Optical Marking Device

Abstract

The present invention relates to an optical marking device comprising at least a first layer and a second layer arranged at least partially opposite each other, at least one of which comprises an optically variable element (4, 5) exhibiting a color change between a first color and a second color that contrasts with the color of the other layer in such a way that the first layer is visible when the optically variable element (4, 5) exhibits the first color and the second layer is visible when the optically variable element (4, 5) exhibits the second color, or alternatively the second layer is visible when the optically variable element (4, 5) exhibits the first color and the first layer is visible when the optically variable element (4, 5) exhibits the second color.

Description

Technical Field

[0001] The present invention relates to the field of security and authentication of products, especially documents.

[0002] In particular, it relates to the security and authentication of identity documents (ID), proxy certificates, management documents, or brand labels.

Background Art

[0003] The production of counterfeits and imitations has now increased significantly in many high-value-added fields such as luxury goods, automotive and aerospace parts, or packaging, especially pharmaceutical packaging such as blister packs.

[0004] With the progress of identity theft, and especially with the authentication of point-based driving licenses in certain countries, personal information and management documents are increasingly being targeted for forgery. Therefore, the security and authentication of this type of product and document are of great importance and involve domestic and international security issues.

[0005] Therefore, there is a need to continuously provide new means to effectively counter forgery, especially the forgery of original recorded documents, or counterfeiting (manufacture of imitations).

[0006] Hereinafter, in this specification, the term "document" refers to an assembly formed by a substrate and information. The substrate can be of various types, can take various forms, and can include polymers or mixtures of polymers. The substrate can, for example, consist entirely or partially of a polymeric material.

[0007] Examples of documents include, among others, identity documents such as passports, identity cards, driving licenses, health cards, etc., as well as proxy certificates such as banknotes and checks, or management documents such as registration certificates.

[0008] Therefore, these documents may be in the form of paper, books, or cards, and the information can be printed and / or marked on the surface in the case of paper or cards, or on the pages in the case of books.

[0009] Considering the important value associated with the information contained, the security of the documents should be enhanced.

[0010] Currently, documents are being secured by security elements. The elements can be classified into three levels of security as a function of the means used for detection. Level 1 security elements are those that can be detected by at least one of the five senses or by a contrasting background. This level includes, in particular, guilloche, optically variable devices such as iridescent printing, holograms, optically variable inks, markers, changeable laser images, or multiple laser images.

[0011] Level 2 security elements are those that can be detected using simple equipment such as an ultraviolet lamp, a convex lens, or a flash of light from a mobile phone. This level includes detectable elements such as microprinting, fluorescent inks, fluorescent fibers, or plates.

[0012] Finally, level 3 security elements are those that can be detected using sophisticated equipment such as a spectrofluorometer or an electron microscope. This category includes, in particular, nanoprint pigments, biometric chips, and fluorescent markers (tagants) that are not detectable by the naked eye.

[0013] Generally, documents incorporate several security elements at various levels.

[0014] Existing security solutions have proven to be advantageous, but they can be difficult to implement and inspect. Therefore, there is a real need for new security means that are easy to implement and stable while ensuring a high level of security and can quickly check the reliability of products or documents. These means do not necessarily have to be mutually exclusive. Summary of the Invention Means for Solving the Problems

[0015] For this purpose, the present invention is an optical marking device including at least one first layer and a second layer that are at least partially arranged facing each other, at least one of the first layer and the second layer includes an optically variable element that shows a color change between a first color and a second color, the first color and the second color show contrast as follows in relation to the colors of other layers: - When the optically variable element shows the first color, the first layer is visible, and when the optically variable element shows the second color, the second layer is visible, or - When the optically variable element shows the first color, the second layer is visible, and when the optically variable element shows the second color, the first layer is visible, relates to an optical marking device.

[0016] Therefore, the device according to the present invention makes it possible to check the authenticity of products such as documents, particularly identity documents, trustee certificates, or administrative documents, but also for pharmaceutical packaging (especially blisters) or luxury packaging (brand identification), etc.

[0017] According to another feature of the present invention, the device includes a design having the optically variable element.

[0018] According to another feature of the present invention, the device includes a substrate having at least one of the first layer and the second layer.

[0019] According to another feature of the present invention, the two layers are in contact with each other.

[0020] According to another feature of the present invention, at least one of the two layers is at least partially reflective in the visible light spectrum and / or has a gray shade.

[0021] According to another feature of the present invention, at least one of the two layers (2, 3) is at least partially diffusing in the visible light spectrum.

[0022] According to another feature of the present invention, the optically variable element contains one or more fluorescent compounds.

[0023] According to another feature of the present invention, the optically variable element contains one or more compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene.

[0024] According to another feature of the present invention, the compounds of the class of 4-bora-3a,4a-diaza-s-indacene used in the present invention have the formula I: [Chemical formula] [wherein, R 1 is C1-C6 alkyl, C5-C6 cycloalkyl, C5-C6 heteroalkyl, phenyl, and the phenyl group may be substituted with one or more groups selected from C1-C2 alkyl, hydroxy, R 5 COO - and halogen; R 2 and R 2’ are independently selected from hydrogen and C1-C2 alkyl; R 3 and R 3’is independently selected from hydrogen, aryl, heteroaryl, cycloalkyl, alkyl, alkenyl and alkynyl, and the aryl, heteroaryl, cycloalkyl, alkyl, alkenyl and alkynyl may be substituted with one or more groups selected from C1-C4 alkyl, aryl, hydroxy and ferrocene [the aryl group may be substituted with one or more groups selected from aryl (this aryl may be substituted with a C1-C2 alkyl group), C1-C2 alkyl, halogen, hydroxy, dimethylamino and nitro]]; R 4 and R 4’ is independently selected from aryl, heteroaryl, cycloalkyl, alkyl and alkenyl, and the aryl, heteroaryl, cycloalkyl, alkyl and alkenyl may be substituted with one or more groups selected from C1-C3 alkyl, aryl, hydroxyl and ferrocene [the aryl group may be substituted with one or more groups selected from aryl (this aryl may be substituted with a C1-C2 alkyl group), C1-C2 alkyl, halogen, hydroxy, dimethylamino and nitro]]; R 5 is C1-C4 alkyl or C2-C4 alkenyl; R 6 and R 6’ is independently selected from halogen, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl or aryl, and the aryl may be substituted with one or more groups selected from C1-C2 alkyl, hydroxy, R 5 COO - and halogen.] may be selected from the compounds of.

[0025] According to another feature of the present invention, the compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene used in the present invention have the formula II:

Chemical formula

[0026] According to another feature of the present invention, the optically variable element comprises one or more compounds of the class of difluoroboron β-diketonates (BF2bdks).

[0027] According to another feature of the present invention, the compounds of the class of difluoroboron β-diketonates (BF2bdks) have the formula III:

Chemical formula

[0028] According to another feature of the present invention, the device includes a polymer, and an optically variable element is incorporated into this polymer.

[0029] According to another feature of the present invention, the polymer is selected from polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, polyvinyl chloride, polyamide, polyaramide, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate, rosin resin, pine resin, photocurable resin, or a mixture thereof.

[0030] According to another feature of the present invention, one of the first color and the second color of the layer containing the optically variable element is the complementary color of the color of the other layer.

[0031] According to another feature of the present invention, these two layers include optically variable elements that exhibit a color change, and the two optically variable elements are at least partially overlapped and configured such that only the first layer is visible when a first stimulus is applied to the device, and only the second layer is visible when a second stimulus is applied to the device.

[0032] According to another feature of the present invention, the optical marking device includes an element configured to polarize light passing through this device.

[0033] According to another feature of the present invention, at least one of these first and second layers contains a mixture of optically variable elements that exhibit a color change between a first color and a second color.

[0034] According to another feature of the present invention, the dye is a fluorophore molecule.

[0035] The present invention also relates to an identity document, a certificate of trust, or an administrative document, or a label that includes at least one of the above-described optical marking devices.

[0036] The features and advantages of the present invention will become more apparent from the following description. However, the following description is for illustrative purposes and should be read in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

[0038] [Optical Marking Device] The present invention relates to an optical marking device for products such as documents. The optical marking device is referred to with reference to FIG. 1.

[0039] In the remainder of this description, the term document refers to an assembly formed by a substrate and information. The substrate can be of various types, can take various forms, and can include a polymer or a mixture of polymers. This substrate can be, for example, wholly or partially made of a polymer material.

[0040] Examples of documents include not only identity documents such as passports, identity cards, driver's licenses, health cards, etc., but also reference documents such as banknotes and checks, or administrative documents such as registration certificates.

[0041] Accordingly, the document can be in the form of paper, a book, or a card, and the information can be printed therein and / or on the surface in the case of paper or a card, or on the pages in the case of a book.

[0042] Device 1 includes at least a first layer and a second layer called an optical marking layer.

[0043] In the figure, Device 1 includes two optical marking layers referenced as 2 and 3.

[0044] Of course, the present invention is not limited to this configuration and may have a multi-layer configuration having two or more layers.

[0045] In the illustrated embodiment, layers 2 and 3 are in direct contact with each other and are accurately superimposed on each other, and this embodiment is particularly advantageous.

[0046] However, an embodiment in which layers 2 and 3 only partially cover each other and / or layers 2 and 3 are not in direct contact with each other and instead are spaced apart, for example, by other layers of Device 1, may also be possible.

[0047] At least one of the two layers 2, 3 includes an optically variable element.

[0048] In the first alternative embodiment shown in FIGS. 2 to 4, each of the two layers 2, 3 includes an optically variable element referenced as 4, 5, respectively.

[0049] In the second alternative embodiment shown in FIGS. 5 to 7, only layer 2 includes an optically variable element referenced as 4.

[0050] In the third alternative embodiment shown in FIGS. 8 to 11, each of the two layers 2, 3 includes an optically variable element referenced as 4, 5, respectively.

[0051] As will be described later, each optically variable element exhibits a color change between a first color and a second color.

[0052] As will be described in detail below in connection with each variant embodiment of the present invention, the optical marking device 1 is configured such that when the optically variable element exhibits the first color, the first layer is visible, and when the optically variable element exhibits the second color, the second layer is visible, or when the optically variable element exhibits the first color, the second layer is visible, and when the optically variable element exhibits the second color, the first layer is visible.

[0053] Advantageously, at least one of the two layers includes a pattern that is at least partially superimposed using the optically variable element.

[0054] The pattern can preferably be a symbol, drawing, photograph, or fixed or variable statement that helps to identify the product having the device 1.

[0055] As will be described in detail later, the pattern can be printed, for example, with ink or varnish or etched by a laser, as will be described in detail below.

[0056] In FIG. 1, the device 1 includes a substrate 11 having optical marking layers 2, 3.

[0057] The substrate 11 is, for example, a layer of a transparent polymer.

[0058] Advantageously, the substrate 11 is a layer of polypropylene, polycarbonate, or polyethylene and has a controlled thickness (for example, in the case of polycarbonate, 10 μm to 800 μm, preferably 50 μm to 600 μm; in the case of polypropylene, 10 μm to 600 μm, preferably 30 to 150 μm; in the case of transparent PET, 5 μm to 50 μm, preferably 10 μm).

[0059] [Optically Variable Element] The "optically variable element" means any physicochemical element that displays a color change between a first color and a second color as a function of a physicochemical stimulus.

[0060] The physicochemical stimuli, also called stimuli, can be light beam irradiation, temperature change, or pressure change, or a change in observation conditions (such as the incident angle of observation of an element).

[0061] In the embodiments described in detail below, the optically variable element contains an active substance containing one or more fluorescent compounds, in particular, compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (class of BDPY) or the class of difluoroboron β-diketonate (BF2bdks), which will be described in detail below, at a given concentration.

[0062] However, the present invention is not limited to this type of optically variable element.

[0063] As an example, the optically variable element may be a thermochromic, liquid crystal ink, or an optically variable ink of the type known under the name "OVI" (registered trademark of SICPA).

[0064] [[ID=‘18]] Preferably, layer 2 or 3 containing the optically variable element also includes a polymer in which one or more compounds are incorporated into the polymer, and in particular the polymer matrix constituting the document or product in question.

[0065] In the remainder of this description, the terms "4,4-difluoro-4-bora-3a,4a-diaza-s-indacene compound", "difluoroboron β-diketonate (BF2bdks)", and "fluorescent dye" are used interchangeably.

[0066] Note that the active substance can be mixed with one or more types of ink.

[0067] 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene compounds are fluorescent dyes, and their first synthesis was reported in 1968 (A. Treibs et al., Justus Liebigs Ann. Chem. 1968, 718, 208). Since then, several other syntheses have been published (e.g., Chem. Eur. J., 2009, 15, 5823; J. Phys. Chem. C, 2009, 113, 11844; Chem. Eur. J., 2011, 17, 3069; J. Phys. Chem. C, 2013, 117, 5373). In addition, a very large number of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene compounds are commercially available, for example, from ThermoFisher Scientific (Waltham, Massachusetts, USA).

[0068] These have excellent absorption and emission properties, and in particular, have fluorescence emission with a relatively narrow excitation band and a high quantum yield φ of 0.5 - 1, and are very fluorescent.

[0069] Furthermore, these compounds have excellent photostability and high thermal stability. In fact, the fluorescent dyes according to the present invention are generally stable up to 300 °C.

[0070] Due to this high thermal stability, these fluorescent dyes can be easily incorporated into a molten polymer matrix, and contrary to any expectation, the performance at the levels of fluorescence absorption and emission is not altered by incorporation into the polymer matrix.

[0071] Due to this good stability, this one or more compounds can be incorporated into related inks, and in contrast to the techniques of the prior art, excellent stability with respect to photobleaching is guaranteed. [[ID=I8]]

[0072] All 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene compounds have an absorption band in visible light, and the color perceived by the naked eye corresponds to the complementary color of the absorbed color. For example, a compound that absorbs around 480 to 490 nm corresponding to a green / blue color is displayed in an orange / red color tone to the naked eye.

[0073] Therefore, this property enables obtaining a security element of level 1.

[0074] Regarding the fluorescence property, all compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene according to the present invention have an excitation band in ultraviolet (UV) and an emission band in the visible region. Therefore, they can be particularly excited by a UV lamp that emits light at 100 nm to 400 nm and can be detected by the naked eye, so that a security element of level 2 can be obtained.

[0075] Finally, the emission wavelength can be determined using a spectrofluorometer or a low-resolution fluorometer of a single network (detection by a photodiode or a photomultiplier tube), which gives level 3 security to the security element according to the present invention.

[0076] The 4-bora-3a,4a-diaza-s-indacene compound used in the present invention has the following formula I:

Chemical formula

[0077] Preferred compounds of formula I are R 1 R 2 R 2’ R 3 R 3’ R 4 R 4’ R 5 R6 and R 6’ one or more of which is a compound defined as follows: R 1 is phenyl substituted with one or more groups selected from methyl, fluoro, hydroxy, acetyl, and methacrylate, preferably selected from methyl, fluoro, hydroxy, and acetyl, more preferably selected from methyl or fluoro; R 2 and R 2 ’ are independently selected from hydrogen and methyl; R 3 and R 3 ’ are independently selected from hydrogen, C1-C3 alkyl, vinyl, aryl, heteroaryl, adamantyl, wherein said vinyl and aryl may be optionally substituted with one or more groups selected from phenyl, C1-C2 alkyl, and said phenyl may be optionally substituted with one or more groups selected from C1-C2 alkyl, hydroxy, bromo, nitro, dimethylamine; preferably, independently selected from hydrogen, methyl, ethyl, n-propyl, vinyl, aryl, heteroaryl, adamantyl, wherein said vinyl and aryl may be optionally substituted with one or more groups selected from phenyl, C1-C2 alkyl, and said phenyl may be optionally substituted with one or more groups selected from C1-C2 alkyl, hydroxy, bromo, nitro, dimethylamine; more preferably, R 3 and R 3 ’ are independently selected from ethyl, n-propyl, methyl, vinyl, phenyl, phenanthryl, naphthyl, pyrenyl, thiophenyl, benzofuranyl, wherein said vinyl, aryl, and naphthyl may be optionally substituted by one or more of methyl, hydroxy, bromo, nitro, and dimethylamino; R 4 and R 4' is independently selected from methyl, vinyl, aryl, heteroaryl, adamantyl, wherein said vinyl and aryl are optionally substituted with one or more groups selected from phenyl, C1-C2 alkyl, and said phenyl may be substituted with one or more groups selected from C1-C2 alkyl, hydroxy, bromo, nitro, dimethylamine, Preferably, R 4 and R 4 ' are independently selected from methyl, vinyl, phenyl, phenanthryl, naphthyl, pyrenyl, thiophenyl, benzofuranyl, and said vinyl, aryl, and naphthyl may be substituted with one or more of methyl, hydroxy, bromo, nitro, and dimethylamino; R 5 is methyl or ethenyl; R 6 and R 6 ' are independently selected from fluoro, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl, or aryl, and said aryl may be substituted with one or more groups selected from C1-C2 alkyl, hydroxy, R5COO- and halogen, and preferably, R6 and R6' are fluoro.

[0078] According to a specific embodiment, the 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene compound used in the present invention has the following formula II:

Chemical formula

[0079] Preferred compounds of formula II are those in which one or more of R 1 , R 2 , R 2’ , R 3 , R 3’ , R 4 , R 4’ and R 5 are compounds defined as follows: R 1 is phenyl substituted with one or more groups selected from methyl, fluoro, hydroxy, acetyl, and methacrylate, preferably selected from methyl, fluoro, hydroxy, and acetyl, more preferably selected from methyl or fluoro; R 2 and R 2 ' are independently selected from hydrogen and methyl; R 3 and R 3 ' are independently selected from hydrogen, methyl, ethyl, and n-propyl, preferably ethyl; R 4 and R 4' is independently selected from methyl, vinyl, aryl, heteroaryl, adamantyl, and said vinyl and aryl may be substituted with one or more groups selected from phenyl, C1-C2 alkyl, said phenyl may be substituted with one or more groups selected from C1-C2 alkyl, hydroxy, bromo, nitro, dimethylamine, Preferably, R 4 and R 4 ' are independently selected from methyl, vinyl, phenyl, phenanthryl, naphthalenyl, pyrenyl, thiophenyl, benzofuranyl, and said vinyl, aryl, and naphthalenyl may be substituted with one or more of methyl, hydroxy, bromo, nitro, and dimethylamino; R 5 is methyl or ethenyl.

[0080] Particularly preferred compounds of formula II are the compounds described in the following table:

[0081]

Table 1A

[0082]

Table 1B

[0083]

Table 1C

[0084]

Table 1D

[0085]

Table 1E

[0086]

Table 1F

[0087]

Table 1G

[0088] For the description of the compounds used in the present invention, the terms and expressions used are understood according to the following definitions, unless otherwise specified.

[0089] The term "halogen" refers to fluoro, chloro, bromo, or iodo. Preferred halogen groups are fluoro and bromo, with fluoro being particularly preferred.

[0090] The term "alkyl" refers to a straight-chain or branched hydrocarbon group of the formula: C n H 2n+1 wherein n is an integer of 1 or more. Preferred alkyl groups are straight-chain or branched C1-C6 alkyl groups.

[0091] The term "alkenyl" refers to a straight-chain or branched unsaturated alkyl group containing one or more carbon-carbon double bonds. Suitable alkenyl groups contain 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and even more preferably 2 or 3 carbon atoms. Non-limiting examples of alkenyl groups are ethenyl (vinyl), 2-propenyl (allyl), 2-butenyl, and 3-butenyl, with ethenyl and 2-propenyl being preferred.

[0092] The term "cycloalkyl" refers to a saturated mono-, di-, or tri-cyclic hydrocarbon group having 3 to 12 carbon atoms, particularly 5 to 10 carbon atoms, and more particularly 6 to 10 carbon atoms, either alone or as part of another group. Suitable cycloalkyl groups include, but are not limited to, cyclopentyl, cyclohexyl, norbornyl, adamantyl, particularly cyclohexyl and adamantyl. Preferred cycloalkyl groups include cyclohexyl, adamant-1-yl, and adamant-2-yl.

[0093] The term "aryl" refers to an aromatic monocyclic polyunsaturated hydrocarbon group (e.g., phenyl), or an aromatic polycyclic polyunsaturated hydrocarbon group (e.g., naphthyl, anthracenyl, phenanthracenyl, pyrenyl). Preferred aryl groups include phenyl, naphthyl, anthracenyl, phenanthracenyl, and pyrenyl.

[0094] The term "heteroaryl" refers to an aromatic ring having 5 to 12 carbon atoms, at least one of which is substituted with an oxygen, nitrogen, or sulfur atom, or -NH, wherein said nitrogen and sulfur atoms may be oxidized, said nitrogen atom may be quaternized, or a cyclic system including 2 to 3 fused rings each typically having 5 or 6 atoms, at least one of which is aromatic, and at least one carbon atom of at least one of said aromatic rings is substituted with an oxygen atom, nitrogen atom, or sulfur atom, or -NH, wherein said nitrogen and sulfur atoms may be oxidized, and said nitrogen atom may be quaternized. Examples of heteroaryl groups include furanyl, thiophenyl, pyrrolyl, pyridinyl, and benzofuranyl.

[0095] These compounds used in the present invention can be synthesized according to methods known to those skilled in the art. In particular, reference can be made to the publication by A. Loudet et al. (Chem. Rev. 2007, 107, 4891 - 4932).

[0096] According to another embodiment, the optically variable element is of the following formula III:

Chemical formula

[0097] Preferred compounds of the class of difluoroboron β-diketonates of formula III are those in which one or more of L 1 L 2 R 1 R 2 and R 3 are compounds defined as follows: L 1 is an unsaturated aliphatic chain, preferably an unsaturated aliphatic chain having 2 to 8 carbon atoms, or is absent; L 2 is an unsaturated aliphatic chain, preferably an unsaturated aliphatic chain having 2 to 8 carbon atoms, or is absent; R 1 is a substituted or unsubstituted aryl group, preferably a substituted or unsubstituted aryl group having at least one electron-donating or electron-withdrawing group; R 2 is a substituted or unsubstituted aryl group, preferably a substituted or unsubstituted aryl group having at least one electron-donating or electron-withdrawing group; R 3 is selected from hydrogen and a substituted or unsubstituted aryl group.

[0098] Preferred compounds of the class of difluoroboron β-diketonates of formula III are those in which one or more of L 1 L 2 R 1 R 2 and R 3 are compounds defined as follows: L 1 is an unsaturated aliphatic chain having 2 to 4 carbon atoms or is absent; L 2is a C2-C4 unsaturated aliphatic chain or does not exist; R 1 is a substituted or unsubstituted aryl group having at least one group selected from hydroxy, alkoxy, alkyl, aryl, dialkylamino, thioalkoxy, and halogen; R 2 is a substituted or unsubstituted aryl group having at least one group selected from hydroxy, alkoxy, alkyl, aryl, dialkylamino, thioalkoxy, and halogen; R 3 is selected from hydrogen and an unsubstituted aryl group.

[0099] Preferred compounds of the class of difluoroboron β-diketonates of formula III are those in which one or more of L 1 L 2 R 1 R 2 and R 3 are compounds defined as follows: L 1 is a C2-C4 unsaturated aliphatic chain or does not exist; L 2 is a C2-C4 unsaturated aliphatic chain or does not exist; R 1 is a substituted or unsubstituted aryl group having at least one group selected from hydroxy, C1-C4 alkoxy, C1-C8 alkyl, aryl, C1-C4 dialkylamino, C1-C4 thioalkoxy, halogen, preferably fluorine; R 2 is a substituted or unsubstituted aryl group having at least one group selected from hydroxy, C1-C4 alkoxy, C1-C8 alkyl, aryl, C1-C4 dialkylamino, C1-C4 thioalkoxy, halogen, preferably fluorine; R 3 is a hydrogen atom.

[0100] Preferred compounds of the class of difluoroboron β-diketonates of formula III are those in which one or more of L 1 L 2 R 1, R 2 , and R 3 one or more of which are compounds defined as follows: L 1 is a C2 unsaturated aliphatic chain or does not exist; L 2 is a C2 unsaturated aliphatic chain or does not exist; R 1 is a substituted or unsubstituted phenyl, biphenyl, or naphthyl having at least one group selected from an aryl group, preferably hydroxy, C1-C4 alkoxy, preferably methoxy, C1-C8 alkyl, preferably tert-butyl, aryl, C1-C4 dialkylamino, preferably dimethylamino; R 2 is a substituted or unsubstituted phenyl, biphenyl, or naphthyl having at least one group selected from an aryl group, preferably hydroxy, C1-C4 alkoxy, preferably methoxy, C1-C8 alkyl, preferably tert-butyl, aryl, C1-C4 dialkylamino, preferably dimethylamino; R 3 is a hydrogen atom.

[0101] Preferred compounds of the class of difluoroboron β-diketonates are of the following formula III2:

Chemical formula

[0102] Preferred compounds of the class of difluoroboron β-diketonates are of the following formula III3:

Chemical formula

[0103] Preferred compounds of the class of difluoroboron β-diketonates are those of the following formula III4: [Chemical formula] (wherein L 1 , R 1 , R 2 , and R 3 are as defined in formula III) is a compound of

[0104] Particularly preferred compounds of the class of difluoroboron β-diketonates of formula III are the compounds shown below:

[0105] [Chemical formula]

[0106] [Chemical formula]

[0107] The term "alkyl" refers to a straight-chain or branched hydrocarbon group of the formula: C n H 2n+1 wherein n is an integer of 1 or more. Preferred alkyl groups are straight-chain or branched C1-C6 alkyl groups.

[0108] The term "alkenyl" refers to a straight-chain or branched unsaturated alkyl group containing one or more carbon-carbon double bonds. Suitable alkenyl groups contain 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and even more preferably 2 or 3 carbon atoms. Non-limiting examples of alkenyl groups are ethenyl (vinyl), 2-propenyl (allyl), 2-butenyl, and 3-butenyl, with ethenyl and 2-propenyl being preferred.

[0109] The term "cycloalkyl", alone or as part of another group, refers to a saturated mono-, di-, or tri-cyclic hydrocarbon group having 3 to 12 carbon atoms, particularly 5 to 10 carbon atoms, more particularly 6 to 10 carbon atoms. Suitable cycloalkyl groups include, but are not limited to, cyclopentyl, cyclohexyl, norbornyl, adamantyl, particularly cyclohexyl and adamantyl. Preferred cycloalkyl groups include cyclohexyl, adamant-1-yl and adamant-2-yl.

[0110] The term "aryl" refers to an aromatic monocyclic polyunsaturated hydrocarbon group (e.g., phenyl), or an aromatic polycyclic polyunsaturated hydrocarbon group (e.g., naphthyl, anthracenyl, phenanthracenyl). Preferred aryl groups include phenyl, naphthyl, anthracenyl, phenanthracenyl, pyrenyl.

[0111] The term "heteroaryl" refers to an aromatic ring having 5 to 12 carbon atoms, at least one of which is substituted with an oxygen, nitrogen, or sulfur atom, or -NH, wherein said nitrogen and sulfur atoms may be oxidized, said nitrogen atom may be quaternized, or a cyclic system containing 2 to 3 fused rings, each typically having 5 or 6 atoms, at least one of which is aromatic, and at least one carbon atom of at least one of said aromatic rings is substituted with an oxygen atom, nitrogen atom, or sulfur atom, or -NH, wherein said nitrogen and sulfur atoms may be oxidized, said nitrogen atom may be quaternized. Examples of heteroaryl groups include furanyl, thiophenyl, pyrrolyl, pyridinyl, and benzofuranyl.

[0112] The term "halogen" refers to fluoro, chloro, bromo, or iodo. Preferred halogen groups are fluoro and bromo, with fluoro being particularly preferred.

[0113] The term "alkoxy" refers to an alkyl group bonded to an oxygen atom.

[0114] The term "alkenyloxy" refers to an alkenyl group bonded to an oxygen atom.

[0115] When the layers 2 and 3 containing the optically variable element are placed on a bright background, an intrinsic color (i.e., the complementary color of the color absorbed by the fluorescent compound) is observed.

[0116] Conversely, when placed on a dark background, the fluorescent color due to the fluorescent compound is observed.

[0117] The physicochemical stimulus is constituted by placing the device 1 on a bright background and then on a dark background, or by placing the device 1 on a dark background and then on a bright background.

[0118] Incorporation into all types of polymers can be achieved. The polymers are, for example, polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, polyvinyl chloride, polyamide, polyaramide, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate, rosin resin, pine resin, photocurable resin, or mixtures thereof, etc. Preferably, incorporation into polymers selected from polycarbonate, thermoplastic polyurethane, and photocurable resin, preferably polycarbonate and thermoplastic polyurethane can be achieved. More preferably, the polymer is polycarbonate.

[0119] The amount of the fluorescent dye to be incorporated is the amount necessary for detecting the absorption and fluorescence characteristics. The fluorescent dyes according to the present invention have the advantage of enabling the detection of these characteristics even when they are incorporated in a very small amount into the polymer.

[0120] In fact, an amount of fluorescent dye from 0.0001 to 5% by mass, preferably from 0.001 to 2% by mass, more preferably from 0.01 to 1% by mass based on the total mass of the polymer is sufficient for detection.

[0121] The amount of fluorescent dye will be adapted by those skilled in the art as a function of the formation of the polymer and the required visual effect.

[0122] Each layer containing the optically variable element is advantageously prepared by techniques known to those skilled in the art, such as rolling, extrusion, calendering, or extrusion calendering. These techniques will be selected as a function of the polymer used. As an example, when the polymer is polycarbonate or thermoplastic polyurethane, the principle of extrusion calendering may be preferred. The assembly of layers in the sense of the present invention can be obtained, for example, by rolling two or more layers of a polymer incorporating one or more fluorescent dyes.

[0123] Advantageously, layers 2 and 3 have a thickness of from 10 μm to 800 μm, preferably from 50 μm to 600 μm in the case of polycarbonate, from 10 μm to 600 μm, preferably from 30 μm to 150 μm in the case of polypropylene, and from 5 μm to 500 μm, preferably 10 μm in the case of PET, and to these thicknesses is added a thickness of ink of from 0.1 μm to 200 μm, preferably from 1 μm to 100 μm.

[0124] When the thickness of the layer is less than 0.100 mm, it is also called a film and has a very suitable application in the case of flat products, especially documents, more specifically identity documents, trustee certificates, or administrative documents, and can be applied to at least a part of one of the faces of the product.

Examples

[0125] [First variant] As can be seen in FIGS. 2 to 4, the optical marking device 1 has a first optical marking layer 2 and a second optical marking layer 3.

[0126] In Figure 4, layer 3 is superimposed on layer 2. Each of layers 2 and 3 includes optical variable elements 4 and 5. The first layer 2 includes a pattern 9 in the form of a disk. The disk 9 incorporates the optical variable element 4 of layer 2. It is, for example, an ink or varnish incorporating an active substance. The second layer 3 includes a pattern 10 in the form of a triangle. The triangle 10 incorporates the optical variable element 5 of layer 2. It is, for example, an ink or varnish incorporating an active substance. The pattern 10 covers the pattern 9. The patterns 9 and 10 are at the centers of their respective layers 2 and 3.

[0127] Of course, the present invention is not limited to this configuration, and the patterns may be off-center.

[0128] Each of the optical variable elements 4 and 5 preferably includes one or more of the above-described fluorescent compounds incorporated in a polymer.

[0129] In Figure 2, the first half 2-1 of the first layer 2, including the first half 9-1 of the disk 9, is shown against a bright background. The second half 2-2 of the first layer 2, including the second half 9-2 of the disk 9, is shown against a dark background.

[0130] In Figure 3, the first half 3-1 of the second layer 3, including the first half 10-1 of the triangle 10, is shown against a bright background. The second half 3-2 of the second layer 3, including the second half 10-2 of the triangle 10, is shown against a dark background.

[0131] The specific colors of layers 2 and 3, and advantageously their brightness, are selected such that for a bright background, the visible pattern is pattern 10 of the second layer 3, and for a dark background, the visible pattern is pattern 9 of the first layer.

[0132] For example, the first half 9-1 is pink (represented by the dotted line), which, as already mentioned, corresponds to the specific color of layer 2. The second half 9-2 is green (represented by the hatching), which, as already mentioned, corresponds to the fluorescent color of layer 2.

[0133] The first half 10-1 is blue (represented by the parallel dotted line), which, as already mentioned, corresponds to the specific color of layer 3. The second half 10-2 is red (represented by the parallel dotted line in a direction different from that of half 10-1), which, as already mentioned, corresponds to the fluorescent color of layer 3.

[0134] In Figure 4, the first half 1-1 of device 1 is placed on a bright background, and the second half 1-2 of device 1 is placed on a dark background.

[0135] For a bright background, the visible layer is the second layer 3, and the blue triangle 10-2 is observed. For a dark background, the visible layer is the first layer 2, and the green circle 9-1 is observed.

[0136] It should be noted that the resulting optical effect is made possible by the concentration of the active substance of the ink or varnish used for creating the pattern in the second layer 3, and the selection of the active substance in the pattern of the first layer 2, which is selected to minimize visibility against a bright background. In the pattern of the first layer 2, its fluorescent color has a contrast with the fluorescent color of layer 3, and advantageously, it is the complementary color (in subtractive synthesis) of the fluorescent color of the second layer 3.

[0137] Therefore, when an operator passes a product with marking device 1 over a bright background and then a black background, he observes a blue triangle and then a green circle.

[0138] In this case, passing through a white background or a dark background is a physical stimulus that enables a color change of the marking device 1.

[0139] Advantageously, it should be added that the specific colors of the first layer 2 and the second layer 3 are selected such that the layer 2 is only visible on a white background.

[0140] Furthermore, the fluorescent color is selected such that only the layer 3 is displayed (dark background). For example, as already mentioned, the fluorescent color of the first layer complements the fluorescent color of the second layer. In fact, the layer 3 filters all wavelengths of radiation shorter than its color.

[0141] The transition from a white background to a black background is a specific case, but of course other background colors can also be used.

[0142] The following table summarizes the various colors of the device 1. [Table 2]

[0143] [Second Variant] As can be seen in FIGS. 5 to 7, the optical marking device 1 has a first optical marking layer 2 and a second optical marking layer 3.

[0144] In FIG. 7, the layer 3 is superimposed on the layer 2. Only the first layer 2 includes the optically variable element 4.

[0145] As can be seen in FIG. 5, the first layer 2 is identical to the first layer 2 described in detail with respect to the first variant embodiment. The second layer 3 does not have an optically variable element. The second layer 3 has a color obtained by any technique known to those skilled in the art (e.g., bulk dyeing, varnish). The color is, for example, red. For a bright background, the color is displayed in bright red, and for a black background, the color is displayed in dark red.

[0146] As can be seen in Figure 7, the first half 1-1 of device 1 is arranged on a bright background, and the second half 1-2 of device 1 is arranged on a dark background. For a bright background, only the second layer 3, red, is visible to the eye. For a dark background, the first layer 2 is displayed, and a green semi-circle 9-2 is observed against a dark red background.

[0147] In this case, the passage from a white background to a dark background is a physical stimulus that enables the color change of the marking device 1.

[0148] It should be noted that the resulting optical effect is made possible by the concentration of the active substance of the ink or varnish used for creating the pattern 9 of the first layer 2, which is selected to minimize the visibility against a bright background, and the selection of the color of the second layer 3. The color of the second layer 3 has a contrast with respect to the fluorescent color and preferably has a contrast with respect to the color corresponding to the complementary color of the fluorescence used in the first layer 2.

[0149] [Third variant] According to this third variant, the marking device 1 includes a first layer 2 and a second layer 3. The second layer 3 is the same as the second layer 3 detailed with respect to the first variant embodiment. The first layer 2 includes a pattern 9 containing an optically variable element, similar to the first variant embodiment. The first layer 2 or the second layer 3 is at least partially reflective in the visible light spectrum.

[0150] For this purpose, the layer 2 can be a metallized polymer layer (polycarbonate, polypropylene, PET) or directly a metal layer. The layer 2 may include micromirrors.

[0151] According to other embodiments not shown, device 1 also includes a metallized substrate 11, or alternatively, layer 2 is coated with a layer of ink having metallic reflective properties.

[0152] According to this third embodiment, the stimulus is a switching of the viewing angle of device 1 as a function of the luminous environment (i.e., a bright or dark environment).

[0153] Depending on the viewing angle, light uptake is minimized or conversely maximized, and the color of device 1 is reversed.

[0154] As shown in FIG. 8, when the viewing direction D extends in a first direction, for example the direction N perpendicular to the plane P of device 1, the second layer 3 exhibits its intrinsic color.

[0155] As shown in FIG. 9, when the viewing direction D forms a non-zero angle with the plane P, the second layer 3 exhibits a fluorescent color.

[0156] As shown in FIG. 10, when the viewing direction D extends in the direction N, the blue triangle 10 of the second layer 3 is visible.

[0157] As shown in FIG. 11, when the direction D forms a non-zero angle with the direction N, the green disk 9 of the first layer 2 is visible.

[0158] According to an embodiment not shown, the first layer 2 includes a gray shade.

[0159] It should be noted that the resulting optical effect is made possible by the concentration of the active substance for creating the pattern of the second layer 3, which minimizes the visibility when normally observed; by the choice of the color of the first layer 2, and preferably its complementary color, which has a contrast with the fluorescent color of the active substance of the second layer 3; and further by the choice of the inversion angle according to the gray scale of the reflective surface (the higher the reflectivity of the surface (the lower the gray level), the smaller the inversion angle, and vice versa).

[0160] According to another variant not shown, the optical effect of color inversion can be obtained when at least one of layers 2 and 3 has light-scattering properties.

[0161] Preferably, layers 2 and 3 having scattering properties are, for example, matt.

[0162] In this case, depending on the viewing angle, the scattering hinders the fluorescence and only the intrinsic color is visible.

[0163] [Another variant] Advantageously, the optical marking device 1 includes a polarizing film (not shown).

[0164] The polarizing film can be composed of, for example, layer 2 or substrate 11. In this case, the substrate 11 does not necessarily have to be transparent, in contrast to the variants described above. By polarization of light, one layer 2 can be displayed and then the other layer 3 can be displayed.

[0165] [Mixing with dyes] According to another variant, each layer incorporating an optically variable element, or at least one of the layers incorporating an optically variable element, can contain a dye mixed with the optically variable element.

[0166] It is, for example, a colored ink incorporating an active substance.

[0167] Depending on the nature and concentration of the dye, it is possible to change the intrinsic color and / or the fluorescent color and / or the color of the device 1 under UV.

[0168] It should be noted that "dye" means any molecule capable of coloring, regardless of its size, its preparation, and the conditions under which the molecule acquires the ability to color.

[0169] In particular, the dye can be dissolved or dispersed (for example, pigments, etc.).

[0170] In particular, the dye may be gonichromic, photochromic, thermochromic, or piezochromic.

[0171] Figures 12 to 15 show the circular design 9 of layer 2 according to one of the first three variants already described.

[0172] The circular design 9 contains a mixture of an active substance based on a "4,4-difluoro-4-bora-3a,4a-diaza-s-indacene compound" of the BDPY class and a dye.

[0173] The transparency of the dye is minimal.

[0174] According to the first possibility, the dye has no fluorescent properties and has the effect of changing its intrinsic color (against a bright background) without changing its fluorescent color.

[0175] This effect is obtained by adding the color of the dye and the intrinsic color of the active substance.

[0176] Thus, for example, if a design 9 containing the active substance and no dye has a solid blue color and a red fluorescent color, a design 9 containing a mixture of the yellow dye and the active substance has an intrinsic green color and the fluorescent color remains red.

[0177] Figure 12 shows the design 9 containing the active substance and no dye against a bright background. It is shown in blue (hatching).

[0178] Figure 13 shows the design 9 containing the active substance and no dye against a dark background. It is shown in red (the reverse of the hatching).

[0179] Figure 14 shows the design 9 containing a mixture of the active substance and the yellow dye against a bright background. It is shown in green (dots).

[0180] Figure 15 shows design 9 containing a mixture of an active substance and a yellow dye against a dark background. The color shown is red (the same hatching as in Figure 13).

[0181] According to another possibility, adding the color of the intrinsic color and the dye (against a bright background) may make the intrinsic color completely unclear.

[0182] Thus, for example, if design 9 containing an active substance and no dye has a pink intrinsic color and a red fluorescent color, design 9 containing a mixture of a blue dye and the active substance has a blue intrinsic color and the fluorescent color remains red.

[0183] This occurs when the color of the added non-fluorescent dye covers the intrinsic color of the active substance, at least to the naked eye.

[0184] According to another possibility, the dye is a fluorescent dye molecule (fluorophore) that does not belong to the class of BDPY and has excitation and fluorescence emission bands different from those of the active substance. As a result, it is possible to change the color emitted under ultraviolet light by a design containing a mixture of the active substance and the fluorescent dye.

[0185] Note that since the additional fluorescence of the added dye can only be seen under UV, the color against a dark background is not changed. Under UV irradiation, there is a phenomenon where the fluorescent color of the active substance BDPY and the color of the added fluorescent dye molecule dye are mixed.

[0186] For example, it is possible to obtain white fluorescence under UV light by mixing an active substance having an intrinsic green color and a fluorescent yellow color with a blue fluorescent dye.

[0187] According to another possibility, the fluorescent dye molecule dye can change not only the fluorescent color but also the intrinsic color. This is possible when mixing a plurality of compounds of the BDPY class.

[0188] [Use] The present invention also relates to an identity document, a proxy certificate, or an administrative document or label comprising at least one optical marking device 1.

[0189] For example, the document may be an identity card, a passport, a permit, a certificate, a diploma, a checkbook, a register, a stamp, a seal, a visa, a bank card, a banknote.

[0190] The pattern may be a national symbol, a symbol of a company or a country, a logo associated with a brand, or a fixed or variable description, or a face value.

[0191] The marking device 1 occupies all or part of the document.

[0192] [Advantages] As is apparent from the foregoing description, the marking device according to the present invention provides effective security advantages for the document by means of physicochemical stimuli, in particular passing through a bright background and then through a dark background, or changing the observation angle, etc.

[0193] Since there is no need to prepare expensive equipment and it can be verified by simple movement, any examiner can easily and quickly verify the document.

[0194] Compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and / or fluorescent compounds of the class of difluoroboron β-diketonates (BF2bdks) ensure a method for easily manufacturing the marking device 1. This is because these fluorescent compounds are easily incorporated into the polymer, exhibit good thermal stability, and enable all the steps necessary for the manufacture of a document in which one or more marking devices 1 are incorporated.

[0195] It should be added that the described embodiments can be combined, provided that they are not incompatible.

Claims

1. An optical marking device according to the first or second configuration, comprising at least one first layer (2) and at least one second layer (3) arranged at least partially facing each other, a) According to the first configuration, both the first layer (2) and the second layer (3) include optically variable elements (4, 5), the first layer includes a first optically variable element, and the second layer includes a second optically variable element, the first layer includes a first pattern provided by the first optically variable element, the second layer includes a second pattern provided by the second optically variable element, the first pattern and the second pattern are arranged to overlap, the first optically variable element shows a color change between a first color and a second color, and the second optically variable element shows a color change between a third color and a fourth color, and shows contrast as follows: - When the first optically variable element (4, 5) of the first pattern shows the first color and the second optically variable element of the second pattern shows the third color, only the first pattern is visible. When the first optically variable element (4, 5) of the first pattern shows the second color and the second optically variable element of the second pattern shows the fourth color, only the second pattern becomes visible, or, - When the first optically variable element (4, 5) of the first pattern shows the first color and the second optically variable element of the second pattern shows the third color, only the second pattern is visible. When the first optically variable element (4, 5) of the first pattern shows the second color and the second optically variable element of the second pattern shows the fourth color, the first pattern becomes visible, or, b) According to the second configuration, one of the first layer (2) and the second layer (3) includes an optically variable element (4, 5), the first layer includes an optically variable element, and the second layer does not include an optically variable element, the first layer includes a pattern provided by the optically variable element, the second layer has a color, the optically variable element shows a color change between a first color and a second color, and shows contrast as follows: - When the optically variable element of the pattern shows the first color, only the pattern is visible. When the optically variable element of the pattern shows the second color, only the color of the second layer becomes visible, or, - When the optical variable element of the symbol shows the first color, only the color of the second layer is visible. When the optical variable element of the symbol shows the second color, only the symbol is visible. In any configuration, The optical variable elements (4, 5) of the pattern contain one or more fluorescent compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and / or the class of difluoroboron β-diketonates (BF ２ bdks), and one or more compounds of the class of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene have the formula I: [Chemical Formula 1] [wherein, R 1 is C1-C6 alkyl, C5-C6 cycloalkyl, C5-C6 heteroalkyl, phenyl, and the phenyl is optionally substituted with one or more groups selected from C1-C2 alkyl, hydroxy, R 5 COO - and halogen; R 2 and R 2’ is independently selected from hydrogen and C1-C2 alkyl; R 3 and R 3’ are independently selected from hydrogen, aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, and alkynyl, and the aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, and alkynyl are optionally substituted with one or more groups selected from C1-C4 alkyl, aryl, hydroxy, and ferrocene, [wherein the aryl is aryl (this aryl is optionally substituted with a C1-C2 alkyl group), C1-C2 alkyl, halogen, hydroxy, dimethylamino, and nitro] optionally substituted with one or more groups selected from; R 4 and R 4’ are independently selected from aryl, heteroaryl, cycloalkyl, alkyl and alkenyl, and said aryl, heteroaryl, cycloalkyl, alkyl and alkenyl are optionally substituted with one or more groups selected from C1-C3 alkyl, aryl, hydroxyl and ferrocene [said aryl being aryl (this aryl is optionally substituted with a C1-C2 alkyl group), C1-C2 alkyl, halogen, hydroxy, dimethylamino and nitro Optionally substituted with one or more groups selected from]]; R 5 is C1-C4 alkyl or C2-C4 alkenyl; R 6 and R 6’ is independently selected from halogen, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl or aryl, and the aryl is C1-C2 alkyl, hydroxy, R 5 COO - and is optionally substituted with one or more groups selected from halogen]] selected from the compounds of One or more compounds of the class of difluoroboron β-diketonates (BF ２ bdks) are of formula III: [Chemical Formula 2] [wherein, L 1 is either an unsaturated aliphatic chain or is absent; L 2 is either an unsaturated aliphatic chain or absent; R 1 is a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; R 2 is a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group; R 3 is selected from hydrogen, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group selected from the compounds of, an optical marking device.

2. The optical marking device according to claim 1, comprising a substrate (11) having at least one of a first layer and a second layer.

3. The optical marking device according to claim 1 or 2, wherein the two layers (2, 3) are in contact with each other.

4. The optical marking device according to any one of claims 1 to 3, wherein at least one of the two layers (2, 3) is at least partially reflective in the visible light spectrum and / or has a gray color tone.

5. The optical marking device according to any one of claims 1 to 4, wherein at least one of the two layers (2, 3) is at least partially scattering in the visible light spectrum.

6. The optical marking device according to any one of claims 1 to 5, comprising a polymer, wherein an optical variable element (4, 5) is incorporated into the polymer.

7. The optical marking device according to claim 6, wherein the polymer is selected from polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, polyvinyl chloride, polyamide, polyaramide, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate, rosin resin, pine resin, photocurable resin, or a mixture thereof.

8. The optical marking device according to any one of claims 1 to 3, wherein one of the first color and the second color of the optical variable element constituted by at least one of the first layer and the second layer is a complementary color of the color of the other layer.

9. Each of the two layers (2, 3) includes an optically variable element (4, 5) that independently exhibits a color change, where the two optically variable elements (4, 5) are arranged such that only the first layer (2) is visible when a first stimulus is applied to the device (1), and only the second layer (3) is visible when a second stimulus is applied to the device (1), and the two optically variable elements (4, 5) are at least partially overlapped. The stimulus is to change the incident angle of observation and / or to pass the device through a bright background and then through a dark background. The optical marking device according to any one of claims 1 to 8.

10. The optical marking device according to any one of claims 1 to 9, comprising an element configured to polarize light passing through the optical marking device (1).

11. The optical marking device according to any one of claims 1 to 10, wherein at least one of the first layer and the second layer (2, 3) includes a dye in addition to the optically variable element (4, 5) that exhibits a color change between a first color and a second color.

12. The optical marking device according to claim 11, wherein the dye is a fluorophore.

13. An identity document, a proxy certificate, or an administrative document, or a label, comprising at least one optical marking device according to any one of claims 1 to 12.

Images