BENDANT SAFETY ELEMENT

Description

[0001] The invention relates to a security element which comprises a diffraction element which reflectively diffracts light in the visible wavelength range in particular, so that the detected diffraction enables verification of a security document or similar object provided with the security element.

[0002] It is known from the prior art to provide objects, in particular documents and data storage media such as ID cards, driver's licenses, identification cards, but also valuable items such as admission tickets, packaging, or similar, with so-called security elements. These elements have at least one feature that can be used to identify the authenticity of the respective object and / or a forgery or falsification, unauthorized duplication, or similar. Such a feature is referred to as a security feature.

[0003] A group of security elements is designed for optical verification. Optical verification involves checking properties and / or stored information, either by a human observer or by capturing an image, or capturing and evaluating optical effects for their presence and / or design.

[0004] One group of security elements includes diffraction elements. A diffraction element has at least one diffraction structure capable of influencing light through the physical effect of diffraction. Widely used diffraction elements include holograms, but also kinegrams, other embossed surface structures, and similar.

[0005] Diffraction gratings are described, for example, in the "Diffraction grating handbook" by C. Palmer, 4th edition, published in 2000 on pages 8 to 19.

[0006] Diffraction structures in the form of volume reflection holograms are described in the chapter "Volume-Reflection Holography" in "OPTICAL DOCUMENT SECURITY" by RL van Renesse, Art House, Boston, Mass., (2005), pages 250-252.

[0007] Embossed surface holograms, for example, are very widespread. In these holograms, a diffraction structure embossed into the surface, provided it is provided with a metal layer, for example, or covered with a transparent layer with a high refractive index, reflects light at the structured interface. Embossed surface holograms belong to the group of so-called thin holograms. Such holograms are widely used, for example, to secure credit cards and bank cards. Another group of holograms includes volume holograms, in which the diffraction structure is stored in the volume of a material. Such holograms are referred to as thick holograms to distinguish them from surface holograms, which are thin holograms. A special type of volume reflection hologram, as used, for example, in ID cards, and its production are described in EP 0 896 260 A2.

[0008] Known security elements that reflectively diffract light are optimized for detection by a human observer. This means that a desired exposure direction of the light intended for diffraction and a desired detection direction under which the diffracted light can be detected enclose an angle at the point of incidence of the diffraction element that allows easy illumination and detection by a human. This means that the direction of incidence and the direction of diffraction differ significantly from each other, so that the angle enclosed by the desired exposure direction and the desired detection direction is preferably greater than 15 degrees to 20 degrees.Particularly suitable diffraction geometries, for example, provide for a diffraction element integrated into the surface of a security document to be illuminated along a surface normal of the diffraction element, and for detection to be performed at an angle of 45 degrees relative to the surface normal. Alternatively, detection can be performed parallel to the surface normal, and light can be irradiated at an angle of 45 degrees relative to the surface normal.

[0009] Documents US 2002 / 191234 A1 and WO 2006 / 021102 A1 each disclose a security element with a diffraction structure configured as a volume reflection hologram and with an additional diffraction structure. These documents do not disclose that the acute angle is less than 10 degrees.

[0010] In the field of security technology, there is a great need to create ever-new security elements that are difficult to imitate or replicate and at the same time can be reliably verified without tools or with the aid of widely available tools.

[0011] The invention is therefore based on the technical problem of creating a novel security element with a diffraction element that diffracts in reflection and whose diffraction structure is as hidden as possible.

[0012] According to the invention, the object is achieved by a security element having the features of claim 1, a security document having the features of claim 8 and a method having the features of claim 9.

[0013] The invention is based on the idea of ​​creating a diffraction element with a diffraction structure for which a diffraction geometry exists in which a desired exposure direction of the light intended for diffraction forms an acute angle with a desired detection direction under which the reflectively diffracted light can be detected at the point of incidence of the diffraction element. This is intended to enable verification, i.e., bringing about diffraction in the diffraction element, in which an incidence direction of the light to be diffracted is almost opposite to the direction of the diffracted light. Such a security element with a diffraction structure which has a diffraction geometry that reflectively diffracts the incident light only at an acute angle relative to the incidence direction is difficult or impossible to perceive when detected in ambient light.The reason for this is that ambient light cannot be irradiated from the detection direction, i.e. on the connecting line between the safety element and the eye.

[0014] However, a security element can be detected using an arrangement in which detection optics and a light source are arranged close to one another in a plane. Such an arrangement can be found, for example, in most multifunctional mobile phones, which have, for example, a camera on the back and a light source, often referred to as a flash, arranged directly next to the camera optics. The distance between the center of the imaging optics and the center of such a light source is, for example, 1 centimeter. At a preferred detection distance of approximately 20 centimeters from the security element, the included angle at an impact point is less than 3 degrees between the direction of incidence of the light and the direction of diffraction.Such a security element, in which diffraction takes place at an acute angle, can thus be easily verified with such a mobile phone, provided that an image is taken using the illumination device integrated in the mobile phone. Definitions

[0015] A diffraction element is a physical unit capable of diffracting light in the visible wavelength range. Diffraction elements can comprise one or more diffraction structures. A diffraction structure is a structure, such as a surface relief or a refractive index modulation in the volume of a material, that causes light to be diffracted. A diffraction element thus comprises at least one diffraction structure, but can also comprise multiple diffraction structures that cause different, distinct light diffractions.

[0016] For example, one or more diffraction structures can be exposed into a photopolymer layer. If, for example, several volume holograms are exposed into the photopolymer layer, this layer has several diffraction structures as described here. Depending on the choice of material for the photopolymer layer, two or more diffraction structures can be arranged in the same volume region and / or adjacent to one another or nested.

[0017] The geometric arrangement of the light radiation required to reconstruct a diffraction structure, for example the hologram, and the diffracted light, which represents the reconstruction of the hologram, relative to the hologram or its diffraction structure is referred to as reconstruction geometry.

[0018] As a generalization of the reconstruction geometry, the term diffraction geometry is used, which analogously describes the arrangement and position in space relative to the diffraction structure of incident light and diffracted light under which diffraction takes place.

[0019] A diffraction geometry or reconstruction geometry is thus defined by a desired exposure direction and a desired detection direction, under which diffracted light can be detected, relative to the diffraction structure. Since the diffraction structure is formed in the physical object of the diffraction element, the diffraction geometry and the reconstruction geometry can be defined in the same way using a desired exposure direction and a desired detection direction, under which diffracted light can be detected, relative to the diffraction element.

[0020] When verifying a diffraction element designed as a security element, the diffraction geometry is thus determined by the arrangement of a light source and, if applicable, its nature, an arrangement of a detection device and, if applicable, its nature, and the arrangement of the diffraction element, each relative to one another in space.

[0021] The exposure direction is the direction along which the light from a light source propagates when directed toward a diffraction element. The target exposure direction is the direction relative to a diffraction structure along which light must impinge on the diffraction structure in order for this incident light to be diffracted by the diffraction structure.

[0022] Typically, the desired exposure direction can be specified by a line connecting the center of a light source's light exit surface to the center of the diffraction structure causing diffraction. A desired detection direction is correspondingly defined by a line from the center of the diffraction structure to a position at which a diffraction image of the corresponding diffraction structure is detected or can be detected by the optics of the detection device.

[0023] Since the light from a light source typically exhibits divergence, and the diffraction structure of a diffraction element frequently also exhibits a planar extension, an exposure direction defined by the connecting line between the light source and the center of the diffraction structure is not identical to the directions of incidence of individual light rays in the sense of geometric optics at the respective points of incidence on the diffraction element with the diffraction structure where diffraction of the respective light beam occurs. When referring to a single beam in the sense of geometric optics, the term "direction of incidence" is used below.

[0024] A similar situation arises for diffracted light upon closer examination. The diffracted light can be diffracted in different directions by the diffraction structure of a diffraction element. These directions are referred to as diffraction directions.

[0025] The desired exposure direction and detection direction, as well as the direction of incidence and the direction of diffraction, are each defined relative to the corresponding diffraction structure or diffraction element. This means that if the orientation of the diffraction element changes in space, the direction of incidence at which diffraction occurs changes accordingly. Thus, the reference system for defining the direction of incidence and the direction of diffraction, as well as the desired exposure direction and detection direction, is usually coupled to the diffraction structure, and the directions are specified via angles to the diffraction element or its surface normal.

[0026] Acute-angle diffraction is defined as diffraction in which the desired exposure direction and the desired detection direction intersect in the diffraction element and enclose an acute angle of less than 10 degrees, preferably less than 5 degrees, more preferably less than 3 degrees.

[0027] In general, directions relative to a diffraction element or a diffraction structure embodied therein can be specified by means of an impact position on or in the diffraction structure, to which the direction points or from which the direction emanates, and two angles in a coordinate system linked to the diffraction structure, the origin of which coincides with the impact position. The coordinate system is usually chosen such that one angle (elevation angle) is measured against the surface normal of the diffraction element above the impact position, and the second angle (azimuthal angle) is measured in the plane of the diffraction element against a coordinate axis that defines the orientation of the diffraction structure. The impact position is also referred to as the impact location.

[0028] In the figures shown below, embodiments are shown for the sake of simplicity, without loss of generality, in which the azimuthal angles of the directions shown are the same (both directions, ie incidence direction and diffraction direction or desired exposure direction and desired detection direction, lie on the same side of the surface normal) or are different by 180 degrees (both directions lie on opposite sides of the surface normal of the diffraction element).

[0029] When we talk about the angle between two directions, we mean the angle in the plane in which the two directions and the common impact position lie. Preferred embodiments

[0030] In a particularly preferred embodiment, a security element is thus created, comprising a reflection-diffracting diffraction element, wherein the diffraction element comprises at least one diffraction structure having a diffraction geometry in which a desired exposure direction of the light intended for diffraction and a desired detection direction under which the reflectively diffracted light can be detected enclose an acute angle at the point of incidence.

[0031] This is, in particular when taking into account a possible divergence of the light used for illumination, an extension of the light radiation used, an extension of the diffraction structure and a consideration of acceptance properties of the detection device, equivalent to creating a security element comprising a reflection-diffracting diffraction element, wherein the diffraction element comprises at least one diffraction structure which has a diffraction geometry in which directions of incidence of the light intended for diffraction and the corresponding diffraction directions of the reflectively diffracted light each enclose an acute angle.

[0032] According to the invention, the acute angle is less than 10 degrees, or more preferably less than 5 degrees, and even more preferably less than 3 degrees. If the acute angle between the desired exposure direction and the desired detection direction, i.e., between the directions of incidence of the light and the directions of diffraction, is chosen to be as small as possible for the diffraction geometry, then detecting and locating this diffraction effect during a visual inspection of the security article associated with the security element is difficult.

[0033] A particularly high angular selectivity and also wavelength selectivity is achieved according to the invention by forming one diffraction structure of the diffraction element as a volume reflection hologram.

[0034] In order to conceal the presence of the diffraction effect of the one diffraction structure occurring at an acute angle in the diffraction element, an additional reflectively diffracting diffraction structure is provided, wherein the additional diffraction structure has an additional diffraction geometry in which an additional desired exposure direction of the light causing a diffraction and a desired detection direction under which the reflectively diffracted light can be detected enclose an angle at the point of incidence which is greater than a multiple of the one acute angle, preferably is significantly greater, i.e. enclose an angle which is greater than three times the one acute angle or greater than four times the one acute angle.

[0035] Preferred are diffraction geometries or reconstruction geometries that deviate from a geometry under which a specular reflection would occur at the diffraction element according to the laws of geometric optics.

[0036] Diffraction structures whose reconstruction geometry or diffraction geometry have a desired exposure direction and a desired detection direction, each of which has an angle greater than 10 degrees, preferably greater than 20 degrees, most preferably greater than 30 degrees, relative to the surface normal of the diffraction element, are more difficult to find by chance.

[0037] To enable reliable differentiation between a conventional retroreflector and the diffraction element, the diffraction element is designed as a hologram in a preferred embodiment. Due to the information stored in them, holograms can be easily distinguished from retroreflectors, which simply reflect the incident light in the direction from which the light originated.

[0038] A further possibility for increasing the usability of the diffraction element is for the diffraction element to comprise a further diffraction structure different from the one diffraction structure, for which a further diffraction geometry different from the one diffraction geometry exists, in which a further desired exposure direction of the incident light and a further desired detection direction under which the reflectively diffracted light can be detected enclose a further acute angle at the point of incidence. The acute angle and the further acute angle can have the same value, but can also have different values. The acute angle and the further acute angle are each smaller than a predetermined value, which is, for example, 3 degrees.

[0039] Particularly preferred are embodiments in which the diffraction structure and the further diffraction structure overlap in a planar manner, preferably completely overlap, ie one diffraction structure completely overlaps the further diffraction structure or vice versa.

[0040] Embodiments are also considered to be surface overlapping in which the two diffraction structures are each formed in several separate regions, which are, however, nested in one another, for example in narrow alternating strips, so that a common diffraction image of the regions of a corresponding diffraction structure is created during diffraction.

[0041] Particularly preferably, a diffraction pattern acquired under one diffraction geometry and another diffraction pattern acquired under the other diffraction geometry differ from each other. For example, with regard to the color or wavelength of the light under which the diffraction patterns are reconstructed.

[0042] In one embodiment, there are one or more light exposure directions located between one desired exposure direction and the other desired exposure direction, for which no acute-angle diffraction can be detected at the diffraction structure. This means that when light to be diffracted is irradiated along this exposure direction or directions, there is no detection direction at an acute angle to the corresponding exposure direction under which a diffraction image is to be detected.

[0043] If, for example, an image in which a diffraction image is recognizable is captured with a mobile phone using the illumination device and the camera built into the mobile phone under one diffraction geometry, and the mobile phone is transferred continuously or step by step to the second diffraction geometry, wherein images are captured continuously or step by step while light from the illumination device of the mobile phone is irradiated onto the diffraction element, the diffraction image disappears in the captured image or images and when the further desired exposure direction and the further desired detection direction of the further diffraction geometry are reached, the further diffraction image is captured in the images.

[0044] In a particularly preferred embodiment, this further diffraction image captured using the further diffraction geometry is different from the one diffraction image that is detectable and captured using the one diffraction geometry. For example, in one embodiment, the diffraction element can comprise a first diffraction structure designed as a volume hologram, which diffracts light of a first wavelength, for example in the green spectral range, at an acute angle, and the further diffraction structure can be designed to diffract light in the red wavelength range at an acute angle. If the light source of the mobile phone used is designed as a white light source, as is common today, a green diffraction image is captured using one diffraction geometry, and a red diffraction image is captured using the further diffraction geometry.In a continuous transition, the color either changes immediately or there are angular ranges in between where no diffraction image can be detected at all.

[0045] Further developments may provide for not just one additional diffraction structure, but a plurality of additional ones diffracting at an acute angle, to be formed in the diffraction element. Particularly preferably, the diffraction patterns detectable by the various additional diffraction structures under the various additional diffraction geometries differ from one another. This significantly complicates imitation or falsification by incorporating only reflective, non-diffracting elements, and significantly simplifies verification.

[0046] One embodiment therefore provides that the diffraction element comprises a plurality of further diffraction structures which are different from the one diffraction structure and from the remaining of the plurality of further diffraction structures, wherein for each of the plurality of further diffraction structures there exists a further diffraction geometry in which a further desired exposure direction of the incident light and a further desired detection direction under which the reflectively diffracted light can be detected enclose a further acute angle at the point of incidence, wherein the further diffraction geometry is in each case different from the one diffraction geometry and the remaining diffraction geometries of the remaining of the plurality of further diffraction structures.

[0047] In one embodiment, it is provided that an exposure angle of the desired exposure direction of one diffraction geometry and a further exposure angle of the further desired exposure direction, each measured against the surface normal at the respective point of incidence, differ by an angular amount that is greater than an amount of the acute angle of one diffraction geometry and greater than a further amount of the further acute angle of the further diffraction geometry.

[0048] For example, the additional diffraction structure is designed as a volume reflection hologram, which diffracts light of the same wavelength as the first diffraction structure, which is also designed as a volume reflection hologram.

[0049] Other embodiments may provide for the diffraction structures to be of different types. For example, the additional diffraction structure may be a volume reflection hologram, and the one diffraction structure that diffracts at an acute angle may be a surface relief hologram.

[0050] Particularly preferably, the additional diffraction structure and the one diffraction structure overlap. This allows the one diffraction structure with acute-angle diffraction to be particularly well "hidden" within the diffraction element.

[0051] It has proven particularly advantageous to design the additional diffraction structure as a conventional volume reflection hologram, which can be viewed, i.e., captured, during spatial illumination. A hologram of a three-dimensional object is particularly advantageous, as it creates an impression of the 3D object in the viewer.

[0052] With such an additional diffraction structure, the diffraction pattern changes depending on the detection direction, since these objects exhibit a greater or lesser parallax depending on the areal extent of the diffraction element. If the target exposure direction of the light to be diffracted is kept constant and correctly selected for diffraction to occur, slightly varying diffraction patterns will result under slightly varying detection directions. Unintentional diffraction or light-influencing effects of one diffraction structure caused by incident light are therefore not immediately noticeable to an observer. The one acute-angle diffraction structure thus remains hidden unless it is verified using a suitable device in which light irradiation and detection occur from almost opposite directions, and with light irradiation from the correct target exposure direction according to the one diffraction geometry.

[0053] It has proven particularly advantageous to design the additional diffraction structure as a volume reflection hologram of regularly arranged objects with a three-dimensional structure. For example, a grating, a volume hologram of a grid-like network, or a volume hologram of reflective or transparent polyhedra arranged in a two- or three-dimensional, preferably regular, grid can be used.

[0054] In a further embodiment, it is provided that the one diffraction geometry and the additional diffraction geometry are designed such that they have a common desired detection direction, i.e. that the one desired detection direction and the additional desired detection direction coincide. If an image is detected in the desired detection direction while light is irradiated in the additional desired exposure direction, the diffraction image of the additional diffraction structure is detected. If additional light to be diffracted is now irradiated in the desired exposure direction of the one diffraction geometry of the one diffraction structure, the diffraction image of the one diffraction structure is additionally detected. The diffraction images are preferably designed such that the one diffraction image of the one diffraction structure and the additional diffraction image of the additional diffraction structure complement each other to form an overall diffraction image.For example, the additional diffraction image can contain alphanumeric characters that are supplemented by alphanumeric characters of the one diffraction image such that words or numbers that can be perceived by an observer are produced in the overall diffraction image. Other embodiments can provide that the additional diffraction image contains the portrait of a person to whom the diffraction element is assigned, in a first wavelength or color, and that the one diffraction image of the one diffraction structure contains the portrait of the same person in a different wavelength or color, and that these complement each other such that a mixed-color portrait results due to the color addition of the two different diffracted wavelengths.

[0055] A variety of further designs are possible here to create mixed color effects or to supplement diffraction images with full color.

[0056] The individual diffraction structures described here, i.e., the one diffraction structure, one or more further diffraction structures, and / or the additional diffraction structure, can be formed in individual, separate material layers that are integrated in the diffraction element in an overlapping manner. For example, the individual diffraction structures can each be exposed as thin or thick holograms in a transparent hologram layer, for example, made of a photopolymer. These individual, separately formed layers can then be layered one above the other and connected to one another. Alternatively, several or all of the diffraction structures can also be exposed together in a photopolymer layer.Depending on the type of material and the diffraction effect, the individual diffraction structures may consist of small, cell-like, for example, square surface elements, which, when nested within each other, create the surface area of ​​the diffraction element. Even with such a design, it is assumed that the individual diffraction structures overlap. The surface elements are preferably chosen to be small enough that they are not noticeable in the diffraction pattern during verification.

[0057] Other embodiments may provide for the various diffraction structures to be formed at least partially adjacent to one another. Thus, several different surface embossed structures can be used.

[0058] Still other embodiments have both diffraction structures that completely or partially overlap, as well as diffraction structures formed side by side. Diffraction structures can also be formed spaced apart from one another in a diffraction element.

[0059] To verify such a security feature, an image is captured under a target detection direction of a diffraction geometry without irradiation of light under the corresponding one target exposure direction and compared with an image captured when illuminated with light along the target exposure direction of the one diffraction geometry. If a diffraction image is recognizable when light is irradiated at an acute angle to the target detection direction, the diffraction element is verified as genuine. To better distinguish the diffraction image from a background, an image captured with light irradiated at an acute angle to the detection direction is compared with an image captured without light irradiated at the acute angle.

[0060] In yet another embodiment, an image of the diffraction element is captured under a plurality of geometries, each under irradiation of light at an acute angle to the detection direction, and the diffraction element or security element is verified as genuine if an exposure and detection direction are found under which a diffraction image is captured.

[0061] In a further development, the security element or diffraction element is only verified as authentic if corresponding diffraction images are captured for at least two or at least three or more different geometries in the multiple captured images. A diffraction image is only considered different from another diffraction image if the difference is not merely a change in the viewing direction of a three-dimensional object holographically imaged in the diffraction structure.

[0062] If a number of diffraction elements are manufactured, the individual diffraction elements can be individually designed. This means that the individual design makes each diffraction element unique from the others. Individualization can be achieved, for example, by storing the personal data of a person to whom the security element with the diffraction structure is assigned in the diffraction structure. This individualization is also referred to as personalization.

[0063] A security document is created by integrating the security element with the diffraction structure into a document body. For example, the diffraction element can be formed as a semi-finished product and then combined with additional substrate or material layers in a lamination body. The security element can also be glued or otherwise attached to a security document as a patch, or it can be inserted into intermediate substrate or material layers. It is also possible to emboss the diffraction element, either completely or partially, into material layers of a document body.

[0064] The invention is explained in more detail below with reference to a drawing. Herein: Fig. 1 schematically shows a security document with a security element designed as a diffraction element; Fig. 2 a sectional view through a security element; Fig. 3 a further sectional view through a security element; Fig. 4 a sectional view through a security element which has an additional diffraction structure which is easily verifiable by a human observer; Fig. 5 a sectional view through a security element in which a diffraction structure and an additional diffraction structure are designed to overlap; Fig. 6 a sectional view through a security element in which a diffraction structure and an additional diffraction structure are designed adjacent to one another; Fig. 7 a sectional view through a security element in which a diffraction structure and a further diffraction structure are designed adjacent to one another;8 shows a further sectional view through a security element in which a diffraction structure for verification, for example with a mobile phone, and an additional diffraction structure for human verification are formed adjacent to one another; Figs. 9a-9e show schematic views schematically showing a diffraction geometry and a diffraction image detectable with the respective diffraction geometry; Figs. 10a to 16a show schematic plan views of diffraction elements with multiple diffraction structures; and Figs. 10b to 16b show schematic sectional views of the diffraction elements with multiple diffraction structures of the . Fig. 10a to 16a .

[0065] In Fig. 1A security document 1 is shown schematically. This can be, for example, an identity card, a driver's license, a bank card, or the like. To protect against forgery and falsification, the security document 1 comprises a security element 10. The security element 10 is designed as a diffraction element 20. The diffraction element 20 comprises a diffraction structure 101. Light 120 from a locally limited light source 130 is radiated along a desired exposure direction 105. An image comprising a diffraction image 160 is captured by a detection device 170 in a desired detection direction 115. The desired exposure direction 105 and the desired detection direction 115 enclose an acute angle 190.Since the light 120 from the light source 130 is slightly divergent and the diffraction element 20 has a planar extension, the light 120 strikes the diffraction element 20 at corresponding incidence locations 180a to 180c from slightly different directions of incidence 110a to 110c. The corresponding diffraction directions 150a to 150c each form an acute angle 190a to 190c with the direction of incidence 110a to 110c at the incidence location 180a to 180c. These angles 190a, 190a to 190c are all smaller than a predetermined angle. With a diffraction element configured in this way, the diffraction image 160 stored in the diffraction element 20 can be completely captured in one image. In the example shown, the desired exposure direction 105 and the direction of incidence marked 110b as well as the desired detection direction 115 and the diffraction direction 150b as well as the impact locations 180, 180b coincide.

[0066] The light source 130 is, for example, an illumination device 210 of a mobile phone 200. The detection device 170 is, for example, a camera 220 of the mobile phone 200 arranged at a close distance from the illumination device 210. The illumination device 210 and the camera 220 are typically located on a rear side 230 of the mobile phone 200. The diffraction image 160 can typically be displayed on a display 240 on a front side 250 of the mobile phone 200. Preferably, the acute angle 190 between the desired exposure direction 105 of the light and the desired detection direction 115, under which the diffraction image 160 is observable, is significantly smaller than 10 degrees, preferably smaller than 5 degrees, and most preferably smaller than 3 degrees.Such a diffraction element 20 can be "detected", for example, with a mobile phone in which the illumination device 210 and the camera 220 are spaced approximately 1 centimeter apart, from a distance in the range between 50 centimeters and 20 centimeters from the point of incidence 180 of the incident light.

[0067] In a simple embodiment, the diffraction element 20 of the security element 10 comprises precisely one diffraction geometry under which light is diffracted and a diffraction image can be captured. Locating the diffraction image 160 can then be used to verify the security element 10. Further improved verification is achieved by additionally determining an exposure angle 111 of the target exposure direction 105 or a detection angle 112 of the target detection direction 115 measured against a surface normal 30 and comparing it with the respective predetermined value. Thus, in addition to locating the diffraction image, it is possible to check whether the geometry used to generate the diffraction image matches the one predefined diffraction geometry 100.Furthermore, verification can be further improved by evaluating specific information stored in the diffraction element and comparing it, for example, with a specification. In the example shown, the letter "B" can be seen in the diffraction image 160.

[0068] The diffraction structure 101, for which the diffraction pattern "B" is acquired during verification under the diffraction geometry 100, is designed as a volume reflection hologram. Volume reflection holograms are characterized by their high angular selectivity with respect to the direction of incidence of the light used for reconstruction and, in addition, their high wavelength selectivity with respect to the diffracted light. For example, when designed as a reflection volume hologram, the diffraction pattern 160 shows the letter "B" in green, which means that light of a green wavelength is diffracted by the diffraction structure of the diffraction element 20, which is designed as a volume reflection hologram.

[0069] Since the diffraction structure 101 of the diffraction element 20, which is assigned to one diffraction geometry 100, generally also influences light incident on the diffraction element from other directions that are not directions of incidence of the diffraction geometry 100, it is advantageous to integrate an additional diffraction structure 401 into the diffraction element 20 in order to "hide" this one diffraction structure. If the diffraction structures 101 and the additional diffraction structure 401 are each formed as volume reflection holograms, these can, for example, be stored in superimposed transparent photopolymer layers, which are each individually exposed one after the other. The additional diffraction structure 401 has an associated diffraction geometry 400, which is characterized by an additional target exposure direction 410 and an additional target detection direction 415.An additional diffraction image 460, which can be captured when the additional diffraction geometry 400 is implemented, shows, for example, the letters A, C, and D with a gap between the letters A and C in the illustrated embodiment. In one embodiment, the additional diffraction structure 401 is designed as a volume reflection hologram with the same wavelength, so that the letters in the additional diffraction image 460 have a green color. Alternatively, however, the information indicated by the letters A, C, and D can also be stored in a different wavelength or with multiple wavelengths in the volume transmission hologram of the additional diffraction structure, so that the letters have a red color, for example, or even have different colors.

[0070] In the illustrated embodiment, the information of the additional diffraction structure 401, which is recognizable in the additional diffraction image 460, and the information of the diffraction image 160 complement each other. The additional diffraction image 460 is captured, for example, by a camera when illuminated with white light perpendicular to the security document at a detection angle of 45 degrees relative to the surface normal 30 of the security document 1, or captured by a human observer. The information of the diffraction image 160, the capital letter "B," captured by the mobile phone 200 under the one diffraction geometry 100, thus supplements the information of the additional diffraction image 460 to form the overall information "ABCD."

[0071] In Fig. 2A schematic sectional view through a security element 10 is shown. The security element comprises, for example, a photopolymer layer 1010 into which a volume reflection hologram 1020 is exposed as a diffraction structure. Light from an illumination device 210 designed as an LED falls at different incidence locations 180, 180a, 180b, 180c along the direction of incidence 110a, 110b, 110c onto the diffraction structure 101 designed as a volume reflection hologram. Diffracted light is reflected from the incidence locations 180, 180a-180c to a camera 220. These directions of the light diffracted back to the camera represent the diffraction directions 150, 150a-150c.Although the directions of incidence 110, 110a-110c are different from the surface normals 30, 30a, 30b, 30c at the corresponding impact locations 180, 180a-180c, the directions of incidence 110, 110a-110c and the corresponding diffraction directions 150, 150a-150c at the respective impact locations 180, 180a-180c each enclose an acute angle 190, 190a-190c. The magnitude of these angles 190, 190a-190c is limited in magnitude, for example, to a value in the range between 0 degrees and 5 degrees, preferably in the range between 0 degrees and 2 degrees or 0 degrees and 3 degrees.

[0072] The LED light source 130 and the camera 220 are in Fig. 2arranged in a plane 260. The exposure direction, which coincides with the desired exposure direction 105, points from the center 135 of the localized light source 130 used to a center 25 of the diffraction element 20. A detection direction, which coincides with the desired detection direction 115, points from this center 25 of the diffraction element 20 to the camera 220. Thus, for an exposure direction 105, there are a plurality of slightly different directions of incidence 110a-110c and, correspondingly, for a detection direction 115, a plurality of slightly different diffraction directions 150a-150c. However, at the point of incidence 180, 180a-180c, an acute angle 190 is enclosed between the respective directions of incidence, and thus also between the desired exposure direction 105 and the desired detection direction 115, which is smaller than a predetermined amount.

[0073] In Fig. 3A non-claimed security element is schematically shown, which comprises a material layer 1100 and a thin-film film applied thereto, for example as a patch, into which a surface relief structure, for example in the form of a Littrow grating 1210, is embossed. Such a structure also diffracts incident light at an acute angle at the point of incidence, if appropriately designed.

[0074] In Fig. 4A schematic sectional view of a security element 10 is shown schematically, in which an additional diffraction structure 401 is formed in the diffraction element 20. The additional diffraction structure 401 is designed to show diffraction under an additional diffraction geometry 400. Light 420 is irradiated by an illumination source 430, which can be a lamp or the sun, here, for example, under an additional target exposure direction 405 perpendicular to the diffraction element 20. This light is detected by an observer, for example a human, with their eyes under an additional target detection direction 415, which is inclined, for example, at 45 degrees relative to the surface normal 30 of the diffraction element 20.The individual directions of incidence 410a to 410c and the corresponding diffraction directions 450a to 450c each enclose a diffraction angle 495a to 495c, all of which are significantly larger than an acute angle at which a diffraction structure can be verified, for example, with a mobile phone camera with the flash activated. In the example shown, the included angles 195a to 195c are all on the order of 45 degrees + / - 5 degrees.

[0075] In Fig. 5 The simultaneous verification of one diffraction structure 101 and the additional diffraction structure 401 is then shown. In this embodiment, the one diffraction structure 101, as in Fig. 2 shown schematically, and the additional diffraction structure 401, as shown schematically in Fig. 4As shown, they are formed in a planar superimposed manner in the diffraction element. Identical technical features are provided with the same reference numerals in all figures. The security element 10 and the diffraction element 20 thus have one diffraction structure and the additional diffraction structure 401, which are both formed in the same material, for example, as volume reflection holograms.

[0076] In Fig. 6 A similar embodiment of a security element 10 with a diffraction element 20 is shown, in which the one diffraction structure 101 is formed adjacent to and not overlapping with the additional diffraction structure 401. It can be seen that light 420 from the lamp or sun passes unhindered through the one diffraction structure 101, since the direction of incidence of this light 420 does not match the diffraction geometry 100 and is therefore unable to be diffracted by the one diffraction structure 101.

[0077] Analogously, the light 120 of the light source 130, for example a mobile phone flash, strikes the additional diffraction structure 401 at an angle at which the latter does not diffract the light, so that this light 120 can pass through the additional diffraction structure 401 unhindered.

[0078] In Fig. 7An embodiment is shown in which one diffraction structure 101 and a further diffraction structure 301 are formed adjacent to one another. The further diffraction structure 301 diffracts incident light 320 according to the further diffraction geometry 300 at an acute angle 390, which, like the acute angle 190, is smaller than a predetermined angle. This predetermined angle is preferably 10 degrees, more preferably 5 degrees, even more preferably 3 degrees. This security element 10 with the diffraction structure 20 can be verified, for example, by pivoting a mobile phone 200 relative to the security element 10 on a circular arc 85, the center 86 of which lies, for example, in the plane of the security element 10. Under two detection directions, which in Fig. 7Diffraction images are captured as shown. One diffraction image 160 is captured in one target detection direction 115, and the other diffraction image 360 ​​is captured in the other target detection direction 315. No diffraction is observed in this embodiment in other detection directions.

[0079] It is understood that embodiments are possible in which a plurality of further diffraction structures are designed for acute-angle diffraction, which can be detected under different desired detection directions, for example by means of a camera and a lighting device of a mobile phone.

[0080] Fig. 8 shows an embodiment similar to that according to Fig. 6, in which, however, the one diffraction structure 101 is designed such that the desired exposure direction 105 of the diffraction geometry 100 has a large exposure angle 111 relative to the surface normal 30 of the diffraction element 20, under which the one diffraction structure diffracts. Preferably, the exposure angle 111 of the diffraction geometry 100 is in each case greater than 50 degrees, in other preferred embodiments greater than 70 degrees or even 75 degrees. Under such a grazing incidence, diffractive security features that are designed to be reflective are not expected by an observer. This is all the more true since the additional diffraction geometry 400 exists, under which the additional diffraction structure 401 is also verifiable by a human observer 5.

[0081] In Fig. 9a is a schematic sectional view through a security document with a security element designed as a diffraction element. In Fig. 9b to 9eDifferent geometries for illumination and detection as well as any associated diffraction images are shown schematically.

[0082] Reference symbols not explicitly mentioned indicate the same features as in the other figures of this description.

[0083] In Fig. 9aA security document 1 is shown schematically. The security document 1 is produced as a lamination body from a plurality of layers laminated to one another, in particular plastic layers, for example made of polycarbonate, polyethylene, terephthalate or other common plastics. The individual layers are not shown here for the sake of simplicity. The security element 10 comprises three exposed photopolymer layers 103, 303, 403 laminated to one another. One photopolymer layer 103 comprises one diffraction structure 101, the further photopolymer layer 303 comprises a further diffraction structure 301, and the third additional photopolymer layer 403 comprises an additional diffraction structure 401. The diffraction structures 101, 301, 401 are exposed, for example, as volume reflection holograms 102, 302, 402 into the photopolymer layers 103, 303, 403.In one embodiment, the information in the volume reflection holograms is all exposed at the same wavelength. In other embodiments, the different diffraction structures 101, 301, 401 can be volume reflection holograms fabricated at different wavelengths.

[0084] In Fig. 9b A diffraction geometry 100 is shown schematically, similar to that in Fig. 1 shown diffraction geometry 100. As diffraction image 160, for example, a monochromatic three-dimensional portrait of a person is shown, to whom the security document 1 according to Fig. 9ais assigned. The diffraction image 160 with the monochromatic three-dimensional portrait can be captured, for example, with a mobile phone using the integrated illumination device. The target exposure direction 105 of the light has an angle of incidence 111 of, for example, 75 degrees relative to the surface normal 30 of the diffraction element 20. The angle 190 enclosed between the target exposure direction 105 and the target detection direction 115 is, for example, less than 3 degrees for all impact locations 180.

[0085] In Fig. 9cA geometry for illumination and detection is shown in which the exposure direction hits the diffraction element at an angle of 65 degrees. Under this exposure direction, no diffraction of the light occurs either at the diffraction structure 101, the further diffraction structure 301, or at the additional diffraction structure 401, which are included in the volume transmission hologram 102, the further volume transmission hologram 302, or the additional volume transmission hologram 402, respectively. Fig. 9a are formed. Consequently, no diffraction pattern can be recorded.

[0086] If the mobile phone, with which the diffraction structures bending at an acute angle can be verified, is tilted further, the Fig. 9dillustrated situation with the further diffraction geometry 300, in which, for example, the detection direction is aligned at 45 degrees relative to the surface normal 30 of the diffraction element 20 and coincides with the desired detection direction 315 of the further diffraction geometry. Under a slightly deviating desired exposure direction 305, which deviates by, for example, less than 3 degrees from the desired detection direction 315, light from the illumination device 210 falls onto the diffraction element 20. If the security document 1 is verified with the mobile phone in this diffraction geometry 300, then, for example, a name, a date of birth and other personal data of the person to whom the security document 1 is assigned are visible under this further diffraction geometry 300.

[0087] In Fig. 9eAn additional diffraction geometry 400 is shown, in which light is irradiated onto the security document parallel to the surface normal 30, and the security document is detected at 45 degrees relative to the surface normal 30. The desired detection directions 415, 315 of the additional diffraction geometry 400 and the further diffraction geometry 300 coincide in this embodiment. If only light is irradiated onto the security document 1 parallel to the surface normal, the diffraction pattern 460 can be seen, which shows a three-dimensional representation of double-pyramidal glass objects arranged in a grid. With a slight change in the detection direction, the diffraction pattern 460 changes slightly.This ensures that, with this illumination parallel to the surface normal, diffraction effects of the one diffraction structure 101 and the further diffraction structure 301 are virtually imperceptible to an observer. While the additional diffraction structure 401 is suitable for verification with the human eye, the diffraction structure 101 and the further diffraction structure 301 are intended for verification, for example, via a mobile phone. However, if an image is captured while the security document is illuminated parallel to the surface normal, measured at a capture direction of 45 degrees relative to the surface normal 30 of the security document 1, an image 60 is captured which shows the diffraction image 460, i.e. the double-pyramid-shaped objects arranged in a grid.If the mobile phone's illumination device is also switched on during image capture, the additional diffraction geometry 300 is also fulfilled, so that the additional diffraction image 360 ​​is also captured by the camera in a superimposed manner. In the illustrated embodiment, the personal information is arranged in rows that coincide with connecting lines 461 of the octahedral objects 462 depicted in the additional diffraction image. Thus, the information of the additional diffraction image 460 and the additional diffraction image 360 ​​complement each other to form a single piece of information. If, for example, the additional diffraction structure 301 is forged, the row in which the information is reproduced deviates from the position of the connecting line 461.

[0088] In other embodiments, other information similar to the embodiment of Fig. 1, be contained in the various diffraction patterns, which are then supplemented, for example, in the form of alphanumeric characters to form words or numbers.

[0089] For verification, it is therefore intended to capture an image of a security document or the security element contained therein under a diffraction geometry determined by the desired exposure direction and the desired detection direction, while simultaneously using the illumination device arranged adjacent to the detection device, so that an acute-angled diffractive reflection can be used as a captured diffraction image for verification, provided it is found. To locate this, the diffraction geometry can be changed by changing the exposure direction and, if necessary, the detection direction relative to the security document. For example, the detection direction can be changed while maintaining the exposure direction by rotating a mobile phone around the exposure direction as the axis of rotation.While the mobile phone is, for example, positioned step by step or continuously relative to the security document in different diffraction geometries, images are captured continuously or at time intervals and evaluated for the presence of a diffraction image or various diffraction images. In the embodiment according to . Fig. 9a to 9e For example, first the portrait of the person is captured, then no diffraction image and then again the personal information, while the mobile phone moves from one geometry via the geometry shown in Fig. 5c to the further diffraction geometry according to Fig. 9d is moved.

[0090] A corresponding computer program product is designed to control this capture sequence. If a diffraction image, a non-diffraction image, and a deviating diffraction image are captured consecutively while the mobile phone is being swung, the document is verified as authentic.

[0091] An alternative verification method involves the mobile phone continuously capturing images while illuminating the security document with white light parallel to the surface normal until the camera captures a diffraction image, for example, featuring identification marks, which an automatic figure recognition program recognizes similarly to a QR code. The mobile phone either visually indicates on its display that it has correctly captured the additional diffraction image and / or emits an audible signal. Subsequently, the mobile phone's illumination device is also activated, and another image is captured. A recognition process is then performed to check whether, in addition to the additional diffraction image, the additional diffraction image of the additional diffraction structure is also recognizable.In a further development, the information of the additional diffraction image and the further superimposed diffraction image are checked when the illumination device is switched on to determine whether they complement each other correctly.

[0092] The Figures 10a to 16a represent top views of diffraction elements with two or more diffraction structures. The Figures 10b to 16bshow the corresponding cross-sections through the diffraction elements. Hatching (\) running from top left to bottom right represents "conventional" additional diffraction structures 401, which have a diffraction geometry in which the desired exposure direction and the desired detection direction enclose an angle whose magnitude is greater than a multiple of a predefined value for an acute angle. Other hatchings each represent a diffraction structure 101 or further diffraction structure 301, which diffract light under a diffraction geometry whose desired exposure direction and the desired detection direction enclose an acute angle whose magnitude is smaller than the predefined value for the acute angle. Non-hatched areas do not diffract any light.

[0093] It will be apparent to the person skilled in the art that embodiments are possible in which a plurality of further diffraction structures diffracting at an acute angle are contained in the diffraction element. List of reference symbols

[0094] 1Security document 5Human observer 10Security element 20Diffraction element 25Center 30Surface normal 35Center 60Figure 85Circular arc 86Center point 100Diffraction geometry 101Diffraction structure 105Target exposure direction 110a to 110cIncident direction 111Exposure angle 112Detection angle 115Target detection direction 120Light 130Light source 135Center 150a to 150cDiffraction direction 160Diffraction image 170Detection direction 180, 180a to 180cImpact location 190, 190a -190cAcute angle 195a to 195cIncluded angle 200Mobile phone 210, 210'Illumination device 220, 220'Camera 230Back 240Display 250Front 260Plane 300Diffraction geometry 301Further diffraction structure 305Further exposure direction 310a, 310bFurther incidence direction 311Further angle of incidence 315Further detection direction 320Light 380, 380a, 380bFurther impact location 390, 390a,390b further acute angle 400 additional diffraction geometry 401 additional diffraction structure 405 additional target exposure direction 410a to 410c additional incidence direction 415 additional target detection direction 420 light 430 illumination source 450a to 450c additional diffraction direction 460 additional diffraction pattern 461 connecting lines 462 double pyramid-shaped objects 480, 480a to 480c additional impact location 495, 495a to 495c diffraction angle 1010 photopolymer layer 1020 volume reflection hologram 1100 material layer 1200 thin-film film 1210 Littrow grating,

Claims

1. Security element (20) comprising a diffraction element (20) diffracting in reflection (20), wherein the diffraction element (20) comprises a diffraction structure (101) for which a diffraction geometry (100) defined by a nominal exposure direction (105) and a nominal detection direction (105) relative to the diffraction structure (101), in which a nominal exposure direction (105) of the light (120) intended for diffraction encloses an acute angle (190) with a nominal detection direction (115), under which the reflectively diffracted light can be detected, at a point of incidence (180) on or in the diffraction element (20), the nominal exposure direction (105) designating the direction relative to the diffraction structure (101) along which the light (120) intended for diffraction can be detected (101) along which light must impinge on the diffraction structure (101) so that this impinging light is diffracted by the diffraction structure as the reflectively diffracted light, the directions of the nominal exposure direction (105) and nominal detection direction (115) with respect to the diffraction element (20) and the diffraction structure (101) embodied therein being determined by means of the impingement location on or in the diffraction structure, to which the nominal exposure direction (105) points and from which the nominal detection direction (115) emanates, and in each case two angles can be indicated in a coordinate system linked to the diffraction structure (101), the origin of which coincides with the point of incidence (180), wherein the one acute angle (190) is less than 10 degrees or preferably less than 5 degrees or even more preferably less than 3 degrees, wherein the diffraction pattern is formed as a volume reflection hologram, wherein the diffraction element (20) has a reflectively diffracting additional diffraction structure (401), the additional diffraction structure (401) having an additional diffraction geometry (400), in which an additional nominal exposure direction (405) of the light (420) causing diffraction and an additional nominal detection direction (415), under which the additionally reflectively diffracted light can be detected, enclose an angle (495) at the point of incidence (480) which is greater than the one acute angle (190).

2. Security element (10) according to claim 1, characterized in that the diffraction geometry (100) deviates from a geometry for a specular reflection at a surface of the diffraction element.

3. Security element (10) according to one of the preceding claims, characterized in that in that the diffraction element (20) comprises a further diffraction structure (301) which differs from the one diffraction structure (101) and for which a further diffraction geometry (300) exists which differs from the one diffraction geometry (100) and in which a further nominal exposure direction (310) of the incident light (320) and a further nominal detection direction (315), under which the reflectively diffracted light can be detected, include a further acute angle (390) at the further point of incidence (380).

4. Security element according to one of claims 1 to 2, characterized in that the diffraction element (20) comprises a plurality of further diffraction structures (301) which are different from the one diffraction structure (101) and from the rest of the plurality of further diffraction structures (301), wherein for each of the plurality of further diffraction structures (301) there exists a further diffraction geometry (300) in which a further nominal exposure direction (305) of the incident light (320) and a further nominal detection direction (315), under which the reflectively diffracted light can be detected, include a further acute angle (395) at the point of incidence (380), the further diffraction geometry (300) is in each case different from the one diffraction geometry (100) and the other diffraction geometries (300) of the remainder of the plurality of further diffraction structures (301).

5. Security element (10) according to one of claims 3 or 4, characterized in that an exposure angle (111) of the nominal exposure direction (110) of the one diffraction geometry (100) measured against the surface normal (30) at the respective point of incidence (180) and a further exposure angle (311) of the further nominal exposure direction (310) at the respective point of incidence (380) differ by an angular amount which is greater than an amount of the acute angle (190) of the one diffraction geometry (300) and is greater than a further amount of the further acute angle (390) of the further diffraction geometry (300).

6. Safety element (10) according to one of the preceding claims, characterized in that the additional diffraction structure (401) and / or the further diffraction structure (301) overlap over a large area with the one diffraction structure (101).

7. Security element (10) according to one of the preceding claims, characterized in that the one nominal detection direction (115), under which the light incident under the one nominal exposure direction (105) and diffracted at the one diffraction structure (101) can be detected, and the additional nominal detection direction (415), under which the light incident under the additional nominal exposure direction (405) and diffracted at the additional diffraction structure (401) can be detected, coincide.

8. Security document (1) with a security element (10) according to one of claims 1 to 7.

9. Method for producing a security element (1) having a diffraction element (20), wherein a diffraction structure (101) of the diffraction element (20) is exposed in a material layer, for which diffraction structure (101) a diffraction geometry (100) exists which is defined by a nominal exposure direction (105) and a nominal detection direction (105) relative to the diffraction structure (101), in which the nominal exposure direction (105) of the light intended for diffraction encloses an acute angle (190) with the nominal detection direction (115), under which the reflectively diffracted light can be detected, at a point of incidence (180) on or in the diffraction element (20), the nominal exposure direction (105) designating the direction relative to the diffraction structure (101), along which light must impinge on the diffraction structure (101) so that this impinging light is diffracted by the diffraction structure as the diffracted light, wherein the directions of the nominal exposure direction (105) and nominal detection direction (115) with respect to the diffraction element (20) and the diffraction structure (101) embodied therein by means of the impingement location on or in the diffraction structure to which the nominal exposure direction (105) points and from which the nominal detection direction (115) and in each case two angles in a coordinate system linked to the diffraction structure (101) linked to the diffraction structure (101), the origin of which coincides with the point of incidence (180), wherein the one acute angle (190) is less than 10 degrees or preferably less than 5 degrees or even more preferably less than 3 degrees, wherein the diffraction pattern is formed as a volume reflection hologram, wherein an additional reflectively diffracting diffraction structure (401) is exposed in the one material layer or the one further material layer or one of the plurality of further material layers or an additional material layer, wherein the additional diffraction structure (401) has an additional diffraction geometry (400) in which an additional nominal exposure direction (405) of the light causing diffraction and a nominal detection direction (415) under which the reflectively diffracted light can be detected, at the additional incident location (480) include an angle (495) which is greater than the one acute angle (190), and if the additional diffraction structure (401) is exposed into the additional material layer, the additional material layer is joined to the one material layer.

10. Method according to claim 9, characterized in that in the material layer or a further material layer, a further diffraction structure (301) different from the one diffraction structure (101) is exposed, for which a further diffraction geometry (300) different from the one diffraction geometry (100) exists, in which a further nominal exposure direction (305) of the incident light and a further nominal detection direction (315), under which the reflectively diffracted light can be detected, include a further acute angle (390) at the point of incidence (380), and insofar as the further diffraction structure (301) is embossed or exposed in the further material layer, the one material layer and the further diffraction structure (301) include a further acute angle (390) at the point of incidence (380) and insofar as the further diffraction structure (301) is embossed or exposed in the further material layer, the one material layer and the further material layer are joined together to form a lamination composite.

11. Method according to claim 9 or 10, characterized in that a plurality of further diffraction structures (301) are embossed and / or exposed in the material layer or a further material layer or a plurality of further material layers, which are separated from the one diffraction structure (101) and from the rest of the plurality of further diffraction structures (301) other of the plurality of further diffraction structures (301) wherein a further diffraction geometry (300) exists for each of the plurality of further diffraction structures (301), in which a further nominal exposure direction (305) of the incident light and a further nominal detection direction (315), under which the reflectively diffracted light can be detected, include a further acute angle (390) at the further point of incidence (380), the further diffraction geometry (300) being in each case different from the one diffraction geometry (100) and the remaining diffraction geometries (300) of the remainder of the plurality of further diffraction structures (301), and if one of the plurality of further diffraction structures (301) is exposed or embossed in the one further material layer or one of the plurality of further material layers, the one material layer and the further material layer or the one material layer and the plurality of further material layers are joined together to form a lamination composite.