Security mark, method and device for reading security mark, security document marked with security mark, and method and system for verifying said security document

Abstract

The present invention relates to a security mark (100), a method and apparatus for reading and decoding the security mark (100), a security document (150) marked with the security mark (100), and a method and system for verifying and authenticating the security document (150). The security mark (100) comprises a machine-readable mark (130) superimposed on a magnetically sensitive layer (120) of material, the magnetically sensitive layer comprising magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles in two regions (120a) and (120b) of different orientation of the particles. The encoded data on the machine-readable mark (130) can only be decoded after the data read from the two regions (120a) and (120b) are collected.

Description

Technical Field

[0001] The present invention relates to the field of magnetically sensitive layers, methods and devices for reading magnetically sensitive layers, and methods and systems for verifying and authenticating documents comprising a magnetically sensitive layer comprising oriented magnetic or magnetizable pigment particles. Background Art

[0002] It is known in the art, for example in the field of security documents, to use inks, compositions, coatings or layers containing oriented magnetic or magnetizable pigment particles, in particular also optically variable magnetic or magnetizable pigment particles, to produce security elements in the form of magnetic induction markings. Coatings or layers containing oriented magnetic or magnetizable pigment particles are disclosed, for example, in US Pat. Nos. 2,570,856, 3,676,273, 3,791,864, 5,630,877 and 5,364,689. Coatings or layers containing oriented magnetic color-shifting pigment particles, which produce attractive optical effects for protecting security documents, have already been disclosed in WO 2002 / 090002 A2 and WO 2005 / 002866 A1.

[0003] The magnetic or magnetizable pigment particles in the printing ink or coating allow the generation of magnetically induced layers, designs, and / or patterns by applying a corresponding magnetic field, thereby locally orienting the magnetic or magnetizable pigment particles in the uncured coating, and subsequently curing the coating. The result is a fixed magnetically induced layer, design, or pattern. Materials and techniques for orienting magnetic or magnetizable pigment particles in coating compositions are disclosed in US Pat. No. 2,418,479, US Pat. No. 2,570,856, US Pat. No. 3,791,864, DE 2006848-A, US Pat. No. 3,676,273, US Pat. No. 5,364,689, US Pat. No. 6,103,361, EP 0406667 B1; US ​​2002 / 0160194; US Pat. No. 2004 / 70062297; US Pat. No. 2004 / 0009308; EP 0710508 A1; WO 2002 / 09002 A2; WO 2003 / 000801 A2; WO 2005 / 002866 A1; WO 2006 / 061301 A1; the disclosures of which are incorporated herein by reference. In this way, a highly counterfeit-resistant magnetic induction layer can be produced. The magnetic induction layer thus obtained produces an angular reflection profile that is substantially asymmetric relative to the normal to the substrate to which it is applied. This is unusual and differs from classic specular or Lambertian reflection / scattering behavior.

[0004] For example, security features used in security documents can generally be categorized as "covert" security features, on the one hand, and "overt" security features, on the other. The protection provided by covert security features relies on the concept that such features are difficult to detect, typically requiring specialized equipment and knowledge for detection, while "overt" security features rely on the concept that they are easily detectable through unaided human senses. For example, such features may be visible and / or detectable via touch, while still being difficult to produce and / or reproduce. Magnetic induction layers are typically used as "overt" (or Level 1) security features, which should allow for direct and unambiguous authentication by humans without any external devices or tools. However, the effectiveness of overt security features depends largely on their easy recognition as security features, as most users (and particularly those without prior knowledge of the security features of the document or item being protected) will only actually perform security checks based on such features if they have actual knowledge of the presence and nature of the security feature.

[0005] Even if the security level of the magnetically sensitive layer is high in terms of resistance to copying, the average consumer may be potentially confused about what exact effect should be seen for a particular obvious security element on a given product. In particular, a flip hologram that produces a pattern or logo-like pattern (a low-security, low-cost security element) may lead to misinterpretation of authenticity by untrained consumers because the flip hologram will also produce an angle-dependent reflection pattern.

[0006] In recent years, a number of authentication methods using portable (handheld) devices (e.g., smartphones) have emerged. Most rely on the smartphone camera's imaging capabilities to extract geometric or topological information below the resolution of the human eye (such as disclosed in WO 0225599 A1), or exceed the human ability to extract signals very close to noise or interpret weak variations in the color or shape of printed designs (such as disclosed in WO2013071960 A1). These methods have the advantage of extracting coded information for identification, but on the other hand require high-resolution printing and / or magnification optics attached to the smartphone camera.

[0007] Other authentication methods have been developed that can be applied to low-resolution printed features and rely on colorimetric analysis of the security feature (as disclosed in US 2011190920), based on holograms, or SICPASMART as disclosed in WO 2015052318A1. TM, which analyzes the color shift characteristics of an optically variable pattern measured during the azimuth displacement of a smartphone around the pattern for augmented reality assistance. These methods rely on the movement of the smartphone camera relative to the marker, which is complex to implement. Furthermore, they rely on external light illumination and are therefore highly sensitive to ambient light conditions (e.g., direct sunlight, dark environments, or lighting with high color imbalance).

[0008] Other authentication methods have been proposed that use features with angular dependence of reflection intensity, such as randomly oriented flakes as disclosed in WO 2012136902A1 and US 20140224879, micro-mirrors as disclosed in WO 2015193152A1 or US 2016378061, diffractive features such as holograms, or relief 3D structures. These are based on two angular positions of a camera to capture two images that are then analyzed.

[0009] Controlling both the smartphone camera and the sample illumination to obtain reproducible measurements of the reflectivity of security features remains a challenge. Smartphone cameras typically use automatic exposure and focus algorithms that are suitable for typical camera uses (e.g., landscape or portrait photos), but such algorithms are not well suited for imaging highly reflective markings with magnetically sensitive layers. The illumination of security features can originate from ambient light, either indoors or outdoors, which is often unknown and difficult to control and can hinder reliable detection of specific security features of the magnetically sensitive layer (e.g., angular reflectivity).

[0010] Thus, currently known smartphone-based authentication techniques have several disadvantages, including the following: they require high-resolution printing of fine structures; and / or they rely on complex smartphone movements to reveal colors, and / or they cannot reliably and accurately authenticate precise angular dependencies due to limited available information.

[0011] It is therefore desirable to propose to the public, and potentially also to relevant inspectors, an improved, accurate and reliable technical solution that is robust to ambient light disturbances, does not rely on high-resolution printing or complex movements of smartphones, and avoids difficult to control and unintuitive tilt or azimuth positions or complex rotational movements.

[0012] In particular, there is a need for authentication methods and devices that can unambiguously distinguish given magnetically sensitive layers from each other or from another obvious security feature produced using other technologies, and from imitations based on another technology that attempts to imitate or simulate the effect, but reproduces the security feature or sign topology and has a certain angular dependence of the reflection intensity.

[0013] It is well known to authorize a user to access a given service (e.g., via a website) over a communication network (e.g., the Internet or a local network) in order to allow the user to perform certain operations (e.g., financial operations on the user's bank account). Typically, the user must "prove" their identity by using an encryption key and / or password used to make a request to the authority managing access: only when the password and / or key is correct is full access to the service granted. However, the confidence level of such access is quite low, as the password or key could be stolen, or the user could log in under a false identity (e.g., on the website or having control over it). Therefore, there is a need to improve the confidence level of personal access credentials.

[0014] On the other hand, it is well known to use a secure government-issued identity document (such as an ID card or passport) to prove the holder's identity to a control agent (e.g., a check-in counter) and then gain access to some services (or to a building). In this case, the agent will control some security markings provided on the holder's identity document that are difficult to forge, possibly checking the similarity of the holder's face to biometric data and / or an identification photograph, and then, that is, when the agent has obtained a sufficient level of confidence in the holder's identity, the agent allows the holder to perform some authorized operation. For example, document WO 2014 / 160582 A1 discloses a method comprising the following steps: generating an association between a user's government-issued identity document and a payment mode at a mobile device; receiving, at the mobile device, the presentation of the user's government-issued identity document in support of a request for payment; verifying whether the presented government-issued identity document is a valid identification of the user; and, in response to verifying the presented government-issued identity document, making a payment using the payment mode. The government-issued identity document may include printed text, magnetic media, and barcodes.

[0015] Also known is an authentication method applicable to security documents, disclosed in document US 2007 / 170248 A1. The authentication method involves capturing an image of the cardholder's face with a reader. Facial recognition software processes the image to generate a hash. The same reader is used to decode a digital watermark and / or barcode. The digital watermark (and / or barcode) includes an associated facial recognition hash. If the hashes match, the personal and identification document is authenticated.

[0016] The purpose of the present invention is to eliminate the necessity for preliminary identity control via an executive and to allow any user to directly access online services provided by private or public operators, while providing the operator with a high level of confidence about the user's real identity (and therefore real authority to perform operations).

[0017] It is therefore an object of the present invention to provide a method for authenticating a magnetically sensitive layer used as an overt security feature printed or affixed to a substrate such as a label, product or document using a portable device, preferably a smartphone, in order to overcome the disadvantages of the prior art.

[0018] Another object of the present invention is to provide a portable device (preferably a smartphone) for authenticating a magnetically sensitive layer applied on a substrate, which is easy to control, has good immunity to ambient light variability, is highly resistant to imitation and can be easily distinguished from other angle-dependent reflective markings.

[0019] Another object of the present invention is to provide a method and a system for verifying the content of a document and authenticating said document marked with a magnetically sensitive layer according to the present invention.

[0020] Another object of the present invention is to provide a corresponding non-transitory computer-readable medium comprising computer code portions or instructions executable by a processor to enable a portable device equipped with a light source and an imager to perform the methods of reading, decoding and authenticating as described herein. Summary of the Invention

[0021] According to one aspect, the present invention relates to a security marking (100) comprising:

[0022] - a flat substrate (110);

[0023] - a magnetic induction layer (120) of a material comprising magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, the magnetic induction layer (120) being applied on the substrate (110) and comprising a first region (120a) and a second region (120b) different from the first region (120a), wherein in the first region (120a), the planar faces of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles are oriented in a first direction, wherein in the second region (120b), the planar faces of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles are oriented in a second direction different from the first direction, the flake-shaped particles in the first region (120a) have planar faces at an elevation angle γ1 relative to the plane of the substrate (110), and the flake-shaped particles in the second region (120b) have planar faces at an elevation angle γ2 relative to the plane of the substrate (110), and each acute angle of the planar faces relative to the plane of the substrate is in the range of about 5° to about 25°;

[0024] - a machine-readable mark (130) comprising a reference pattern (133) and a code pattern (134) representing encoded data, the machine-readable mark (130) being applied on the top surface (121) of the magnetic sensing layer (120) or on the substrate (110) between the substrate and the back surface (122) of the magnetic sensing layer (120), the first area (134a) of the code pattern (134) being arranged in front of the first area (120a), and the remaining second area (134b) of the code pattern (134) being arranged in front of the second area (120b).

[0025] In the above safety mark (100),

[0026] a) The pigment particles may include:

[0027] a magnetic metal selected from the group consisting of cobalt, iron, gadolinium, and nickel;

[0028] Magnetic alloys of iron, chromium, manganese, cobalt, nickel or mixtures of two or more of these;

[0029] Magnetic oxides of chromium, manganese, cobalt, iron, nickel or mixtures of two or more of them; or

[0030] a mixture of two or more of the above; or

[0031] b) The code pattern may be any one of a one-dimensional barcode, a stacked one-dimensional barcode, a two-dimensional barcode, and a three-dimensional barcode.

[0032] The first region (120a) and the second region (120b) of the magnetic sensing layer (120) may belong to the same single material layer. Alternatively, the first region (120a) and the second region (120b) of the magnetic sensing layer (120) may belong to a first sublayer and an adjacent second sublayer forming the magnetic sensing layer (120), respectively (by "adjacent", it is meant that the first sublayer and the second sublayer may be in direct contact or may be spaced apart).

[0033] In the above security mark (100), the machine-readable mark (130) can be applied on the top surface (121) of the magnetic sensing layer (120) and encoded with dark symbols, and a dark primer layer (140) can be applied on the substrate (110), and the back surface (122) of the magnetic sensing layer (120) is applied on the top surface (141) of the dark primer layer (140).

[0034] According to another embodiment of the security mark (100), the machine-readable mark (130) can be applied on the top surface (121) of the magnetic sensing layer (120) and encoded in light symbols, a dark primer layer (140), preferably a black primer, can be applied on the substrate (110), and the back surface (122) of the magnetic sensing layer (120) can be applied on the top surface (141) of the dark primer layer (140).

[0035] In the above security marking (100), the machine-readable marking (130) may be applied to the substrate (110) and encoded in a hidden symbol.

[0036] According to another aspect, the present invention relates to a method for reading and decoding the above security marking (100) using a portable device (200), the portable device (200) being equipped with a light source (201) operable to deliver illumination light, an imager (202) and a processor, the light source (201) being operable to deliver illumination light, the processor being equipped with a memory and being adapted to perform image processing and decoding operations, the method comprising the following steps:

[0037] - placing a security mark (100) within the field of view of the imager (202);

[0038] - illuminating the security mark (100) using illumination light delivered by the light source (201);

[0039] - acquiring a first digital image of the security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory;

[0040] - acquiring, using the imager (202), a second digital image of the security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2, and storing the acquired second digital image in the memory;

[0041] - forming a composite digital image of the code pattern (134) by aligning a first portion of the code pattern (134) corresponding to a first region (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to a second region (134b) of the code pattern detected on the second digital image, relative to the reference pattern (133) detected in the first digital image and the second digital image, based on the stored first digital image and the stored second digital image, through image processing using the processor, and storing the obtained composite digital image in the memory;

[0042] - reading and decoding the code pattern (134) from the stored composite digital image using the processor.

[0043] The present invention also relates to a portable device (200) for reading and decoding the above security marking (100), comprising:

[0044] - a light source (201) operable to deliver illumination light;

[0045] - an imager (202); and

[0046] - a processor provided with a memory and adapted to carry out the steps of the above method for reading and decoding the security marking (100) on the digital image of said security marking (100) acquired by the imager (202).

[0047] Another aspect of the invention relates to a security document (150) that is delivered to a user by an authorized institution and that comprises:

[0048] - A security mark (100) according to the present invention applied to the security document (150), wherein the coded data in the code pattern (134) of the security mark (100) contain digital identity data corresponding to a user and a digital signature of the user's digital identity data, the digital signature delivered by the authorized institution being obtained by signing the user's digital identity data with an encryption key.

[0049] Another aspect of the present invention relates to a method for authenticating the above security file (150) of a user using the above portable device (200), the portable device also being equipped with a communication unit operable to send and receive data via a communication network (CN) relative to a server (S) of an authority connected to a database (DB) storing the encryption key and the corresponding decryption key, the method comprising the following steps:

[0050] - positioning the security mark (100) within the field of view of the imager (202);

[0051] - illuminating the security marking (100) of the security document (150) using the light source (201);

[0052] - acquiring, using the imager (202), a first digital image of the illuminated security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1, and storing the acquired first digital image in the memory;

[0053] - acquiring, with the imager (202), a second digital image of the illuminated security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2, and storing the acquired second digital image in the memory;

[0054] - forming, via image processing using the processor, a composite digital image of the code pattern (134) based on the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to a first area (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to a second area (134b) of the code pattern detected on the second digital image with respect to the reference pattern (133) detected in the first digital image and the second digital image;

[0055] - reading and decoding the code pattern (134) from the synthesized digital image via image processing and decoding operations using the processor, extracting user identification data and a digital signature of the user identification data from the decoded data of the code pattern (134), and storing the extracted user identification data and digital signature in the memory;

[0056] - sending a first message (M1) comprising the extracted user identity data stored in the memory and the digital signature to the server (S) via the communication unit;

[0057] - decrypting, at the server (S), the extracted digital signature received in the first message (M1) from the portable device (200) using a decryption key stored in the database (DB), and checking whether the extracted user identity data received in the first message (M1) matches the received extracted digital signature; and

[0058] - In case of a match, a server message (SM) is sent back to the portable device (200) indicating a successful verification of the user identity data.

[0059] According to a variant, the above aspect of verifying the security token (150) may comprise, before the step of sending the server message back to said portable device (200), the following preliminary steps:

[0060] - illuminating the magnetic sensing layer (120) using the light source (201), and acquiring a plurality of digital images of the illuminated magnetic sensing layer (120) using the imager (202), by moving the imager (202) relative to the magnetic sensing layer (120) in a plane parallel to the substrate (110), so that for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic sensing layer (120);

[0061] - for each acquired digital image, using the processor to respectively calculate the corresponding intensity I of the light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and storing the calculated reflected light intensity and the corresponding viewing angle to obtain a corresponding reflected light intensity curve I(θ);

[0062] - sending a second message (M2) containing the obtained reflected light intensity curve I(θ) to the server (S) via the communication network (CN) using a communication unit;

[0063] - at the server (S), comparing the reflected light intensity curve I(θ) received in the second message (M2) with a reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the database (DB); ref (θ) for comparison;

[0064] - determining at the server (S) whether the magnetic induction layer (120) is genuine based on the comparison result; and

[0065] - If the magnetic induction layer (120) is determined to be authentic, a server message (SM) indicating successful verification of the user's identity data and an indication that the security tag (100) is authentic is sent back to the portable device (200), and a server authorization message (SAM) containing access data granting the user access to a service is sent by the server (S) to the user's communication device via the communication network (CN). The user's communication device may be the portable device (200) itself.

[0066] According to an alternative variant, the above aspects of verifying the security mark (150) may be such that, in the case of delivery by the server of a server message (SM) indicating a successful verification of the user identity data, the method further comprises the steps of:

[0067] - illuminating the magnetic sensing layer (120) using the light source (201), and acquiring a plurality of digital images of the illuminated magnetic sensing layer (120) using the imager (202), by moving the imager (202) relative to the magnetic sensing layer (120) in a plane parallel to the substrate (110), so that for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic sensing layer (120);

[0068] - for each acquired digital image, using the processor to respectively calculate the corresponding intensity I of the light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and determining a corresponding reflected light intensity curve I(θ) using the calculated reflected light intensity and the corresponding viewing angle;

[0069] - comparing the reflected light intensity curve I(θ) with the reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the memory via the processor; ref (θ) for comparison;

[0070] - determining whether the magnetic induction layer (120) is authentic based on the comparison result, and, if the magnetic induction layer (120) is determined to be authentic, sending a message (M) indicating that the security mark (100) is authentic to the server (S) via the communication network (CN) using the communication unit; and

[0071] - when the server (S) receives a message (M) from the portable device (200) indicating that the security token (100) is authentic, the server (S) sends back a server authorization message (SAM) containing access data granting the user access to the service to the user's communication device via the communication network (CN). The user's communication device may be the portable device (200) itself.

[0072] Yet another aspect of the present invention relates to a system for authenticating a security document (150) delivered by an authorized institution to a user according to the present invention, the system comprising:

[0073] - a server (S) of said authority, connected to the database (DB) and operable to send and receive data via the communication network (CN);

[0074] - a portable device (200) according to the invention for reading and decoding a security mark (100) according to the invention applied to said security document (150), said portable device (200) comprising:

[0075] a light source (201) operable to deliver illumination light;

[0076] Imager (202);

[0077] a communication unit operable to send and receive data with respect to said server (S) via said communication network (CN); and

[0078] a processor provided with a memory and adapted to perform image processing and decoding operations to execute the steps of the above method for reading and decoding a security mark (100) on a digital image of said security mark captured by an imager (202),

[0079] - wherein said server (S) and said portable device (200) are further adapted to perform the steps of a method of authenticating a user's security file (150) by:

[0080] illuminating the security mark (100) using the light source (201), the security mark (100) being within the field of view of the imager (202);

[0081] Acquiring a first digital image of the illuminated security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory;

[0082] acquiring, using the imager (202), a second digital image of the illuminated security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2, and storing the acquired second digital image in the memory;

[0083] forming a composite digital image of the code pattern (134) by aligning a first portion of the code pattern (134) corresponding to a first region (134a) of the code pattern (134) detected on the first digital image and a second portion of the code pattern (134) corresponding to a second region (134b) of the code pattern (134) detected on the second digital image, relative to the reference pattern (133) detected in the first digital image and the second digital image, based on the stored first digital image and the stored second digital image via image processing using the processor;

[0084] - reading and decoding the code pattern (134) from the synthesized digital image, and extracting user identification data and a digital signature of the user identification data from the decoded data of the code pattern (134) via image processing and decoding operations using the processor, and storing the extracted user identification data and digital signature in the memory;

[0085] - sending a first message (M1) comprising the extracted user identity data stored in the memory and the digital signature to the server (S) via the communication unit;

[0086] - decrypting, at the server (S), the extracted digital signature received in the first message (M1) from the portable device (200) using a decryption key stored in the database (DB), and checking whether the extracted user identity data received in the first message (M1) matches the received extracted digital signature; and

[0087] - In case of a match, a server message (SM) is sent back to the portable device (200) indicating a successful verification of the user identity data.

[0088] A first variant of the above system for authenticating a security document (150) delivered by an authority to a user according to the invention, wherein the server (S) is further adapted to send data to the user's communication device via the communication network (CN); and

[0089] The server (S) and the portable device (200) are further adapted to perform the following preliminary steps before the step of sending a server message (SM) back to the portable device:

[0090] - illuminating the magnetic sensing layer (120) using the light source (201), and acquiring a plurality of digital images of the illuminated magnetic sensing layer (120) using the imager (202), by moving the imager (202) relative to the magnetic sensing layer (120) in a plane parallel to the substrate (110), so that for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic sensing layer (120);

[0091] - for each acquired digital image, using the processor to respectively calculate the corresponding intensity I of the light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and storing the calculated reflected light intensity and the corresponding viewing angle to obtain a corresponding reflected light intensity curve I(θ);

[0092] - sending a second message (M2) containing the obtained reflected light intensity curve I(θ) to the server (S) via the communication network (CN) using a communication unit;

[0093] - at the server (S), comparing the reflected light intensity curve I(θ) received in the second message (M2) with a reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the database (DB); ref (θ) for comparison;

[0094] - determining at the server (S) whether the magnetic induction layer (120) is genuine based on the comparison result; and

[0095] - In the event that the magnetic induction layer (120) is determined to be authentic, a server message (SM) indicating successful verification of the user's identity data and an indication that the security mark (100) is authentic is sent back to the portable device (200), and a server authorization message (SAM) containing access data granting the user access to the service is sent by the server (S) to the user's communication device via the communication network (CN).

[0096] According to a second variant of the above system for authenticating a security document (150) delivered by an authority to a user, the server (S) is further adapted to transmit data to a communication device of the user via a communication network (CN); and

[0097] The server (S) and the portable device (200) are further adapted to perform the following steps:

[0098] - illuminating the magnetic sensing layer (120) with the light source, and acquiring a plurality of digital images of the illuminated magnetic sensing layer (120) with the imager (202), by moving the imager (202) relative to the magnetic sensing layer (120) in a plane parallel to the substrate (110), so that for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic sensing layer (120);

[0099] - for each acquired digital image, using the processor to respectively calculate the corresponding intensity I of the light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and determining a corresponding reflected light intensity curve I(θ) using the calculated reflected light intensity and the corresponding viewing angle;

[0100] - comparing the reflected light intensity curve I(θ) with the reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the memory via the processor; ref (θ) for comparison;

[0101] - determining whether the magnetic induction layer (120) is authentic based on the comparison result, and, if the magnetic induction layer (120) is determined to be authentic, sending a message (M) indicating that the security mark (100) is authentic to the server (S) via the communication network (CN) using the communication unit; and

[0102] - When the server (S) receives a message (M) from the portable device (200) indicating that the security mark (100) is authentic, the server (S) sends back to the user's communication device via the communication network (CN) a server authorization message (SAM) containing access data granting the user access to the service.

[0103] The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which like reference numerals refer to like elements throughout the different figures, and in which are illustrated in a non-limiting manner salient aspects and features of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] Figure 1 A plate-shaped pigment particle is schematically illustrated, wherein the Cartesian axes (X, Y, Z) are attached to a (substantially flat) face of the particle.

[0105] Figure 2A 1 is a schematic diagram of a magnetic induction layer (120) comprising two regions (120a, 120b) according to an embodiment of the present invention, wherein magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles have different orientations relative to the plane of the back side (122) of the magnetic induction layer (120): the first region (120a) has reflective flake-shaped pigment particles with a first elevation angle γ1; and the second region (120b) has reflective flake-shaped pigment particles with a second elevation angle γ2.

[0106] Figure 2B Schematically illustrated Figure 1 A cross section of a magnetic induction layer (120) comprising magnetically oriented, plate-shaped magnetic or magnetizable pigment particles in a single layer of material applied to a flat substrate (110) is provided. The magnetic induction layer (120) comprises two distinct regions (120a, 120b) in the single layer (120), wherein the reflective pigment particles have different elevation angles γ1 and γ2.

[0107] Figure 2C A cross-section of a magnetic induction layer (120) according to an embodiment of the present invention is schematically illustrated, wherein the magnetic induction layer (120) includes magnetically oriented plate-shaped magnetic or magnetizable pigment particles in two layers on a flat substrate (110). The magnetic induction layer (120) includes two regions, wherein a first region (120a) is a first layer of material including magnetically oriented reflective plate-shaped magnetic or magnetizable pigment particles having a first elevation angle γ1, and a second region (120b) is a second layer of material including magnetically oriented reflective plate-shaped magnetic or magnetizable pigment particles having a second elevation angle γ2, wherein the first layer and the second layer have an abutting edge.

[0108] Figure 3Schematically illustrated is a perspective exploded view of a security mark (100) according to an embodiment of the present invention, the security mark (100) comprising a flat substrate (110), a magnetically sensitive layer (120) having two regions (120a) and (120b) with different orientations of their magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, having a top surface (121) and a back surface (122), and a machine-readable mark (130) having a top surface (131) and a back surface (132), wherein the machine-readable mark (130) partially overlaps the magnetically sensitive layer (120).

[0109] Figure 4A A cross section of a security mark (100) is schematically illustrated, comprising a flat substrate (110), a magnetic sensing layer (120) having two zones applied on the substrate, and a machine-readable mark (130) printed on a top surface (121) of the magnetic sensing layer, wherein the machine-readable mark (130) partially overlaps the magnetic sensing layer (120).

[0110] Figure 4B A cross section of a security mark (100) is schematically illustrated, comprising a flat substrate (110), a dark primer (140) having a top surface (141) and a back surface (142), a magnetic sensing layer (120) having two regions applied to the substrate, and a machine-readable mark (130), wherein the dark primer has its back surface (142) applied to the top surface of the substrate (110) and the back surface (122) of the magnetic sensing layer (120) is applied to the top surface (141) of the dark primer, and the machine-readable mark (130) partially overlaps the magnetic sensing layer (120).

[0111] Figure 4C A cross-section of a security mark (100) is schematically illustrated, the security mark (100) comprising a flat substrate (110), a magnetic sensing layer (120) and a machine-readable mark (130), wherein the machine-readable mark (130) is printed on a top surface of the substrate (110), and a back surface (122) of the magnetic sensing layer (120) is applied to a top surface (131) of the machine-readable mark (130), and the machine-readable mark (130) partially overlaps with the magnetic sensing layer (120).

[0112] Figure 5A A top view illustrating an example of a machine-readable code (130) in the form of a small QR code having a reference pattern (133) for locating a code pattern (134) during a decoding operation, and a magnetically sensitive layer ( Figure 3 ) and a first region above the first region (120a) of the magnetic sensing layer and a second region above the second region (120b) of the magnetic sensing layer.

[0113] Figure 5B A top view illustrating an example of a machine-readable code (130) in the form of a large QR code having a reference pattern (133) for locating a code pattern (134) during a decoding operation, and a magnetically sensitive layer ( Figure 3 ) and a first region above the first region (120a) of the magnetic sensing layer and a second region above the second region (120b) of the magnetic sensing layer.

[0114] Figure 5C A top view illustrating an example of a machine-readable code (130) in data matrix form having a reference pattern (133) having an L-shape for locating a code pattern (134) during a decoding operation, and a first region (134a) above a first region (120a) of a magnetic sensing layer (shown in FIG. 2 ) and a second region (134b) above a second region (120b) of the magnetic sensing layer.

[0115] Figures 6A-6B A portable device (200) is illustrated that captures images of a security tag (100) at two different viewing angles θ1 and θ2, the security tag including a magnetic sensing layer (120) having two regions (120a) and (120b), wherein illumination of the first region (120a) and the second region (120b) are shown as (210a) and (210b), respectively, and reflected light from the first region and the second region are shown as (220a) and (220b), respectively.

[0116] Figure 7 It is an example from Figure 5A A schematic flow chart of a process (700) for extracting encoded data from a machine-readable tag (130).

[0117] Figures 8A-8B Pose estimation flow chart illustrating two methods (800a) and (800b) of reading and decoding a security tag (100) according to the present invention using an imager of a portable device.

[0118] Figure 9 An example of a security document (150) according to the present invention (a user's identity card issued by an authorized agency) is illustrated.

[0119] Figure 10 Example of verification according to the present invention Figure 9 Method of secure documentation.

[0120] Figure 11 Example basis Figure 9 A method is shown for verifying a security document system.

[0121] Figures 12A-12BA process for preparing a magnetically sensitive layer (120) on a substrate (110) is illustrated, wherein the layer (120) comprises biaxially oriented reflective platelet-shaped magnetic or magnetizable pigment particles.

[0122] Figure 13 A process for preparing a magnetic induction layer (120) on a substrate (110) is exemplified, wherein the layer (120) comprises uniaxially oriented reflective platelet-shaped magnetic or magnetizable pigment particles.

[0123] Figures 14A-14D A photographic image of a security mark (100) is shown wherein the magnetically sensitive layer (120) is obtained using the method and apparatus shown in Figures 12-13. DETAILED DESCRIPTION

[0124] The following definitions are used to explain the meaning of terms discussed in the specification and recited in the claims.

[0125] As used herein, the term "at least one" is intended to define one or more than one, such as one or two or three.

[0126] As used herein, the term "about" means that the amount or value of interest can be the specified specific value or some other value in its neighborhood. Generally, the term "about" indicating a value is intended to indicate a range within ±5% of that value. As an example, the phrase "about 100" indicates a range of 100 ± 5, i.e., a range of 95 to 105. Generally, when the term "about" is used, it is expected that similar results or effects according to the present invention can be obtained within a range of ±5% of the specified value.

[0127] As used herein, the term "and / or" means that all or only one of the elements of the group may be present. For example, "A and / or B" should mean "only A, or only B, or both A and B." In the case of "only A," the term also encompasses the possibility that B is not present, that is, "only A, but not B."

[0128] As used herein, the terms "comprising" and "containing" are intended to be non-exclusive and open-ended. Thus, for example, a mixture comprising / containing compound A may include other compounds in addition to A. However, the terms "comprising" and "containing" also encompass, as specific examples thereof, the more restrictive meanings of "consisting essentially of" and "consisting of," such that, for example, a "mixture comprising A, B, and optionally C" may also consist (essentially) of A and B, or (essentially) of A, B, and C.

[0129] The security tag (100) described herein comprises a flat substrate (110) which is preferably selected from the group consisting of paper or other fibrous materials (including woven and non-woven fibrous materials), such as cellulose, paper-containing materials, glass, metal, ceramics, plastics and polymers, metallized plastics or polymers, composite materials, and mixtures or combinations of two or more thereof. Typical paper, paper-like or other fibrous materials are made from a variety of fibers, including but not limited to abaca, cotton, flax, wood pulp, and blends thereof. However, according to different embodiments, the substrate (110) may be based on plastics and polymers, metallized plastics or polymers, composite materials, and mixtures or combinations of two or more thereof. Suitable examples of plastics and polymers include polyolefins (such as polyethylene (PE) and polypropylene (PP) (including biaxially oriented polypropylene (BOPP)), polyamides, polyesters (such as polyethylene terephthalate (PET)), poly(1,4-butylene terephthalate) PBT), poly(ethylene 2,6-naphthoate) (PEN), and polyvinyl chloride (PVC). Spunbond olefin fibers (such as those sold under the trademark (those sold under the trade name "Shanghai Xintai Plastics Co., Ltd.") can also be used as substrates. Typical examples of metalized plastics or polymers include the plastic or polymer materials described above with metals arranged continuously or discontinuously on the surface. Typical examples of metals include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), alloys thereof, and combinations of two or more of the above metals. The metallization of the plastic or polymer materials described above can be accomplished by electrodeposition, high vacuum coating, or by sputtering. Typical examples of composite materials include, but are not limited to, paper and at least one plastic or polymer material (such as those described above) and multilayer structures or laminates of plastic and / or polymer fibers incorporated into paper-like or fiber materials (such as those described above). Of course, the substrate may include additional additives known to those skilled in the art, such as fillers, sizing agents, whitening agents, processing aids, reinforcing or wet-strengthening agents, and the like.

[0130] According to an embodiment of the invention, a security marking (100), such as that shown in FIG2 , comprises a magnetically sensitive layer (120) made of a material comprising a plurality of magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles as described, wherein the pigment particles are fixed or frozen (fixed / frozen) in their position and orientation within the material.

[0131] like Figure 1As shown, in contrast to needle-shaped pigment particles, which can be considered one-dimensional particles, plate-shaped pigment particles are quasi-two-dimensional particles due to their large aspect ratio. Plate-shaped pigment particles can be considered two-dimensional structures, where the dimensions along axes X and Y are substantially greater than the dimension (i.e., thickness) along axis Z. Plate-shaped pigment particles are also known in the art as flat platelets or flakes.

[0132] The oriented reflective flake-shaped magnetic or magnetizable pigment particles have a non-isotropic reflectivity due to their flat shape. As used herein, the term "non-isotropic reflectivity" means that the proportion of incident radiation from a first angle reflected by the particles into a certain (viewing) direction (a second angle) is a function of the orientation of the particles, i.e., a change in the orientation of the particles relative to the first angle can result in a reflection of different magnitudes into the viewing direction. Preferably, the reflective flake-shaped magnetic or magnetizable pigment particles described herein have a non-isotropic reflectivity for incident electromagnetic radiation in some part or the entire wavelength range of about 400 to about 1000 nm (i.e., from visible light to NIR wavelengths), more preferably about 400 to about 700 nm (i.e., the visible range), such that a change in the orientation of the particles results in a change in the reflection of the particles into a certain direction. Thus, even if there is a change in the orientation of the particles per unit surface area (e.g., per μm 2The intrinsic reflectivity of the flaky particles is uniform across their entire surface, but due to their shape, the reflectivity of the particles is non-isotropic, as the visible area of ​​the particle depends on the direction from which it is viewed. As known to those skilled in the art, the reflective flaky magnetic or magnetizable pigment particles described herein differ from conventional pigments in that conventional pigment particles exhibit the same color and reflectivity regardless of particle orientation, whereas the magnetic or magnetizable pigment particles described herein exhibit reflectance, color, or both, that depends on the particle orientation within the layer's material. The flaky pigment particles, initially randomly distributed within a layer of material, are oriented by applying a strong (uniform) magnetic field through the layer and then fixed / frozen in place by the subsequent hardening of the layer's material. These flaky pigment particles then have their flat faces preferentially oriented in the (uniaxial) direction of the applied magnetic field according to a statistical distribution with a sharp peak (e.g., Gaussian). The pigment particles are thus statistically oriented, and their planes have corresponding elevation angles relative to the plane of the layer. The angle between two planes is defined by the angle between vectors perpendicular to the respective planes, and also by the angle between two straight lines of the respective planes perpendicular to the (straight) line at the intersection of the two planes. Here, a straight line along the plane of the oriented pigment particles is aligned (essentially, according to a statistical distribution) with the orientation direction of said pigment particles. The full width at half maximum (FWHM) of this statistical distribution allows an estimation of the corresponding standard deviation of the orientation of the flat surfaces relative to the direction of the magnetic field lines. Thus, the normal direction of the surface of the (uniaxially) oriented flake pigment particles can have an inclination angle around the uniaxial direction of orientation, which is in practice less than 30°. In order to have a better relative orientation of the surfaces of the different pigment particles (i.e. in order to reduce the inclination angle and thus have a better relative parallelism of the surfaces), a second magnetic field is applied (before hardening), the field lines of which are oriented in the second direction (e.g. along the direction of the magnetic field lines). Figure 1 Y-axis shown): This biaxial orientation of the faces of the pigment particles significantly reduces the standard deviation described above, and the faces of the pigment particles are (statistically) parallel to each other while still being oriented in a given direction corresponding to the elevation angle. In a preferred embodiment of the present invention, a biaxial magnetic induction layer is used, in which the faces of the pigment particles in each region of the magnetic induction layer are biaxially oriented.

[0133] Suitable examples of flaky magnetic or magnetizable pigment particles include, but are not limited to, pigment particles comprising a magnetic metal selected from the group consisting of cobalt (Co), iron (Fe), and nickel (Ni); a magnetic alloy of iron, manganese, cobalt, nickel, or a mixture of two or more thereof; a magnetic oxide of chromium, manganese, cobalt, iron, nickel, or a mixture of two or more thereof; or a mixture of two or more thereof. The term "magnetic" with respect to metals, alloys, and oxides refers to ferromagnetic or ferrimagnetic metals, alloys, and oxides. The magnetic oxide of chromium, manganese, cobalt, iron, nickel, or a mixture of two or more thereof may be a pure or mixed oxide. Examples of magnetic oxides include, but are not limited to, iron oxide (such as hematite (Fe2O3), magnetite (Fe3O4), chromium dioxide (CrO2), magnetic ferrite (MFe2O4), magnetic spinel (MR2O4), magnetic hexaferrite (MFe12O19), magnetic orthoferrite (RFeO3), magnetic garnet M3R2(AO4)3), where M represents a divalent metal, R represents a trivalent metal, and A represents a tetravalent metal.

[0134] Other examples of flake-shaped, magnetic or magnetizable pigment particles include, but are not limited to, pigment particles comprising: a magnetic layer M made of one or more magnetic metals such as cobalt (Co), iron (Fe) or nickel (Ni); and magnetic alloys of iron, cobalt or nickel, wherein the magnetic or magnetizable pigment particles may be a multilayer structure including one or more additional layers. Preferably, the one or more additional layers are layer A, or layer B, or a combination of one or more layers A (such as layer A described above) and one or more layers B (such as layer B described above), wherein layer A is independently made of one or more selected from the group consisting of: metal fluorides (such as magnesium fluoride (MgF2)), silicon oxide (SiO), silicon dioxide (SiO2), titanium oxide (TiO2), and aluminum oxide (Al2O3), more preferably silicon dioxide (SiO2); layer B is independently made of one or more selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, and more preferably selected from the group consisting of aluminum (Al), chromium (Cr) and nickel (Ni), and more preferably aluminum (Al). Typical examples of the flaky magnetic or magnetizable pigment particles as the above-mentioned multilayer structure include, but are not limited to, an A / M multilayer structure, an A / M / A multilayer structure, an A / M / B multilayer structure, an A / B / M / A multilayer structure, an A / B / M / B multilayer structure, an A / B / M / B / A / multilayer structure, a B / M multilayer structure, a B / M / B multilayer structure, a B / A / M / A multilayer structure, a B / A / M / B multilayer structure, and a B / A / M / B / A / multilayer structure, wherein layer A, magnetic layer M, and layer B are selected from those mentioned above.

[0135] According to one embodiment, at least a portion of the preferably flake-shaped magnetic or magnetizable particles consists of flake-shaped optically variable magnetic or magnetizable pigment particles. Optically variable pigments are pigments that exhibit a change in brightness or a combination of a change in brightness and a change in hue. According to one embodiment, at least a portion of the flake-shaped, magnetic or magnetizable particles consists of particles that exhibit a metallic color, more preferably silver or gold.

[0136] The platelet-shaped, magnetic or magnetizable pigment particles are preferably selected from the group consisting of magnetic thin film interference pigment particles, magnetic cholesteric liquid crystal pigment particles, interference coating pigment particles comprising a magnetic material, and mixtures of two or more thereof.

[0137] Magnetic thin-film interference pigment particles are known to those skilled in the art and are disclosed in, for example, US Pat. No. 4,838,648; WO 2002 / 073250 A2; EP 0 686 675 B1; WO 2003 / 000801 A2; US Pat. No. 6,838,166; WO 2007 / 131833 A1; EP 2 402 401 B1; WO 2019 / 103937 A1; WO 2020 / 006286 A1, and the literature cited therein. Preferably, the magnetic thin-film interference pigment particles include pigment particles having a five-layer Fabry-Perot multilayer structure and / or pigment particles having a six-layer Fabry-Perot multilayer structure and / or pigment particles having a seven-layer Fabry-Perot multilayer structure and / or pigment particles having a multilayer structure combining one or more Fabry-Perot structures.

[0138] The preferred five-layer Fabry-Perot multilayer structure consists of an absorber / dielectric / reflector / dielectric / absorber multilayer structure, wherein the reflector and / or absorber is also a magnetic layer, preferably, the reflector and / or absorber is a magnetic layer comprising nickel, iron and / or cobalt, and / or a magnetic alloy comprising nickel, iron and / or cobalt, and / or a magnetic oxide comprising nickel (Ni), iron (Fe) and / or cobalt (Co).

[0139] A preferred six-layer Fabry-Perot multilayer structure consists of:

[0140] Absorber / dielectric / reflector / magnetic / dielectric / absorber multilayer structure.

[0141] A preferred seven-layer Fabry-Perot multilayer structure consists of:

[0142] Absorber / dielectric / reflector / magnetic / reflector / dielectric / absorber multilayer structure, such as disclosed in US 4,838,648.

[0143] Preferred pigment particles having a multilayer structure combining one or more Fabry-Perot structures are the pigment particles described in WO 2019 / 103937 A1 and are composed of a combination of at least two Fabry-Perot structures, each of which independently comprises a reflector layer, a dielectric layer, and an absorber layer, wherein the reflector and / or absorber layer can each independently comprise one or more magnetic materials and / or wherein the magnetic layer is sandwiched between the two structures. WO 2020 / 006 / 286 A1 and EP 3 587 500 A1 disclose further preferred pigment particles having a multilayer structure.

[0144] Preferably, the reflector layer described herein is independently made of one or more selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, more preferably selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), gold (Au), platinum (Pt), tin (Sn), titanium (Ti), palladium (Pd), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni) and their alloys, even more preferably selected from the group consisting of aluminum (Al), chromium (Cr), nickel (Ni) and their alloys, and still more preferably aluminum (Al). Preferably, the dielectric layer is independently made of one or more than one selected from the group consisting of metal fluorides (such as magnesium fluoride (MgF2), aluminum fluoride (AlF3), cerium fluoride (CeF3), lanthanum fluoride (LaF3), sodium aluminum fluoride (for example, Na3AlF6), neodymium fluoride (NdF3), samarium fluoride (SmF3), barium fluoride (BaF2), calcium fluoride (CaF2), lithium fluoride (LiF)), and metal oxides (such as silicon oxide (SiO), silicon dioxide (SiO2), titanium oxide (TiO2), aluminum oxide (Al2O3)), more preferably the group consisting of magnesium fluoride (MgF2) and silicon dioxide (SiO2), and even more preferably magnesium fluoride (MgF2). Preferably, the absorber layer is independently made of one or more selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), palladium (Pd), molybdenum (Pt), titanium (Ti), vanadium (V), iron (Fe), tin (Sn), tungsten (W), molybdenum (Mo), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni), metal oxides thereof, metal sulfides thereof, metal carbides thereof, and metal alloys thereof, more preferably selected from the group consisting of chromium (Cr), nickel (Ni), and metal alloys thereof. Preferably, the magnetic layer comprises nickel (Ni), iron (Fe), and / or cobalt (Co); and / or a magnetic alloy comprising nickel (Ni), iron (Fe), and / or cobalt (Co); and / or a magnetic oxide comprising nickel (Ni), iron (Fe), and / or cobalt (Co).

[0145] When magnetic thin film interference pigment particles comprising a seven-layer Fabry-Perot structure are preferred, it is particularly preferred that the magnetic thin film interference pigment particles comprise a seven-layer Fabry-Perot absorber / dielectric / reflector / magnetic / reflector / dielectric / absorber multilayer structure consisting of a Cr / MgF2 / Al / Ni / Al / MgF2 / Cr multilayer structure.

[0146] The magnetic thin film interference pigment particles described herein can be multilayer pigment particles that are considered safe for human health and the environment and are based on, for example, a five-layer Fabry-Perot multilayer structure, a six-layer Fabry-Perot multilayer structure, and a seven-layer Fabry-Perot multilayer structure, wherein the pigment particles include one or more magnetic layers, the one or more magnetic layers including a magnetic alloy having a composition that is substantially nickel-free and includes from about 40 wt% to about 90 wt% iron, from about 10 wt% to about 50 wt% chromium, and from about 0 wt% to about 30 wt% aluminum. Typical examples of multilayer pigment particles that are considered safe for human health and the environment can be found in EP 2 402 401 B1, the contents of which are incorporated herein by reference in their entirety.

[0147] Suitable magnetic cholesteric liquid crystal pigment particles exhibiting optically variable properties include, but are not limited to, magnetic monolayer cholesteric liquid crystal pigment particles and magnetic multilayer cholesteric liquid crystal pigment particles. Such pigment particles are disclosed, for example, in WO 2006 / 063926 A1, US Pat. No. 6,582,781, and US Pat. No. 6,531,221. WO 2006 / 063926 A1 discloses monolayers having high brightness and color shift properties, as well as additional specific properties such as magnetizability, and pigment particles obtained therefrom. The disclosed monolayers and pigment particles obtained therefrom by comminuting the monolayers comprise a three-dimensionally crosslinked cholesteric liquid crystal mixture and magnetic nanoparticles. US 6,582,781 and US 6,410,130 disclose platelet-shaped cholesteric multilayer pigment particles comprising the sequence A1 / B / A2, wherein A1 and A2 may be identical or different and each comprise at least one cholesteric layer, and B is an interlayer that absorbs all or part of the light transmitted by layers A1 and A2 and imparts magnetic properties to the interlayer. US 6,531,221 discloses platelet-shaped cholesteric multilayer pigment particles comprising the sequence A / B and optionally C, wherein A and C are absorbing layers comprising pigment particles imparting magnetic properties, and B is a cholesteric layer.

[0148] Suitable interference-coated pigment particles comprising one or more magnetic materials include, but are not limited to, structures consisting of a substrate selected from the group comprising a core coated with one or more layers, wherein at least one of the core and the one or more layers has magnetic properties. For example, suitable interference-coated pigment particles include a core made of a magnetic material such as the magnetic materials described above, the core coated with one or more layers made of one or more metal oxides, or they have a core made of synthetic or natural mica, layered silicates (e.g., talc, kaolin, and diatomaceous earth), glass (e.g., borosilicate), silicon dioxide (SiO2), aluminum oxide (Al2O3), titanium oxide (TiO2), graphite, and mixtures of two or more thereof. In addition, one or more additional layers may be present, such as a coloring layer, etc.

[0149] The platelet-shaped, magnetic or magnetizable pigment particles described herein preferably have a size d50 (as measured by direct optical granulometry) of between about 2 μm and about 50 μm.

[0150] The platelet-shaped magnetic or magnetizable pigment particles described herein may be surface treated to protect them from any degradation that may occur in coating compositions and coating layers and / or to facilitate their incorporation into such coating compositions and coating layers; typically corrosion inhibitor materials and / or wetting agents may be used.

[0151] The magnetically sensitive layer (120) described herein is prepared by a process comprising the following steps: a) applying a coating composition comprising the reflective flake-shaped magnetic or magnetizable pigment particles described herein; b) exposing the coating composition to a magnetic field of a magnetic field generating device, thereby orienting at least a portion of the reflective flake-shaped magnetic or magnetizable pigment particles, and c) hardening the coating composition, thereby fixing the reflective flake-shaped magnetic or magnetizable pigment particles in the position and orientation they have adopted.

[0152] Preferably, the coating compositions described herein include the reflective flaky magnetic or magnetizable pigment particles described herein dispersed in a binder material, wherein the reflective flaky magnetic or magnetizable pigment particles are present in an amount of from about 2 wt-% to about 40 wt-%, more preferably from about 4 wt-% to about 30 wt-%, these weight percentages being based on the total weight of the coating composition including the binder material, the reflective flaky magnetic or magnetizable pigment particles, and other optional components of the coating composition. The coating compositions described herein may also include one or more coloring components selected from the group consisting of organic pigment particles, inorganic pigment particles, and organic dyes and / or one or more additives. The latter include, but are not limited to, compounds and materials for adjusting the physical, rheological, and chemical parameters of the coating composition, such as viscosity (e.g., solvents, thickeners, and surfactants), consistency (e.g., anti-settling agents, fillers, and plasticizers), foaming properties (e.g., defoamers), lubricity (waxes, oils), UV stability (light stabilizers), adhesion properties, antistatic properties, storage stability (inhibitors), etc. The additives described herein may be present in the coating composition in amounts and forms known in the art, including so-called nanomaterials, where at least one dimension of the additive is in the range of 1 to 1000 nm.

[0153] The applying step a) described in the previous paragraph is performed by a printing process, which is preferably selected from the group consisting of the following: screen printing, rotogravure printing and flexographic printing. These processes are well known to the technical staff and are for example described in Printing Technology, JM Adams and PADolin, Delmar Thomson Learning, the 5th edition, pages 293, 332 and 352. When the coating composition comprising reflective flaky magnetic or magnetizable pigment particles as herein described is still enough wet or soft, so that when the pigment particles can move and rotate (that is, when the coating composition is in the first state), the coating composition is subjected to a magnetic field to realize the orientation of the particles. The step of making reflective flaky magnetic or magnetizable pigment particles magnetic orientation comprises that when the applied coating composition is "wet" (that is, still liquid and not too viscous), it is exposed to the definite magnetic field generated by the magnetic field generating device, so that reflective flaky magnetic or magnetizable pigment particles are oriented along the field lines of the magnetic field to form an orientation pattern.

[0154] After, partly simultaneously with, or simultaneously with the application of the coating composition, the reflective flake-shaped magnetic or magnetizable pigment particles are oriented by using an external magnetic field to orient the particles according to a desired orientation pattern. The orientation pattern thus obtained may be any pattern other than random orientation and other than a pattern in which the reflective flake-shaped magnetic or magnetizable pigment particles have their magnetic axes oriented parallel or perpendicular to the layer (120).

[0155] The method for producing the magnetic induction layer (120) described herein comprises, partly simultaneously with step b) or after step b), a step c) of hardening the coating composition to fix the partially reflective flaky magnetic or magnetizable pigment particles in the desired pattern in the positions and orientations they adopt to form the magnetic induction layer, thereby converting the coating composition into a second state. By this fixing, a solid coating or layer is formed. The term "hardening" refers to a process that includes drying or solidifying, reacting, curing, crosslinking or polymerizing the binder components of the applied coating composition, including the optional presence of a crosslinking agent, the optional presence of a polymerization initiator, and the optional presence of further additives, in such a way that a substantially solid material adheres to the surface on which it is formed. As mentioned herein, the hardening step c) can be carried out using different means or processes depending on the materials included in the coating composition that also includes the reflective flaky magnetic or magnetizable pigment particles. The hardening step can generally be any step that increases the viscosity of the coating composition so that a substantially solid material adheres to the supporting surface. The hardening step may involve a physical treatment based on the evaporation of volatile components (such as solvents) and / or water evaporation (i.e., physical drying). Here, hot air, infrared light, or a combination of hot air and infrared light may be used. Alternatively, the hardening treatment may include a chemical reaction, such as curing, polymerizing, or crosslinking the binder and optional initiator compound and / or optional crosslinking compound included in the coating composition. This chemical reaction may be initiated by heat or IR irradiation as outlined above for the physical hardening treatment, but may preferably include initiating a chemical reaction by a radiation mechanism, including but not limited to ultraviolet-visible radiation curing (hereinafter referred to as UV-Vis curing) and electron beam radiation curing (electron beam curing); oxidative polymerization (oxidative reticulation, typically induced by the combined action of oxygen and one or more catalysts, preferably selected from the group consisting of cobalt catalysts, vanadium-containing catalysts, zirconium-containing catalysts, bismuth-containing catalysts, and manganese-containing catalysts); crosslinking reaction, or any combination thereof. Radiation curing is particularly preferred, and UV-Vis light radiation curing is even more preferred, as these techniques advantageously result in very rapid curing processes and thus significantly reduce the preparation time of any document including the magnetic induction layer described herein. In addition, radiation curing has the following advantages: after being exposed to curing radiation, produces the almost instantaneous increase of coating composition viscosity, thereby any further movement of particle is minimized.Therefore, any information loss after magnetic orientation step can be avoided basically.Particularly preferably under the influence of the actinic light with the wavelength component in the UV-Vis electromagnetic spectrum by photopolymerization radiation curing.For example, the equipment that is used for UV-visible-curing can comprise continuous or pulsed laser (, GaN), high power light emitting diode (LED) lamp or arc discharge lamp (such as medium pressure mercury arc (MPMA) or metal vapor arc lamp) as actinic radiation source.

[0156] If a primer (140), preferably a dark primer and more preferably a black primer, is present between the substrate (110) and the magnetic induction layer (120), the steps of applying and hardening the primer composition are performed before preparing the magnetic induction layer (120). The primer composition described herein can be applied by various coating processes, preferably selected from the group consisting of: inkjet printing, offset printing, flexographic printing, gravure printing, screen printing, pad printing, and roller coating.

[0157] The magnetic sensing layer (120) described herein comprises (at least) two regions (see Figure 2A): a first zone (120a), which includes magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, the flat faces of which are oriented in a first direction and have a first elevation angle γ1 relative to a substrate (110), the first elevation angle corresponding to the angle between the flat face and the plane of the substrate (110); and a second zone (120b) different from the first zone (120a), which includes magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, the flat faces of which are oriented in a second direction different from the first direction and have a second elevation angle γ2 relative to the substrate (110), the second elevation angle corresponding to the angle between the flat face and the plane of the substrate (110). To define the elevation angles in two regions of the magnetically sensitive layer (which are consistent with a generally counterclockwise rotation direction corresponding to some given right-handed standard orthogonal triple defined on a reference plane (top surface) of the substrate (e.g., with the x and y axes lying in this plane and the z axis oriented outward), the elevation angle γ1 of the flat face of the pigment particle in the first region is the angle counted counterclockwise between the plane of the substrate and the plane of the face, i.e., for a positive rotation about the straight line L1 that intersects the flat face with the reference plane (from the reference plane toward the flat face), while the elevation angle γ2 of the flat face of the pigment particle in the second region is the angle between the plane of the substrate and the plane of the face, again counted counterclockwise, but this time for a positive rotation about the straight matching line obtained by rotating the straight line L2 that intersects the flat face with the reference plane in the reference plane so that it is aligned with line L1. This method of determining the elevation angles in two different regions of particle orientation facilitates unambiguous comparison of the elevation angles and the orientation direction. In each zone of the magnetic sensing layer (120), consistent with experimental tests conducted according to the present invention, the acute angle of the flat surface relative to the plane of the substrate (110) is preferably in the range of from about 5° to about 25°. In addition, as a result of the experimental tests, the two different orientation directions of the flat surface in the two zones (120a) and (120b) are preferably at an angle of at least 30° so that when the illuminated security mark (100) is observed at two viewing angles corresponding to the optimal reflection of light from the first zone and the second zone, respectively, there is an acceptable contrast between the two zones. In the example shown in FIG2 , in which the faces of the pigment particles in each zone (120a, 120b) are substantially parallel to each other (i.e., the normals of the faces in each zone are substantially parallel, see Figure 2A), when measured in the counterclockwise direction as specified above, the first elevation angle γ1 has a value in the range of about 5° to about 25° (5°≤γ1≤25°), preferably in the range of about 5° to about 20° (5°≤γ1≤20°), and when measured in the counterclockwise direction as specified above, the second elevation angle γ2 has a value in the range of about 155° to about 175° (155°≤γ2≤175°), more preferably in the range of about 160° to about 175° (160°≤γ2≤175°). The acute angle formed by the faces of the pigment particles in the second region (120b) of the magnetically sensitive layer (120), i.e., the angle complementary to the elevation angle γ2, is therefore in the range of about 5° (e.g., 180°-175°=5°) to about 25° (e.g., 180°-155°=25°).

[0158] exist Figure 2B In the embodiment shown, the magnetically sensitive layer (120) comprises magnetically oriented, plate-like magnetic or magnetizable pigment particles in a single layer of material applied to a flat substrate (110). Figure 2C In the embodiment shown in , the magnetic sensing layer (120) comprises two different sub-layers forming two regions (120a) and (120b), respectively, wherein the first sub-layer and the second sub-layer are adjacent, i.e. have adjoining edges forming a common boundary. According to another embodiment ( Figure 2C (not shown), two different sub-layers forming the two regions (120a) and (120b), respectively, are spaced apart from each other.

[0159] Instead of using a magnetosensitive layer comprising reflective platelet-shaped magnetic or magnetizable pigment particles having a magnetic orientation with the elevation angles described herein, it is possible to use diffractive, reflective, refractive microstructures, such as diffraction gratings, as well as layers comprising microlens or micromirror structures, said structures comprising micromirrors whose faces have the specific elevation angles described herein.

[0160] According to the present invention, Figure 3 As shown in FIG5 , a machine-readable mark (130) (which is in the form of a two-dimensional barcode and includes a reference pattern (133) and a code pattern (134) representing encoded data) is applied on the top surface (121) of the magnetic sensing layer (120), or applied on the substrate (110) between the substrate (110) and the back surface (122) of the magnetic sensing layer (120), with a first area (134a) of the code pattern (134) being arranged in front of the first area (120a), and a remaining second area (134b) of the code pattern (134) being arranged in front of the second area (120b). The reference pattern (133) is used to accurately locate the code pattern (134) during image processing operations when reading and decoding the machine-readable mark (130). Figure 5B An embodiment of a QR code and its characteristic reference pattern (133) in the form of three squares is illustrated. Figure 5C An embodiment of a data matrix code with its L-shaped reference pattern (133) is illustrated. Other machine-readable code formats (e.g., dot matrices) can be used with their reference patterns in the present invention. It is also possible to use a machine-readable mark in which the reference pattern is marked separately from the code pattern in an area outside the magnetically sensitive layer (but still must be within the field of view of the reader when reading the machine-readable mark).

[0161] The machine-readable markings (130) described herein may be produced by any suitable means, including printing processes (particularly inkjet printing), etching and ablation methods (particularly laser etching or burning), embossing methods, and the like.

[0162] Figure 3The present invention is an exploded view of a security mark (100) according to an embodiment of the present invention, the security mark comprising a flat substrate (110), a magnetic sensing layer (120) having two regions (120a) and (120b) having different orientations of their magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, and a machine-readable mark (130) in the form of a QR code, wherein the two regions have different orientations of their magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles, the magnetic sensing layer having a top surface (121) and a back surface (122), and the machine-readable mark having a top surface (131) and a back surface (132), wherein the machine-readable mark (130) partially overlaps the magnetic sensing layer (120). Here, the machine-readable mark (130) is applied on top of the magnetic sensing layer (120), which is applied on the substrate (110). The first region (134a) of the code pattern (134) is disposed in front of the first region (120a), and the second region (134b) of the code pattern (134) is disposed in front of the second region (120b). The effect of the present invention is that two different images of the machine-readable mark (130) need to be taken at two different viewing angles in order to obtain the complete coded data from the code pattern, these viewing angles corresponding to the elevation angles and orientations of the pigment particles in the two regions (120a) and (120b), respectively. In practice, due to the difference in the reflectivity of light from the two regions (120a) and (120b) of the magnetic sensing layer (120) when imaged at a single viewing angle, only a portion of the imaged code pattern can be reliably detected, namely, the portion of the code pattern corresponding to the region of the code pattern in front of the region of the magnetic sensing layer that provides the best contrast (if the viewing angle is a right angle corresponding to the elevation angle of the face of the pigment particles in the region, because the elevation angle of the face of the pigment particles sets the viewing angle at which the specular reflection of light from the face is maximum for a given light source position). Therefore, it is impossible to simultaneously obtain the required contrast for detecting the coded data for both regions (134a) and (134b) of the code pattern (134) from a single viewing angle. In order to reliably detect the full coded data, it is necessary first to acquire two images of the machine-readable mark (130) at two different viewing angles corresponding to the elevation angles of the pigment particle planes in the first region (120a) and the second region (120b) of the magnetically sensitive layer (120) so as to obtain only the corresponding portion of the code pattern (130) that can be reliably detected on each image, and secondly to reconstruct an image of the full code pattern from the two acquired images so as to reconstruct the two detected portions of the code pattern. This reconstruction must use the imaged reference pattern (133) so as to have a common reference position element on both images in order to accurately reconstruct the two detected portions and reassemble a decodable image of the full code pattern (130). Where such a reconstruction is possible, it implicitly means that the imaging operation has been performed according to the very specific structure of the security mark and that the security mark (100) is therefore most likely to be authentic: this is another advantage of the present invention.

[0163] Figures 4A-4C Different embodiments of the security mark (100) according to the present invention are illustrated. In the diagram showing a cross section of the security mark (100) Figure 4A In the example, a magnetic sensing layer (120) is applied on a substrate (110), and a machine-readable mark (130) is applied on a top surface (121) of the magnetic sensing (single) layer (120), wherein the machine-readable mark (130) partially overlaps with the magnetic sensing layer (120).

[0164] In the cross section showing the security mark (100) Figure 4B In an example, a dark primer (140) (preferably a black primer) is provided between a substrate (110) and a magnetic sensing layer (120): the back side (142) of the dark primer (140) is applied on the top side of the substrate (110), and the back side (122) of the magnetic sensing layer (120) is applied on the top side (141) of the dark primer, wherein the machine-readable mark (130) may be encoded in a light symbol or a dark symbol, partially overlapping the magnetic sensing layer (120).

[0165] In the cross section showing the security mark (100) Figure 4C In an example, a machine-readable mark (130) is applied on the top surface of the substrate (110), preferably encoded with a dark symbol, and the back surface (122) of the magnetic sensing layer (120) is applied on the top surface (131) of the machine-readable mark (130), wherein the machine-readable mark (130) partially overlaps with the magnetic sensing layer (120).

[0166] As mentioned above, reading and decoding the two-zone magnetic sensing layer (120) requires taking (at least) two images of the security mark (100). According to the present invention, the method for reading and decoding the security mark (100) uses a portable device (200) (as shown in Figure 6, such as a smartphone) equipped with a light source (201) to deliver illumination light (preferably in the visible spectrum or NIR spectrum (i.e., wavelengths from 400nm to 1000nm)), an imager (202) to take digital images (e.g., a smartphone camera), and a processor (not shown) equipped with a memory (not shown) and suitable for performing image processing and decoding operations, and the method comprises the following steps:

[0167] (i) illuminating a security marker (100) disposed within the field of view of an imager (202) using illumination light delivered by the light source (201), for example, a smartphone's LED ("light emitting diode") flash adjacent to the imager (the smartphone's camera).

[0168] (ii) capturing a first digital image of the security mark (100) using an imager (202) at a first viewing angle θ1, which is associated with a first elevation angle γ1 of the pigment particles in the first region (120a) of the magnetic sensing layer (120), and storing the captured first digital image in a memory. For the example of a smartphone, the viewing angle θ1 at which the intensity of light reflected from the surface of the pigment particles in the first region (120a) is maximum when the imager is very close to a (quasi-point-shaped) light source corresponds to an imager position substantially perpendicular to the surface of the pigment particles in the first region (120a). With this viewing angle θ1, only the portion of the code pattern (134) applied to the first region (120a) of the magnetic sensing layer (120) can be reliably read (with good contrast) in the first digital image, because the portion of the code pattern (134) applied to the second region (120b) of the magnetic sensing layer (120) does not reflect sufficient light (θ1 does not match the elevation angle γ2).

[0169] (iii) acquiring a second digital image of the security mark (100) at a second viewing angle θ2, associated with a second elevation angle γ2 of the pigment particles in the second region (120b) of the magnetic sensing layer (120), using the imager (202), and storing the acquired second digital image in a memory. In the above example of a smartphone in which the imager is very close to the light source, the viewing angle θ2 at which the intensity of light reflected by the plane of the pigment particles in the second region (120b) is maximum corresponds to an imager position substantially perpendicular to the plane of the pigment particles in the second region (120b). At this viewing angle θ2, only the portion of the code pattern (134) applied to the second region (120b) of the magnetic sensing layer (120) can be reliably read (with good contrast) in the second digital image, because the portion of the code pattern (134) applied to the first region (120a) of the magnetic sensing layer (120) does not reflect sufficient light (θ2 is not suitable for the elevation angle γ1).

[0170] (iv) forming a composite digital image (i.e., reconstructing a digital image) of the code pattern (134) from the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to a first region (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to a second region (134b) of the code pattern detected on the second digital image relative to a reference pattern (133) (detected in the first digital image and the second digital image) through image processing using a processor, and storing the obtained composite digital image in a memory. Here, the first portion of the code pattern (134) is a portion of the code pattern in a first region (134a) applied on the top surface (121) of the first region (120a) of the magnetic sensing layer (120), and the second portion of the code pattern (134) is a portion of the code pattern in a second region (134b) applied on the top surface (121) of the second region (120b) of the magnetic sensing layer (120).

[0171] (v) Reading and decoding the code pattern (134) from the stored composite digital image (ie, from the reconstructed digital image of the full code pattern that enables simultaneous and reliable detection and decoding of both regions of the code pattern) using a processor.

[0172] As explained above, the only possibility to reliably detect and decode the machine-readable marking (130) is to take two images of the first region (134a) and the second region (134b) of the code pattern (134) at two viewing angles suitable for the specific orientation of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles in the first region (120a) and the second region (120b) of the magnetically sensitive layer (120), respectively. The fact that the machine-readable marking of the security marking (100) can be decoded means that the two-region structure of the magnetically sensitive layer (120) has been confirmed using viewing angles corresponding to the appropriate elevation angles (i.e., the appropriate orientation) of the planes of the pigment particles in the two regions (120a) and (120b). Therefore, the possibility of decoding the machine-readable marking (130) constitutes a first level of authentication of the security marking (100).

[0173] According to the present invention, another level of authentication of the security mark (100) can be achieved by exploiting the material properties of the security mark (100) at a greater depth. This can be accomplished by moving the imager (202) of the portable device (200) over (and parallel to) the security mark while illuminating the security mark (100) with a light source (201) while viewing the image at various viewing angles θ. iA plurality of digital images of the security mark are taken at locations (i=1, ..., N), and a corresponding "curve" I (θ) of the intensity I of the light reflected from the region at the various viewing angles is formed based on the acquired digital images and for each region of the magnetic sensing layer. i )(i=1,…,N). Each curve I(θ) allows a more detailed analysis of the reflectivity of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles in the corresponding region of the magnetic sensing layer (120) (because intensity is a function of reflectivity). In particular, based on a similarity criterion of the curves, the exact shape of the reflectivity curves R(θ) to I(θ) (R(θ) is the average reflectivity) (which is a characteristic of the nature and orientation of the pigment particles and the material of the sensing layer of the relevant region and shows a peak of a characteristic shape around viewing angle values ​​associated with the elevation angle values ​​of the pigment particles in this region) can be compared with the reference reflectivity curve R ref (θ)~I ref The curves I(θ) are compared with the curves I(θ) (known to the authority to which the security marking has been delivered) to decide whether the shapes of the two curves are reasonably consistent. For example, correlation can be used to compare the curves. Another approach is to perform a linear regression to estimate the linear relationship between the measured curve and the reference curve and to assess how close the slope is to unity and how close the goodness of fit is to unity. Preferably, each curve I(θ) is obtained based on the measured average intensity I of the reflected light from the corresponding zone. This constitutes a strong authenticity verification of the material structure of the security marking and therefore also of the authenticity of the data encoded in the machine-readable marking of the security marking. Another advantage of the present invention which also facilitates the authentication of the security marking is the type of movement of the imager over the security marking to be performed in order to acquire a plurality of digital images of the machine-readable marking appropriately depending on the relative arrangement of the pigment particles in the different zones of the magnetically sensitive layer. For example, in the case of the magnetic induction layer as shown in FIG2 , in the case where the orientation directions of the pigment particles in the first zone (120a) and the second zone (120b) are both included in a plane perpendicular to the plane of the substrate (110), in order to obtain multiple digital images in order to obtain the reflectivity curve I(θ), a relative translational movement (along the direction included in the perpendicular plane) of the imager (202) and the security mark (100) is required. However, with different designs of the two (or more) zones of orientation of the pigment particles of the magnetic induction layer (for example, the orientation directions are at an angle less than 180° or greater than 180°), the relative movement will correspond to a rotational movement. Preferably, the reflectivity curve I(θ) is obtained from the measured average intensity I. However, other metrics can be used for authentication of the security mark. Other embodiments may include an authentication algorithm based on a classifier or a neural network-based machine learning, which is capable of distinguishing a true intensity profile (or other measured or extracted features, such as a variation profile or image entropy) from an inauthentic intensity profile.

[0174] As an example of an equivalent method for authenticating a security mark, instead of measuring the (possibly averaged) intensity of light reflected by the magnetically sensitive layer to obtain a reflectivity curve, machine learning can be applied to the image at various viewing angles θ. i The above-mentioned multiple digital images of the security mark taken at (i=1,...,N) This method includes the following three steps: feature extraction, model training and selection, and prediction.

[0175] Regarding the feature extraction step, the imager returns a series of RGB images I(θ), where θ min ≤θ≤θ max If necessary, the image can be cropped to save only the region of interest (RoI) around the security marker. These images can be linearized and converted to grayscale (as described in "Digital Image Processing" by RC Gonzalez, TE Woods (4th edition, Pearson, 2017)). However, separate processing of the color channels is also possible.

[0176] For each image, one or several metric functions f(θ) are calculated. A comprehensive description of image metrics applied to images can be found in the book by RC Gonzales and TE Woods mentioned above. The metrics can be calculated directly on the image intensity or on the image intensity via a transformation such as the Discrete Fourier Transform (DFT) or the Discrete Wavelet Transform (DWT). Among the useful metrics that can be used, we find the mean, the standard deviation and the entropy. Depending on the metric used, we may need to scale it with the mean intensity of a reference neighboring RoI (this operation allows to compensate for the variable exposure time of the imager and any changes in the illumination of the marker).

[0177] For all measurements to have the same scale, the metric must be estimated on a uniformly sampled grid of angles. These angles must be symmetric about the sample normal. We can denote this uniform grid as θ = [θ1…θ N ], where N is the number of angles (e.g., N=21). In practice, scanning at evenly spaced angles may not always be possible, and interpolation of metrics may have to be performed. At the end of the scanning procedure, we obtain the feature vector x T =[f(θ1) f(θ1) … f(θ N )]=[x1 x1… x N By further performing M scans on different security markers to account for their variability, we build a dataset X of size N × M T =[x1 … x M ].

[0178] Regarding the steps of model training and selection, general machine learning techniques for classification and detection are described in CM Bishop's "Pattern Recognition and Machine Learning" (Springer, 2009). Here, the authentication problem is reduced to distinguishing real feature vectors from fake or attacked ones. However, while the real feature vectors are known and available, other feature vectors are unknown or rare. Therefore, directly training a two-class classifier is not feasible. As described in O. Mazhiliser's "One-Class Classifiers: A Review and Analysis of Suilability in the Context of Mobile-Masquerader Detection" (South African Computer Journal, column 36, pages 29-48, 2006), authentication can be shown to be equivalent to one-class classification. In this scenario, the classifier model relies solely on the real feature vectors to learn its parameters and decision boundaries. Among them, support vector data description (SVDD), v-support vector classification (v-SVC), Gaussian mixture model (GMM) and deep learning models (such as Autocoder) are of practical significance. The choice of model is determined by its performance during training and is also constrained by its complexity. Under equivalent performance, simpler models are preferred.

[0179] Before training the model, the dataset X is preprocessed as shown in the following figure and the following steps are performed:

[0180] - Sample cleaning. Discard defective samples, such as those that are saturated or missing features.

[0181] - Sample normalization. The eigenvectors are normalized to unit energy.

[0182] - Feature normalization. Feature mean μ(θ d ) and characteristic standard deviation σ(θ d ) are estimated and removed feature by feature.

[0183] - Sample detrending: A low-order polynomial with fixed order P is estimated and detrended for each sample.

[0184] - Feature reduction. Remove inter-feature correlations and reduce the dimensionality of the problem. Here, for example, the reduction can be from N = 21 to K = 3-5. Lower dimensional optimization problems converge faster and allow easier inspection. This step is achieved by generating a vector subspace V = [v1 ... v K] is done by principal component analysis (PCA) (see CM Bishop’s book, “Pattern Recognition and Machine Learning” (Springer, 2009)). After PCA, we project the dataset X onto the subspace V, which results in a feature-reduced dataset X′ with size K×N. T =[x′1 … x′ N ]. This dataset is used to learn the parameters Θ of a candidate one-class classification model. Finally, the best candidate is retained for prediction.

[0185] Regarding the prediction step, the dataset is subjected to data cleaning, sample normalization, feature standardization, trend elimination, subspace projection, and calculation of the model decision function. Finally, after feature reduction by subspace projection, the decision function of the classifier using the learned parameters is calculated (see also I. Goodfellow, Y. Bengio, A. Courville, "Deep Learning" (MIT Press, 2016)).

[0186] In the example of embodiment of the above method based on the reflectivity curve I(θ), it is related to the QR code (see Figure 3 and Figure 5A ), wherein the overlap of the magnetically sensitive layer (120) and the machine-readable mark (130) is selected to preserve the detection of the code against the reference pattern (133) and the clock (in this way, the code pattern (134) can always be located, although not necessarily decoded at all viewing angles). QR codes are a well-known standardized symbology that is graphically constructed in a manner that allows the following three basic operations to be performed based on features or graphical elements obtained from the image of the QR code:

[0187] 1) Positioning of the code using a specific graphic design (reference pattern (133)) that is robustly and accurately detectable by suitable image processing algorithms.

[0188] 2) From a series of alternating dark modules and light modules arranged along one or more lines in two orthogonal directions (in Figure 5A The sampling grid and module size are extracted from the clock visible on the .

[0189] 3) Data, coding mode and error correction area are contained in Figure 5A In the QR code in the other area (on the right edge). According to a specific encoding algorithm, the data is encoded as light modules and dark modules in specific areas of the symbol.

[0190] A machine-readable code (130) of a security mark (100) is read and decoded using a portable device (200), the portable device (200) comprising:

[0191] - a light source (201) for delivering illumination light;

[0192] - an imager (202) (camera) for taking a digital image of the security marking (100); and

[0193] - a processor provided with a memory and adapted to perform the steps of the above method on a digital image of the security marking (100) taken by the imager (202).

[0194] like Figure 7 As shown, using a decoding method (700), a first sequence of digital images of a security mark (100) is acquired (701) at different viewing angles of the imager (202) relative to the security mark (100): the viewing angle is close to a first viewing angle θ1 (which is associated with the elevation angle γ1 of the pigment particles in the first region (120a) of the magnetically sensitive layer). The acquired sequence of digital images is used to estimate (702) the imager pose relative to the machine-readable mark (130) in the manner described below (in this context, the combination of position and orientation is called the pose of an object in computer vision). The imager pose is checked against various acceptance criteria: for example, 15°±3° relative to the normal of the substrate (110), and the digital images from the sequence are checked for sufficient sharpness (703). For example, by checking Weber contrast, Michelson RMS contrast. If the digital image under consideration is not accepted (703, "N", i.e., "No"), the next digital image (701) of the sequence is considered. If a pose passes the acceptance criteria, the digital image corresponding to the pose is further processed (703, "Y", i.e., "Yes"). The digital image is then corrected for perspective distortion and resampled using a predetermined resolution (704). Using the imager pose information and a priori knowledge of the location of the magnetic sensing layer (120) in the design of the security mark, a mask can be constructed to retain only the portion of the digital image where the first region of the magnetic sensing layer exists (705).

[0195] The same process (706 to 710) is repeated with the imager (202) at various viewing angles near a second viewing angle θ2 associated with an elevation angle γ2 of the pigment particles within the second region (120b) of the magnetically sensitive layer (120).

[0196] The digital image obtained at step (704) after being masked at step (705) and the digital image obtained at step (709) after being masked at step (710) are combined at step (711) to form a resulting composite digital image. The composite digital image obtained at step (711) is then decoded (including error correction) by a decoder at step (712) and the data content of the code pattern (134) is extracted. The combination of the two digital images at step (711) can be achieved via known digital image processing algorithms that stitch the two digital images and adjust the contrast and intensity across the machine-readable mark. Another possibility is to perform the above operations on two digital images A and B of the security mark (100) (the two digital images were taken at viewing angles close to θ1 and θ2 as described above) and:

[0197] - locating a "partial" code pattern (corresponding to the first part of the code pattern (134)) from image A and constructing a sampling grid using standard code detection techniques;

[0198] - forming a binary representation B1 of a partial code pattern of image A;

[0199] - locating the "partial" code pattern (corresponding to the second part of the code pattern (134)) from image B and constructing a sampling grid using standard code detection techniques;

[0200] - a binary representation B2 of a partial code pattern forming the image B;

[0201] - combining the obtained binary representations B1 and B2 of the code patterns of images A and B by applying the truth table to each corresponding module of the binary representation (i.e. a “black” module in B1 and a black module in B2 give a black module of the combined binary representation CB; a “white” module in B1 and a white module in B2 give a white module in CB; a black (or white) module in B1 and a white (or black) module in B2 give a white module in CB); and

[0202] - applying a standard code error correction algorithm to the obtained combined binary representation CB of the (full) code pattern in order to recover potential errors that may have been present and obtain an error-free composite digital image of the code pattern (134).

[0203] The pose estimation of the imager (202) can be performed using several known methods. Figure 8A and Figure 8B Two of the postures are schematically shown respectively.

[0204] One possible approach to pose estimation is as follows (see Figure 8A ):

[0205] The machine-readable mark (130) is applied to a flat surface, and the acquired digital image sequence (801) is sent to a commercially available plane extraction library (802) (such as Vuforia, ARCore or ARKit). The library returns an estimated pose of the imager relative to the plane of the applied machine-readable mark (803).

[0206] Another possible approach to pose estimation is as follows (see Figure 8B ) (If the reference pattern is not suitable for pose estimation, a fiducial marker (e.g., CCTag) may be added to the safety marker):

[0207] The acquired digital image (804) is processed (via conventional image processing) to extract the graphic design information (i.e., the location of the reference pattern) (805) and the reference pattern (133) is detected (806) by using a known pattern matching or detector specific to the type of tag (e.g., CCTag, ARTag, ARToolKit tag, etc.) (here, QR code), and the detected reference pattern location is used to provide a pose estimate (807), for example, by using the SolvePnP program from the OpenCV library (e.g., see the article by V. Lepetit et al., "An align o(n) solution to the pnp problems" (International Journal of Computer Vision, 81(2), pp. 155-166, 2009). However, many other pose estimation methods are known to those skilled in the art.

[0208] Other types of machine-readable markings may be used to implement the present invention, such as a data matrix having a reference pattern in the form of an L-shape (see Figure 5C ).

[0209] Figure 9 An example of a security document (150) according to the invention is shown, here an identification card of a user John Doe with printed identity data (151) indicating the user's name, his address and date of birth. The security document has been delivered to the user by an authorized institution, and the authorized institution has applied a security mark (100) to the document. The code pattern (134) of the machine-readable mark (130) of the security mark (100) contains the encoded digital identity data of the user (here corresponding to the printed identity data) and a digital signature of these digital identity data. The digital signature is delivered by the authorized institution and is obtained using an encryption key (stored in the database of the authorized institution together with a corresponding decryption key). The security mark (100) corresponds to Figure 5CThe security marking is shown (ie, a two-dimensional GS1 Data Matrix barcode). Depending on the data storage capacity of the machine-readable marking, additional identity data may be encoded in the code pattern (130) (eg, biometric data of the user, and in some cases a photograph of the user).

[0210] Figure 10 Is verified by the controller Figure 9 This method of verifying a security document (150) utilizes a controller having a portable device (200) as shown in FIG6 and further equipped with a communication unit operable to connect to a database (DB) (see also FIG6 ) via a communication network (CN) Figure 11 ), wherein an encryption key K for digitally signing the coded data in the code pattern (134) is stored together with a corresponding decryption key K', the method comprising the following steps (see also FIG6 ):

[0211] - (1000) placing (by a controller) a security mark (100) on a security document (150) within the field of view of an imager (202) of a portable device (200);

[0212] - (1001) illuminating the security marking (100) of the security document (150) using a light source (201) of the portable device (200);

[0213] - (1002) acquiring, using an imager (202), a first digital image of the illuminated magnetically sensitive layer (120) at a first viewing angle θ1 associated with a first elevation angle γ1 of the magnetically oriented reflective plate-shaped magnetic or magnetizable pigment particles within a first region (120a) of the magnetically sensitive layer (120), and storing the acquired first digital image in a memory;

[0214] - (1003) acquiring, using the imager (202), a second digital image of the illuminated magnetically sensitive layer (120) at a second viewing angle θ2 associated with a second elevation angle γ2 of the magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles within the second region (120b) of the magnetically sensitive layer (120), and storing the acquired second digital image in a memory;

[0215] - (1004) forming a composite digital image of the code pattern (134) from the first digital image and the second digital image by aligning a first portion of the code pattern (134) corresponding to a first area (134a) of the code pattern (134) detected on the first digital image and a second portion of the code pattern (134) corresponding to a second area (134b) of the code pattern (134) detected on the second digital image, relative to a reference pattern (133) (here, an L-shape of a data matrix) detected in the stored first digital image and the stored second digital image, via image processing using a processor;

[0216] - (1005) reading and decoding the code pattern (134) from the obtained synthetic digital image via image processing and decoding operations using a processor, extracting the user identity data UID and the digital signature UIDS of the user identity data from the decoded data of the code pattern, and storing the extracted user identity data UID and digital signature UIDS in a memory;

[0217] - (1006) sending a first message (M1) containing the extracted user identity data UID and the digital signature UIDS stored in the memory to the server (S) via the communication unit;

[0218] - (1007) decrypting, at the server (S), the extracted digital signature UID received in the first message (M1) from the portable device (200) using a decryption key K' stored in the database (DB), and checking whether the extracted user identity data UID received in the first message (M1) matches the decrypted extracted digital signature UID;

[0219] - (1008) in case of a match, sending a server message (SM) back to the portable device (200) indicating successful verification of the user identity data; and

[0220] - (1009) In case the extracted user identity data UID received in the first message (M1) does not match the decrypted extracted digital signature UID, a server alert message (SALM) is sent back to the portable device (200) indicating a failure in the verification of the user identity data.

[0221] In case the portable device (200) receives the server alert message (SALM), a controller using the portable device is notified that the security document is not genuine and, for example, the controller can take necessary measures against the user who has produced the forged security document.

[0222] Figure 11Schematically shown is a security file adapted to perform the above-mentioned operation for allowing the controller to authenticate the user (eg Figure 9 The diagram shows a system for operating a secure file (150) that has been delivered to a server (S) of an authorized institution of a user, which is connected to a database (DB) storing an encryption key K and its corresponding decryption key K'. The portable device (200) of the controller is a smartphone. Here, the screen of the smartphone displays a server message (SM) indicating that the authentication of the secure file was successful (e.g., displaying the message OK).

[0223] The above method of verifying a user's security documents according to the present invention, and the corresponding system for implementing the operations necessary to perform said verification, may have some variants involving deep authentication of security tokens, in particular when the verification method is used to grant the user access to certain online services (e.g., banking transactions, online registration, online payment, etc.).

[0224] In a first variant embodiment of the verification method, we consider a user equipped with a smartphone that is appropriately programmed (e.g. by downloading a suitable application running on the smartphone for image processing and decoding operations) so as to also function as a portable device (200) according to the invention (as shown in FIG6 ). The smartphone is equipped with a communication unit operable to communicate via a communication network (CN) with respect to an identity card (corresponding to a card) that has been delivered to the user. Figure 9 The server (S) of the authority that digitally signs the security document (150) shown in FIG. 1 sends and receives data. The server (S) is connected to a database (DB) that stores an encryption key K and a corresponding decryption key K' used to digitally sign the coded data in the code pattern (134) of the machine-readable mark (130) of the security mark (100) applied to the identity card. The following steps are performed:

[0225] - (1200) placing (by the user) the security mark (100) on the security document (150) within the field of view of the imager (202) of the smartphone (200);

[0226] (1201) illuminating the security marking (100) of the security document (150) using a light source (201) of the smartphone (200), said illumination being produced by a user activating a flashlight of the smartphone;

[0227] - (1202) acquiring, with the imager (202), a first digital image of the magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles in the first region (120a) of the magnetically oriented layer (120) at a first viewing angle θ1 associated with a first elevation angle γ1 of the magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles in the first region (120a) of the magnetically oriented layer (120) and storing the acquired first digital image in a memory of the smartphone;

[0228] - (1203) acquiring (by the user) a second digital image of the illuminated magnetically sensitive layer (120) using the imager (202) at a second viewing angle θ2 associated with a second elevation angle γ2 of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles within the second region (120b) of the magnetically sensitive layer (120), and storing the acquired second digital image in a memory of the smartphone;

[0229] - (1204) forming a composite digital image of the code pattern (134) from the first digital image and the second digital image by aligning a first portion of the code pattern (134) corresponding to a first area (134a) of the code pattern (134) detected on the first digital image and a second portion of the code pattern (134) corresponding to a second area (134b) of the code pattern (134) detected on the second digital image with respect to a reference pattern (133) (L-shape of a data matrix) detected in the stored first digital image and the stored second digital image, by image processing using a processor of the smartphone;

[0230] - (1205) reading and decoding the code pattern (134) from the obtained composite digital image via image processing and decoding operations using a processor of the smartphone, extracting the user identity data UID and the digital signature UIDS of the user identity data from the decoded data of the code pattern, and storing the extracted user identity data UID and the digital signature UIDS in a memory of the smartphone;

[0231] - (1206) sending a first message (M1) containing the extracted user identity data UID and the digital signature UIDS stored in the memory to the server (S) via the communication unit of the smartphone (200);

[0232] - (1207) decrypting, at the server (S), the extracted digital signature UID received in the first message (M1) from the smartphone (200) using the decryption key K' stored in the database, and checking whether the extracted user identity data UID received in the first message (M1) matches the decrypted extracted digital signature UID;

[0233] - (1208) illuminating the magnetic sensing layer (120) with a light source (201) and acquiring a plurality of digital images, for example ten images, of the illuminated magnetic sensing layer (120) with an imager (202), by moving the imager (202) relative to the magnetic sensing layer (120) in a plane parallel to the substrate (110) (this movement of the imager of the smartphone is performed by the user, here a translation), with the imager (202) being at a corresponding different viewing angle θ relative to the magnetic sensing layer (120) for each different digital image;

[0234] (1209) for each acquired digital image, using a processor of the smartphone, respectively calculating the corresponding average intensity I of light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and storing (in a memory of the smartphone) the calculated average intensity of the reflected light and the corresponding viewing angle to obtain a corresponding reflected light intensity curve I(θ);

[0235] - (1210) using the communication unit of the smartphone (200) to send a second message (M2) containing the obtained reflected light intensity curve I(θ) to the server (S) via the communication network (CN);

[0236] -(1211) at the server (S), comparing the reflected light intensity curve I(θ) received in the second message (M2) with the reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the database (DB) ref (θ) for comparison;

[0237] -(1212) determining at the server (S) whether the magnetic sensing layer (120) is genuine based on the comparison result;

[0238] - (1213) in the event that the magnetic sensing layer (120) is determined to be authentic, a server message (SM') indicating successful verification of the user's identity data is sent back to the smartphone (200) together with an indication that the security mark (100) is authentic, and a server authorization message (SAM) containing access data granting the user access to the online service (e.g. a password for online registration) is sent by the server (S) to the smartphone (200) of the user via the communication network (CN); and

[0239] -(1214) in the event that the extracted user identity data UID received in the first message (M1) does not match the decrypted extracted digital signature UID, or in the event that the magnetic sensing layer (120) is determined to be forged, sending back to the smartphone (200) a server alert message (SALM) indicating a failure in the verification of the user identity data.

[0240] In a second variant embodiment of the verification method, the reflectivity curves I(θ) and I are compared by the portable device (200). ref (θ), we still consider a user equipped with his smartphone, which is appropriately programmed to also function as a portable device (200) according to the present invention (as shown in FIG6). The smartphone is equipped with a communication unit operable to communicate via a communication network (CN) with respect to an identity card (corresponding to a Figure 9 The server (S) of the authority that provides the security document (150) shown in FIG. 1 sends and receives data. The server (S) is connected to a database (DB) that stores an encryption key K and a corresponding decryption key K' used for digitally signing the coded data in the code pattern (134) of the machine-readable mark (130) of the security mark (100) applied to the identity card. The following steps are performed:

[0241] - (1300) placing (by the user) the security mark (100) on the identification card (150) within the field of view of the imager (202) of the smartphone (200);

[0242] (1301) illuminating the security marking (100) of the security document (150) using the light source (201) of the smartphone (200), the illumination being produced by the user activating a flashlight of the smartphone;

[0243] - (1302) using an imager (202) of the smartphone (200) to acquire (by a user taking a picture) a first digital image of the illuminated magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles in a first region (120a) of the magnetically oriented layer (120) at a first viewing angle θ1 associated with a first elevation angle γ1 of the magnetically oriented reflective platelet-shaped magnetic or magnetizable pigment particles in a first region (120a) of the magnetically oriented layer (120), and storing the acquired first digital image in a memory of the smartphone;

[0244] - (1303) acquiring (by the user) a second digital image of the illuminated magnetically sensitive layer (120) at a second viewing angle θ2 associated with a second elevation angle γ2 of the magnetically oriented reflective flake-shaped magnetic or magnetizable pigment particles within the second region (120b) of the magnetically sensitive layer (120) using the imager (202), and storing the acquired second digital image in a memory of the smartphone (200);

[0245] -(1304) forming a composite digital image of the code pattern (134) from the first digital image and the second digital image by aligning a first portion of the code pattern (134) corresponding to a first area (134a) of the code pattern (134) detected on the first digital image and a second portion of the code pattern (134) corresponding to a second area (134b) of the code pattern (134) detected on the second digital image, via image processing with a processor of the smartphone;

[0246] - (1305) reading and decoding the code pattern (134) from the obtained composite digital image via image processing and decoding operations of the processor of the smartphone (200), extracting the user identity data UID and the digital signature UIDS of the user identity data from the decoded data of the code pattern, and storing the extracted user identity data UID and digital signature UIDS in a memory of the smartphone;

[0247] - (1306) sending a first message (M1) containing the extracted user identity data UID and the digital signature UIDS stored in the memory to the server (S) via the communication unit of the smartphone (200);

[0248] - (1307) decrypting, at the server (S), the extracted digital signature UIDS received in the first message (M1) from the smartphone (200) using the decryption key K' stored in the database (DB), and checking whether the extracted user identity data UID received in the first message (M1) matches the decrypted extracted digital signature UIDS;

[0249] - (1308) in case of a match, sending a server message (SM) back to the smartphone (200) indicating successful verification of the user identity data;

[0250] - (1309) upon delivery by the server of a server message (SM) indicating successful verification of the user's identity data, illuminating (by the user) the magnetically sensitive layer (120) of the machine-readable marking (130) on the identification card (150) with a light source (201) and acquiring a plurality of digital images of the illuminated magnetically sensitive layer (120) with an imager (202) of the smartphone (200), the imager (202) being at a correspondingly different viewing angle θ relative to said magnetically sensitive layer (120) by moving the imager (202) relative to the magnetically sensitive layer (120) in a plane parallel to the substrate (here, the user performs a translation of the imager parallel to the security marking);

[0251] -(1310) for each acquired digital image, using a processor to calculate the corresponding average intensity I of light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and determining a corresponding reflected light intensity curve I(θ) using the calculated average intensity of the reflected light and the corresponding viewing angle;

[0252] -(1311) comparing the reflected light intensity curve I(θ) with the reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the memory of the smartphone via the processor of the smartphone (200) ref (θ) for comparison;

[0253] - (1312) based on the result of the comparison, determining via the processor of the smartphone (200) whether the magnetic induction layer (120) is authentic, and if the magnetic induction layer (120) is determined to be authentic, sending a message (M) indicating that the security mark (100) is authentic to the server (S) via the communication network (CN) using the communication unit of the smartphone; and

[0254] -(1313) In case the server (S) receives a message (M) from the smartphone (200) indicating that the security token (100) is authentic, the server (S) sends back to the user's smartphone (200) via the communication network (CN) a server authentication message (SAM) containing access data granting the user access to the online service.

[0255] Examples of safety markings

[0256] Examples E1-E4 were performed using UV-Vis curable screen printing inks of the formulation given in Table 1 and the first and second magnetic assemblies described below.

[0257] Table 1

[0258]

[0259] (*) 5-layered flaky magnetic pigment particles exhibiting metallic silver color, with a diameter d 50 The PTFE-coated PTFE film was in the form of a thin sheet of about 19 μm and about 1 μm thick (obtained from VIAVI Solutions, Santa Rosa, CA).

[0260] Magnetic field generating device for biaxial orientation ( Figures 12A-12B )

[0261] The magnetic assembly is used for biaxial orientation of the pigment particles. The magnetic assembly consists of nine bar dipole magnets (M1-M9).

[0262] Each of the nine bar dipole magnets (M1-M9) has the following dimensions: 100 mm (L1) × 10 mm (L2) × 10 mm (L3). The magnetic field generating device is embedded in a non-magnetic holder made of polyoxymethylene (POM (not shown)) with the following dimensions: 250 mm × 150 mm × 12 mm. The nine bar dipole magnets (M1-M9) are made of NdFeB N40.

[0263] Nine bar dipole magnets (M1-M9) are arranged in a row with a distance (d1) of approximately 10 mm between each other, and the top surfaces of the nine bar dipole magnets (M1-M9) are flush. The magnetic axis of each of the nine bar dipole magnets (M1-M9) is substantially parallel to the thickness (L3) of the magnet, and the magnetic directions of two adjacent magnets (M1-M9) point in opposite directions (alternating magnetization). The magnetic field is substantially uniform, and the magnetic field lines are substantially coplanar in region A.

[0264] Magnetic field generation for uniaxial orientation ( Figure 13 )

[0265] The magnetic field generating device is used for uniaxial orientation of pigment particles and comprises two bar dipole magnets (M2, M1) and two pole pieces (P2, P1).

[0266] The two bar dipole magnets (M2, M1) each have the following dimensions: 40 mm (L1) x 40 mm (L2) x 10 mm (L3). The two bar dipole magnets (M1, M2) are made of NdFeB N42.

[0267] The two bar dipole magnets (M1, M2) are spaced a distance (d1) of about 40 mm from each other. The magnetic axes of the two bar dipole magnets (M1, M2) are substantially parallel to the length (L1) of the magnets, and the magnetic directions of the two bar dipole magnets (M1, M2) point in the same direction.

[0268] The two pole pieces (P2, P1) each have the following dimensions: 60mm (L4) x 40mm (L5) x 3mm (L6). The two pole pieces (P1, P2) are made of iron.

[0269] Two bar dipole magnets (M1, M2) and two pole pieces (P1, P2) are arranged to form a rectangular cube with a central rectangular cube gap consisting of an area A, wherein in area A the magnetic field is substantially uniform and the magnetic field lines are substantially parallel to each other, so that the distance (d2) between the two pole pieces (P1, P2) is about 40 mm, i.e. the distance (d2) between the two pole pieces (P1, P2) is the length (L1) of the two bar dipole magnets (M1, M1). Figure 13As shown, the magnetic field in region A is substantially uniform.

[0270] E1 (Figure 2, Figures 12A-12B , Figure 14A )

[0271] The UV-Vis curable screen printing ink of Table 1 was applied to black coated paper (45 mm × 60 mm) (110) to form a first coating layer (30 mm × 19 mm) (120a), wherein the applying step was performed using a laboratory screen printing device using a 90T screen to form a layer with a thickness of about 20 μm.

[0272] When the coating layer (120a) is still wet and not yet at least partially solidified, the substrate (110) is placed on top of the center of a support plate (300mm×40mm×1mm) made of high-density polyethylene (HDPE). The support plate carrying the substrate (110) is moved beside the magnetic field generating device at a speed of about 10cm / sec, with a distance (d5) between the surface of the magnetic field generating device facing the substrate (110) and the nearest edge of the first coating layer (120a) being about 20mm, and a height between the nearest edge of the first coating layer (120a) and the bottom surface of the magnetic field generating device being half the length (1 / 2L1) of the bar dipole magnets (M1-M9). Figure 12A The support plate carrying the substrate (110) is concomitantly moved while adopting an angle formed by the first coating layer (120a) and a tangent to the magnetic field lines of the magnetic field of the magnetic field generating device in the region A, wherein the magnetic field is uniform, said angle α having a value of about 20° so as to allow the particles to be oriented at an elevation angle of about 20°, thereby allowing the particles to be oriented at an elevation angle γ1 of about 20°.

[0273] The first coating layer (120a) is at least partially cured to form a first region (120a), the curing being performed by a curing unit (UV LED lamp (FireFly 395nm, 4W / cm 2 , from Phoseon)) is performed, the curing unit being arranged above the substrate path at a distance (d4) of about 15 mm from the center of the length (L1) of the bar dipole magnets (M1-M9), next to the space between the eighth and ninth dipole magnets (M8 and M9), and next to the ninth bar dipole magnet (M9) at a distance (d3) of 10 mm.

[0274] Using the same laboratory 90T screen printing apparatus, the UV-Vis curable screen printing ink of Table 1 was applied to the black coated paper (110) to form a second coating layer (30 mm x 19 mm) (120b) adjacent to the first area (120a) (along the 19 mm edge). The resulting combined coating layer (120a and 120b) had a total surface area of ​​30 mm x 38 mm.

[0275] When the second coating layer (120b) is still wet and has not yet been at least partially cured, the substrate (110) is placed on the center top of a support plate (300mm×40mm×1mm) made of high-density polyethylene (HDPE). The support plate carrying the substrate (110) is moved at a speed of about 10 cm / sec at a position where the distance (d5) between the surface of the magnetic field generating device facing the substrate (110) and the nearest edge of the second coating layer (120b) is about 20 mm, and the height between the nearest edge of the second coating layer (120b) and the bottom surface of the magnetic field generating device is half (1 / 2L1) of the length (L1) of the bar dipole magnets (M1-M9), and the same magnetic field generating device (such as Figures 12A-12B The support plate carrying the substrate (110) is moved concomitantly while adopting an angle α formed by the coating layer (120b) and the tangent of the magnetic field lines of the magnetic field of the magnetic field generating device in the area A, wherein the magnetic field is uniform, said angle α having a value of about 160° so as to allow the particles to be oriented at an elevation angle γ2 of about 160°.

[0276] The second coating layer (120b) is at least partially cured to form the second region (120b), the curing being performed by a curing unit (UV LED lamp (FireFly 395nm, 4W / cm 2 , from Phoseon)) is performed, the curing unit is arranged above the substrate path at a distance (d4) of about 15 mm from the center of the length (L1) of the bar dipole magnets (M1-M9), next to the space between the eighth and ninth dipole magnets (M8 and M9), and next to the ninth bar dipole magnet (M9) at a distance (d3) of 10 mm to form a second zone (120b), thereby providing a magnetic induction layer (120).

[0277] A QR code (25 mm x 25 mm) was printed on the magnetically sensitive image (120) by inkjet printing using a Konica Minolta print head (KM1024i) with black ink (SicurajetSUV black from Siegwerk) so that the QR code was located in the center of the layer (120). A mercury lamp (500 mJ / cm 2 ) at least partially cures the inkjet printed QR code.

[0278] The resulting sample of Example E1 is Figure 14A (left: viewing angle θ1 is +22°; right: viewing angle θ2 is -22°).

[0279] E2( Figure 2C 、 Figure 13 、 Figure 14B )

[0280] The UV-Vis curable screen printing ink of Table 1 was applied to black coated paper (45 mm × 60 mm) (110) to form a first coating layer (30 mm × 19 mm) (120a), wherein the applying step was performed using a laboratory screen printing apparatus using a 90T screen to form a layer having a thickness of about 20 μm.

[0281] When the first coating layer (120a) is still wet and not yet at least partially cured, the substrate (110) is placed on top of a support plate (300mm×40mm×1mm) made of high-density polyethylene (HDPE). The support plate carrying the substrate (110) is placed in the center of the gap of the magnetic assembly, such as Figure 13 As shown, the angle α formed by the first coating layer (120a) and the tangent of the magnetic field lines of the magnetic field of the magnetic field generating device in the region A is adopted, wherein the magnetic field is uniform, and α has a value of about 8°, thereby allowing the particles to be oriented at an elevation angle γ1 of about 8°.

[0282] After about 1 second, the first coating layer (120a) is at least partially cured to form a first region (120a), the curing being performed by Figure 13 The curing unit shown (UV LED lamp (FireFly 395nm, 4W / cm 2 , from Phoseon)) execution.

[0283] Using the same laboratory 90T screen printing apparatus, the UV-Vis curable screen printing ink of Table 1 was applied to the black coated paper (110) to form a second coating layer (30 mm x 19 mm) (120 b) adjacent to the first area (120 a) (along the 19 mm edge). The resulting combined coating layer (120 a and 120 b) had a total surface area of ​​30 mm x 38 mm.

[0284] When the second coating layer (120b) is still wet and not yet at least partially cured, the substrate (110) is placed on top of a support plate (300mm×40mm×1mm) made of high-density polyethylene (HDPE). The support plate carrying the substrate (110) and the second coating layer (120b) are placed in the center of the gap of the magnetic assembly, such as Figure 13As shown, while adopting the angle α formed by the second coating layer (120b) and the tangent of the magnetic field lines of the magnetic field of the magnetic field generating device in the region A, wherein the magnetic field is uniform, α has a value of about 172°, thereby allowing the particles to be oriented at an elevation angle γ2 of about 172°.

[0285] After about 1 second, the second coating layer (120b) is at least partially cured to form the second region (120b), said curing being performed by a curing unit (UV LED lamp (FireFly 395nm, 4W / cm 2 , from Phoseon)) is performed to form a second region (120b), thereby providing a magnetic sensing layer (120).

[0286] A QR code (25 mm x 25 mm) was printed on the magnetically sensitive image (120) by inkjet printing using a Konica Minolta print head (KM1024i) with black ink (SicurajetSUV black from Siegwerk) so that the QR code was located in the center of the layer (120). A mercury lamp (500 mJ / cm 2 ) at least partially cures the inkjet printed QR code.

[0287] The resulting sample of Example E2 is Figure 14B (left: viewing angle θ1 is +10°; right: viewing angle θ2 is -10°).

[0288] E3 and E4 ( Figure 2C 、 Figures 12A-12B 、 Figure 13 、 Figures 14C-14D )

[0289] A 10 mm x 10 mm substrate (110) obtained in Example E1 or Example E2, carrying only the magnetic induction layer (120) (10 mm x 5 mm), was applied and glued onto white coated paper (50 mm x 50 mm).

[0290] A QR code (25 mm x 25 mm) was printed on the magnetically sensitive image (120) by inkjet printing using a Konica Minolta print head (KM1024i) with black ink (SicurajetSUV black from Siegwerk) such that the blank area of ​​the QR code was located on the top surface of the layer (120), as shown in FIG. Figure 14C and 14D As shown. Using a mercury lamp (500mJ / cm 2 ) at least partially cures the inkjet printed QR code.

[0291] The resulting sample for Example E3 is Figure 14C(Left: viewing angle θ1 is +22°; right: viewing angle θ2 is -22°). Figure 14D (left: viewing angle θ1 is +10°; right: viewing angle θ2 is -10°).

[0292] The above-disclosed subject matter is to be considered illustrative rather than restrictive and is intended to provide a better understanding of the invention as defined by the independent claims.

Claims

1. A security mark (100), characterized in that: The safety markings include: a flat substrate (110); A magnetic induction layer (120) of a material comprising magnetically oriented reflective flake magnetic or magnetizable pigment particles, the magnetic induction layer being applied on the substrate (110) and comprising a first region (120a) and a second region (120b) different from the first region (120a), wherein in the first region (120a), the flat surfaces of the magnetically oriented reflective flake magnetic or magnetizable pigment particles are oriented in a first direction, and in the second region (120b), the flat surfaces of the magnetically oriented reflective flake magnetic or magnetizable pigment particles are oriented in a second direction different from the first direction, the flake particles in the first region (120a) have flat surfaces at a first elevation angle γ1 relative to the plane of the substrate (110), and the flake particles in the second region (120b) have flat surfaces at a second elevation angle γ2 relative to the plane of the substrate (110), and each acute angle of the flat surfaces relative to the plane of the substrate is in a range of about 5° to about 25°; A machine-readable mark (130) comprising a reference pattern (133) and a code pattern (134) representing encoded data, wherein the machine-readable mark (130) is applied on the top surface (121) of the magnetic induction layer (120) or applied on the substrate (110) between the substrate and the back surface (122) of the magnetic induction layer (120), wherein a first region (134a) of the code pattern (134) is arranged in front of the first region (120a), and a remaining second region (134b) of the code pattern (134) is arranged in front of the second region (120b).

2. The security mark according to claim 1, wherein: a) the pigment particles include: a magnetic metal selected from the group consisting of cobalt, iron, gadolinium, and nickel; Magnetic alloys of iron, chromium, manganese, cobalt, nickel or mixtures of two or more of these; Magnetic oxides of chromium, manganese, cobalt, iron, nickel or mixtures of two or more of them; or a mixture of two or more of the above; or b) The code pattern is any one of a one-dimensional barcode, a superimposed one-dimensional barcode, a two-dimensional barcode and a three-dimensional barcode.

3. The security mark according to claim 1 or 2, wherein: The first region (120a) and the second region (120b) of the magnetic induction layer (120) belong to the same single material layer.

4. The security mark according to claim 1 or 2, wherein: The first region (120a) and the second region (120b) of the magnetic induction layer (120) respectively belong to a first sublayer and an adjacent second sublayer forming the magnetic induction layer (120).

5. The security mark according to claim 1 or 2, wherein: The machine-readable mark (130) is applied on the top surface (121) of the magnetic sensing layer (120) and is encoded in a dark symbol, and a dark primer layer (140) is applied on the substrate (110), and the back surface (122) of the magnetic sensing layer (120) is applied on the top surface (141) of the dark primer layer (140).

6. The security mark according to claim 1 or 2, wherein: The machine-readable mark (130) is applied on the top surface (121) of the magnetic sensing layer (120) and is encoded in a light symbol, and a dark primer layer (140) is applied on the substrate (110), and the back surface (122) of the magnetic sensing layer (120) is applied on the top surface (141) of the dark primer layer (140).

7. The security mark according to claim 1 or 2, wherein: The machine-readable marking (130) is applied to the substrate (110) and is encoded in a dark symbol.

8. A method for reading and decoding a security marking (100) according to any one of claims 1 to 7 using a portable device (200), the portable device (200) being equipped with a light source (201) operable to deliver illumination light, an imager (202), and a processor, the light source (201) being operable to deliver illumination light, the processor being equipped with a memory and being adapted to perform image processing and decoding operations, the method comprising the steps of: placing the security mark (100) within the field of view of the imager (202); illuminating the security mark (100) using illumination light delivered by the light source (201); Acquiring a first digital image of the security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory; acquiring a second digital image of the security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2 using the imager, and storing the acquired second digital image in the memory; forming, through image processing using the processor, a composite digital image of the code pattern (134) based on the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to the first area (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to the second area (134b) of the code pattern detected on the second digital image relative to the reference pattern (133) detected in the first digital image and the second digital image, and storing the obtained composite digital image in the memory; as well as The code pattern (134) is read and decoded from the stored composite digital image using the processor.

9. A portable device (200) for reading and decoding a security marking (100) according to any one of claims 1 to 7, comprising: a light source (201) operable to deliver illumination light; Imager (202); as well as A processor provided with a memory and adapted to perform the following steps: illuminating the security mark (100) using illumination light delivered by the light source (201); Acquiring a first digital image of the security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory; acquiring a second digital image of the security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2 using the imager, and storing the acquired second digital image in the memory; forming, through image processing using the processor, a composite digital image of the code pattern (134) based on the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to the first area (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to the second area (134b) of the code pattern detected on the second digital image relative to the reference pattern (133) detected in the first digital image and the second digital image, and storing the obtained composite digital image in the memory; as well as The code pattern (134) is read and decoded from the stored composite digital image using the processor.

10. A security document (150) delivered to a user by an authorized institution, characterized in that The security documents include: A security mark (100) according to any one of claims 1 to 7 applied to the security document (150), wherein the encoded data in the code pattern (134) of the security mark (100) contains digital identity data corresponding to the user and forming the user's digital identity data and a digital signature of the user's digital identity data, the digital signature delivered by the authorized institution being obtained by signing the user's digital identity data with an encryption key.

11. A method of authenticating a user's security document (150) according to claim 10 using a portable device (200) according to claim 9, wherein: The portable device (200) is also equipped with a communication unit operable to send and receive data via a communication network (CN) with respect to a server (S) of an authority connected to a database (DB) storing encryption keys and corresponding decryption keys, the method comprising the following steps: placing the security mark (100) within the field of view of the imager (202); illuminating the security mark (100) of the security document (150) using the light source (201); Acquiring a first digital image of the illuminated security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory; acquiring, using the imager (202), a second digital image of the illuminated security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2, and storing the acquired second digital image in the memory; forming, via image processing using the processor, a composite digital image of the code pattern (134) based on the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to the first area (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to the second area (134b) of the code pattern detected on the second digital image relative to the reference pattern (133) detected in the first digital image and the second digital image; reading and decoding the code pattern (134) from the synthesized digital image via image processing and decoding operations using the processor, extracting user identification data and a digital signature of the user identification data from the decoded data of the code pattern, and storing the extracted user identification data and digital signature in the memory; sending a first message M1 comprising the extracted user identity data and the digital signature stored in the memory to the server S via the communication unit CN; decrypting, at the server (S), the extracted digital signature received in the first message (M1) from the portable device (200) using the decryption key stored in the database (DB), and checking whether the extracted user identity data received in the first message (M1) matches the received extracted digital signature; and In case of a match, a server message, SM, is sent back to the portable device (200) indicating successful verification of the user identity data.

12. The method according to claim 11, wherein Prior to the step of sending a server message back to the portable device (200), the method comprises the following preliminary steps: The magnetic induction layer (120) is illuminated by the light source (201), and a plurality of digital images of the illuminated magnetic induction layer (120) are acquired by the imager (202), wherein the imager (202) is moved relative to the magnetic induction layer (120) in a plane parallel to the substrate (110), and for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic induction layer (120); For each acquired digital image, using the processor to respectively calculate the corresponding intensity I of light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and storing the calculated reflected light intensity and the corresponding viewing angle to obtain a corresponding reflected light intensity curve I(θ); Using a communication unit to send a second message M2 including the obtained reflected light intensity curve I(θ) to the server S via the communication network CN; At the server (S), the reflected light intensity curve I(θ) received in the second message (M2) is compared with the reference reflected light intensity curve I(θ) for the magnetic sensing layer (120) stored in the database (DB). ref (θ) for comparison; determining at the server (S) whether the magnetic induction layer (120) is genuine based on the result of the comparison; and In the event that the magnetic induction layer (120) is determined to be authentic, a server message (SM) indicating successful verification of the user's identity data and an indication that the security mark (100) is authentic are sent back to the portable device (200), and a server authorization message (SAM) containing access data granting the user access to the service is sent by the server (S) to the user's communication device via the communication network (CN).

13. The method according to claim 11, wherein In case a server message (i.e. SM) indicating a successful verification of the user identity data is delivered by the server (i.e. S), the method further comprises the following steps: The magnetic induction layer (120) is illuminated by the light source (201), and a plurality of digital images of the illuminated magnetic induction layer (120) are acquired by the imager (202), and the imager (202) is moved relative to the magnetic induction layer (120) in a plane parallel to the substrate (110), so that for each different digital image, the imager (202) is at a corresponding different viewing angle θ relative to the magnetic induction layer (120); For each acquired digital image, the processor is used to calculate the corresponding intensity I of the light reflected by the magnetic sensing layer (120) and collected by the imager (202) at the corresponding viewing angle θ, and a corresponding reflected light intensity curve I(θ) is determined using the calculated reflected light intensity and the corresponding viewing angle; The processor compares the reflected light intensity curve I(θ) with the reference reflected light intensity curve I for the magnetic sensing layer (120) stored in the memory. ref (θ) for comparison; determining whether the magnetic induction layer (120) is authentic based on the comparison result, and, if the magnetic induction layer (120) is determined to be authentic, sending a message (M) indicating that the security mark (100) is authentic to the server (S) via the communication network (CN) using the communication unit; and When the server, i.e. S, receives a message, i.e. M, from the portable device (200) indicating that the security mark (100) is authentic, the server, i.e. S, sends back a server authorization message, i.e. SAM, to the user's communication device via the communication network, i.e. CN, containing access data allowing the user to access the service.

14. A system for verifying a security document (150) delivered by an authorized institution to a user according to claim 10, comprising: a server of the authority, ie S, connected to a database, ie DB, storing encryption keys and corresponding decryption keys and operable to send and receive data via a communication network, ie CN; as well as The portable device (200) according to claim 9, for reading and decoding the security mark (100) according to any one of claims 1 to 7 applied to the security document (150), the portable device (200) comprising: a light source (201) operable to deliver illumination light; Imager (202); a communication unit operable to send and receive data with respect to said server (S) via said communication network (CN); and A processor provided with a memory and adapted to perform image processing and decoding operations and to execute the following steps: illuminating the security mark (100) using illumination light delivered by the light source (201); Acquiring a first digital image of the security mark (100) at a first viewing angle θ1 associated with the first elevation angle γ1 using the imager (202), and storing the acquired first digital image in the memory; acquiring a second digital image of the security mark (100) at a second viewing angle θ2 associated with the second elevation angle γ2 using the imager, and storing the acquired second digital image in the memory; forming, through image processing using the processor, a composite digital image of the code pattern (134) based on the stored first digital image and the stored second digital image by aligning a first portion of the code pattern (134) corresponding to the first area (134a) of the code pattern detected on the first digital image and a second portion of the code pattern (134) corresponding to the second area (134b) of the code pattern detected on the second digital image relative to the reference pattern (133) detected in the first digital image and the second digital image, and storing the obtained composite digital image in the memory; and reading and decoding the code pattern (134) from the stored composite digital image using the processor; The system is further adapted to perform the following steps: extracting user identification data and a digital signature of the user identification data from decoded data of the code pattern through image processing and decoding operations using the processor, and storing the extracted user identification data and digital signature in the memory; sending a first message M1 comprising the extracted user identity data and the digital signature stored in the memory to the server S via the communication unit CN; decrypting, at the server (S), the extracted digital signature received in the first message (M1) from the portable device (200) using the decryption key stored in the database (DB), and checking whether the extracted user identity data received in the first message (M1) matches the received extracted digital signature; and In case of a match, a server message, SM, is sent back to the portable device (200) indicating successful verification of the user identity data.

15. The system according to claim 14, wherein: The server (S) is further adapted to send data to the communication device of the user via the communication network (CN); and The server, ie S, and the portable device (200) are further adapted to perform the steps of the method according to claim 12 to authenticate the user's security file (150).

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