels and the optimal cross-sectional shape of the cylindrical lenses are the possibilities of precision offset printing full and the Intaglio pressure almost fully utilized.

In Fig. 4 It is assumed that in the micro-refraction image, the line pattern has only three lines of a width of two pixels each. In this case, the limits of intaglio printing at line 14 are not exhausted, but those of the offset printing at line 16. As in Fig. 3 is the ideal cross-sectional shape in Fig. 4 drawn with a solid line. Broken lines indicate less ideal cross-sectional shapes.

Fig. 5 shows cross-sectional shapes of the cylindrical lenses with which special optical effects can be generated. At 5a) is a relatively flat prismatic cross-sectional shape, in particular trapezoidal shape shown. At 5b) the same trapezoidal shape is shown with greater peak height. An even greater peak height have the in Fig. 5c ) shown trapezoidal shapes. With such lens structures, sudden changes in the image contents can be achieved with only a slightly changed viewing angle, the effect being all the more noticeable the greater the peak height.

Fig. 5d ) shows alternating cross-sectional shapes: a parabolic lens is followed by an asymmetrical cross-sectional shape composed of parabolic trains, again followed by a parabolic lens, etc. The effects obtainable with such lens structures are very complex.

In the Fig. 5e ) have a triangular cross-sectional shape. The triangles may be equilateral or have uneven sides or alternatively be equilateral and non-equilateral as shown.

Fig. 5f ) shows cylindrical lenses with the cross-sectional shape of a polygon, which may have the same or unequal sides, as shown.

Fig. 5g ) shows cylindrical lenses with mixed cross-sectional shapes between prismatic and parabolic.

In general, the more complex the cross-sectional shapes of the cylindrical lenses, the more diverse are the producible optical effects.

Even more varied and complex are the optical effects that are similar to those in Fig. 6 can be achieved embodiments of the lens structure shown. In Fig. 6a ), a circular area 20 of parallel circular lines is placed in an outer area 22 of straight lines. In Fig. 6b ) there are two adjacent surface areas 24, 26 with 90 ° against each other twisted line patterns. In Fig. 6c ) is within the outer surface region 22 of straight lines, a square region 28 of straight, but rotated by 90 ° lines. In Fig. 6d ), the lines in the area 30 have alternating directions, are wavy or jagged. In Fig. 6e ), an irregularly shaped area 34 of straight, 90 ° twisted lines is arranged in an outer surface area 32 of straight lines. With such lens structures, which must be tuned to the underlying line patterns, various optical effects occur when the refraction image is pivoted about different axes or the viewing angle is changed in different planes.

At the in Fig. 7 shown certificate of authenticity two flat security elements 42 and 44 are arranged on a substrate 40 at a distance from each other. Symbolically, the security element 42 is represented by the designation "A1" and the security element 44 by "A3". Both security elements 42, 44 are connected by transition zones 46, 48 inextricably linked. Under an indissoluble linkage here is an interaction between the security elements 42, 44 understood, which is mediated by the transition zones by an overlay effect. at at least one of the security elements 42, 44 is preferably a micro-refraction image of the type described above. The other security element has a periodic structure which is matched to the lens structure of the micro-refraction image and at the same time corresponds to the line pattern of the micro-refraction image. Refraction image is covered. The non-detachable link can then consist in an optical effect, for example a light strip, blinking dots, brightly lit picture elements or the like, which shifts from one security element through the transition zones into the other security element as the viewing angle changes. While one security element is determined by a central certification authority, the other may be determined by any third party (eg, by a product manufacturer or product distributor). The one security element is then uniform, while the other is variable.

This in Fig. 7 The certificate of authenticity shown may be used as a seal of authenticity applied to a product or packaging. Such a seal of authenticity is in Fig. 8 shown. The substrate 40 is coated on the back with an adhesive. The security elements and the transition zone therebetween are deposited as a separate layer on the substrate. In order to ensure controlled destruction of the same upon removal of the seal of authenticity, longitudinal perforation or punching lines are provided along the desired tear lines. It can also be achieved by the tear lines that at least part of the seal remains intact after the removal of the authenticity seal from the product or from the packaging.

At the in FIGS. 9a and 9b In the embodiment shown, a substrate 100 made of a transparent material is used. On one of the surfaces of the substrate 100, the line pattern 102 is applied. On the surface facing away therefrom, a moldable transparent mass 104 is applied by a screen-printing method. With an Intaglio engraving plate 106, the transparent mass 104 is then embossed and formed into a lens structure. The lens structure may alternatively be applied on the same surface as the line structure. In the FIG. 9b shown embodiment, in which both structures are arranged on opposite surfaces, but has the Advantage that the achievable optical effects are promoted by the spatial distance.

Finally, it is also provided in a development, to arrange a line structure on both surfaces of the transparent substrate, in which case the lens structure is applied over one of the line structures. In this embodiment, an even greater variety of optical effects is possible. The two line structures are applied in this embodiment with simultaneous offset printing.

Claims (13)

1. An authenticity certificate with at least one security element (42 ; 44) that is applied on a substrate (40 ; 100) and has a periodic line structure, and with a periodic lens structure of parallel cylinder lenses covering the periodic security element (42 ; 44), wherein

   - the period of the cylinder lenses corresponds to the period of the line pattern (102),

   - the lenses are aligned parallel to the lines of the line structure and

   - the height of the cylinder lenses on the apex lies in a range of about half to about a whole width of the period,

   in which at least one security element (42; 44) to be determined by a third party and one security element (42; 44) to be determined by a central certification authority are arranged on the same substrate (40; 100) and the lens structure extends at least partially over both security elements (42; 44),
   in which at least one of the security elements (42; 44) is a micro-refraction image, consisting of the substrate (40; 100), the periodic line pattern (102) applied on the substrate (40; 100) and the periodic lens structure made up of the cylinder lenses parallel to the lines of the line pattern (102) covering the line pattern (102), wherein the period of the cylinder lenses corresponds to the period of the line pattern (102), the lines consist of elementary printing points (BP), the number of elementary printing points (BP) in a period is equal to or greater than four and equal to or less than sixteen and the height of the cylinder lenses on the apex lies in a range of about half to an entire width of a period, characterized in that the authenticity certificate consists of several layers, of which one is equipped with adhesive properties vis-à-vis a product to be protected and at least one further, whose removal destroys the authenticity certificate, is pre-perforated or pre-punched along prescribed tear lines, wherein the substrate (40; 100) consists of a transparent material and the line pattern (102) is arranged on the surface of the substrate (40; 100) averted from the lens structure,
   wherein an elementary printing point (BP) has a lateral length between 4 µm and 8 µm.
2. The authenticity certificate according to claim 1, characterized in that the two security elements (42; 44) are connected by a transition zone (46; 48) which produces a visually verifiable link of the two security elements (42; 44).
3. The authenticity certificate according to claim 1 or 2, characterized in that in the case of the micro-refraction image the lenses are arranged flush with the lines of the line pattern (102).
4. The authenticity certificate according to claim 1 or 2 or 3, characterized in that adjacent lenses in the micro-refraction image are spaced apart from one another.
5. The authenticity certificate according to claim 4, characterized in that the distance between two adjacent lenses corresponds to the width of a few elementary printing points (BP).
6. The authenticity certificate according to any of the preceding claims, characterized in that the line pattern (102) of the micro-refraction image is applied in offset printing.
7. The authenticity certificate according to any of claims 1 to 6, characterized in that the lens structure of the micro-refraction image is applied from a transparent mass (104) in an intaglio printing method.
8. The authenticity certificate according to any of claims 1 to 6, characterized in that the lens structure of the micro-refraction image is applied from a transparent mass (104) by means of stamping with an intaglio engraving plate (106).
9. The authenticity certificate according to any of the preceding claims, characterized in that the lenses of the micro-refraction image have a semicircular to parabolic cross-sectional shape.
10. The authenticity certificate according to any of the preceding claims, characterized in that the lenses of the micro-refraction image have a prismatic cross-sectional form.
11. The authenticity certificate according to any of the preceding claims, characterized in that the lenses of the micro-refraction image have a mixed prismatic/parabolic cross-sectional shape.
12. The authenticity certificate according to any of the preceding claims, characterized in that the lines of the micro-refraction image have respective different colors in the periods of the line pattern (102).
13. The authenticity certificate according to any of the preceding claims, characterized in that the lines of the micro-refraction image have blank sections in the periods of the line pattern (102) for the representation of image contents.

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