A security document with a see-through feature, and methods for manufacturing and authentication thereof

Abstract

 A method for manufacturing a security document by providing transparent external layers (101, 102), at least one semi-transparent internal layer (103-106) with a see-through area (110) which is more transparent than the majority of the remainder of the document, laminating the layers (101-106) to form the security document and applying to the document, before and/or after lamination of layers (101-106), personalized data (121-123) and a see-through security feature in the see-through area (110), the see-through feature comprising a first partial image (111) applied on one side of the at least one semi-transparent internal layer (104) and a second partial image (112) applied on the other side of the at least one semi-transparent internal layer (104), wherein the first and second partial images (111, 112) form a complete image (113) when viewed in transmitted light. The method further comprises the steps of, before applying the see-through security feature: obtaining the personalized data (121-123) for the security document, obtaining the complete image (113) for the see-through security feature, and dividing the complete image (113) to the first partial image (111) and to the second partial image (112) using a function having a value dependent on at least part of the personalized data (121-123) for the security document.

Description

[0001] The present invention relates to security documents with a see-through security feature.

[0002] See-through security features, also known as recto-verso or look-through, are one of known counterfeit protection methods. A typical see-through security feature comprises two partial images applied on opposite sides of a semi-transparent substrate, which form a complete image when viewed in transmitted light. See-through security features are commonly applied to documents having a uniform semi-transparent substrate, such as a semi-transparent plastic or paper substrate printed at both sides.

[0003] A European patent EP0388090 "Sheet with security device" describes a sheet comprising a see-through feature, which is provided in a region of the sheet which is more transparent than a majority of the remainder of the sheet. The sheet has a paper substrate.

[0004] The aim of the present invention is to provide an improved security document with a see-through security feature.

[0005] The object of the invention is a method for manufacturing a security document by providing transparent external layers, at least one semi-transparent internal layer with a see-through area which is more transparent than the majority of the remainder of the document, laminating the layers to form the security document and applying to the document, before and/or after lamination of layers, personalized data and a see-through security feature in the see-through area, the see-through feature comprising a first partial image applied on one side of the at least one semi-transparent internal layer and a second partial image applied on the other side of the at least one semi-transparent internal layer, wherein the first and second partial images form a complete image when viewed in transmitted light. The method further comprises the steps of: before applying the see-through security feature obtaining the personalized data for the security document, obtaining the complete image for the see-through security feature, and dividing the complete image to the first partial image and to the second partial image using a function having a value dependent on at least part of the personalized data for the security document.

[0006] Preferably, the method further comprises the steps of, when dividing the complete image: generating a mask having a size of the complete image and comprising a plurality of regions using the function having a value dependent on at least part of the personalized data for the security document and assigning the regions of the complete image which coincide with the regions of the mask to the first partial image and the remaining regions to the second partial image.

[0007] Preferably, the function having a value dependent on at least part of the personalized data for the security document is a hash function.

[0008] Preferably, the complete image comprises at least part of the personalized data for the security document.

[0009] Preferably, the see-through security feature is applied by ink jet printing before lamination.

[0010] Preferably, the see-through security feature is applied by laser engraving after lamination.

[0011] The object of the invention is also a security document having a form of a laminate of transparent external layers and at least one semi-transparent internal layer with a see-through area which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area, the see-through feature comprising a first partial image applied on one side of the at least one semi-transparent internal layer and a second partial image applied on the other side of the at least one semi-transparent internal layer, wherein the first and second partial images form a complete image when viewed in transmitted light, and wherein the security document comprises personalized data, wherein the fragmentation of the complete image to the first and second partial images is having a value dependent on at least part of the personalized data comprised in the security document.

[0012] Preferably, at least one semi-transparent internal layer comprises a first internal layer of a first transparency with an opening corresponding to the see-through area and a second semi-transparent layer of a second transparency, higher than the first transparency.

[0013] Preferably, the first internal layer of the first transparency is opaque.

[0014] Preferably, the document further comprises an integrated circuit chip with memory in which there is stored a definition of the function on which the fragmentation of the complete image is dependent and/or a mask for verifying the authenticity of the fragmentation of the complete image and/or the first and second partial images and/or the complete image.

[0015] The object of the invention is also a method for authenticating a security document in a form of a laminate of transparent external layers and at least one semi-transparent internal layer with a see-through area which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area, the see-through feature comprising a first partial image applied on one side of the at least one semi-transparent internal layer and a second partial image applied on the other side of the at least one semi-transparent internal layer, wherein the first and second partial images form a complete image when viewed in transmitted light, and wherein the security document comprises personalized data. The method comprises the steps of: obtaining at least part of the personalized data of the security document, generating a mask having a size of the complete image and comprising a plurality of regions, using a function having a value dependent on the obtained at least part of the personalized data and verifying whether the first partial image and/or the second partial image are compliant with the generated mask.

[0016] The object of the invention is also a device for authenticating a security document in a form of a laminate of transparent external layers and at least one semi-transparent internal layer with a see-through area which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area, the see-through feature comprising a first partial image applied on one side of the at least one semi-transparent internal layer and a second partial image applied on the other side of the at last one semi-transparent internal layer, wherein the first and second partial images form a complete image when viewed in transmitted light, and wherein the security document comprises personalized data. The device comprises a document reader configured to obtain at least part of the personalized data of the security document, as well as the first partial image and/or the second partial image and a verification module configured to generate a mask having a size of the complete image and comprising a plurality of regions, using a function having a value dependent on the obtained at least part of the personalized data and to verify whether the first partial image and/or the second partial image are compliant with the generated mask.

[0017] The object of the invention is shown by way of exemplary embodiments on a drawing, in which:

Fig. 1 shows a top view of the security document,

Fig. 2 shows an assembly view of one exemplary embodiment of the security document,

Fig. 3 shows an assembly view of another exemplary embodiment of the security document,

Fig. 4 shows the steps of a first embodiment of the method according to the invention,

Fig. 5 shows the steps of a second embodiment of the method according to the invention,

Figs. 6-9 show examples of separation of a complete image to a first and to a second partial image using a mask having a value dependent on personalized data,

Fig. 10 shows a structure of a device for authenticating a security document.

[0018] Fig. 1 shows a top view of the security document according to the invention, which may have a form of a plastic card 100 with a dimensions of e.g. approximately 8 cm x 5 cm and with an integrated circuit chip 124 with data 123 stored therein and with a plurality of standard identification elements related to personalized data, such as a photo 121 of a face, embossed, printed and/or engraved name and an ID number 122 of the document holder. As shown in Figs. 2 and 3, the document is a laminate of transparent external layers 101, 102 and at least one semi-transparent internal layer 104 with a see-through area 110 which is more transparent than the majority of the remainder of the document. The see-through area 110 has a see-through security feature comprising a first partial image 111 applied on one side of the at least one semi-transparent internal layer 104 and a second partial image 112 applied on the other side of the at least one semi-transparent internal layer 104, wherein the first partial image 111 and the second partial image 112 form a complete image 113 when viewed in transmitted light.

[0019] Fig. 2 shows an assembly view of one exemplary embodiment of the security document. The document is a laminate of plastic layers. The embodiment shown in Fig. 2 comprises transparent layers 101, 102, between which there is an internal layer 103 of a first transparency with an opening 110 corresponding to the see-through area and a second semi-transparent layer 104 of a second transparency, higher than the first transparency. Preferably, the internal layer 103 of a first transparency is opaque. The first and second partial images 111, 112 can be applied by laser engraving the opposite sides of the semi-transparent layer 104 after lamination of the layers.

[0020] Fig. 3 shows an assembly view of another exemplary embodiment of the security document. The document is a laminate of plastic layers. The embodiment shown in Fig. 3 is similar to that shown in Fig. 2, but it comprises two additional transparent or semi-transparent layers 105, 106 located at opposite sides of the semi-transparent layer 104. The total transparency of the layers 104, 105, 106 should be higher than the total transparency of layers 103, 104, 105, 106, such that the transparency of the area 110 is higher than the transparency of the remaining portion of the document. The see-through security feature can be is applied by ink jet printing the first image and the second image on layers 105, 106 before lamination of the layers. It can be also applied by laser engraving of a laminated document, or by any other method applicable for applying see-through security features. The first partial image 111 (e.g. the recto image) can be applied by using different print or engraving parameters than the second partial image 112 (e.g. the verso image) in order to achieve similar shades of the complete image 113 when viewed in transmitted light.

[0021] The total transparency of all layers in the see-through area 110 should be such as to allow the see-through feature to be seen in certain light conditions.

[0022] The layers 101-106 can be made of materials typical to plastic card laminates, such as polycarbonate, polyvinyl chloride and/or polyester.

[0023] The definition of the function, the mask image 114, the partial images 111, 112 and/or the complete image 113 can be stored in the integrated circuit chip 124, which facilitates verification of the security document.

[0024] Fig. 4 shows the steps of a first embodiment of the method according to the invention. First, in step 201 at least part of personalized data for applying to the document 100 is obtained, such as a name of the document holder, a personal ID number, a date of issuance of the document, a photo etc. Next, in step 202 a complete see-through image is obtained. The complete see-through image can be common for a group of documents, for example it can be a country code, a document type, a common symbol, year of issuance etc. Alternatively, the complete see-through image can be personalized and include a personal ID number, a name, a surname, a photo etc. Exemplary complete see-through images 113 are shown in Figs. 6-9. Next, a mask image 114 is generated in step 203 as a function of the at least part of personalized data. The mask image 114 has the size of the complete see-through image 113 and comprises a plurality of regions 115 generated as a function having a value dependent on the at least part of the personalized data 121-123 for the security document.

[0025] For example, the function can be a hash function for the card holder's name. The hash function should generate substantially unique outputs for unique personalized data. For example, an MD5 hash function can generate a 128-bit hash value, which guarantees with a very high probability that all card holder names will be assigned different hash values.

[0026] The hash value can be used to generate a mask. As a simple example, shown with reference to Fig. 6, the MD5 hash value for personalized data = "JOHN SMITH" is (in a hexadecimal form) "f3c686cf530baf2269e7442163cb602e". The individual bits of the hash value can be used to define the regions of the mask image. For example, the mask image 114 can be divided into 4x4 squares and the consecutive squares can be defined as active/inactive depending on the value (1/0) of the first 16 bits of the hash value (which in this example is "F3C6" = "1111001111000110"), as shown in the example of Fig. 6. In practice, more bits of the 128-bit MD5 hash value should be used, or even longer hash value should be used, in order to guarantee uniqueness of the mask.

[0027] In step 204, the first partial image 111 and the second partial image 112 are generated, by overlaying the mask 114 on the complete image 113. The regions of the complete image 113 which coincide with the regions of the mask can be assigned to the first partial image 111 and the remaining regions can be assigned to the second partial image 112.

[0028] Next, blank layers 101-106 are provided in step 205. The personalized data 121-123 and the partial see-through images 111, 112 are applied in step 206, for example by Ink-jet method. Then, the layers are laminated in step 207.

[0029] Fig. 5 shows the steps of a second embodiment of the method according to the invention. Steps 211-214 are equivalent to steps 201-204 of the method shown in Fig. 4. In step 215, a blank or partially personalized laminate is provided. In step 216, the see-through images and optionally the rest of the personalized data are applied to the laminate, for example by laser engraving.

[0030] Figs. 7-9 show further exemplary embodiments of masks 114 applied to exemplary complete images 113 and resulting partial images 111, 112.

[0031] Fig. 7 shows an example, wherein the mask 114 comprises a plurality of rectangles, wherein the top-left corner point and the bottom-right corner points are defined by the function having a value dependent on at least part of the personalized data. In order to avoid a situation where a large rectangle would cover most of the mask region, the maximum size of the rectangle is limited.

[0032] Fig. 8 shows an example, wherein the mask 114 comprises a plurality of regions obtained by drawing lines having coordinates defined by the function having a value dependent on at least part of the personalized data and active regions selected in areas between the lines.

[0033] Fig. 9 shows an example, wherein the mask 114 comprises a plurality of regions obtained by drawing ellipses having center points and radii defined by the function having a value dependent on at least part of the personalized data.

[0034] Fig. 10 shows a structure of a device for authenticating the security document according to the invention. The device comprises a document reader 301 configured to obtain at least part of the personalized data 121-123 of the security document (for example by an optical reader or an IC chip interface), as well as the first partial image 111 and/or the second partial image 112 (for example by an optical reader). A verification module 302 is configured to generate a mask 114 having a size of the complete image 113 and comprising a plurality of regions 115, as a function having a value dependent on the obtained at least part of the personalized data 121-123 and to verify whether the first partial image 111 and/or the second partial image 112 are compliant with the generated mask 114. The mask 114 can be generated by a mask generator 304 on the basis of the value of the hash function 303, wherein the mask generator 304 receives the personalized data 121-123 from the document reader 301. The hash function 303 and the mask generator 304 operate in the same manner as corresponding units in the system for manufacturing the card. The verification can be performed by an image comparator 305 receiving as input the mask 114 from the mask generator 304 and the partial images 111, 112 from the document reader 301 and providing an output determining whether the images overlap or not.

[0035] The security document with a see-through security feature is improved in that the see-through security feature is personalized not only by applying personalized data in the see-through area, but also by personalized method of generating the regions which belong to the first and second partial images. In order to falsify the security document according to the invention by changing the personalized data, the see-through security feature should be changed as well. This not only requires additional manipulation within the see-through area, but knowledge of the function having a value dependent on the personalized data as well, in case when the hash function is not stored on the card chip. Therefore, the see-through security feature according to the invention can be used for authenticating the document and for verifying the data contained therein.

Claims

1. A method for manufacturing a security document by providing transparent external layers (101, 102), at least one semi-transparent internal layer (103-106) with a see-through area (110) which is more transparent than the majority of the remainder of the document, laminating the layers (101-106) to form the security document and applying to the document, before and/or after lamination of layers (101-106), personalized data (121-123) and a see-through security feature in the see-through area (110), the see-through feature comprising a first partial image (111) applied on one side of the at least one semi-transparent internal layer (104) and a second partial image (112) applied on the other side of the at least one semi-transparent internal layer (104), wherein the first and second partial images (111, 112) form a complete image (113) when viewed in transmitted light, the method characterized by further comprising the steps of: before applying the see-through security feature: obtaining the personalized data (121-123) for the security document, obtaining the complete image (113) for the see-through security feature, and dividing the complete image (113) to the first partial image (111) and to the second partial image (112) using a function having a value dependent on at least part of the personalized data (121-123) for the security document.

2. The method according to claim 1, further comprising the steps of: when dividing the complete image: generating a mask (114) having a size of the complete image and comprising a plurality of regions (115) using the function having a value dependent on at least part of the personalized data (121-123) for the security document and assigning the regions (115) of the complete image (113) which coincide with the regions of the mask to the first partial image (111) and the remaining regions to the second partial image (112).

3. The method according to any of previous claims, wherein the function having a value dependent on at least part of the personalized data (121-123) for the security document is a hash function.

4. The method according to any of previous claims, wherein the complete image (113) comprises at least part of the personalized data (121-123) for the security document.

5. The method according to any of previous claims, wherein the see-through security feature is applied by ink jet printing before lamination.

6. The method according to any of previous claims, wherein the see-through security feature is applied by laser engraving after lamination.

7. A security document having a form of a laminate of transparent external layers (101, 102) and at least one semi-transparent internal layer (103-106) with a see-through area (110) which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area (110), the see-through feature comprising a first partial image (111) applied on one side of the at least one semi-transparent internal layer (104) and a second partial image (112) applied on the other side of the at least one semi-transparent internal layer (104), wherein the first and second partial images (111, 112) form a complete image (113) when viewed in transmitted light, and wherein the security document comprises personalized data (121-123) characterized in that the fragmentation of the complete image (113) to the first and second partial images (111, 112) is dependent on at least part of the personalized data (121-123) comprised in the security document.

8. The security document according to claim 7, wherein the at least one semi-transparent internal layer comprises a first internal layer (103) of a first transparency with an opening corresponding to the see-through area (110) and a second semi-transparent layer (104) of a second transparency, higher than the first transparency.

9. The security document according to claim 8, wherein the first internal layer (103) of the first transparency is opaque.

10. The security document according to any of claims 7-9, further comprising an integrated circuit chip (124) with memory in which there is stored a definition of the function on which the fragmentation of the complete image (113) is dependent and/or a mask (114) for verifying the authenticity of the fragmentation of the complete image (113) and/or the first and second partial images (111, 112) and/or the complete image (113).

11. A method for authenticating a security document in a form of a laminate of transparent external layers (101, 102) and at least one semi-transparent internal layer (103-106) with a see-through area (110) which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area (110), the see-through feature comprising a first partial image (111) applied on one side of the at least one semi-transparent internal layer (104) and a second partial image (112) applied on the other side of the at least one semi-transparent internal layer (104), wherein the first and second partial images (111, 112) form a complete image (113) when viewed in transmitted light, and wherein the security document comprises personalized data (121-123), the method characterized by comprising the steps of:

- obtaining at least part of the personalized data (121-123) of the security document,

- generating a mask (114) having a size of the complete image (113) and comprising a plurality of regions (115), using a function having a value dependent on the obtained at least part of the personalized data (121-123),

- verifying whether the first partial image (111) and/or the second partial image (112) are compliant with the generated mask (114).

12. A device for authenticating a security document in a form of a laminate of transparent external layers (101, 102) and at least one semi-transparent internal layer (103-106) with a see-through area (110) which is more transparent than the majority of the remainder of the document, wherein a see-through security feature is applied in the see-through area (110), the see-through feature comprising a first partial image (111) applied on one side of the at least one semi-transparent internal layer (104) and a second partial image (112) applied on the other side of the at last one semi-transparent internal layer (104), wherein the first and second partial images (111, 112) form a complete image (113) when viewed in transmitted light, and wherein the security document comprises personalized data (121-123), the device characterized by comprising:

- a document reader (301) configured to obtain at least part of the personalized data (121-123) of the security document, as well as the first partial image (111) and/or the second partial image (112),

- a verification module (302) configured to generate a mask (114) having a size of the complete image (113) and comprising a plurality of regions (115), using a function having a value dependent on the obtained at least part of the personalized data (121-123) and to verify whether the first partial image (111) and/or the second partial image (112) are compliant with the generated mask (114).

Drawing