Document with a security feature

Abstract

Document (100) with a security feature, comprising: a first substrate layer (103), wherein the first substrate layer (103) has a first substrate layer region (105) which is completely impregnated with an infrared-absorbing fluid, wherein the first substrate layer region (105) has microperforations (111a-c) which form a perforation pattern; a second substrate layer (107), wherein the second substrate layer (107) is arranged on the first substrate layer (103), wherein the second substrate layer (107) has a second substrate layer region (109), wherein the second substrate layer region (109) and the first substrate layer region (105) are aligned with each other, and wherein the second substrate layer region (109) is formed to be more transparent to infrared light than the infrared-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region (105);and wherein the first substrate layer region (105) and the second substrate layer region (109) form a composite infrared 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 watermarks as a security feature, which can be checked by a user, for example, under transmitted light. Methods for forging common watermarks may already be known to counterfeiters.

[0003] It is therefore an object of the present invention to provide a document with a security feature that is particularly difficult to forge, as well as 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, wherein the first substrate layer has a first substrate layer region which is completely impregnated with an infrared-absorbing fluid, wherein the first substrate layer region has microperforations which form a perforation pattern; a second substrate layer, wherein the second substrate layer is arranged on the first substrate layer, wherein the second substrate layer has a second substrate layer region, wherein the second substrate layer region and the first substrate layer region are aligned with each other, and wherein the second substrate layer region is formed to be more transparent to infrared light than the infrared-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region;and wherein the first substrate layer area and the second substrate layer area form a composite infrared security feature.

[0006] This achieves the technical advantage that the composite infrared security feature can represent a distinctive security feature which, due to a characteristic combination of IR transmission through the perforation pattern and IR absorption at the first substrate layer, is particularly difficult to counterfeit. The distinctive security feature can be defined by the perforation pattern. An infrared image generated by irradiation with infrared light can, for example, be compared manually and / or by a verification device with a reference image to verify the authenticity of the document.

[0007] The microperforations can have a diameter of up to 0.55 mm.

[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 second substrate layer may be partially impregnated with the infrared-absorbing fluid, particularly outside the second substrate layer area, or with a lower proportion than the first substrate layer area.

[0011] 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.

[0012] According to one embodiment, the second substrate layer area includes a recess which is aligned with the microperforations of the first substrate layer area.

[0013] This achieves the technical advantage that infrared light can pass through the opening to the first substrate layer area.

[0014] According to one embodiment, the second substrate layer area is free of the infrared light-absorbing fluid.

[0015] This achieves the technical advantage that infrared light is absorbed less or not at all by the second substrate layer area.

[0016] According to one embodiment, the infrared-absorbing fluid contains carbon particles.

[0017] This offers the technical advantage that the properties of the carbon particles can be used to detect, for example by spectroscopy, the dye impregnation. The characteristic absorption of the carbon particles can be used to verify the authenticity of the document, for example by spectroscopy based on the absorption maximum in the carbon absorption band.

[0018] The infrared-absorbing fluid can have a predetermined volume fraction of carbon, where a shade of the first substrate layer area impregnated with the infrared-absorbing fluid has an L-value according to ISO 5631-2 that is less than 24.

[0019] According to one embodiment, the second substrate layer area has further particles which reflect or absorb incident light with a wavelength outside the infrared light range.

[0020] This achieves the technical advantage that reflection or absorption of the incident light at a wavelength outside the infrared light range can be used to verify the authenticity of the document.

[0021] According to one embodiment, the additional particles are arranged in a pattern that forms a further security feature.

[0022] This achieves the technical advantage that the pattern of the additional particles can be used with a pattern, reflection, or absorption of a reference image to verify the authenticity of the document.

[0023] According to one embodiment, the perforation pattern forms at least one alphanumeric character, in particular a nominal value and / or a graphic code of the document.

[0024] This provides the technical advantage that the perforation pattern can be efficiently checked manually and / or automatically.

[0025] According to one embodiment, the microperforations are covered with an infrared-light-transparent protective film.

[0026] This achieves the technical advantage that the microperforations can be particularly resistant to contamination and / or tampering. The protective film can be designed to exhibit characteristic wear patterns, which can be used to verify the authenticity of the document.

[0027] According to one embodiment, the microperforations comprise a first microperforation and a second microperforation, wherein the infrared-transparent protective film has a first protective film area covering the first microperforation, wherein the first protective film area has infrared-absorbing particles configured to reduce the intensity of light in the infrared wavelength range, and wherein the infrared-transparent protective film has a second protective film area covering the second microperforation, wherein the second protective film area is free of the infrared-absorbing particles or has a lower proportion of the infrared-absorbing particles than the first protective film area.

[0028] This achieves the technical advantage that the micro-perforations can allow infrared light of varying intensity to pass through, which can be used to verify the authenticity of the document.

[0029] According to one embodiment, the first substrate layer area is also UV light reflective.

[0030] This achieves the technical advantage that the reflection of incident light at the first substrate layer area can be used to verify the authenticity of the document.

[0031] According to one embodiment, the first substrate layer area is covered with a UV-reflecting layer.

[0032] This achieves the technical advantage that the reflection of incident light at the UV-reflective layer can be used to verify the authenticity of the document.

[0033] According to one embodiment, the infrared-absorbing fluid also has UV-reflecting pigments.

[0034] This achieves the technical advantage that the reflection of incident light at the UV-reflecting pigments can be used to verify the authenticity of the document.

[0035] According to one embodiment, the first substrate layer area extends over the entire first substrate layer.

[0036] This achieves the technical advantage that the entire first substrate layer can be captured to verify the authenticity of the document.

[0037] According to one embodiment, the first substrate layer comprises cotton or is formed from cotton.

[0038] 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.

[0039] According to one embodiment, the second substrate layer is a polymer layer, in particular a plastic layer, or a paint layer.

[0040] 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.

[0041] If the second substrate layer is a color layer, then the technical advantage is achieved that it can be applied particularly efficiently.

[0042] 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, wherein the support layer is arranged between the first substrate layer and the third substrate layer, wherein the microperforations extend through the support layer or wherein the support layer has a recess which is aligned with the microperforations, and wherein the microperforations extend through the third substrate layer or wherein the third substrate layer has a recess which is aligned with the microperforations.

[0043] 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 infrared-absorbing fluid. The document can therefore have the same or different security features on both sides.

[0044] According to one embodiment, the first substrate layer is completely impregnated with the infrared-absorbing fluid.

[0045] 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.

[0046] According to one embodiment, the first substrate layer has a third substrate layer area which is free of the infrared-absorbing fluid.

[0047] This achieves the technical advantage that a difference in the absorption of IR light between the first substrate layer area and the third substrate layer area can be detected to verify the authenticity of the document.

[0048] According to one embodiment, the third substrate layer area has a first surface area tone value, wherein the first substrate layer area has a second surface area tone value, wherein the first surface area tone value gradually transitions into the second surface area tone value in a transition area between the first substrate layer area and the third substrate layer area; and / or wherein the first surface area tone value and the second surface area tone value form a contrast at a surface boundary between the first substrate layer area and the third substrate layer area.

[0049] If the first surface area tone value gradually transitions into the second surface area tone value in the transition area between the sub-area and the further sub-area, then the technical advantage is achieved that the gradual transition of the surface area tone values ​​in the transition area can be detected in order to verify the authenticity of the document.

[0050] If the first surface area tone value and the second surface area tone 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.

[0051] According to one embodiment, the second substrate layer region is aligned with at least one further microperforation of the first substrate layer, which forms part of the perforation pattern, wherein the third substrate layer region and / or the transition region and / or the surface boundary has the at least one further microperforation.

[0052] This achieves the technical advantage that the microperforations can transmit infrared light with varying contrast to the first substrate layer, which can be used to verify the authenticity of the document. For example, the contrast in the first substrate layer area can be relatively high and in the third substrate layer area relatively low. Intermediate contrasts can occur in the transition zone, and both relatively low and relatively high contrasts can be present at the surface boundary.

[0053] At least one additional microperforation can have a diameter of up to 0.55 mm.

[0054] 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 a surface of the document with infrared light; capturing the infrared light transmitted through the document at a surface of the document opposite the surface in an infrared image; comparing the infrared image with a reference infrared image, wherein the authenticity of the document is confirmed if the infrared image matches the reference infrared image.

[0055] This offers the advantage of efficient document verification. Illuminating the document can be achieved, for example, using an infrared LED in a verification device. Capturing the transmitted infrared light in the infrared image can be done, for example, using an infrared camera in the verification device. The surface can be the second substrate layer or a surface of the document opposite the second substrate layer, particularly the first substrate layer.

[0056] 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; completely impregnating a first substrate layer region of the first substrate layer with an infrared-absorbing fluid; forming microperforations in the first substrate layer region, which form a perforation pattern; providing a second substrate layer, wherein the second substrate layer has a second substrate layer region; arranging the second substrate layer on the first substrate layer, wherein the second substrate layer region and the first substrate layer region are aligned with each other, and wherein the second substrate layer region is formed to be more transparent to infrared light than the infrared-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region.

[0057] This offers the advantage of efficient document production.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 an infrared-absorbing fluid. The infrared-absorbing fluid may contain carbon particles and / or UV-reflecting pigments.

[0064] The first substrate layer 103 has a first substrate layer region 105, which is completely impregnated with the infrared-absorbing fluid. The first substrate layer region 105 can extend over, i.e., along the transverse direction 101-1 and longitudinal direction 101-2 of the document 100, the entire first substrate layer 103, or, as shown in the Fig. 1 The first substrate layer 103 is shown to extend over a portion of it. Furthermore, the first substrate layer area 105 can be UV-reflective and / or covered with a UV-reflective layer.

[0065] The first substrate layer area 105 exhibits microperforations 111a-c, which form a perforation pattern. In the Fig. 1 A perforation pattern is schematically represented in the form of a line. However, more complex patterns are also possible, such as a graphic motif, a graphic code, or a face value of the document.

[0066] The microperforations 111a-c can be covered with an infrared-transparent protective film. The microperforations 111a-c can comprise a first microperforation 111a and a second microperforation 111b. The infrared-transparent protective film can have a first protective film area covering the first microperforation 111a. This first protective film area can contain infrared-absorbing particles designed to reduce the intensity of light in the infrared wavelength range. The infrared-transparent protective film can have a second protective film area covering the second microperforation 111b. This second protective film area can be free of infrared-absorbing particles or contain a lower proportion of infrared-absorbing particles than the first protective film area.

[0067] Document 100 comprises a second substrate layer 107, which is arranged on the first substrate layer 103. The second substrate layer 107 can be a polymer layer, in particular a plastic layer, or a paint layer.

[0068] The second substrate layer 107 has a second substrate layer region 109. The second substrate layer region 109 and the first substrate layer region 105 are aligned with each other, i.e., they have, for example, a common overlapping area that includes the microperforations 111a-c. The second substrate layer region 109 is more transparent to infrared light than the infrared-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region 105.

[0069] The first substrate layer area 105 and the second substrate layer area 109 form a composite infrared security feature that can generate a predetermined infrared image when irradiated with infrared light.

[0070] The second substrate layer region 109 can contain further particles that reflect or absorb incident light with a first wavelength lying outside the infrared range. The further particles of the second substrate layer region 109 can be arranged in a pattern that forms a further security feature.

[0071] Fig. 2 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 2schematically 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.

[0072] As in the Fig. 2 schematically represented, the first substrate layer 103 can have a third substrate layer area 113 which can be free of the infrared-absorbing fluid.

[0073] The third substrate layer area 113 can have a first surface area tone value, and the first substrate layer area 105 can have a second surface area tone value. The first surface area tone value can gradually transition into the second surface area tone value in a transition area 117 between the first substrate layer area 105 and the third substrate layer area 113. Alternatively or additionally, the first surface area tone value and the second surface area tone value can contrast at a surface boundary 119 between the first substrate layer area 105 and the third substrate layer area 113.

[0074] As further in the Fig. 2As shown schematically, the second substrate layer region 109 can be aligned with at least one further microperforation 115a-c of the first substrate layer 103, which forms part of the perforation pattern. The third substrate layer region 113 and / or the transition region 117 and / or the surface boundary 119 can have at least one further microperforation 115a-c.

[0075] 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.

[0076] 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. The third substrate layer 123 can be connected to a fourth substrate layer 125.

[0077] The microperforations 111a-c can extend through the carrier layer 121. Alternatively, the carrier layer 121 can have a recess that is aligned with the microperforations 111a-c.

[0078] Furthermore, the microperforations 111a-c can extend through the third substrate layer 123, or the third substrate layer 123 can have a recess aligned with the microperforations 111a-c. The fourth substrate layer 125 can be a transparent protective layer, in particular a transparent varnish.

[0079] Fig. 4 shows a schematic flowchart of a procedure 400 for verifying the authenticity of a document 100 according to an embodiment.

[0080] The procedure 400 includes illuminating 401 a surface of the document 100 with infrared light.

[0081] Method 400 further comprises capturing 403 the infrared light transmitted through document 100 on a surface of document 100 opposite the surface in an infrared image.

[0082] The procedure 400 further comprises comparing 405 the infrared image with a reference infrared image, confirming the authenticity of the document 100 if the infrared image matches the reference infrared image.

[0083] Fig. 5 shows a schematic flowchart of a process 500 for producing a document 100 with a security feature according to an embodiment.

[0084] The process 500 includes providing 501 a first substrate layer 103.

[0085] The process 500 further comprises a complete impregnation 503 of a first substrate layer area 105 of the first substrate layer 103 with an infrared-absorbing fluid.

[0086] The process 500 further comprises forming 505 microperforations 111a-c in the first substrate layer area 105, which form a perforation pattern.

[0087] The method 500 further comprises providing 507 a second substrate layer 107 with a second substrate layer area 109.

[0088] Method 500 further comprises arranging 509 of the second substrate layer 107 on the first substrate layer 103, wherein the second substrate layer region 109 and the first substrate layer region 105 are aligned with each other, and wherein the second substrate layer region 109 is formed to be more transparent to infrared light than the infrared light-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region 105.

[0089] 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.

[0090] 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

[0091] 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 111a-c Microperforations 113 Third substrate layer area 115a-c Further microperforations 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 a surface of the document with infrared light 403 Detecting the transmitted infrared light 405 Comparing the infrared image with a reference infrared image 500 Method for producing a document 501 Providing a first substrate layer 503 Completely impregnating a first substrate layer area 505 Forming microperforations 507 Providing a second substrate layer 509 Arranging the second substrate layer on the first substrate layer

Claims

1. Document (100) with a security feature, comprising: a first substrate layer (103), wherein the first substrate layer (103) has a first substrate layer region (105) which is completely impregnated with an infrared-absorbing fluid, wherein the first substrate layer region (105) has microperforations (111a-c) which form a perforation pattern; a second substrate layer (107), wherein the second substrate layer (107) is arranged on the first substrate layer (103), wherein the second substrate layer (107) has a second substrate layer region (109), wherein the second substrate layer region (109) and the first substrate layer region (105) are aligned with each other, and wherein the second substrate layer region (109) is formed to be more transparent to infrared light than the infrared-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region (105);and wherein the first substrate layer region (105) and the second substrate layer region (109) form a composite infrared security feature.; 2. Document (100) according to claim 1, wherein the second substrate layer area (109) comprises a recess which is aligned with the microperforations (111a-c) of the first substrate layer area (105).

3. Document (100) according to claim 1 or 2, wherein the second substrate layer region (109) is free of the infrared light-absorbing fluid.

4. Document (100) according to one of the preceding claims, wherein the infrared-absorbing fluid comprises carbon particles.

5. Document (100) according to one of the preceding claims, wherein the second substrate layer region (109) comprises further particles which reflect or absorb incident light with a wavelength outside the infrared light range.

6. Document (100) according to claim 5, wherein the further particles are arranged in a pattern forming a further security feature.

7. Document (100) according to one of the preceding claims, wherein the perforation pattern forms at least one alphanumeric character, in particular a nominal value and / or a graphic code of the document (100).

8. Document (100) according to one of the preceding claims, wherein the microperforations (111a-c) are covered with an infrared light-transparent protective film.

9. Document (100) according to claim 8, wherein the microperforations (111a-c) comprise a first microperforation (111a) and a second microperforation (111b), wherein the infrared-transparent protective film has a first protective film area covering the first microperforation (111a), wherein the first protective film area comprises infrared-absorbing particles configured to reduce the intensity of light in the infrared wavelength range, and wherein the infrared-transparent protective film has a second protective film area covering the second microperforation (111b), wherein the second protective film area is free of the infrared-absorbing particles or has a lower proportion of the infrared-absorbing particles than the first protective film area.

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

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

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

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

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

15. 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 paint layer.

16. 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), wherein the microperforations (111a-c) extend through the support layer (121) or wherein the support layer (121) has a recess which is aligned with the microperforations (111a-c), and wherein the microperforations (111a-c) extend through the third substrate layer (123) or wherein the third substrate layer (123) has a recess which is aligned with the microperforations (111a-c).

17. Document (100) according to one of the preceding claims, wherein the first substrate layer (103) is completely impregnated with the infrared-absorbing fluid.

18. Document (100) according to any one of claims 1 to 16, wherein the first substrate layer (103) has a third substrate layer region (113) which is free of the infrared-absorbing fluid.

19. Document (100) according to claim 18, wherein the third substrate layer region (113) has a first surface area tone value, wherein the first substrate layer region (105) has a second surface area tone value, wherein the first surface area tone value gradually transitions into the second surface area tone value in a transition region (117) between the first substrate layer region (105) and the third substrate layer region (113); and / or wherein the first surface area tone value and the second surface area tone value form a contrast at a surface boundary (119) between the first substrate layer region (105) and the third substrate layer region (113).

20. Document (100) according to claim 18 or 19, wherein the second substrate layer region (109) is aligned with at least one further microperforation (115a-c) of the first substrate layer (103) which forms part of the perforation pattern, wherein the third substrate layer region (113) and / or the transition region (117) and / or the surface boundary (119) has the at least one further microperforation (115a-c).

21. Method (400) for verifying the authenticity of the document (100) according to any one of claims 1 to 20, comprising: illuminating (401) a surface of the document (100) with infrared light; capturing (403) the infrared light transmitted through the document (100) at a surface of the document (100) opposite the surface in an infrared image; comparing (405) the infrared image with a reference infrared image, wherein the authenticity of the document (100) is confirmed if the infrared image matches the reference infrared image.

22. Method (500) for producing a document (100) with a security feature, comprising: providing (501) a first substrate layer (103); completely impregnating (503) a first substrate layer area (105) of the first substrate layer (103) with an infrared-absorbing fluid; forming (505) microperforations (111a-c) in the first substrate layer area (105) forming a perforation pattern; providing (507) a second substrate layer (107), wherein the second substrate layer (107) has a second substrate layer area (109);Arranging (509) the second substrate layer (107) on the first substrate layer (103), wherein the second substrate layer region (109) and the first substrate layer region (105) are aligned with each other, and wherein the second substrate layer region (109) is formed to be more transparent to infrared light than the infrared light-absorbing fluid in order to allow incident infrared light to pass through to the first substrate layer region (105).

Images