Security document including an optically variable security feature

Abstract

A security document (10) includes a first security element (40) embedded in a substrate (1) of the same. The first security element (40) is part of an optically variable security feature (3) and is not visible when the security document (10) is viewed at a first observation angle, but becomes visible when the security document (10) is viewed at a second observation angle. This is achieved by hiding the first security element (40) behind an opaque layer (31) of the substrate (1), and providing appropriate openings (42) in the opaque layer, with which the security element (40) is aligned such that it can only be seen when the security document (10) is viewed at the second observation angle. The openings (42) can be through-holes (43, see figures 2, 3) or zones without an opaque material (39, see figures 4, 5).

Description

Technical Field

[0001] The present disclosure generally relates to security documents, in particular, personalizable security documents such as identification documents, driver's licenses and the like, which include a portrait of a holder of the security document.Background

[0002] Generally, in the market of physical identification documents, security features are included to increase the document's security. In some applications, a laser-engraved image is considered vital, as the image features are engraved into a polycarbonate substrate rather than on the surface of the substrate, making it more difficult to tamper with the document. A laser-engraved security feature in a polycarbonate substrate may include a black and white (in particular, grayscale) image, a color image, or special features like the Mirage security feature of HID.

[0003] Physical identification documents such as driver's licenses, passports and the like may include a color portrait of a holder of the security document. Such color portraits are usually printed onto a surface of the security document using commonly known printing processes.

[0004] WO 98 / 19869 A1 discloses a security feature with a perforation pattern, wherein the perforation pattern extends over a surface of a document and represents an image with brightness tones.

[0005] EP 4 358 032 A1 discloses a method of generating a personalized output image for a security document such as a passport or the like, where the personalized output image is formed on a data page of the security document.

[0006] The present disclosure is directed, at least in part, to improving the security of such security documents, without being limited to a particular type of security document.Summary of the Disclosure

[0007] According to one aspect of the present disclosure, a security document has a substrate having a first side and a second side opposite to the first side in a thickness direction of the substrate, the substrate including a plurality of substrate layers laminated with each other, and a first security element embedded in the substrate. The plurality of substrate layers includes a first substrate layer that is opaque when viewed from the first side under light of a first wavelength range. The first substrate layer includes a first plurality of openings. The first security element is provided below the first substrate layer in the thickness direction such that it does not overlap the first plurality of openings when viewed along the thickness direction. The first security element is disposed such that it is not visible via the plurality of first openings when the security document is viewed from the first side under the light of the first wavelength range at a first observation angle, and visible via the plurality of first openings when the security document is viewed from the first side under the light of the first wavelength range at a second observation angle different from the first observation angle.

[0008] Other features and aspects of the present disclosure will be apparent from the following description and the accompanying drawings.Brief Description of the Drawings

[0009] Fig. 1 shows a plan view of an exemplary personalizable security document in accordance with the present disclosure; Fig. 2 shows a schematic cross-sectional view of an exemplary security feature in accordance with the present disclosure; Fig. 3 shows a schematic cross-sectional view of another exemplary security feature in accordance with the present disclosure; Fig. 4 shows a schematic cross-sectional view of another exemplary security feature in accordance with the present disclosure; Fig. 5 shows a schematic cross-sectional view of yet another exemplary security feature in accordance with the present disclosure; and Fig. 6 shows an exemplary data page of a security document in accordance with the present disclosure. Detailed Description

[0010] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described herein are intended to teach the principles of the present disclosure, enabling those of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be considered as, a limiting description of the scope of protection. Rather, the scope of protection shall be defined by the appended claims.

[0011] The present disclosure is based at least in part on the realization that, although many different security features for security documents are available in the market, as time passes, forgers are finding ways to mimic or attack such security elements. Accordingly, it is important to keep the security documents secure through new and additional security features. This can be achieved by providing an optically variable layered security feature including openings in one or more layers of the security document, such that security elements inside the body of the document can be viewed in a controlled manner that is difficult to replicate without using the correct equipment and possessing the necessary knowledge. In particular, through changing the observation angle of a security document, one may be able to observe one or more optical changes in the security feature. This optical variance can be observed in the normal visible light spectrum, or in the ultraviolet (UV) or infrared (IR) light spectrum.

[0012] In particular, when the optically variable feature is to be viewed under UV light, one or more substrate layers of the security document, which are generally formed from a material such as polyvinyl chloride (PVC), thermoplastic polyurethane (TPU) and polycarbonate (PC), may have a property that they emit light in the visible wavelength range upon irradiation with UV light. In this manner, such a substrate layer may form part of the security feature, i.e., produce one of the two or more different optical appearances upon irradiation with UV light.

[0013] By providing a plurality of through-holes in the security document, and having at least one opaque layer that covers a material that emits light of a certain wavelength upon irradiation with UV light, when the document is viewed in a direction essentially perpendicular to the security document, the material layer covered by the opaque layer is not visible. Instead, the light that is generated by the underlying substrate layer can be observed through the openings formed in the opaque layer. This creates the first optical appearance of the security feature of the present disclosure. When the security document is tilted by a prescribed angle, the material layer underneath the opaque layer becomes irradiated with the UV light and emits the light of the first wavelength in the visible range, which is different from the light that is irradiated by the substrate layer. This results in a second, different optical appearance of the security feature of the present disclosure.

[0014] When the plurality of openings that are formed in the security document are essentially circular, the change in optical appearance can be observed by tilting the secure document in any arbitrary direction, at least as long as the material that is provided underneath the opaque layer is provided essentially in the entire area below the opaque portions of the opaque layer. Alternatively, if the plurality of through-holes or openings are formed as slots having a prescribed direction of extension, the change in appearance of the security feature may only be observed when the document is tilted in a direction that is essentially perpendicular to the direction of extension of the slots. When the security document is tilted along the direction of extension of the slots, no change may be observed.

[0015] The openings in the opaque layer do not necessarily have to be formed as through-holes in one or more substrate layers of a substrate of the security document. Instead, the openings may be defined by a printed layer that is applied onto one of the substrate layers of the security document. In such a case, the printed opaque layer may be aligned with one or more underlying material layers, which may also be printed on another substrate layer, and which have the above-described effect of emitting light in the visible range upon irradiation with light of a given wavelength range such as UV or IR.

[0016] The plurality of openings defined by the opaque layer may form a pattern that results in a predetermined or personalized image to be provided on the security document. A predetermined image is an image that is the same for all security documents, whereas a personalized image is an image that is different for each security document, for example, resembles a portrait of a holder of the security document. It will be appreciated that such a portrait may be formed by providing the openings in the opaque layer such that they have different sizes, resulting in different amounts of light that are reflected or emitted through the same by the underlying security elements. This is described, for example, in WO 08 / 19869 A1. Of course, the skilled person will realize that there are also other ways to form image features inside the opaque layer, for example, by varying a density of the openings, by using image forming techniques such as dithering or the like, etc.

[0017] The security feature disclosed herein can be combined with additional security features of data pages of documents such as passports or the like. In particular, a hinge portion of a data page can be a part of the security feature of the present disclosure, i.e., may either form one of the security elements that are visible through the openings in the opaque layer, or may include openings that are aligned with the openings in the opaque layer, for example, in case said openings penetrate the entire data page. This may further increase the security of the document due to the link between the different security elements.

[0018] The term "openings" as used herein encompasses all forms and shapes of openings such as windows, holes, through-holes, slots, perforations, etc.

[0019] Fig. 1 shows a plan view of an exemplary security document 10 in accordance with the present disclosure. As shown in Fig. 1, security document 10 includes a substrate 1 having a substantially rectangular shape. In the present embodiment, as shown in Fig. 1, security document 10 is a personalized security document that includes a primary portrait 2 of a person to which the document belongs. Primary portrait 2 is formed in an image-forming region provided on a first side S1 of substrate 1 in a known manner.

[0020] In the example shown in Fig. 1, personalized security document 10 is an ID card or a driver's license or the like. However, the present disclosure is not limited to such an example, and security document 10 may also be part of a passport or other security documents.

[0021] As shown in Fig. 1, exemplary security document 10 further includes a security feature 3 including a personalized image 4 that is formed in a region of substrate 1 in a manner that will be described in more detail below. For example, personalized image 4 may resemble primary portrait 2 formed on first side S1 of substrate 1 by laser engraving. Additionally, personalized information 5 may also be provided on first side S1 of substrate 1 in a known manner.

[0022] Fig. 2 shows a schematic cross-sectional view of security feature 3, i.e., the portion of substrate 1 in which personalized image 4 is formed, in accordance with a first exemplary embodiment of the present disclosure. As shown in Fig. 2, security document 10 has substrate 1 having first side S1 and a second side S2 opposite to first side S1 in a thickness direction d of substrate 1. Substrate 1 includes a plurality of substrate layers 31, 32, 33, 34 laminated with each other in a known manner. The material forming substrate layers 31, 32, 33, 34 may be a plastic such as PVC, TPU or PC.

[0023] Further, as shown in Fig. 2, security document 10 also includes a first security element 40 embedded in substrate 1. In the example shown in Fig. 2, first security element 40 is configured as a first layer of material 46 that is applied on a first surface 33a of a substrate layer 33 of the plurality of substrate layers 31, 32, 33, 34. For example, first layer of material 46 may be formed on first surface 33a by screen printing, offset printing, flexographic printing, etc., by hot-stamping of metallic foils, or by applying a Diffractive Optically Variable Image Device (DOVID).

[0024] First layer of material 46 is configured to emit light of a first wavelength in the visible range upon irradiation with light of a first wavelength range. In the present disclosure, the first wavelength range may be visible light, or it may be IR light or UV light. In case of visible light, the emitted light of a first wavelength is light that is reflected by first layer of material 46. In case of UV or IR light, generally, the light of the first wavelength in the visible range is light that is generated by excitation of the first layer of material 46, which excitation results in a fluorescence of first layer of material 46. The skilled person will recognize that first layer of material 46 may include any type of known material that exhibits such a fluorescence under UV or IR light.

[0025] As shown in Fig. 2, the plurality of substrate layers 31, 32, 33, 34 includes a first substrate layer 31 that is opaque when viewed from first side S1 under the light of a first wavelength range. Here, the meaning of the expression "opaque" is that essentially no light of the first wavelength range is transmitted through first substrate layer 31 (preferably, a transmittance is less than about 50%, more preferably less than about 25%). In other words, when security feature 3 is viewed along thickness direction d, the portions underneath opaque substrate layer 31 are not visible, but hidden. First substrate layer 31 is an opaque PC layer, for example, a white PC layer that is commonly used in security documents. In other embodiments, substrate layer 31 may include a printed ink layer that is applied to a surface of a substrate layer that may be at least partially transparent in a sufficient amount to render substrate layer 31 opaque.

[0026] As shown in Fig. 2, first substrate layer 31 includes a first plurality of openings 42. In other words, first substrate layer 31 includes a plurality of portions through which the light of the first wavelength range can pass. This can be achieved by providing a plurality of through-holes in first substrate layer 31. However, as will be explained in more detail below, this may also be achieved by providing an opaque material layer or coating on, for example, a transparent substrate layer, which substrate layer does not include through-holes. In both such cases, however, first substrate layer 31 includes / defines the first plurality of openings 42.

[0027] As shown in Fig. 2, first security element 40 is provided below first substrate layer 31 in thickness direction d such that it does not overlap the first plurality of openings 42 when viewed along the thickness direction. In the example that is shown in Fig. 2, portions of first layer of material 46 are provided to overlap opaque portions of first substrate layer 31 when viewed along thickness direction d. In other words, first security element 40 includes a second plurality of openings 44 that is aligned with the first plurality of openings 42. Here, it is not absolutely necessary that the second plurality of openings 44 have a same size as the first plurality of openings 42. In other words, first layer of material 46 does not necessarily need to have the same dimensions as the opaque portions of first substrate layer 31. However, in some embodiments, this may be the case, as indicated by the dashed line in Fig. 2. In such a case, second plurality of openings 44 may have a same size as first plurality of openings 42. It will be immediately recognized that this can be achieved by first providing first layer of material 46 as a continuous layer on first surface 33a of substrate layer 33, and forming first plurality of openings 42 and second plurality of openings 44 at the same time when forming a plurality of through-holes or perforations 43 penetrating substrate 1 from first side S1 to second side S2, as shown in Fig. 2.

[0028] Regardless of whether first security element 40 is entirely covered by the opaque portions of first substrate layer 31 or not, first security element 40 is disposed such that it is not visible when security document 10 is viewed from first side S1 under the light of the first wavelength range at a first observation angle, as indicated by the arrows pointing downward to the right in Fig. 2, and visible when security document 10 is viewed from first side S1 under the light of the first wavelength range at a second observation angle different from the first observation angle, as indicated by the arrows pointing downward to the left in Fig. 2. In case security element 40 covers the same area as the opaque portions of first substrate layer 31, the first observation angle may be substantially along thickness direction d, that is, perpendicular to the surface of substrate 1.

[0029] Generally, when security document 10 is viewed from first side S1 under the light of the first wavelength range at the first observation angle, no light can directly impinge on security element 40, such that no light can be reflected or emitted by the same. Accordingly, security element 40 is not visible.

[0030] However, when security document 10 is tilted by a prescribed angle, and security document 10 is viewed under the light of the first wavelength range at the second observation angle, at least some light of the first wavelength range can directly impinge on security element 40, such that the same may reflect or emit the light of the first wavelength in the visible range. Accordingly, when the security document 10 is viewed at the second observation angle, the image that is formed by first plurality of openings 42 has the color that corresponds to the reflected or emitted light of the first wavelength. This color is different from the color that is observed when security document 10 is viewed at the first observation angle, for example, perpendicular to the surface of substrate 1.

[0031] Here, it will be appreciated that it is not necessary that the image formed by the first plurality of openings 42 is perceived as an image having a specific color when security document 10 is viewed at the first observation angle. In other words, in accordance with the present disclosure, it is not necessary that the color of the image formed by first plurality of openings 42 changes from a first color to a second color upon change of the observation angle. It is sufficient when the image assumes the color corresponding to the first wavelength when the observation angle is changed. Of course, as will be described in more detail, a change from a different color to the color corresponding to the light of the first wavelength is also contemplated.

[0032] As shown in Fig. 2, the plurality of substrate layers 31, 32, 33, 34 may include a spacer substrate layer 32 that is arranged between first substrate layer 31 and first security element 40 in thickness direction d. Preferably, the spacer substrate 32 may have a thickness of between 20 µm and 100 µm, more preferably around 50 µm. Spacer substrate layer 32 may be a transparent or clear PC layer that is commonly used in security documents including a plurality of different layers. Due to the presence of spacer substrate layer 32, it can be assured that security element 40 is visible through first plurality of openings 42 at the second observation angle, and that the angle under which security document 10 has to be observed in order to be able to see security element 40 is not too large. The angle under which security element 40 is observed may be appropriately modified by providing spacer substrate layer 32 with different thicknesses.

[0033] As also shown in Fig. 2, security document 10 may further include a second security element 50 embedded in substrate 1. Second security element 50 is visible through first plurality of openings 42 when security document 10 is viewed from first side S1 under the light of the first wavelength range at the first observation angle. In the example that is shown in Fig. 2, second security element 50 is formed by one of the plurality of substrate layers 31, 32, 33, 34, in particular, second substrate layer 33, which, in the exemplary embodiment, is configured as a substantially transparent or clear substrate layer such as a PC layer having a thickness of, for example, between 20 µm and 400 µm, for example, around 100 µm. Second substrate layer 33 may have the inherent property that, upon irradiation with UV light, it emits light in the visible range, for example, light with a bluish color. Accordingly, the light that is emitted by second substrate layer 33 when security document 10 is viewed at the first observation angle may result in a blue color image generated by the plurality of openings 42 corresponding to second security element 50. In other words, first security element 40 corresponds to an image that is perceived as having a first color, and second security element 50 corresponds to an image that is perceived as having a second color. Accordingly, in some embodiments, second substrate layer 33 itself may be considered as an additional second security element 50 in accordance with the present disclosure.

[0034] As previously described, the first plurality of openings 42 form an image 4, preferably a personalized image. Image 4 has different appearances, preferably different colors, when security document 10 is viewed from first side S1 under the light of the first wavelength range at the first observation angle and at the second observation angle, respectively. However, it should be mentioned that it is not necessary that image 4 is a personalized image, instead, it may be a predetermined image, i.e., an image including image features or symbols that are the same for all security documents 10.

[0035] In some embodiments, an additional layer of material 45 provided on first substrate layer 31 may be provided as a further security element, as an alternative or in addition to second substrate layer 33. Layer of material 45 may be an ink layer, and may emit light of a different wavelength in the visible range upon irradiation with light in the first wavelength range. This results in a change in the color of image 4 due to an effect that is similar to dithering. At the first observation angle, the color of image 4 is the color of the light emitted by layer of material 45 (and, optionally, second security element 50). At the second observation angle, the color of image 4 is the color that results from the light that is emitted by layer of material 45 and the light that is emitted by first security elements 45. Accordingly, the color of image 4 may change from a first color such as red to a second color such as orange when changing the observation angle.

[0036] Fig. 3 shows another schematic cross-sectional view of an exemplary security feature 3 in accordance with the present disclosure. The configuration of security feature 3 shown in Fig. 3 is similar to that of security feature 3 shown in Fig. 2, such that only the differences will be described in the following.

[0037] As shown in Fig. 3, security document 10 may further include a third security element 60 embedded in substrate 1, with third security element 60 being visible through first plurality of openings 42 when security document 10 is viewed from first side S1 under the light of the first wavelength range at a third observation angle different from the first observation angle and the second observation angle, and not being visible when security document 10 is viewed from first side S1 under the light of the first wavelength range at the first observation angle and the second observation angle. This can be achieved by providing third security element 60 as a second layer of material 62 that is applied on a second surface 33b of a third substrate layer such as substrate layer 33 of the plurality of substrate layers. Advantageously, second layer of material 62 emits light of a second wavelength in the visible range upon irradiation with the light of the first wavelength range.

[0038] The second layer of material 62 is provided on a rear surface 33b of third substrate layer 33, i.e., a surface of substrate layer 33 opposite to first surface 33a, on which first layer of material 46 is provided. Due to the separation of first layer of material 46 and second layer of material 62 along thickness direction d, it will be appreciated that, depending on the observation angle, only one of first layer of material 46 and second layer of material 62 may be visible when security document 10 is viewed from first side S1 under the light of the first wavelength range.

[0039] In some embodiments, both first layer of material 46 and second layer of material 62 may be configured such that they emit light upon irradiation with UV light, visible light or IR light. In other examples, however, first layer of material 46 and second layer of material 62 may be configured such that they reflect light of different wavelengths upon irradiation with the light of the first wavelength range. First layer of material 46 and second layer of material 62 are not fully overlapping, i.e., are provided in different portions underneath the opaque portions of first substrate layer 31. However, in other embodiments, both first layer of material 46 and second layer of material 62 may fully overlap with the opaque portions of first substrate layer 31, i.e., may be generated from continuous material layers when perforating substrate 1 such that through-holes 43 extend through the same. Here, it will be appreciated that, due to the separation of the substrate layers along thickness direction d, depending on the observation angle, two different colors may be observed. In combination with the third color that is due to the emission by third substrate layer 33 itself, this may result in an optically variable image 4 that changes colors between three distinct colors upon a change in the observation angle.

[0040] Fig. 4 shows another exemplary cross-sectional view of a security feature 3 in accordance with the present disclosure. While in the previously described examples through-holes 43 extend through substrate 1, i.e., penetrate all substrate layers 31, 32, 33, 34, in the example shown in Fig. 4, there are no such through-holes 43. Instead, openings 42 are only formed in an opaque layer of material 39 that is applied onto a surface 31a of first substrate layer 31, preferably, a transparent first substrate layer 31. Also in this manner, it becomes possible to define openings 42, through which security element 40 can be selectively seen depending on the observation angle. It will be appreciated that this facilitates providing security element 40 such that it does not fully overlap the opaque portions of opaque layer of material 39. In other words, the area that is occupied by each portion of security element 40 disposed below a corresponding portion of opaque layer of material 39 may be different from the area of the opaque portion, as shown in Fig. 4.

[0041] Security element 40 is also not visible when security document 10 is viewed from first side S1 under a first observation angle, for example, along thickness direction d. On the other hand, when security document 10 is tilted by a prescribed angle, the light of the first wavelength range may impinge on security element 40, and may either be reflected by the same, or may result in an emission of the light of the first wavelength as described above.

[0042] Substrate layer 33 may also form second security element 50, i.e., may be visible when security document 10 is viewed from first side S1 under the light of the first wavelength range at the first observation angle. Third substrate layer 33 may be a substrate layer having a predetermined color that is visible through first plurality of openings 42 when security document 10 is viewed along thickness direction d. Additionally, first substrate layer 31 may serve as a first spacer substrate layer, and a further substrate layer 32 may function as an additional spacer substrate layer provided between first security element 40 and second security element 50, i.e., third substrate layer 33.

[0043] As shown in Fig. 4, as well as in Figs. 2 and 3, security document 10 may further have a second substrate layer 34 that is opaque when viewed under the light of first wavelength range. In particular, second substrate layer 34 may be arranged below first security element 40 in thickness direction d. In the configuration shown in Fig. 4, substrate layer 34 prevents first security element 40 from being observed from second side S2 of substrate 1. In the embodiments shown in Figs. 2 and 3, however, substrate layer 34 may result in that, also from second side S2, through-holes 43 result in that an optically variable image 4 can be seen when security document 10 is viewed from second side S2 under the light of the first wavelength range.

[0044] Fig. 5 shows another cross-sectional view of yet another exemplary embodiment of the present disclosure. The embodiment shown in Fig. 5 is similar to the embodiment in Fig. 4, such that only the differences will be described. In the embodiment shown in Fig. 5, third security element 60 is provided as second layer of material 62 that, in the present case, is applied on a same surface of substrate layer 32 as first layer of material 46. Again, the configuration that is shown in Fig. 5 results in that, depending on the observation angle, corresponding image 4 may be observed as having three distinct colors, provided that the properties of first material layer 46 and second material layer 62 are selected appropriately as including different materials emitting light of different wavelengths upon irradiation with UV, visible or IR light, or simply as coatings having different colors when viewed in reflection under the light of the first wavelength range.

[0045] In the previously described embodiments, each of the first plurality of openings 42 may have a size of between 20 µm and 5 mm, preferably between 50 µm and 200 µm. Here, it will be appreciated that, as initially mentioned, not all openings 42 need to have the same size. In particular, in order to form image 4, the sizes of openings 42 may be different, depending on the image to be formed. In some embodiments, each opening 42 may be substantially circular. It will be appreciated that this results in the above-described change in the color of image 4 upon a change in the observation angle regardless of the direction along which the document is tilted. In other words, the color change can be observed regardless of the direction of tilting of security document 10. In other embodiments, however, openings 42 may have different geometries, for example, may be formed as slots or the like, which extend along an extension direction with a length that is substantially larger than the width of said slots. In this case, the color change will only be observed when security document 10 is tilted in a direction substantially perpendicular to the direction of extension of the slots. In case the slots extend all the way through substrate 1, the slots are only formed in a portion of substrate 1, for example, the portion corresponding to security element 3 shown in Fig. 1, in order to maintain the integrity of substrate 1.

[0046] Preferably, the first observation angle is along thickness direction d, and the second observation angle is between 1° and 45° to the thickness direction d, preferably, between 5° and 45° to the thickness direction d, more preferably, between 10° and 30° to the thickness direction d. Here, it will be appreciated that the second observation angle depends, in particular, on the distance between first substrate layer 31 that is opaque and first security element 40 along thickness direction d, as well as the dimensions of the first plurality of openings 42. Additionally, the change between the visibility of first security element 40 and second security element 50 will generally be gradual, i.e., there will not be a complete switching between two different colors upon a specific threshold angle. The same applies to the visibility of first security element 40. Generally, when security document 10 is viewed from first side S1 at the first observation angle, first security element 40 will not be visible, because it is completely obscured by opaque substrate layer 31, especially in cases where first security element 40 completely overlaps with the opaque portions of first substrate layer 31. In a strict sense, first security element 40 should immediately become visible when security document 10 is only slightly tilted. In practice, however, it will be appreciated that a certain tilt angle will be necessary in order to result in an effect that is observable by the human eye. As such, the second observation angle may be considered as the observation angle at which a human observer can clearly recognize first security element 40.

[0047] As previously mentioned, it may be advantageous when the first wavelength range is in one of the ultraviolet range and the infrared range. Corresponding materials which exhibit luminescence, i.e., fluorescence in the respective wavelength ranges are readily available to the skilled person, and may be appropriately selected depending on the application.

[0048] Fig. 6 shows another exemplary embodiment of a security document 10. In the embodiment that is shown in Fig. 6, security document 10 is a data page of a security document such as a passport or the like. Here, as shown in Fig. 6, in addition to substrate layers 31, 32, 33, 34, security document 10 includes a hinge portion 75, which is used to attach security document 10 forming the data page to a passport or the like in a known manner. Hinge portion 75 may be formed as a material layer that partially extends into substrate 1, for example, into a combined layer formed by second and third substrate layers 32, 33 after lamination of security document 10. Although not shown in Fig. 6, in some embodiments, hinge portion 75 may extend over the entire cross-section of substrate 1 perpendicular to thickness direction d, or may be provided on an outer surface of the stack of layers forming security document 10. In the example shown in Fig. 6, through-holes 43 also extend through at least a portion of hinge portion 75. As such, hinge portion 75 forms part of security feature 3.

[0049] As shown in Fig. 6, exemplary data page 10 also includes the opaque substrate layers 31, 34, as well as first security element 40 embedded in substrate 1, for example, between second and third substrate layers 32, 33, which may again be transparent substrate layers such as PC layers. Opaque substrate layers 31, 34 may also be commonly used opaque plastic layers, for example, white PC layers or the like.

[0050] Security document 10 further includes additional substrate layers 73 and 74, in which personalization data 78 may be provided in a known manner. Likewise, background layers 80, 82 may be formed on additional substrate layers 73, 74 in a known manner. Further, security document 10 may also include further security elements such as an optically variable ink 84, in which a personalized image can be laser engraved, and a Diffractive Optically Variable Image Device (DOVID) 86. Protective layers 71 and 72 may form the outer layers of security document 10 on first side S1 and second side S2, respectively.

[0051] Exemplary data page 10 may have a total thickness h along thickness direction d of between 600 µm and 900 µm, and the portion formed by substrate layers 31, 32, 33 and 34, which includes first security element 40, may have a height h2 along thickness direction d of between 200 µm and 600 µm.

[0052] It will be appreciated that all the configurations that were described for the embodiment of the exemplary ID card also apply to the embodiment of the exemplary data page shown in Fig. 6. In particular, it is not necessary that the plurality of through-holes 43 are formed to extend through the entirety of substrate 1. Instead, as described above, one or both of first opaque layer 31 and second opaque layer 34 may be formed as an opaque layer of material that is applied on a surface of, for example, one of transparent substrate layers 32, 33.Industrial applicability

[0053] With the above-described techniques, a security document 10 is made with an optically variable security feature 3. Detailed knowledge of the manner in which image 4 is to be formed is required to successfully generate the optically variable security feature. Accordingly, it is very difficult to forge or tamper with security document 10.

[0054] It will be appreciated that the foregoing description provides examples of the disclosed systems and methods. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the general disclosure.

[0055] Recitation of ranges of values herein are merely intended to serve as a shorthand method for referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All method steps described herein can be performed in any suitable order, unless otherwise indicated or clearly contradicted by the context.

[0056] Although the preferred embodiments of the present disclosure have been described herein, improvements and modifications may be incorporated without departing from the scope of the following claims.

Claims

1. A security document (10) comprising: - a substrate (1) having a first side (S1) and a second side (S2) opposite to the first side in a thickness direction (d) of the substrate (1), the substrate (1) including a plurality of substrate layers (31, 32, 33, 34) laminated with each other; and - a first security element (40) embedded in the substrate (1), - wherein the plurality of substrate layers (31, 32, 33, 34) includes a first substrate layer (31) that is opaque when viewed from the first side (S1) under light of a first wavelength range, the first substrate layer (31) including a first plurality of openings (42), - the first security element (40) is provided below the first substrate layer (31) in the thickness direction (d) such that it does not overlap the first plurality of openings (42) when viewed along the thickness direction, and - the first security element (40) is disposed such that it is not visible via the plurality of openings (42) when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at a first observation angle, and visible via the plurality of first openings (42) when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at a second observation angle different from the first observation angle.

2. The security document of claim 1, wherein the first security element (40) includes a second plurality of openings (44) that is aligned with the first plurality of openings (42), preferably, wherein the second plurality of openings (44) have a same size as the first plurality of openings (42).

3. The security document of claim 1 or 2, wherein the plurality of substrate layers (31, 32, 33, 34) includes a spacer substrate layer (32) arranged between the first substrate layer (31) and the first security element (40) in the thickness direction (d), preferably, wherein the spacer substrate layer (32) has a thickness of between 20 µm and 100 µm, more preferably between 40 µm and 60 µm.

4. The security document of any one of claims 1 to 3, wherein the first security element (40) is configured as a first layer of material (46) that is applied on a first surface (33a) of a second substrate layer (33) of the plurality of substrate layers (31, 32, 33, 34), preferably by screen printing, offset printing, flexographic printing, hot-stamping of a metallic foil, or applying a Diffractive Optically Variable Image Device (DOVID), the first layer of material (46) emitting light of a first wavelength in the visible range upon irradiation with the light of the first wavelength range.

5. The security document of any one of claims 1 to 4, further comprising a second security element (50) embedded in the substrate (1), the second security element (50) being visible through the first plurality of openings (42) when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at the first observation angle.

6. The security document of claim 5, wherein the second security element (50) is formed by one of the plurality of substrate layers (31, 32, 33, 34).

7. The security document of claim 5 or 6, wherein the first plurality of openings (42) form an image (4), preferably a personalized image, the image (4) having different appearances, preferably different colors, when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at the first observation angle and at the second observation angle, respectively.

8. The security document of any one of claims 1 to 7, further comprising a third security element (60) embedded in the substrate (1), the third security element (60) being visible through the first plurality of opening (42) when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at a third observation angle different from the first observation angle and the second observation angle, and not being visible when the security document (10) is viewed from the first side (S1) under the light of the first wavelength range at the first observation angle and the second observation angle.

9. The security document of claim 8, wherein the third security element (60) is configured as a second layer of material (62) that is applied on a second surface (33a, 33b) of a third substrate layer (33) of the plurality of substrate layers (31, 32, 33, 34), preferably by screen printing, offset printing, flexographic printing, hot-stamping of a metallic foil, or applying a Diffractive Optically Variable Image Device (DOVID), the second layer of material (62) emitting light of a second wavelength in the visible range upon irradiation with the light of the first wavelength range.

10. The security document of any one of claims 1 to 9, wherein the first plurality of openings (42) is formed by a plurality of through holes (43) penetrating the substrate (1) from the first side (S1) to the second side (S2).

11. The security document of any one of claims 1 to 9, wherein the first plurality of openings (42) is defined by an opaque layer of material (39) that is applied onto a surface (31a) of the first substrate layer (31), preferably, a transparent first substrate layer (31).

12. The security document of any one of claims 1 to 11, further comprising a second substrate layer (34) that is opaque when viewed under the light of the first wavelength range, the second substrate layer (34) being arranged below the first security element (40) in the thickness direction (d).

13. The security document of any one of claims 1 to 12, wherein each of the first plurality of openings (42) has a size of between 20 µm and 5 mm, preferably between 50 µm and 200 µm.

14. The security document of any one of claims 1 to 13, wherein the first wavelength range is in one of the ultraviolet (UV) range and the infrared (IR) range, and the first security element (40) emits light in the visible range upon excitation with the light of the first wavelength range.

15. The security document of any one of claims 1 to 14, wherein the first observation angle is along the thickness direction (d), and the second observation angle is between 1° and 45° to the thickness direction (d), preferably, between 5° and 45° to the thickness direction (d), more preferably, between 10° and 30° to the thickness direction (d).

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