EP4209355B1 - Security document with micro-grid structure - Google Patents

Description

The invention relates to a security document and a method for producing a security document which has a transparent volume region extending from an upper side into the interior of a document body, in which laser-induced microstructures are formed.

It is known from the prior art to provide security documents, such as identity cards, passports, driving licenses, identity cards, visas, banknotes, credit cards, bank cards and the like, with features that make it difficult or impossible to imitate and/or falsify the corresponding object and that are intended to make it easier and possible to find a forgery, imitation or falsification. Such features are generally referred to as security features. Physical configurations that form or include a security feature are also referred to as security elements.

A wide variety of security features are known in the state of the art. One group of security features uses optical effects that arise from interaction with light. This includes all features that can be checked by image capture, e.g. using an optical capture device and/or by human inspection. A subgroup of these security features uses diffraction effects of light. For example, it is known to provide security documents with holograms. A hologram stores an interference structure of light. The information stored in the interference structure can be reconstructed by irradiating it with suitable light. Holograms have the disadvantage that they are complex to produce. Furthermore, it is usually necessary to integrate the holograms when the security document is produced.

In order to subsequently provide security documents with a security feature that is as forgery-proof as possible, techniques have been developed in which material changes are brought about inside a document body using laser radiation. For example, it is now common practice to engrave certain information, preferably individualizing or personalizing information such as For example, to store a name, a date of birth, a passport photo or similar information via material redactions in a security document body.

The EN 10 2007 023 560 A1 describes a multilayer body with a carrier substrate and with a transparent layer that is at least partially arranged in a window or in a transparent region of the carrier substrate. The transparent layer has at least a first and a second partial region with varying refractive index, which are arranged next to one another in the layer plane spanned by the transparent layer and are at least partially arranged in the window or in the transparent region of the carrier substrate. Each of the partial regions has a multiplicity of periodically arranged nodes that form an optically active element and are formed by varying the refractive index, which are arranged in planes that run essentially parallel to one another. The planes in the at least first partial region are not parallel to the planes in the at least second partial region. In at least one of the partial regions, the planes run neither parallel nor perpendicular to the layer plane. In this way, both the light falling on the front and the back of the multilayer body is diffracted by the optically active elements and the elements form a different optical effect in front and rear views in incident light.

The US 5 856 048 A describes an information medium with easily selectable and identifiable information, which is practically forgery-proof and has increased security against misuse, and a method for reading such a medium. This information medium comprises a substrate and a layer with information recorded thereon by printing infrared-absorbing ink, the layer being provided on the surface of the layer. A layer provided with a relief hologram is attached to the printed layer via an adhesive layer, the hologram-provided layer consisting of a reflective layer transparent to the infrared range and a layer provided as a relief hologram on the surface of the reflective layer. For reading, the layer recorded as a hologram is reconstructed by visible light, while the printed layer is reconstructed by infrared light, and the medium is identified on the basis of the information thus reconstructed.

The invention is based on the technical object of creating a security document with a novel security feature, which can preferably be integrated into an otherwise finished security document body and offers a high level of protection against imitation and/or falsification. In addition, the object of the invention is to create a method with which such a security document can be produced.

The invention is solved by a security document with the features of patent claim 1 and a method with the features of patent claim 6. Advantageous embodiments of the invention emerge from the subclaims.

Basic idea of the invention

The invention is based on the idea of creating a document body of a security document that has a transparent volume region that extends from a top side into the interior of the document body. By means of highly focused laser radiation, microstructures are introduced into the interior of the document body, preferably into the interior of the transparent volume region, which are local material changes in the interior of the document body, for example in the interior of the transparent volume region. These are designed as a whole in such a way that together they form a micro-lattice structure that diffracts incident light so that an optical effect can be perceived in the diffracted light. In order to be able to form such microstructures, very strong laser focusing is used, which causes a well-localized material change in the transparent volume region. Optics are used for this purpose that have a numerical aperture of greater than 0.3, preferably even greater than 0.4, in air.

The advantage of the invention is that it creates a security feature that is relatively easy to verify, i.e. to check for its presence and its characteristics. The check is carried out by shining light onto the security document. and the resulting diffraction effect is evaluated. On the other hand, such a diffraction structure is not easy to reproduce.

Definitions

A material is considered transparent if it allows images to be created using geometric optics. The material can be colored if necessary, but then an image using geometric optics is only possible in a limited wavelength range. If a material is transparent and colorless, an image can be created using geometric optics in the entire visible wavelength range through the material. For light in the wavelength range from 200 nm to 800 nm, for which the material is transparent, this material has a transmittance of preferably at least 75 percent, in particular more than 80 percent. The transparent material can be single-layered or multi-layered.

A layer that prevents light from passing through is considered opaque. Layers whose transmittance is preferably less than 25%, more preferably less than 10%, are considered opaque. Specularly reflective layers, including partially mirrored layers, are considered opaque layers if they prevent light from passing through.

Diffraction and interference are optical effects that exploit the wave nature of light and produce observable optical effects on structures in the material in which light propagation deviates from the laws of geometric optics.

A material is considered reflective if it reflects light of a certain wavelength that hits it. A material is considered transmissive if it allows incident light to pass through it. A material is considered absorbent if it neither reflects nor allows incident light to pass through it. A large number of materials exhibit all three of the effects described for one and the same wavelength, although one effect is usually dominant. A material is therefore considered reflective if it reflects light of a particular wavelength. predominantly reflects the light and only a smaller proportion is absorbed or allowed to pass through.

A special type of reflection is specular reflection, in which light is reflected back with almost no attenuation and an angle between a surface normal at the point of impact and the incident light beam is equal to an angle from the surface normal to the emerging light beam. Metallic surfaces, such as silver, gold or aluminum, exhibit specular reflection. For certain wavelengths, thin-film systems made of layers with different refractive indices can also form reflective layers, although these are usually limited in terms of both the wavelength and the angular range of the incident light that is specularly reflected.

A substrate layer is defined here as a layer that is a self-supporting layer. A substrate layer can be, for example, a paper or textile layer, a plastic film or similar. A printed layer or a vapor-deposited metal layer do not represent substrate layers, as they are not structurally independent for handling.

A lamination body is a body made up of several substrate layers. The material in a lamination body that comes from one of the substrate layers that are joined together to form the lamination body is referred to here as a material layer. If substrate layers of the same chemical composition are joined together, for example in a thermal lamination process using pressure, the material layers in the document body often cannot be distinguished from one another due to their chemical and/or physical structure, but can only be identified in the finished document body, for example by fillers or by means of coatings that were formed on their surfaces before joining.

Diffracting micrograting structures in the sense described here are not holograms. The microstructures are usually larger than the wavelength of the light that is to be diffracted.

The invention is defined in claims 1 and 6.

Preferred embodiments

In principle, security documents are conceivable in which the micro-lattice structure diffracts light in the non-visible wavelength range, i.e. in the UV wavelength range, i.e. at wavelengths of less than 380 nm to about 100 nm, or in the infrared wavelength range at wavelengths between 780 nm and 1 mm. However, embodiments in which the at least one micro-lattice structure diffracts light in the visible wavelength range, i.e. in the wavelength range between 780 nm and 380 nm, are particularly preferred.

Since diffraction is a phenomenon that depends on the wave character of light, microstructure gratings generally exhibit diffraction effects that cause a color splitting of white light. This means that light of different wavelengths is diffracted differently. Therefore, the at least one transparent volume region is preferably colorless, i.e. it does not exhibit any pronounced absorption of one or individual wavelengths in the visible wavelength range. While grating structures that are flat, i.e. formed in a plane, such as thin line gratings, micrograting structures, whose microstructures form a three-dimensional pattern and are difficult for counterfeiters to produce or replicate.

Grid structures are therefore preferred which have microstructures which are formed at different distances from an upper side of the document body or of the at least one transparent volume region.

Particularly preferably, the at least one microlattice structure is three-dimensional.

In a preferred embodiment, the microstructures have dimensions in the range of 1 µm to 25 µm at least along one spatial direction, preferably along all spatial directions. This means that the microstructures have a maximum dimension along any spatial direction in the range between 1 µm and 25 µm. The microlattice structure is created by their orderly structured arrangement in a pattern. Preferably, the pattern of the microstructures is periodic, which means that sections of the three-dimensional pattern can be mapped onto another section of the pattern by a parallel shift.

The grid structure preferably comprises microstructures arranged in equally spaced planes that are formed at an angle to the surface, which replicate a section or sections of a blaze grid or also step-like structures that "recreate" or form notches or trenches formed in space in the transparent volume. Due to the very good focusability and focusing of the laser, pattern elements can be created from a large number of microstructures, in particular with a pulsed laser and the relative movement of the optics to the document body, which appear periodically in the grid structure, i.e. the pattern parts formed by the microstructures can be converted into one another by translation.

The microstructures can be formed, for example, via refractive index variations and/or discolorations of the transparent material in the region of the at least one transparent volume region of the document body. While the refractive index variations are generally not visible to an observer without the diffraction effects that occur on the pattern formed from them, the discolorations can be detected by a human observer, in particular due to their large number. The pattern structures formed by the large number of microstructures, which form the micro-lattice structure and are therefore formed repeatedly in the volume, can be recognized by an observer even without the diffraction effects. Since these are preferably formed three-dimensionally in space, they differ significantly from, for example, printed structures that are formed in one or more planes spaced apart from one another parallel to the surface. This offers another possibility for verifying such a security document with a micro-lattice structure.

However, reliable protection against replicas is provided by verification in which light is shined onto the micro-lattice structure, for example light from a laser or coherent light from a white light source, and the resulting diffraction patterns of the light are observed, which arise from the interaction of the light with the micro-lattice structure.

In one embodiment, the at least one transparent volume region extends from the top to the bottom of the document body. In these embodiments, at least one window region is thus formed in the security document, in which light can pass through the document body from the top to the bottom. If, for example, coherent laser light or coherent white light is radiated through the micro-lattice structure in the at least one transparent volume region, it diffracts at the micro-lattice structure, so that a typical diffraction effect is shown. In the case of coherent white light, for example, the light is split into different spectral colors at different angles. Coherent laser light also shows a light pattern that consists of different lines or light points that are spaced apart from one another. The resulting structure depends on the three-dimensional structure of the micro-lattice structure. This is therefore preferably the case with such a Embodiment in which the at least one transparent volume region extends from the top to the bottom, designed as a transmission grating.

In order to make verification possible in a simple manner even in security documents in which no window region is to be formed by the at least one transparent volume region, a further development provides that a reflective layer is formed on a side of the at least one transparent volume region facing away from the top of the document body, which reflects light passing through the at least one volume region and striking the reflective layer back into the transparent volume region. In some embodiments, this can be the underside of the security document. As a rule, however, the reflective layer will be formed inside the document body. In embodiments in which the volume region is formed as a window region, the security document can, however, be arranged in front of a reflective layer, for example a mirror, in order to be able to observe the diffraction effect in reflection.

The reflective layer is particularly preferably designed to be mirror-like, so that transmission grating effects that are generated by the micro-grid structure in the at least one transparent volume region are reflected back by a mirroring on the reflective layer, so that the diffraction effects of the micro-grid structure can be verified in reflection. This means that when light is irradiated via the top of the document body, the diffracted light exits the top of the document body again and can be observed from the top, for example, can be projected onto a screen. Due to the preferred three-dimensionality of the micro-grid structure, there are, for example, depending on the specific design, different angles at which particularly efficient diffraction can be observed on the micro-grid structure for light of a certain wavelength.

A micro-lattice structure observable in reflection can also be achieved by combining the micro-structures that cause shading of the specularly reflective layer with the specularly reflective layer. The micro-lattice structure is created by shaded non-reflective areas or alternatively by remaining reflective areas. For this purpose, the Microstructures are preferably formed adjacent to the reflective layer, but in the at least one transparent volume.

If the at least one transparent volume region is formed, for example, by a single transparent substrate layer, the reflective, preferably mirror-like, reflection layer can be vapor-deposited, for example, on the underside in a section. It is of course also possible for further transparent substrate layers to be stacked over the substrate layer provided with the reflective layer in order to form the at least one transparent volume region. If the reflective layer is provided as a separating layer between the at least one transparent volume region and the at least one further transparent volume region, transparent substrate layers can be stacked on top of one another on both sides of the reflective layer, at least in the region in which the layer is reflective, in order to form the lamination body with a see-through window, in the middle of which a reflective layer is formed, into which the micro-perforations are then introduced by means of the laser radiation in a further development.

In a further development, it is thus provided that micro-openings are formed in the opaque, preferably reflective, layer, which diffract light and form a transmission grating. In a preferred embodiment, it is provided that the micro-grid structure comprises a periodic three-dimensional pattern of microstructures.

According to another alternative, it is provided that the document body, in addition to the at least one transparent volume region, has at least one further transparent volume region opposite the at least one transparent volume region extending from the underside into the interior of the document body, wherein the at least one transparent volume region and the at least one further transparent volume region are separated at least by an opaque layer, which is preferably the reflective layer, and wherein laser-induced micro-perforations are formed in the one opaque layer, preferably the reflective layer, at which transmitted light is diffracted, wherein the micro-perforations form a transmission grating. The layer separating the at least one volume region and the at least one further volume region can also be reflective, preferably specularly reflective, on one side, e.g. on the side facing the at least one transparent volume region, and absorbent or diffusely scattering on the side facing away. In this embodiment, if one layer is specularly reflective, in addition to the diffraction effect caused by the micro-lattice structure formed by the micro-structures, a further different diffraction effect can be observed through the transmission grating if the security document is illuminated, for example, from the underside through the at least one further transparent volume region. The diffraction effect on the micro-lattice structure formed by the micro-structures in the at least one volume region can be detected and verified in reflection by light irradiated via the top side, which is diffracted by the micro-lattice structure and then reflected by the reflective layer. The transmission grating formed by the micro-perforations can also be verified when illuminated through the underside, wherein the transmission grating can then be detected from the top side.

In the preferred method, a reflective layer is thus formed at a distance from an upper side of the document body under the at least one transparent volume region, which reflects light passing through the at least one volume region and striking the reflective layer back into the transparent volume area. Preferably, the reflective layer is designed as a mirror layer. For this purpose, for example, a thin metallic layer is either vapor-deposited onto the underside of the document body or at least vapor-deposited in a section onto one of the substrate layers, which is then inserted into the document body as an inner layer.

In one embodiment, it is provided that the document body is assembled as a lamination body from substrate layers layered on top of one another and one of the substrate layers is reflective in at least one section or is provided with a reflective coating and is assembled with the other substrate layers in such a way that the at least one transparent volume region is formed between, on the one hand, the upper side and, on the other hand, the at least one section of the reflective substrate layer or the reflective coating with which this at least one section is provided.

In one embodiment, it is provided that the at least one transparent volume region extends from the top side to the opposite bottom side of the document body.

In one embodiment, the microstructures can be designed such that they modify the reflective layer so that the unmodified regions form a microlattice structure in the form of a reflection grating.

The modification can be carried out, for example, via microstructuring in the form of micro-perforations.

In some embodiments, the micro-perforations form a micro-lattice structure of a transmission grating and the unmodified regions of the reflective layer form a micro-lattice structure in the form of a reflection grating. Additionally or alternatively, micro-structures can be formed in the interior of the at least one transparent volume region, which form a micro-lattice structure, preferably a three-dimensional micro-lattice structure.

Fig. 1

eine schematische Ansicht eines Dokumentkörpers mit einer Mikrogitterstruktur;

Fig. 2

eine schematische Explosionszeichnung und Erläuterung der Herstellung eines Sicherheitsdokuments;

Fig. 3

ein schematischer Ausschnitt eines Dokumentkörpers mit einer Mikrogitterstruktur;

Fig. 4

eine weitere schematische Darstellung eines Ausschnitts eines Dokumentkörpers mit einer Mikrogitterstruktur; und

Fig. 5

noch eine weitere schematische Darstellung eines Ausschnitts eines Dokumentkörpers mit einer Mikrogitterstruktur.

The invention is explained in more detail below with reference to a drawing.

Fig.1

a schematic view of a document body with a microlattice structure;

Fig.2

a schematic exploded drawing and explanation of the production of a safety document;

Fig.3

a schematic section of a document body with a microlattice structure;

Fig.4

a further schematic representation of a section of a document body with a micro-grid structure; and

Fig.5

yet another schematic representation of a section of a document body with a microgrid structure.

In Fig.1 A security document 1 is shown schematically. This comprises a document body 10, which is preferably produced as a laminated body from several substrate layers. The document body 10 has an upper side 11 and an opposite lower side 12. End faces 13-16 extend all the way around between the upper side 11 and the lower side 12.

In Fig.2 is shown schematically how the document body 10 after Fig.1 manufactured as a lamination body. Identical technical features are designated with the same reference numerals in all figures.

The document body 10 is made from a substrate layer 120 with a top side 121 and a bottom side 122 and a further substrate layer 130 with a top side 131 and a bottom side 132. For example, the document body 10 is made here from just two substrate layers, the substrate layer 120 and the further substrate layer 130. It is clear to those skilled in the art that document bodies can be made from any number of substrate layers. Numbers between two and fifteen, preferably between five and seven substrate layers are usual. For the present invention, the specific number of substrate layers is of secondary importance.

In the embodiment shown, the substrate layer 120 and the further substrate layer 130 are each transparent substrate layers, i.e. they consist of a material which, after being joined together, allows light in the visible wavelength range to pass through in accordance with geometric optics, provided the material is not changed. One section of the substrate layer 120 is provided with a print layer 150. In the embodiment shown, the print layer 150 is used to form individualizing information 152, which includes a portrait image 154, a name 156 and a location 158 where the corresponding person to whom the produced security document 1 is assigned lives. In addition, for example, a background 159 is formed so that the top side 121 in section 60 is opaque due to the print layer 150. The background print can be designed as a guilloche print, for example. This is not shown here for the sake of simplicity.

A hologram patch 140 is layered between the substrate layer 120 and the further substrate layer 130 before the substrate layer 120 and the further substrate layer 130 are bonded to the document body 10 using heat energy and pressure, which is Fig.1 Preferably, the substrate layer 120 and the further substrate layer 130 are made from the same plastic material, so that a monolithic document body 10 is created. If the print layer 150 is also made from the same polymer as a binder, delamination due to the print layer 150 being applied over the entire surface in section 60 is not increased.

In a section 70 in which the top side 121 of the substrate layer 120 is not printed, a transparent volume region is formed in the document body 10, which extends from the top side 11 into the interior of the document body 10. In the embodiment shown, the transparent volume region 100 is formed by the material layer 20 and the further material layer 30, which have emerged from the substrate layers 120 and 130. In other embodiments, the at least one transparent volume region 100 can also be formed from more or only one substrate layer.

In the illustrated embodiment, which is not according to the claims, the transparent volume region extends from the top side 11 to the bottom side 12 of the document body 10. Microstructures 200 are formed in the interior of the transparent volume region 100, the pattern 220 of which forms a micro-lattice structure 210 which diffracts light, preferably in the visible wavelength range. In the illustrated embodiment, the pattern 220 schematically has pattern regions 231-233 which form stepped, inclined planes formed in the interior at angles α1-α3 with respect to local surface normals 251-253 of the top side 11 of the document body. It is clear to the person skilled in the art that these are formed from microstructures arranged next to one another, which are formed at different depths, relative to the top side 11 of the document body 10, in the at least one transparent volume 100. The microstructures can be formed, for example, by refractive index differences in the transparent material of the at least one transparent volume region 100. Alternatively and/or additionally, the microstructures or some microstructures can also be

Discolorations, for example blackening, may be formed. It is clear to the person skilled in the art that the microstructures do not have to form fully closed planes or step structures, but can form them in some embodiments.

The pattern regions 231-233 can also be formed next to one another and separately from one another and can be formed as microstructures that can be perceived separately, at least when viewed under a microscope. In the embodiment shown, the pattern 220 is periodic. The individual pattern regions 231-233 can be converted into one another by means of a translation. This means that the pattern regions are formed at the same distance from one another along a spatial direction. In addition, the pattern regions 231-233 are of the same type, i.e. the same in terms of their geometric structure. It is clear to those skilled in the art that small variations do not affect the periodicity that is necessary for the formation of a microstructure grid.

The microstructures can be introduced into an otherwise finished security document 1 or the associated document body 10. The specific design of the microstructures can thus individualize the document body 10 from other document bodies by introducing a different microgrid structure from the microgrid structures that are introduced into the other security documents of a plurality of security documents. This allows individual groups of security documents to be individualized or individual security documents from a totality of security documents to be individualized.

In Figures 3 to 5 sections of a document body 10 are shown schematically, which correspond, for example, to section 70 of the security document 1 or document body 10 according to Fig.1 In the embodiment according to Fig.3 are as in the document body 10 after Fig.1 in the at least one transparent volume region 100 microstructures are introduced which form a periodic pattern, which forms a transmission grating for the diffraction of light. Light 300 radiated via the underside 12 of the document body or at least one transparent volume region 100 is diffracted at the micrograting structure 210 and emerges from the top side 11 of the security document or at least one transparent volume region 100 as light 310 diffracted in transmission. If the incident light 300 is coherent white light, a light pattern separated by wavelength and thus having different colored areas can be seen on a screen (not shown) on which the light 310 diffracted in transmission strikes. Depending on the specific design of the micro-lattice structure, which takes place via the arrangement of the microstructures in the at least one transparent volume region, the diffraction takes place at different angles and a different degree of color splitting takes place. If monochromatic laser light is emitted, it is diffracted, for example, into different points or lines of varying intensity.

In the embodiment according to Fig.4 is before joining the one substrate layer 120 after Fig.2 with the further substrate layer 130 after Fig.2 either the top side 121 of one substrate layer 120 or the bottom side 132 of the other substrate layer 130 is coated with a metal layer. For example, this can be done by vapor deposition or any other transfer method. It is also possible to add a thin metal foil between the substrate layers. The metal layer forms a reflective layer 160, which in the embodiment shown reflects specularly.

The at least one transparent volume region 100 is formed between the top side 11 and the reflective layer 160. A further transparent volume region 110 is formed below the reflective layer 160 and the bottom side 12 of the document body. In the embodiment shown, micro-perforations are created in the reflective layer 160 by means of the laser radiation, which together create a transmission grating. If light 300 is now irradiated via the bottom side, diffraction takes place at the perforations and light 310 diffracted in transmission can again be detected, for example on a screen not shown. If, on the other hand, light 320 is irradiated via the top side 11, it is diffractedly reflected by the remaining reflective layer 160 and also creates a typical diffraction pattern.

In addition, a micro-lattice structure can be formed in the at least one transparent volume region 100 via micro-structurings in the transparent volume, the diffracted light 330 of which can be reflected at the remaining, not through the micro-openings removed sections of the reflective layer can be detected in reflection when light 320 is irradiated via the upper side 11 of the security document or the section 70 shown.

In Fig.5 an embodiment is shown in which microstructures are formed in the at least one transparent volume above the reflective layer 160, which preferably reflects in a specular manner, which form the microlattice structure 210. Light 320 radiated in via the upper side is diffracted here at the microstructures and, due to the reflective layer 160, is emitted from the upper side 11 of the section 70 of the security document 1 or document body 10 as reflected light 330, the diffraction pattern of which can be captured and viewed on a screen (not shown) or captured by means of a camera or other device. The further material layer 30 can be transparent or non-transparent, for example opaque.

The various embodiments described can be verified using any optical measuring device that can record the spatially resolved and, if necessary, wavelength-resolved diffraction pattern of a transmission and/or reflection grating. The corresponding security document can be verified by comparing the recorded diffraction pattern of the light with an expected diffraction pattern or several expected diffraction patterns.

It will be understood by those skilled in the art that highly simplified embodiments are described here and that the illustrations are not to scale.

List of reference symbols

1

Security document

10

Document body

11

Top

12

bottom

13 - 16

Front sides

20

Material layer

30

additional material layer

60

a section

70

further section

100

transparent volume range

110

further transparent volume area

120

a substrate layer

121

Top

122

bottom

130

additional substrate layer

131

Top

132

bottom

140

Hologram patch

150

Printing layer

152

individualizing information

154

Portrait picture

156

Surname

158

Location

159

background

160

reflective layer

200

Microstructuring

210

Microlattice structure

220

Pattern

231 - 233

Sample areas

α1 - α3

angle

251 - 253

Surface normal

300

incident light

310

light diffracted in transmission

320

incident light

330

diffracted and reflected light

Claims (7)

1. A security document (1) comprising a

   document body (10) with an upper side (11) and an opposite lower side (12), wherein the document body (10) has at least one transparent volume region (100), wherein the at least one transparent volume region (100) extends from the upper side (11) into the interior of the document body (10),

   wherein laser-induced microstructures (200) are formed in the interior of the document body (10),

   wherein

   by means of the microstructures (200) at least one micro-lattice structure (210) is formed in the interior of the document body (10) which diffracts light (300),

   wherein

   an opaque layer (160) is formed on a side of the at least one transparent volume region (100) facing away from the upper side (11) of the document body (10), characterized in that,

   according to one alternative, the one opaque layer is formed as a reflective layer (160), which reflects light (300) passing through the at least one volume region (100) and incident on the reflective layer back into the transparent volume region (100),

   wherein at least some of the microstructures (200) modify the reflective layer (160) and a micro-lattice structure (210) in the form of a reflection grating is formed thereby by unmodified regions of the reflective layer (160),

   and/or, according to another alternative,

   the document body has, in addition to the at least one transparent volume region (100) opposite the at least one transparent volume region (100), at least one further transparent volume region (110) extending from the lower side (12) into the interior of the document body (10), wherein the at least one transparent volume region (100) and the at least one further transparent volume region (110) are separated by the one opaque layer (160), and wherein laser-induced microperforations, at which transmitted light is diffracted, are formed in the opaque layer (160) at least as a part of the microstructures (200), wherein the micro-perforations form a transmission grating.
2. The security document (1) according to claim 1, characterized in that the at least one microlattice structure (210) is three-dimensional and at least the portion of the microstructures (200) which forms the three-dimensional microlattice structure (210) are formed in the at least one transparent volume region (100).
3. The security document (1) according to claim 1 or 2 according to the other alternative, characterized in that the one opaque layer (160) is the reflective layer.
4. The security document (1) according to any one of the preceding claims, characterized in that the microstructures (200) have dimensions in the range of 1 µm to 25 µm at least in one respective spatial direction, preferably in all spatial directions.
5. The security document (1) according to any one of the preceding claims, characterized in that the microstructures (200) are formed by refractive index variations in the at least one transparent volume region (100) and/or colorations of the transparent material in the at least one transparent volume region (100) and/or as micro-perforations in the opaque and/or reflective layer.
6. A method for producing a security document (1) comprising the steps:

   producing or providing a document body (10) with an upper side (11) and an opposite lower side, wherein at least one transparent volume region (100) is formed in the document body (10), which extends from the upper side (11) into the interior of the document body (10), wherein microstructures (200) are formed in the interior of the document body (10) by laser radiation, wherein an optical system with a numerical aperture NA of greater than 0.3 in air is used for focusing the laser radiation and by means of the microstructures (200) a microlattice structure (210) is formed in the interior of the document body (10) which diffracts light,

   characterized in that

   an opaque layer is formed at a distance from an upper side (11) of the document body (10) below the at least one transparent volume region (100),

   wherein, according to one alternative, the one opaque layer is configured to be reflective, so that the opaque reflective layer reflects light passing through the at least one volume region (100) and incident on the reflective layer back into the transparent volume region (100), wherein at least some of the microstructures (200) modify the reflective layer (160) and thereby form a microlattice structure (210) in the form of a reflective grating through unmodified regions of the reflective layer (160),

   and/or, according to another alternative, microperforations are formed in the opaque layer, which diffract light and form a transmission grating.
7. The method according to claim 6, characterized in that at least some of the microstructures (200) are formed in the at least one transparent volume region (100) to be three-dimensional as the at least one micro-lattice structure (210).

Images