Document with a security feature

Abstract

Document (100) with a security feature, comprising: a first substrate layer (103) having a first substrate layer region (105), wherein the substrate layer region (105) is impregnated with a black fluid over the entire thickness of the first substrate layer (103), the black fluid having carbon particles; a second substrate layer (107) with a second substrate layer region (109), wherein the second substrate layer (107) is arranged above the first substrate layer (103), the second substrate layer region (109) having a light reflection characteristic which differs from a light reflection characteristic of the first substrate layer region (105), wherein the first substrate layer region (105) and the second substrate layer region (109) form a composite security feature.

Description

[0001] The present invention relates to a document with a security feature, a method for verifying the authenticity of the document and a method for producing the document.

[0002] Documents such as passports or banknotes often use security features to verify their authenticity. A large proportion of forgeries of these documents and their security features, known as impression forgeries, are frequently produced using household duplicating devices such as inkjet or laser printers.

[0003] It is therefore an object of the present invention to provide a document with a security feature which is difficult to forge using household duplicating devices, and to provide appropriate methods for verifying and producing the document.

[0004] This task is solved by the features of the independent claims. Advantageous further developments are the subject of the dependent patent claims, the description, and the drawings.

[0005] According to a first aspect, the problem according to the invention is solved by a document with a security feature comprising: a first substrate layer having a first substrate layer region, wherein the substrate layer region is impregnated with a black fluid over the entire thickness of the first substrate layer, the black fluid comprising carbon particles; a second substrate layer with a second substrate layer region, wherein the second substrate layer is arranged above the first substrate layer, wherein the second substrate layer region has a light reflection characteristic which differs from a light reflection characteristic of the first substrate layer region, wherein the first substrate layer region and the second substrate layer region form a composite security feature.

[0006] This achieves the technical advantage that the composite security feature formed by the first and second substrate layer regions can be used to verify the document's authenticity. The light reflection characteristics, particularly those of the first substrate layer region, can be predetermined or selected such that they are still achievable when the document is produced using a designated device, but not by ordinary household copying devices when attempting to produce the document, for example, in a counterfeiting attempt. For instance, household copying devices such as inkjet or laser printers, which are typically designed for white substrates, may not achieve the required light reflection characteristics in the first substrate layer region impregnated with the black fluid.

[0007] The carbon particles can be designed to absorb IR light, which can be used to verify the authenticity of the document. The second substrate layer can be applied to the first substrate layer, particularly by means of screen printing.

[0008] The first substrate layer can have a thickness between 50 µm and 100 µm, preferably between 60 µm and 90 µm, and particularly preferably between 70 µm and 80 µm.

[0009] The first substrate layer can have a basis weight between 130 g / m² and 150 g / m².

[0010] The document can be one of the following: a personal identity card, a passport, an access control card, an authorization card, a company ID card, a tax stamp, a ticket, a birth certificate, a driver's license, a vehicle registration document, or a means of payment, such as a banknote, a bank card, or a credit card.

[0011] According to one embodiment, a first hue value of light reflected by the first substrate layer region differs from a second hue value of light reflected by the second substrate layer region, wherein the first hue value defines the light reflection characteristic of the first substrate layer region, and wherein the second hue value defines the light reflection characteristic of the second substrate layer region.

[0012] This achieves the technical advantage that the light reflection characteristics can be efficiently captured by a user and / or a device for automatic document verification.

[0013] The light reflected by the first substrate layer can have a first hue defined by its wavelength, to which the first hue value is assigned. The first hue can be black. The light reflected by the second substrate layer can have a second hue defined by its wavelength, to which the second hue value is assigned. The second hue can be gray. The first and second hue values ​​can depend on the color model used. The corresponding hue value can be, for example, an RGB value, a CMYK value, or a value from another color model.

[0014] According to one embodiment, the difference between the first hue value and the second hue value does not exceed a predetermined hue threshold.

[0015] The predetermined hue threshold can be set or chosen such that a device intended for producing the document will not exceed the predetermined hue threshold, but ordinary household copying devices will exceed the predetermined hue threshold when attempting to produce the document, for example, when attempting to forge it. For instance, household copying devices such as inkjet or laser printers may typically be designed for white substrates and may not achieve the first and / or second hue value of the document on dark substrates. The difference can be calculated, for example, as the square root of the sum of the squares of the individual RGB differences. More generally, the difference can be a scalar.

[0016] The predetermined hue threshold can be a first hue threshold. The difference between the first hue value and the second hue value can exceed a second predetermined hue threshold, which can be greater than zero and less than the first hue threshold.

[0017] According to one embodiment, the black fluid has a predetermined volume fraction of carbon particles, such that the first shade value of the impregnated first substrate layer area has, in some areas or on average, an L-value according to ISO 5631-2 that is less than 24.

[0018] This achieves the technical advantage that the light reflection characteristic of the first substrate layer area can have such a dark, especially black, hue value due to the impregnation of the first substrate layer area with the carbon particle-containing fluid that ordinary household duplicating devices can no longer achieve this hue value in a copy of the first substrate layer area.

[0019] According to one embodiment, the second hue value of the second substrate layer area has an average L-value according to ISO 5631-2 that is greater than 24.

[0020] This achieves the technical advantage that the second color value can be efficiently detected by a user and / or a device for checking the document.

[0021] According to one embodiment, the second substrate layer area has further particles which reflect or absorb the incident light with a predetermined wavelength to produce the second hue value, wherein the further particles are arranged in a pattern that forms a further security feature.

[0022] This achieves the technical advantage that the security feature formed by the additional particles can be used to verify the authenticity of the document.

[0023] According to one embodiment, the additional security feature is an alphanumeric character, in particular a nominal value, a graphic code and / or a pattern of the document.

[0024] This achieves the technical advantage that the additional security feature can be efficiently checked manually and / or automatically.

[0025] According to one embodiment, the first substrate layer area is also UV light reflective.

[0026] This achieves the technical advantage that the reflection of incident UV light at the first substrate layer area can be used to verify the authenticity of the document.

[0027] According to one embodiment, the first substrate layer area is covered with a UV-reflecting layer.

[0028] This achieves the technical advantage that the reflection of incident UV light at the UV-reflective layer can be used to verify the authenticity of the document.

[0029] According to one embodiment, the black fluid also contains UV-reflecting pigments.

[0030] This achieves the technical advantage that the reflection of incident UV light by the UV-reflecting pigments can be used to verify the authenticity of the document.

[0031] According to one embodiment, the first substrate layer area extends over the entire first substrate layer.

[0032] This achieves the technical advantage that the entire first substrate layer can be captured to verify the authenticity of the document.

[0033] According to one embodiment, the first substrate layer area has a particle arrangement of carbon particles, wherein the particle arrangement forms a predetermined particle pattern.

[0034] This achieves the technical advantage that the particle arrangement can be compared with a reference particle arrangement in a reference image, particularly via light absorption in the visible spectrum and / or IR spectrum, to verify the authenticity of the document.

[0035] According to one embodiment, the first substrate layer is completely impregnated with the fluid.

[0036] This achieves the technical advantage of efficient production of the first substrate layer. For example, the requirements for the first substrate layer regarding the degree of contamination before impregnation are low, so that even used documents such as banknotes can be used efficiently for document production.

[0037] According to one embodiment, the first substrate layer region has at least one sub-region which is free of the black fluid.

[0038] This achieves the technical advantage that a further difference in light reflection characteristics, and especially color values, between the sub-area and the remainder of the first substrate layer area impregnated with the black fluid can be detected to verify the authenticity of the document.

[0039] According to one embodiment, the subregion of the first substrate layer region free of the black fluid reflects a reflected light with a third hue when exposed to incident visible light, wherein the first substrate layer region has at least one further subregion which is completely impregnated with the black fluid, wherein the further subregion reflects a further reflected light with a first hue when exposed to incident visible light, wherein the first hue gradually transitions into the third hue in a transition region between the subregion and the further subregion; and / or wherein the first hue and the third hue form a contrast at a surface boundary between the subregion and the further subregion.

[0040] If the first color value gradually transitions into the third color value in the transition area between the sub-area and the next sub-area, then the technical advantage is achieved that the gradual transition of the surface area tonal values ​​in the transition area can be detected in order to verify the authenticity of the document.

[0041] If the first hue value and the second hue value form a contrast at the surface boundary between the sub-area and the further sub-area, then the technical advantage is achieved that the contrast at the surface boundary can be detected in order to verify the authenticity of the document.

[0042] According to one embodiment, the second substrate layer area overlaps the sub-area and the further sub-area, with the second hue value being different from the third hue value.

[0043] This provides the technical advantage that a further difference between the third color value and the first color value can be detected, in comparison to the difference between the second color value and the first color value, for verifying the authenticity of the document.

[0044] According to one embodiment, the first substrate layer comprises cotton or is formed from cotton.

[0045] This offers the technical advantage of efficiently producing the first substrate layer for documents, making it particularly sustainable and / or durable. For example, the first substrate layer can contain or consist of cotton fibers.

[0046] According to one embodiment, the second substrate layer is a polymer layer, in particular a plastic layer, or a paint layer.

[0047] If the second substrate layer is a polymer layer, then the technical advantage is achieved that it can be particularly resistant to damage and / or manipulation.

[0048] If the second substrate layer is a color layer, then the technical advantage is achieved that it can be applied particularly efficiently.

[0049] According to one embodiment, the first substrate layer is connected to a support layer, wherein the document has a third substrate layer which is connected to the support layer, the support layer being arranged between the first substrate layer and the third substrate layer.

[0050] This achieves the technical advantage of producing an efficient multi-layered document. The third substrate layer can be identical to the first or different. For example, the third substrate layer can be free of the black fluid, or the black fluid can have a different volume fraction than the first substrate layer. The document can thus, for instance, have the same or different security features on both sides.

[0051] The substrate layer can be a polymer layer, in particular a plastic layer. The substrate layer can have a thickness between 25 µm and 75 µm, preferably between 35 µm and 65 µm, and particularly preferably between 45 µm and 55 µm.

[0052] The third substrate layer can have a thickness between 50 µm and 100 µm, preferably between 60 µm and 90 µm, and particularly preferably between 70 µm and 80 µm.

[0053] The third substrate layer can have a basis weight between 130 g / m² and 150 g / m².

[0054] According to one embodiment, the first substrate layer area impregnated with the black fluid is opaque to visible light and / or IR light.

[0055] This provides the technical advantage of being able to detect the opacity to visible light and / or IR light in order to verify the authenticity of the document.

[0056] According to one embodiment, the first substrate layer, and in particular the third substrate layer, is coated with a protective layer, in particular a transparent varnish, or is free of a protective layer.

[0057] If the first substrate layer, and especially the third substrate layer, is coated with a protective layer, this offers the technical advantage of making the corresponding substrate layer particularly resistant to damage and / or tampering. The protective layer can be designed to exhibit characteristic wear patterns, which can be used to verify the authenticity of the document.

[0058] If the first substrate layer, and especially the third substrate layer, is free from a protective layer, then the technical advantage is achieved that the document can be produced efficiently, especially in a resource-saving manner.

[0059] According to a second aspect, the problem according to the invention is solved by a method for verifying the authenticity of the document according to the first aspect, comprising: illuminating the document with visible light; capturing light reflected from the document in an image of the document; capturing the light reflection characteristics of the first substrate layer area and the second substrate layer area in the captured image; comparing a difference between the light reflection characteristics of the first substrate layer area and the second substrate layer area with a reference value, wherein the authenticity of the document is confirmed if the difference corresponds with the reference value.

[0060] This offers the advantage of efficient document verification. Illuminating the document can be achieved, for example, using a light-emitting diode (LED) in a verification device. Capturing the light reflected from the document and forming an image can be done, for example, using a camera in the verification device.

[0061] According to a third aspect, the problem according to the invention is solved by a method for producing a document with a security feature, comprising: providing a first substrate layer; impregnating a first substrate layer region of the first substrate layer over the entire thickness of the first substrate layer with a black fluid, wherein the black fluid comprises carbon particles; providing a second substrate layer with a second substrate layer region, wherein the second substrate layer region has a light reflection characteristic that differs from a light reflection characteristic of the first substrate layer region; arranging the second substrate layer on the first substrate layer, wherein the second substrate layer region is arranged above the first substrate layer region, and wherein the first substrate layer region and the second substrate layer region form a composite security feature.

[0062] This offers the advantage of efficient document production. The second substrate layer can be applied to the first substrate layer, particularly using screen printing.

[0063] The method may further include determining the light reflection characteristics, so that a device intended for the production of the document still achieves the light reflection characteristics, but ordinary household duplicating devices no longer achieve the light reflection characteristics when attempting to produce the document, for example, when attempting to forge the document.

[0064] The embodiments of the document described above and below according to the first aspect are also embodiments of the method according to the second aspect and the method according to the third aspect.

[0065] The embodiments of the method described above and below according to the second aspect are also embodiments of the document according to the first aspect and of the method according to the third aspect.

[0066] The embodiments of the method described above and below according to the third aspect are also embodiments of the document according to the first aspect and of the method according to the second aspect.

[0067] Further examples of implementation are explained in more detail with reference to the accompanying drawings. These show: Fig. 1 is a schematic representation of a document with a security feature according to one embodiment in a perspective view; Fig. 2 is a schematic representation of a document with a security feature according to one embodiment in a perspective view; Fig. 3 is a schematic representation of a document with a security feature according to one embodiment in a perspective view; Fig. 4 is a schematic flowchart of a method for verifying the authenticity of a document according to one embodiment; and Fig. 5 is a schematic flowchart of a method for producing a document according to one embodiment.

[0068] Fig. 1Figure 1 shows a schematic representation of a document 100 with a security feature according to an embodiment in a perspective view. The transverse direction 101-1 of the document 100, the longitudinal direction 101-2 of the document 100, and the vertical direction 101-3 of the document 100 are shown in the Figure 1 schematically represented.

[0069] Document 100 comprises a first substrate layer 103. The first substrate layer 103 may comprise cotton or be formed from cotton. The first substrate layer 103 may be completely impregnated with a fluid. The first substrate layer area 105 may also be UV light reflective.

[0070] The first substrate layer 103 has a first substrate layer region 105 with a light reflection characteristic. The first substrate layer region 105 is impregnated with the black fluid over the entire thickness, i.e., in the vertical direction 101-3 of the document 100, of the first substrate layer 103. The first substrate layer region 105 can extend over the entire first substrate layer 103, i.e., along the transverse direction 101-1 and longitudinal direction 101-2 of the document 100, or, as shown in the Fig. 1 shown, extending over a part of the first substrate layer 103. The first substrate layer area 105 can be described as follows: Fig. 1 The first substrate layer area 105, impregnated with the black fluid, may be covered by a UV-reflecting layer not shown. Furthermore, it may be opaque to visible light and / or IR light.

[0071] The black fluid contains carbon particles, so that the first substrate layer region 105 impregnated with the black fluid can reflect an initial reflected light with a first hue value when exposed to incident visible light. This first reflected light can thus exhibit a first hue defined by its wavelength, to which the first hue value is assigned. The first hue value can define the light reflection characteristics of the first substrate layer region 103. The first hue can be black.

[0072] The black fluid can have a predetermined volume fraction of carbon particles such that the first hue value of the impregnated first substrate layer area 105 has, in some areas or on average, an L-value according to ISO 5631-2 that is less than 24. The carbon particles can be configured to absorb IR light. The first substrate layer area 105 can have a particle arrangement of the carbon particles forming a predetermined particle pattern. The black fluid can also contain UV-reflecting pigments.

[0073] Document 100 comprises a second substrate layer 107 with a second substrate layer area 109, which can be arranged above the first substrate layer area 105. Even if this is in the Fig. 1Not shown, the second substrate layer 107 may only cover part of the first substrate layer 103 and / or have further substrate layer areas that are light-transparent.

[0074] The second substrate layer 107 can be a polymer layer, in particular a plastic layer, or a color layer. The second substrate layer region 109 has a light reflection characteristic that differs from the light reflection characteristic of the first substrate layer region (105). The second substrate layer region 109 can be free of the black fluid and reflect a second reflected light with a second hue when exposed to incident visible light. This second reflected light can thus have a second hue defined by its wavelength, to which the second hue value is assigned. The second hue value can define the light reflection characteristic of the second substrate layer region 109. The second hue can be a shade of gray. The second hue value of the second substrate layer region 109 can have an average L-value according to ISO 5631-2 that is greater than 24.The first hue value of light reflected through the first substrate layer area 103 may differ from the second hue value of light reflected through the second substrate layer area 107.

[0075] The second substrate layer area 109 may contain further particles that reflect or absorb the incident light at a predetermined wavelength to produce the second color value. These further particles may be arranged in a pattern that forms an additional security feature. This additional security feature may be an alphanumeric character, in particular a nominal value, a graphic code, and / or a pattern of the document.

[0076] The first substrate layer area 105 and the second substrate layer area 109 form a composite security feature. The difference between the first and second hue values ​​cannot exceed a predetermined hue threshold.

[0077] The second substrate layer 107 can further comprise a further substrate layer region 111, which is arranged above the first substrate layer region 105. The further substrate layer region 111 can be, as shown in the Figure 1 as shown, may be formed non-overlapping with the second substrate layer area 109. Alternatively, the further substrate layer area 111 may be formed, even if this is shown in the Figure 1 not shown, it may be formed overlapping with the second substrate layer area 109.

[0078] The further substrate layer area 111 can be free of the black fluid and reflect a further reflected light with a different hue when exposed to the incident visible light. This further hue can differ from the second hue, in particular, it can differ slightly from the second hue.

[0079] The first substrate layer area 105, the second substrate layer area 109 and the further substrate layer area 111 can form the composite security feature, wherein a difference between the second hue value and the further hue value can be within a predetermined hue interval and, in particular, can be greater than zero.

[0080] Fig. 2Figure 1 shows a schematic representation of a document 100 with a security feature according to an embodiment in a perspective view. The transverse direction 101-1 of the document 100, the longitudinal direction 101-2 of the document 100, and the vertical direction 101-3 of the document 100 are shown in the Figure 2 schematically represented. To avoid repetition, the following section will explain the differences between the two. Fig. 2 Document 100 shown, relating to the one in Fig. 1 The document shown is described in section 100.

[0081] As in the Fig. 2 The first substrate layer region 105 can, as shown, have at least one subregion 113. This subregion 113 can be free of the black fluid and, in the case of incident visible light, reflect a third reflected light with a third hue. This third reflected light can thus have a third hue defined by its wavelength, to which the third hue value is assigned.

[0082] The first substrate layer region 105 can have at least one further sub-region 115, which is completely impregnated with the black fluid. This further sub-region 115 can reflect the first reflected light with the first color value from the incident visible light. As in the Fig. 2 As shown, the second substrate layer area 109 can extend over or overlap with sub-area 113 and the further sub-area 115. The second color value can differ from the third color value.

[0083] The first hue value can gradually transition into the third hue value in a transition zone 117 between subzone 113 and the further subzone 115. Alternatively or additionally, the first hue value and the third hue value can form a contrast at a surface boundary 119 between subzone 113 and the further subzone 115.

[0084] Fig. 3 Figure 1 shows a schematic representation of a document 100 with a security feature according to an embodiment in a perspective view. The transverse direction 101-1 of the document 100, the longitudinal direction 101-2 of the document 100, and the vertical direction 101-3 of the document 100 are shown in the Figure 3 schematically represented. To avoid repetition, the following section will explain the differences between the two. Fig. 3 Document 100 shown, relating to the one in Fig. 1 The document shown is described in section 100.

[0085] As in the Fig. 3As shown, the first substrate layer 103 can be connected to a support layer 121. The document 100 can have a third substrate layer 123, which is connected to the support layer 121. The support layer 121 can be arranged between the first substrate layer 103 and the third substrate layer 123. A fourth substrate layer 125 can be arranged on top of the third substrate layer 123.

[0086] The third substrate layer 123 can be in the Fig. 3The third substrate layer region, not shown, is impregnated with the black fluid or alternatively free of the black fluid, such that the third substrate layer region impregnated with the black fluid or free of the fluid reflects a third reflected light with a third hue value when exposed to incident visible light. The third hue value can be the same as the first hue value or different from the first hue value, for example, based on the same or different volume fraction of the carbon particles of the fluid for the first substrate layer region 105 and for the third substrate layer region.

[0087] The fourth substrate layer 125 can be in the Fig. 3The fourth substrate layer region 109 (not shown) is arranged above the first substrate layer region 105, wherein the fourth substrate layer region is free of the black fluid and reflects a fourth reflected light with a fourth hue value when exposed to the incident visible light. The fourth hue value can be the same as the second hue value or slightly different from the second hue.

[0088] The third and fourth substrate layer regions can form a further composite security feature, where the further difference between the third and fourth hue values ​​does not exceed a predetermined further hue threshold. This further difference between the third and fourth hue values ​​can be greater than the difference between the first and second hue values. The further hue threshold can also be greater than the first hue threshold.

[0089] Even if this is in the Fig. 3 Unless shown, the first substrate layer 103, and in particular the third substrate layer 123, may be coated with a protective layer, in particular a transparent varnish, or may be free of a protective layer.

[0090] Fig. 4shows a schematic flowchart of a procedure 400 for verifying the authenticity of a document 100 according to an embodiment.

[0091] Procedure 400 includes illuminating 401 the document 100 with visible light.

[0092] Method 400 further comprises capturing 403 a light reflected from document 100 in an image of document 100.

[0093] The method 400 further comprises a detection 405 of the light reflection characteristics of the first substrate layer area 105 and the second substrate layer area 109 in the detected image.

[0094] The procedure 400 further comprises comparing 407 a difference between the light reflection characteristics of the first substrate layer area 105 and the second substrate layer area 109 with a reference value, confirming the authenticity of the document 100 if the difference matches the reference value.

[0095] Fig. 5 shows a schematic flowchart of a process 500 for producing a document 100 with a security feature according to an embodiment.

[0096] The process 500 includes providing 501 a first substrate layer 103.

[0097] The process 500 comprises a permeation 503 of a first substrate layer area 105 of the first substrate layer 103 over the entire thickness of the first substrate layer 103 with a black fluid, wherein the black fluid has carbon particles.

[0098] The method 500 comprises providing 505 a second substrate layer 107 with a second substrate layer area 109, wherein the second substrate layer area 109 has a light reflection characteristic which differs from a light reflection characteristic of the first substrate layer area 105.

[0099] Method 500 comprises arranging 507 the second substrate layer 107 on the first substrate layer 103, wherein the second substrate layer area 109 is arranged above the first substrate layer area 105, wherein the first substrate layer area 105 and the second substrate layer area 109 form a composite security feature.

[0100] It is self-evident that the features of the various exemplary embodiments described herein, in particular the embodiments of Figure 1 , 2 and 3The elements can be combined with one another unless specifically stated otherwise. As shown in the description and drawings, individual elements depicted in conjunction need not be directly connected to one another; intermediate elements may be provided between the connected elements. The term "for example" is meant merely as an example and not as the best or optimal. Certain embodiments have been illustrated and described herein, but it is obvious to the person skilled in the art that a multitude of alternative and / or similar implementations can be realized instead of the embodiments shown and described without departing from the concept of the present invention.

[0101] All features shown or described in connection with individual embodiments of the invention can be provided in any combination in the object according to the invention in order to simultaneously realize their advantageous effects. REFERENCE MARK LIST

[0102] 100 Document 101-1 Transverse direction of the document 101-2 Longitudinal direction of the document 101-3 Vertical direction of the document 103 First substrate layer 105 First substrate layer area 107 Second substrate layer 109 Second substrate layer area 111 Further substrate layer area 113 Sub-area of ​​the first substrate layer area 115 Further sub-area of ​​the first substrate layer area 117 Transition area 119 Surface boundary 121 Support layer 123 Third substrate layer 125 Fourth substrate layer 400 Method for verifying the authenticity of a document 401 Illuminating the document with visible light 403 Detecting light reflected from the document 405 Detecting the light reflection characteristics 407 Comparing a difference 500 Method for producing a document 501 Providing a first substrate layer 503 Impregnating a first Substrate layer area 505 Providing a second substrate layer 507 Arranging the second substrate layer on top of the first substrate layer

Claims

1. Document (100) with a security feature, comprising: a first substrate layer (103) having a first substrate layer region (105), wherein the substrate layer region (105) is impregnated with a black fluid over the entire thickness of the first substrate layer (103), the black fluid having carbon particles; a second substrate layer (107) with a second substrate layer region (109), wherein the second substrate layer (107) is arranged above the first substrate layer (103), the second substrate layer region (109) having a light reflection characteristic which differs from a light reflection characteristic of the first substrate layer region (105), wherein the first substrate layer region (105) and the second substrate layer region (109) form a composite security feature.

2. Document (100) according to claim 1, wherein a first hue value of light reflected by the first substrate layer region (103) differs from a second hue value of light reflected by the second substrate layer region (107), wherein the first hue value defines the light reflection characteristic of the first substrate layer region (103), and wherein the second hue value defines the light reflection characteristic of the second substrate layer region (109).

3. Document (100) according to claim 1 or 2, wherein the difference between the first hue value and the second hue value does not exceed a predetermined hue threshold.

4. Document according to claim 2 or 3, wherein the black fluid has a predetermined volume fraction of carbon particles such that the first hue value of the impregnated first substrate layer area (105) has, in some areas or on average, an L-value according to ISO 5631-2 that is less than 24.

5. Document according to any one of claims 2 to 4, wherein the second hue value of the second substrate layer area (109) has an average L-value according to ISO 5631-2 that is greater than 24.

6. Document (100) according to one of the preceding claims, wherein the second substrate layer region (109) comprises further particles which reflect or absorb the incident light with a predetermined wavelength in order to generate, in particular, the second hue value, wherein the further particles are arranged in a pattern which forms a further security feature.

7. Document according to claim 6, wherein the further security feature is an alphanumeric character, in particular a nominal value, a graphic code and / or a pattern of the document.

8. Document (100) according to one of the preceding claims, wherein the first substrate layer region (105) is furthermore UV light reflective.

9. Document (100) according to one of the preceding claims, wherein the first substrate layer region (105) is covered with a UV-reflecting layer.

10. Document (100) according to one of the preceding claims, wherein the black fluid further comprises UV-reflecting pigments.

11. Document (100) according to one of the preceding claims, wherein the first substrate layer region (105) extends over the entire first substrate layer (103).

12. Document (100) according to one of the preceding claims, wherein the first substrate layer region (105) has a particle arrangement of the carbon particles, wherein the particle arrangement forms a predetermined particle pattern.

13. Document (100) according to one of the preceding claims, wherein the first substrate layer (103) is completely impregnated with the black fluid.

14. Document (100) according to one of claims 1 to 12, wherein the first substrate layer region (105) has at least one sub-region (113) which is free of the black fluid.

15. Document (100) according to claim 14, wherein the sub-region (113) of the first substrate layer region (105) free of the black fluid reflects a reflected light with a third hue value when exposed to incident visible light, wherein the first substrate layer region (105) has at least one further sub-region (115) which is completely impregnated with the black fluid, wherein the further sub-region (115) reflects a further reflected light with a first hue value when exposed to incident visible light, wherein the first hue value gradually transitions into the third hue value in a transition region (117) between the sub-region (113) and the further sub-region (115); and / or wherein the first hue value and the third hue value form a contrast at a surface boundary (119) between the sub-region (113) and the further sub-region (115).

16. Document according to claim 14 or 15, wherein the second substrate layer area overlaps the sub-area (113) and the further sub-area (115), wherein the second hue value is different from the third hue value.

17. Document (100) according to any of the preceding claims, wherein the first substrate layer (103) comprises cotton or is formed from cotton.

18. Document (100) according to one of the preceding claims, wherein the second substrate layer (107) is a polymer layer, in particular a plastic layer, or a color layer.

19. Document (100) according to one of the preceding claims, wherein the first substrate layer (103) is connected to a support layer (121), wherein the document (100) has a third substrate layer (123) which is connected to the support layer (121), wherein the support layer (121) is arranged between the first substrate layer (103) and the third substrate layer (123).

20. Document (100) according to one of the preceding claims, wherein the first substrate layer region (105) impregnated with the black fluid is opaque to visible light and / or IR light.

21. Document (100) according to one of the preceding claims, wherein the first substrate layer (103), and in particular the third substrate layer (123), is coated with a protective layer, in particular a transparent varnish, or is free of a protective layer.

22. Method (400) for verifying the authenticity of the document (100) according to any one of claims 1 to 21, comprising: illuminating (401) the document (100) with visible light; capturing (403) any light reflected from the document (100) in an image of the document (100); capturing (405) the light reflection characteristics of the first substrate layer region (105) and the second substrate layer region (109) in the captured image; comparing (407) any difference between the light reflection characteristics of the first substrate layer region (105) and the second substrate layer region (109) with a reference value, wherein the authenticity of the document (100) is confirmed if the difference matches the reference value.

23. Method (500) for producing a document (100) with a security feature, comprising: providing (501) a first substrate layer (103); impregnating (503) a first substrate layer region (105) of the first substrate layer (103) over the entire thickness of the first substrate layer (103) with a black fluid, wherein the black fluid has carbon particles; providing (505) a second substrate layer (107) with a second substrate layer region (109), wherein the second substrate layer region (109) has a light reflection characteristic which differs from a light reflection characteristic of the first substrate layer region (105);Arranging (507) the second substrate layer (107) on the first substrate layer (103), wherein the second substrate layer area (109) is arranged above the first substrate layer area (105), the first substrate layer area (105) and the second substrate layer area (109) forming a composite security feature.

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