RU2787990C2 - Optical marking device - Google Patents

Abstract

FIELD: information protection.

SUBSTANCE: group of inventions relates to an optical marking device, as well as to a protected document and a label, which contain such an optical marking device. In this case, the optical marking device contains one first layer (2) and second layer (3) at least partially located opposite to each other, while at least one of the specified first and second layers contains optically changeable element (4, 5) showing change in color from the first color to the second color. Moreover, the specified first and second colors contrast with color of another layer in such a way that, when optically changeable element (4, 5) shows the specified first color, first layer (2) is visible, and when optically changeable element (4, 5) shows the specified second color, second layer (3) is visible, or, when optically changeable element (4, 5) shows the specified first color, second layer (3) is visible, and when optically changeable element (4, 5) shows the specified second color, first layer (2) is visible. At the same time, optically changeable element (4, 5) contains one or more fluorescent compounds of 4,4-difluor-4-boro-3a,4a-diaza-s-indacene grade and/or grade of β-diketonates of boron difluoride (BF2bdk).

EFFECT: obtainment of an optical marking device.

18 cl, 15 dwg, 2 tbl

Description

The present invention relates to the field of security and authentication (authentication) of products, in particular documents.

More specifically, it refers to the security and authentication of identity, fiduciary or administrative documents, or company labels.

There is currently a significant increase in counterfeiting and production of counterfeit goods in many high value-added areas such as luxury goods, parts for the automotive and aviation industries, or packaging, especially for pharmaceuticals such as blister packs.

With the increase in cases of "identity" theft and, in particular, the introduction of driver's licenses in some countries with a system of registration of violations using points, identity documents and administrative documents are increasingly being falsified. Thus, the security and authenticity of these types of products and documents are of key importance and affect both national and international security issues.

Therefore, it is necessary to constantly create new means to effectively combat counterfeiting, in particular with changing the original document or counterfeiting (production of counterfeit goods).

In the context of the present description, the term "document" refers to a set consisting of a substrate and information. The support may be of any kind, may be of any shape, and may include a polymer or mixture of polymers. Said support may, for example, consist wholly or partly of a polymeric material.

Examples of documents that can be mentioned in particular are identity documents such as passports, identity cards, driver's licenses or medical cards, as well as fiduciary documents such as banknotes and checks, or administrative documents such as registration certificates.

Thus, the documents may be in the form of paper, in the form of a book or card, and the information may be either printed and/or applied to the surface if it is paper or card, or applied to sheets in the case of a book.

Because of the great value associated with the information they contain, these documents must be well protected.

Documents are currently protected by security elements that can be classified into three levels of security depending on the means used to detect them. Thus, Level 1 security elements are elements that can be detected by at least one of the five senses or by using a contrasting background. This level specifically includes guilloches, optically variable devices such as iridescent printing, holograms, optically variable inks, markers, variable laser images, or multiple laser images.

Level 2 security features are items that are detected using simple equipment such as an ultraviolet lamp, convex lenses, or a cell phone flash. This level of security includes detectable items such as microprinting, fluorescent inks, and fluorescent fibers or plates.

Finally, level 3 security elements are elements that are detected using sophisticated equipment such as, for example, a spectrofluorimeter or an electron microscope. This category includes, in particular, nanopigment coating technology, biometric chips, as well as fluorescent markers that are not detectable by the naked eye (tagants).

In general, a document includes several security elements of various levels.

WO2010022952 A1 describes a security element for a data carrier; the security element comprises an ink layer and an effect layer that is substantially transparent when viewed from a first angle and exhibits a color tone when viewed from at least one second angle, referred to as the effect angle.

Although existing security solutions have proven to be beneficial, their implementation and/or verification is sometimes difficult. Therefore, there is an urgent need for new security tools that are easy to use, stable and provide the ability to quickly verify the authenticity of products or documents while maintaining a high level of security. These means should not be mutually exclusive.

Therefore, the present invention relates to an optical marking device comprising at least a first layer and a second layer located at least partially opposite each other, where at least one of said first and second layers contains an optically variable element showing a color change from of the first color to the second color, wherein said first and second colors contrast with the color of the other layer such that when the optically variable element exhibits said first color, then the first layer is visible, and when the optically variable element exhibits said second color, then visible is the second layer, or when the optically variable element exhibits said first color, then the second layer is visible, and when the optically variable element exhibits said second color, then the first layer is visible.

Thus, the device of the present invention makes it possible to verify the authenticity of products such as documents, in particular identity documents, fiduciary or administrative documents, but also such as drug packaging (in particular blister packs), or even luxury goods. (trademark identification).

According to another feature of the invention, the device includes a design provided with said optically variable element.

According to another feature of the invention, the device includes a substrate carrying at least one of said first and second layers.

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

According to another feature of the invention, at least one of the two layers at least partly reflects visible light and/or has gray tints.

According to another feature of the invention, at least one of the two layers (2, 3) at least partially scatters light in the visible part of the spectrum.

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

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

According to another feature of the invention, the 4-boro-3a,4a-diaza-s-indacene compound or compounds used in the present invention may be selected from compounds of the following formula I:

, (I)

, (I)

wherein

R ¹ is a C1-C6 alkyl group, a C5-C6 cycloalkyl group, a C5-C6 heteroalkyl group, a phenyl group, said phenyl group being optionally substituted with one or more groups selected from a C1-C2 alkyl group, a hydroxy group, R ⁵ COO ^- and halogen;

R ² and R ^2' are independently selected from hydrogen and a C1-C2 alkyl group;

R ³ and R ^3' are independently selected from hydrogen, aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, alkynyl, wherein said aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, alkynyl group is optionally substituted with one or more groups selected from C1-C4 -alkyl group, aryl group, hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl group, C1-C2 alkyl group, halogen, hydroxy group, dimethylamino group, nitro group, wherein said aryl group is optionally substituted with C1 –C2-alkyl group;

R ⁴ and R ^4' are independently selected from an aryl, heteroaryl, cycloalkyl, alkyl, alkenyl group, wherein said aryl, heteroaryl, cycloalkyl, alkyl, and alkenyl group is optionally substituted with one or more groups selected from a C1-C3 alkyl group, an aryl group , hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl group, C1-C2 alkyl group, halogen, hydroxy group, dimethylamino group, nitro group, wherein said aryl group is optionally substituted with C1-C2 alkyl group;

R ⁵ is a C1-C4 alkyl group or a C2-C4 alkenyl group.

R ⁶ and R ^6' are independently selected from halogen, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl or aryl, said aryl group being optionally substituted with one or more groups selected from C1-C2-alkyl group, hydroxy group, R ⁵ COO- and halogen.

According to another feature of the invention, the compound or compounds of the 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene class are selected from compounds of formula II:

, (II)

, (II)

wherein

R ¹ means C1-C6-alkyl, C5-C6-cycloalkyl, C5-C6-heteroalkyl, phenyl group, and the specified phenyl group is optionally substituted with one or more groups selected from C1-C2-alkyl group, hydroxy group, R ⁵ COO ^- and halogen;

R ² and R ^2' are independently selected from hydrogen and a C1-C2 alkyl group;

R ³ and R ^3' are independently selected from hydrogen and a C1-C3 alkyl group;

R ⁴ and R ^4' are independently selected from an aryl, heteroaryl, cycloalkyl, alkyl, alkenyl group, wherein said aryl, heteroaryl, cycloalkyl, alkyl, and alkenyl group is optionally substituted with one or more groups selected from a C1-C3 alkyl, aryl, hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl, C1-C2 alkyl, halogen, hydroxy, dimethylamino, nitro, wherein the aryl group is optionally substituted with C1-C2 alkyl;

R ⁵ is a C1-C4 alkyl or C2-C4 alkenyl group.

According to another feature of the invention, the optically variable element contains one or more compounds of the class of boron difluoride β-diketonates (BF2bdk).

According to another feature of the invention, the compound or compounds of the class of boron difluoride β-diketonates (BF2bdk) are selected from compounds of formula III:

, (III)

, (III)

wherein

L ¹ is an unsaturated aliphatic chain or absent,

L ² is 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, and

R ³ is selected from hydrogen, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

According to another feature of the invention, the device comprises a polymer comprising an optically variable element.

According to another feature of the invention, the polymer is selected from polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, poly(vinyl chloride), polyamides, polyaramids, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate, rosins, pine resins, photopolymerizable resins or mixtures of the foregoing.

According to another feature of the invention, one of said first and second colors of the layer containing the optically variable element is a complementary color to the color of the other layer.

According to another feature of the invention, two layers comprise an optically variable element exhibiting a color change, wherein the two optically variable elements are at least partially superimposed on each other and are designed in such a way that only the first layer is visible upon application of the first stimulation of the device and only the second layer is visible. when applying a second stimulation device.

According to another feature of the invention, the device comprises an element configured to polarize light passing through said optical marking device.

According to another feature of the invention, at least one of said first and second layers comprises a mixture of an optically variable element exhibiting a color change from a first color to a second color with a dye.

According to another feature of the invention, the dye is a fluorophore.

The invention also relates to an identity document, fiduciary or administrative document or label containing at least one optical marking device as described above.

Other features and advantages of the invention will become more apparent upon reading the description below. The latter is given for purposes of illustration only and should be read in conjunction with the accompanying drawings, in which:

- fig. 1 schematically shows a sectional view of an optical marking device according to the present invention;

- fig. 2 to 4 show a top view, respectively, of the first layer, the second layer and the device according to the first embodiment of the invention;

- fig. 5 to 7 show a top view, respectively, of the first layer, the second layer and the device according to the second embodiment of the invention;

- fig. 8 to 11 show a top view, respectively, of the first layer, the second layer and the device according to the third embodiment of the invention; and

- fig. 12 to 15 show a top view, respectively, of the first layer, the second layer, and the device according to the fourth embodiment of the invention.

Optical marking device

The present invention relates to an optical marking device for a product such as a document. The optical marking device is indicated in the figures by the number 1.

In the context of the description, the term "document" refers to a set of substrate and information. The support may be of any kind, may be of any shape, and may include a polymer or mixture of polymers. Said substrate may, for example, consist wholly or partly of a polymeric material.

Examples of documents include, in particular, identity documents such as passports, identity cards, driver's licenses or health cards (medical cards), as well as fiduciary documents such as banknotes and checks, or administrative documents such as registration certificates. .

Thus, the documents may be in the form of paper, in the form of a book or card, and the information may be printed on them/or printed on the surface if it is paper or card, or printed on sheets in the case of a book.

The device 1 contains at least a first layer and a second layer, called optical marking layers.

In the figures, device 1 includes two optical marking layers, labeled 2 and 3.

Of course, the invention is not limited to this configuration only, and a multi-layer configuration having more than two layers can also be provided.

In the illustrated embodiments, layers 2 and 3 are exactly superimposed on each other, in direct contact with each other, which is particularly advantageous.

However, a variant is possible in which the layers 2 and 3 only partially cover each other and/or in which they are not in direct contact with each other, but are instead separated, for example separated by other layers of the device 1.

At least one of the two layers 2, 3 contains an optically variable element.

In the first embodiment shown in FIG. 2–4, each of the two layers 2, 3 contains an optically variable element, denoted respectively by the numbers 4, 5.

In the second embodiment shown in FIG. 5–7, only layer 2 contains an optically variable element, labeled 4.

In the third embodiment shown in FIG. 8–11, each of the two layers 2, 3 contains an optically variable element, denoted respectively by the numbers 4, 5.

Each optically variable element exhibits a color change from a first color to a second color, as will be described below.

The optically variable device 1 is configured such that when the optically variable element exhibits a first color, then the first layer is visible, and when the optically variable element exhibits said second color, then the second layer is visible, or when the optically variable element exhibits the first color, then the second layer is visible, and when the optically variable element exhibits said second color, then the first layer is visible, as will be described in more detail below with respect to each embodiment of the invention.

Preferably, at least one of the two layers contains a pattern that is at least partially superimposed on the optically variable element.

The drawing may preferably be a symbol, a drawing, a photograph, or a fixed or variable statement that can help identify products equipped with device 1.

The design may be printed, for example with ink or varnish, or etched with a laser, as will be described in detail below.

In FIG. 1 device 1 includes a substrate 11 carrying optical marking layers 2, 3.

The substrate 11 is, for example, a transparent polymer layer.

Preferably the substrate 11 is a layer of polypropylene, polycarbonate or polyethylene with a controlled thickness (e.g. 10 µm to 800 µm, preferably 50 µm to 600 µm for polycarbonate; 10 µm to 600 µm, preferably 30 µm to 150 µm for polypropylene and 5 µm to 500 µm, preferably 10 µm for transparent polyethylene).

optically variable element

"Optically variable element" means any physical chemical element that exhibits a color change between a first color and a second color depending on some physical chemical stimulus.

The physico-chemical stimulus, also referred to as stimulation, may be a light emission, a change in temperature or a change in pressure, or a change in the observation condition (such as a change in the viewing angle of an element).

In the embodiments of the invention, which are described in detail below, the optically variable element contains a given concentration of active substance, including one or more fluorescent compounds, especially from the class 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene (class BDPY) or the class of boron difluoride β-diketonates (BF ₂ bdk) detailed below.

However, the invention is not limited only to this kind of optically variable elements.

For example, it may also be a thermochromic substance, a liquid crystal ink, or an optically variable ink of the type known as "OVI" (registered trademark of SICPA).

Preferably, the layer 2 or 3 containing the optically variable element also contains a polymer in which said compound or compounds are included, in particular a polymer matrix representing the document in question or the product in question.

Hereinafter in the text of the description, the terms "4,4-difluoro-4-boro-3a,4a-diaza-s-indacene compound(s)," "boron difluoride β-diketonates (BF2bdk)" and "fluorescent dye(s) (and )" are used interchangeably.

It should be noted that the active substance may be miscible with one or more inks.

4,4-difluoro-4-boro-3a,4a-diaza-s-indacene compounds are fluorescent dyes, the first synthesis of which was published in 1968 (A. Treibs et al., Justus Liebigs - Ann. Chem. 1968 , 718, 208). Since then, several reports have been published on other synthesis methods (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), and a large number of 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene compounds are now commercially available, e.g. from ThermoFisher Scientific (Waltham, MA, USA).

These compounds have remarkable absorption and emission properties and in particular exhibit relatively narrow excitation and fluorescent emission bands with high quantum yields φ of 0.5 to 1, making them highly fluorescent.

Moreover, these compounds have good photostability as well as thermal stability. In fact, the fluorescent dyes of the invention are generally stable at temperatures up to 300°C.

Due to their high thermal stability, these fluorescent dyes can be easily incorporated into polymer matrices in the molten state and, contrary to expectations, their efficiency in terms of absorption and emission of fluorescence does not change when they are incorporated into a polymer matrix.

This good stability allows the compound or compounds to be incorporated into the relevant ink, which guarantees high photobleaching stability, unlike prior art technologies.

All 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene compounds show an absorption band in the visible region of the spectrum, and the color perceived by the naked eye corresponds to the color that is complementary to the absorbed color. For example, a compound that absorbs at about 480-490 nm, which is green/blue, will be perceived as orange/red to the naked eye.

Thus, this property allows you to get the level 1 security elements.

With regard to fluorescent properties, all compounds of the class 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene according to the invention show excitation bands in the ultraviolet (UV) region of the spectrum and emission bands in the visible part of the spectrum. Therefore, they can be excited, in particular, under the influence of a UV lamp emitting in the range from 100 nm to 400 nm, and this fluorescence can be detected with the naked eye, which makes it possible to obtain level 2 security elements.

Finally, the emission wavelength can be determined using a spectrofluorimeter or a low resolution single network fluorimeter (photodiode or photomultiplier tube detection), which makes the security elements of the present invention level 3 security.

The 4-boro-3a,4a-diaza-s-indacene compound or compounds used in the present invention may be selected from compounds of the following formula I:

, (I)

, (I)

wherein

R ¹ is a C1-C6 alkyl group, a C5-C6 cycloalkyl group, a C5-C6 heteroalkyl group, a phenyl group, said phenyl group being optionally substituted with one or more groups selected from a C1-C2 alkyl group, a hydroxy group, R ⁵ COO ^- and halogen;

R ² and R ^2' are independently selected from hydrogen and a C1-C2 alkyl group;

R ³ and R ^3' are independently selected from hydrogen, aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, alkynyl, wherein said aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, and alkynyl group is optionally substituted with one or more groups selected from C1-C4 -alkyl group, aryl group, hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl group, C1-C2 alkyl group, halogen, hydroxy group, dimethylamino group, nitro group, wherein said aryl group is optionally substituted with C1 –C2-alkyl group;

R ⁴ and R ^4' are independently selected from an aryl, heteroaryl, cycloalkyl, alkyl, alkenyl group, wherein said aryl, heteroaryl, cycloalkyl, alkyl, and alkenyl group is optionally substituted with one or more groups selected from a C1-C3 alkyl group, an aryl group , hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl group, C1-C2 alkyl group, halogen, hydroxy group, dimethylamino group, nitro group, wherein said aryl group is optionally substituted with C1-C2 alkyl group;

R ⁵ is a C1-C4 alkyl group or a C2-C4 alkenyl group.

R ⁶ and R ^6' are independently selected from halogen, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl or aryl, said aryl group being optionally substituted with one or more groups selected from C1-C2-alkyl group, hydroxy group, R ⁵ COO- and halogen.

Preferred compounds of formula I are those in which one or more of R ¹ , R ² , R ^2' , R ³ , R ^3' , R ⁴ , R4', R5, R6 and R6' are defined as follows:

R ¹ means a phenyl group substituted with one or more groups selected from a methyl group, a fluoro group, a hydroxy group, an acetyl group and a methacrylate group, preferably from a methyl group, a fluorine group, a hydroxy group and an acetyl group, more preferably from a methyl or fluorine group;

R ² and R ^2' are independently selected from hydrogen and a methyl group;

R ³ and R ^3' are independently selected from hydrogen, C1-C3 alkyl, vinyl, aryl, heteroaryl, adamantyl, said vinyl and aryl groups being optionally substituted with one or more groups selected from phenyl, C1-C2 alkyl groups, wherein said phenyl group is optionally substituted with one or more groups selected from C1-C2 alkyl group, hydroxy group, bromine, nitro group, dimethylamino group,

preferably hydrogen, methyl, ethyl, n-propyl, vinyl group, aryl group, heteroaryl group, adamantyl, wherein said vinyl and aryl groups are optionally substituted with one or more groups selected from phenyl, C1-C2 alkyl group, wherein said phenyl the group is optionally substituted with one or more groups selected from C1-C2 alkyl group, hydroxy group, bromine atom, nitro group, dimethylamino group,

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 groups are optionally substituted with one or more groups selected from from methyl, hydroxy, bromine, nitro and dimethylamino;

R ⁴ and R ^4' are independently selected from a methyl, vinyl, aryl, heteroaryl, adamantyl group, wherein said vinyl and aryl groups are optionally substituted with one or more groups selected from a phenyl group, C1-C2 alkyl group, wherein said phenyl group optionally substituted with one or more groups selected from C1-C2 alkyl group, hydroxy group, bromo group, nitro group, dimethylamino group; preferably R ⁴ and R ^4' are independently selected from methyl, vinyl, phenyl, phenanthryl, naphthalenyl, pyrenyl, thiophenyl, benzofuranyl, said vinyl, aryl and naphthalenyl group being optionally substituted with one or more of methyl, hydroxy, bromo, nitro groups and dimethylamino groups;

R ⁵ is a methyl or ethenyl group;

R ⁶ and R ^6' are independently selected from fluoro, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl or aryl, said aryl group being optionally substituted with one or more groups selected from C1-C2-alkyl group, hydroxy group, R ⁵ COO- and halogen, preferably R ⁶ and R ^6' are fluoro.

According to another embodiment, the compound or compounds of the 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene class used in the present invention may be selected from compounds of formula II:

, (II)

, (II)

wherein

R ¹ means C1-C6-alkyl, C5-C6-cycloalkyl, C5-C6-heteroalkyl, phenyl group, and the specified phenyl group is optionally substituted with one or more groups selected from C1-C2-alkyl group, hydroxy group, R ⁵ COO ^- and halogen;

R ² and R ^2' are independently selected from hydrogen and a C1-C2 alkyl group;

R ³ and R ^3' are independently selected from hydrogen and a C1-C3 alkyl group;

R ⁴ and R ^4' are independently selected from an aryl, heteroaryl, cycloalkyl, alkyl, alkenyl group, wherein said aryl, heteroaryl, cycloalkyl, alkyl, and alkenyl group is optionally substituted with one or more groups selected from a C1-C3 alkyl, aryl, hydroxy group and ferrocene, wherein said aryl group is optionally substituted with one or more groups selected from aryl, C1-C2 alkyl, halogen, hydroxy, dimethylamino, nitro, wherein the aryl group is optionally substituted with C1-C2 alkyl;

R ⁵ is a C1-C4 alkyl or C2-C4 alkenyl group.

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 and R ⁵ are defined as follows:

R ¹ is a phenyl group substituted with one or more groups selected from a methyl group, a fluoro group, a hydroxy group, an acetyl group and a methacrylate group, preferably from a methyl group, a fluorine group, a hydroxy group and an acetyl group, more preferably from a methyl or fluorine group;

R ² and R ^2' are independently selected from hydrogen and a methyl group;

R ³ and R ^3' are independently selected from hydrogen, a methyl group, an ethyl group, an n-propyl group, preferably an ethyl group;

R ⁴ and R ^4' are independently selected from a methyl, vinyl, aryl, heteroaryl, adamantyl group, wherein said vinyl and aryl groups are optionally substituted with one or more groups selected from a phenyl group, C1-C2 alkyl group, wherein said phenyl group optionally substituted with one or more groups selected from C1-C2 alkyl group, hydroxy group, bromo group, nitro group, dimethylamino group; preferably R ⁴ and R ^4' are independently selected from methyl, vinyl, phenyl, phenanthracenyl, naphthalenyl, pyrenyl, thiophenyl, benzofuranyl, said vinyl, aryl and naphthalenyl group being optionally substituted with one or more of methyl, hydroxy, bromo, nitro groups and dimethylamino groups;

R ⁵ is a methyl or ethenyl group.

Particularly preferred compounds of formula II are those shown in the following table.

No. Fluorescent dye 1

2

3

four

five

6

7

8

nine

10

eleven

12

13

fourteen

15

sixteen

17

eighteen

nineteen

20

21

22

23

24

25

26

27

28

29

thirty

31

32

33

(OH in the o, m, or p position) 34

35

36

37

38

39

To describe the compounds used in the present invention, terms and expressions are used, which should be interpreted, unless otherwise stated, according to the following definitions.

The term "halogen" means fluorine, chlorine, bromine or iodine. Preferred halogen groups are a fluoro group and a bromo group, with a fluorine group being particularly preferred.

The term "alkyl" means a hydrocarbon radical of the formula C _n H _2n+1 , straight or branched, in which n is an exponent equal to or greater than 1. Preferred alkyl groups are linear or branched C1-C6 alkyl groups.

The term "alkenyl" means an unsaturated alkyl group, straight or branched, containing one or more carbon-carbon double bonds. Suitable alkenyl groups contain 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, 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 groups, with butenyl, ethenyl and 2-propenyl groups being preferred.

The term "cycloalkyl", as such or as part of another group, means a saturated mono-, di- or tricyclic hydrocarbon radical having from 3 to 12 carbon atoms, preferably from 5 to 10 carbon atoms, in particular from 6 to 10 carbon atoms . Suitable cycloalkyl radicals include, but are limited to, cyclopentyl, cyclohexyl, norbornyl, adamantyl, preferably cyclohexyl and adamantyl. Preferred cycloalkyl groups include cyclohexyl, adamant-1-yl and adamant-2-yl groups.

The term "aryl" means a polyunsaturated hydrocarbon radical - aromatic, monocyclic (eg phenyl) or polycyclic (eg naphthyl, anthracenyl, phenanthracenyl, pyrenyl). Preferred aryl groups include phenyl, naphthyl, anthracenyl, pyrenyl groups.

The term "heteroaryl" means an aromatic ring having 5 to 12 carbon atoms in which at least one carbon atom has been replaced by an oxygen, nitrogen or sulfur atom, or -NH, where said nitrogen and sulfur atoms may optionally be oxidized and said atom nitrogen may optionally be quaternized, or a cyclic system containing from 2 to 3 fused rings, each of which typically contains 5 or 6 atoms, and at least one of these rings is aromatic, with at least one carbon atom at at least one aromatic ring is substituted with an oxygen, nitrogen or sulfur atom or –NH, wherein said nitrogen and sulfur atoms may optionally be oxidized and said nitrogen atom may optionally be quaternized. Examples of heteroaryl groups include furanyl, thiophenyl, pyrrolyl, pyridinyl and benzofuranyl groups.

The compounds used in the present invention can be synthesized by methods known to the person skilled in the art. One can refer in particular to the work of A. Loudet et al. (Chem. Rev. 2007, 107, 4891-4932).

According to another embodiment of the invention, the optically variable element contains a fluorescent composition containing a compound of the class of boron difluoride β-diketonates (BF ₂ bdk) included in the polymer matrix, selected from the compounds of the following formula III:

, (III)

, (III)

wherein

L ¹ is an unsaturated aliphatic chain or absent,

L ² is 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, and

R ³ is selected from hydrogen, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

Preferred compounds of the boron difluoride β-diketonate class of formula I are compounds in which one or more of L ¹ , L ² , R ¹ , R ² and R ³ are defined as follows:

L ¹ is an unsaturated aliphatic chain, preferably C2-C8, or absent,

L ² is an unsaturated aliphatic chain, preferably C2-C8, or absent,

R ₁ is a substituted or unsubstituted aryl group, preferably a substituted or unsubstituted aryl group with 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 with at least one electron donating or electron withdrawing group, and

R ₃ is selected from hydrogen and a substituted or unsubstituted aryl group.

Preferred compounds of the boron difluoride β-diketonate class of formula I are compounds in which one or more of L ¹ , L ² , R ¹ , R ² and R ³ are defined as follows:

L ¹ is an unsaturated aliphatic chain, C2-C4, or absent,

L ² is an unsaturated aliphatic chain, C2-C4, or absent,

R ₁ is a substituted or unsubstituted aryl group with at least one group selected from hydroxy, alkoxy, alkyl, aryl, dialkylamino, thioalkoxy, halogen,

R ₂ is a substituted or unsubstituted aryl group with at least one group selected from hydroxy, alkoxy, alkyl, aryl, dialkylamino, thioalkoxy, halogen, and

R ₃ is selected from hydrogen and an unsubstituted aryl group.

Preferred compounds of the boron difluoride β-diketonate class of formula I are compounds in which one or more of L ¹ , L ² , R ¹ , R ² and R ³ are defined as follows:

L ¹ is an unsaturated aliphatic chain, C2-C4, or absent,

L ² is an unsaturated aliphatic chain, C2-C4, or absent,

R ₁ is a substituted or unsubstituted aryl group with 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 with at least one group selected from hydroxy, C1-C4 alkoxy, C1-C8 alkyl, aryl, C1-C4 dialkylamino, C1-C4 thioalkoxy, halogen, preferably fluorine, and

R ₃ is a hydrogen atom.

Preferred compounds of the boron difluoride β-diketonate class of formula I are compounds in which one or more of L ¹ , L ² , R ¹ , R ² and R ³ are defined as follows:

L ¹ is an unsaturated aliphatic chain, C2, or non-existent,

L ² is an unsaturated aliphatic chain, C2, or non-existent,

R ₁ is an aryl group, preferably a phenyl, diphenyl or naphthyl group, unsubstituted or substituted with at least one group selected from hydroxy, C1-C4 alkoxy, preferably methoxy, C1-C8 alkyl, preferably t-butyl, aryl group, C1-C4 alkylamino group, preferably dimethylamino group,

R ₂ is an aryl group, preferably a phenyl, diphenyl or naphthyl group, unsubstituted or substituted with at least one group selected from hydroxy, C1-C4 alkoxy, preferably methoxy, C1-C8 alkyl, preferably t-butyl, an aryl group, a C1-C4 alkylamino group, preferably a dimethylamino group, and

R ₃ is a hydrogen atom.

Preferred compounds of the class of β-diketonates of boron difluoride are compounds of the following formula III ₂ :

, (III₂)

, (III ₂ )

in which R ¹ , R ² and R ³ are defined as in formula I.

Preferred compounds of the class of boron difluoride β-diketonates are compounds of the following formula III ₃ :

, (III₃)

, (III ₃ )

in which L ¹ , R ¹ , R ² and R ³ are defined as in formula III.

Preferred compounds of the class of β-diketonates of boron difluoride are compounds of the following formula III ₄ :

, (III₄)

, (III ₄ )

in which L ² , R ¹ , R ² and R ³ are defined as in formula III.

Especially preferred compounds of the boron difluoride β-diketonate class of formula III are those listed below:

The term "alkyl" means a hydrocarbon radical of the formula C _n H _2n+1 , straight or branched, in which n is an exponent equal to or greater than 1. Preferred alkyl groups are linear or branched C1-C6 alkyl groups.

The term "alkenyl" means an unsaturated alkyl group, straight or branched, containing one or more carbon-carbon double bonds. Suitable alkenyl groups contain 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, 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 groups, with ethenyl and 2-propenyl groups being preferred.

The term "cycloalkyl", as such or as part of another group, means a saturated mono-, di- or tricyclic hydrocarbon radical having from 3 to 12 carbon atoms, preferably from 5 to 10 carbon atoms, in particular from 6 to 10 carbon atoms. Suitable cycloalkyl radicals include, but are not limited to, cyclopentyl, cyclohexyl, norbornyl, adamantyl, in particular cyclohexyl and adamantyl. Preferred cycloalkyl groups include cyclohexyl, adamant-1-yl and adamant-2-yl groups.

The term "aryl" means a polyunsaturated hydrocarbon radical, aromatic, monocyclic (eg phenyl) or polycyclic (eg naphthyl, anthracenyl, phenanthracenyl, pyrenyl). Preferred aryl groups include phenyl, naphthyl, anthracenyl, phenanthracenyl, pyrenyl groups.

The term "heteroaryl" means an aromatic ring having from 5 to 12 carbon atoms, in which at least one carbon atom is replaced by an oxygen, nitrogen or sulfur atom, or -NH, and these nitrogen and sulfur atoms may optionally be oxidized, and the specified atom nitrogen may optionally be quaternized, or a cyclic system containing from 2 to 3 fused rings, each of which typically contains 5 or 6 atoms, and at least one of these rings is aromatic, with at least one carbon atom at at least one aromatic ring is substituted with an oxygen, nitrogen or sulfur atom or –NH, wherein said nitrogen and sulfur atoms may optionally be oxidized and said nitrogen atom may optionally be quaternized. Examples of heteroaryl groups include furanyl, thiophenyl, pyrrolyl, pyridinyl and benzofuranyl groups.

The term "halogen" means fluorine, chlorine, bromine or iodine. Preferred halogen groups are a fluoro group and a bromo group, with a fluorine group being particularly preferred.

The term "alkoxy" means an alkyl group bonded to an oxygen atom.

The term "alkenyloxy" means an alkenyl group bonded to an oxygen atom.

Thus, if a layer 2, 3 containing an optically variable element is applied to a light background, then its own color (ie, a complementary color to the color absorbed by the fluorescent compound or compounds) is observed.

Conversely, against a dark background, the fluorescence color due to the fluorescent compound(s) is observed.

The physicochemical stimulus consists in placing device 1 first on a light background and then on a dark background, or, conversely, first on a dark background and then on a light background.

Incorporation can take place in all kinds of polymers such as polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, poly(vinyl chloride), polyamides, polyaramids, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate, rosin, pine resin, photopolymerizable resins, or mixtures of the foregoing. Preferably, the incorporation may be in a polymer selected from polycarbonate, thermoplastic polyurethane and photopolymerizable resins, preferably polycarbonate and thermoplastic polyurethane, more preferably the polymer is polycarbonate.

The amount of fluorescent dye added is that which is necessary to determine the absorption and fluorescence properties. The fluorescent dyes of the invention have the advantage that they allow these properties to be determined even when incorporated into the polymer in very small amounts.

In fact, from 0.0001 to 5 wt.% in terms of the total weight of the polymer, preferably from 0.001 to 2 wt.%, based on the total weight of the polymer, is quite sufficient for the determination of the amount of fluorescent dyes, even more preferably from 0.01 to 1 wt. %, based on the total weight of the polymer.

The amount of fluorescent(s) dye(s) is selected by a person skilled in the art depending on the molding of the polymer and the desired visual effect.

Each layer containing the optically variable element is preferably produced by methods well known to the person skilled in the art, such as, for example, rolling, extrusion, calendering or extrusion calendering. These methods are selected depending on the polymer used. For example, if the polymer is polycarbonate or thermoplastic polyurethane, the extrusion calendering principle is preferred. A set of layers in the context of the present invention can be obtained, for example, by rolling two or more layers of a polymer containing one or more fluorescent dyes.

Preferably the layer 2, 3 has in particular a thickness of 10 µm to 800 µm, preferably 50 µm to 600 µm, for polycarbonate; 10 µm to 600 µm, preferably 30 µm to 150 µm, for polypropylene; and 5 µm to 500 µm, preferably 10 µm for PET, and to this is added an ink thickness of 0.1 µm to 200 µm, preferably 1 µm to 100 µm.

If the layer has a thickness of less than 0.100 mm, then it is also called a film and can find very specific use in the case of flat products, in particular documents, more specifically identity documents, fiduciary or administrative documents, and can be applied, at least partially, on one of the front sides of the product.

First option

As can be seen from FIG. 2-4, the optical marking device 1 includes a first optical marking layer 2 and a second optical marking layer 3.

In FIG. 4 layer 3 superimposed on layer 2.

Each of the layers 2, 3 includes an optically variable element 4, 5.

The first layer 2 contains drawing 9 in the form of a circle.

Circle 9 accommodates optically variable element 4 of layer 2.

This is, for example, ink or varnish containing an active substance.

The second layer 3 contains a pattern 10 in the shape of a triangle.

The triangle 10 accommodates the optically variable element 5 of layer 2.

This is, for example, ink or varnish containing an active substance.

Figure 10 covers Figure 9.

Figures 9, 10 are located in the center of their respective layer 2, 3.

Of course, the invention is not limited to this configuration, and, conversely, the patterns can be offset from the center.

Each of the optically variable elements 4, 5 contains one or more fluorescent compounds as described above, preferably incorporated into the polymer.

In FIG. 2, the first half 2-1 of the first layer 2, including the first half 9-1 of the circle 9, is shown against a light background.

The second half 2-2 of the first layer 2, including the second half 9-2 of circle 9, is shown against a dark background.

In FIG. 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 light 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.

The proper color of the layers 2, 3 and their illumination are preferably chosen in such a way that the pattern 10 of the second layer 3 is visible on a light background, while the pattern 9 of the first layer 2 is visible on a dark background.

For example, the first half of 9-1 has a pink coloration (shown in dotted lines), which, as already mentioned, corresponds to the native color of layer 2.

The second half of 9-2 has a green color (shown by hatching), which, as already mentioned, corresponds to the fluorescence color of layer 2.

The first half of 10-1 has a blue coloration (shown by parallel dotted lines), which, as already mentioned, corresponds to the native color of layer 3.

The second half of 10-2 has a red coloration (shown by parallel dotted lines in a direction different from that of half 10-1), which, as already mentioned, corresponds to the fluorescence color of layer 3.

In FIG. 4, the first half 1-1 of device 1 is placed on a light background, while the second half 1-2 of device 1 is placed on a dark background.

On a light background, the second layer 3 and the blue triangle 10-2 are observed.

On a dark background, the first layer 2 and the green circle 9-1 are observed.

It should be noted that the resulting optical effect is due to the concentration (in the second layer 3) of the active substance of the ink or varnish used to create the pattern, chosen in such a way as to minimize its visibility against a light background, as well as the choice of the active substance in the pattern of the first layer 2, the fluorescence color of which contrasts with the color of layer 3, is preferably the complementary color (in subtractive synthesis) to the color of the second layer 3.

Thus, if the operator passes a product equipped with marking device 1 first through a light background and then through a dark background, he can observe first a blue triangle and then a green circle.

Passing through a light (white) background or a dark background is precisely in this case a physical stimulus that causes a change in the color of the marking device 1.

It should be added that the eigencolors of the first layer 2 and the second layer 3, respectively, are chosen so that only layer 2 is visible against a white (light) background.

Moreover, the fluorescence colors are chosen so that only layer 3 is visible (against a dark background). For example, the fluorescence color of the first layer is complementary to the fluorescence color of the second layer, as noted above. In fact, layer 3 filters all wavelengths of radiation below its color.

It should be noted that the transition from a light background to a dark background is a special case; of course, backgrounds of other colors can also be used.

The following table summarizes the different colors of device 1.

Layer 2 (bottom)
A/B color pair Layer 3 (top)
Pair of colors C/D own color A C Device color perceived against a light background A Fluorescence color B D Device color perceived against a dark background D

Second option

As can be seen in FIG. 5 to 7, the optical marking device 1 comprises a first optical marking layer 2 and a second optical marking layer 3.

In Fig.7 layer 3 is superimposed on layer 2.

Only the first layer 2 contains the optically variable element 4.

As can be seen in FIG. 5, the first layer 2 is identical to the first layer 2 described in detail in the first embodiment.

The second layer 3 does not have an optically variable element.

The second layer 3 has a color obtained by any means known to the person skilled in the art (eg bulk dyeing, varnishing).

The color is, for example, red.

On a light background, the color appears light red, and on a dark background, the color appears dark red.

As can be seen in FIG. 7, the first half 1-1 of the device 1 is placed on a light background, while the second half 1-2 of the device 1 is placed on a dark background.

On a light background, only the second layer 3 (red) is visible.

On a dark background, the first layer 2 is visible, and the green semicircle 9-2 is observed on a dark red background.

The transition from a light background to a dark background in this case serves as a physical stimulus that causes a change in the color of the marking device 1.

It should be noted that the achieved optical effect is due to the concentration of the active substance of the ink or varnish used to obtain the pattern 9 of the first layer 2, chosen in such a way as to minimize its visibility on a light background, as well as the choice of the color of the second layer 3, the color of which contrasts with the color fluorescence, and preferably a color corresponding to the complementary color to the fluorescence color in the first layer 2.

Third option

According to this third variant, the marking device 1 comprises a first layer 2 and a second layer 3.

The second layer 3 is identical to the second layer 3 described in detail in the first embodiment.

The first layer 2 contains, like the first embodiment, a pattern 9 including an optically variable element.

The first layer 2 or the second layer 3 are reflective, at least partially, in the visible part of the spectrum.

For this purpose, layer 2 may be a metallized polymer layer (polycarbonate, polypropylene, polyethylene terephthalate (PET)) or the metal layer itself. Layer 2 may also contain micro-mirrors.

In other embodiments not shown, the device 1 also comprises a substrate 11 which is metallised, or a layer 2 coated with a layer of metallic ink.

According to this third variant, the stimulus is a change in the viewing angle of the device 1 depending on the light environment (ie light or dark environment).

Depending on the viewing angle, there is a minimization or, conversely, a maximization of light absorption, which causes a change in the color of the device 1.

As can be seen in FIG. 8, when the viewing direction D extends in the first direction, for example in the N direction perpendicular to the plane P of the device 1, the second layer 3 exhibits its own color.

As can be seen in FIG. 9, when the viewing direction D forms a non-zero angle with the P plane, the second layer 3 shows the fluorescence color.

As can be seen in FIG. 10, when the viewing direction D extends towards the N direction, the blue triangle 10 of the second layer 3 is visible.

As can be seen in FIG. 11, when the D direction forms a non-zero angle with the N direction, the green circle 9 of the first layer 2 is visible.

In a variant not shown, the first layer 2 has shades of gray.

It should be noted that the achieved optical effect is due to the concentration of the active substance to form the pattern of the second layer 3 in order to minimize its visibility during normal observation, the choice of the color of the first layer 2, which contrasts with the complementary color of the fluorescence of the active substance of the second layer 3, and preferably the complementary color, and also the grayscale rotation angle of the reflective surface (the larger the reflective surface (low gray level), the smaller the rotation angle, and vice versa).

According to another variant (not shown), an optical color change effect can be achieved when at least one of the layers 2, 3 has optical diffusion properties.

Preferably, the diffusion layer 2, 3 is, for example, matt.

In this case, depending on the viewing angle, diffusion prevents fluorescence and only the intrinsic color of the layer appears.

Another variant

Advantageously, the optical marking device 1 comprises a polarizing film (not shown).

The polarizing film may consist, for example, of layer 2 or substrate 11.

In this case, the substrate 11 is not necessarily transparent, in contrast to the options described above.

The polarization of light allows you to view first one of the layers 2, then another layer 3.

Dye mixing

According to another variant, each of the layers including the optically variable element, or at least one of the layers including the optically variable element, may contain a dye mixed with the optically variable element.

This may be, for example, a colored paint containing an active substance.

Depending on the nature of the dye and its concentration, it is possible to change the intrinsic color and/or the color of the fluorescence and/or the color under UV radiation of the device 1.

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.

In particular, the dye may be dissolved or dispersed (such as, for example, a pigment).

In particular, the dye may be monochrome, photochromic, thermochromic or piezochromic.

Fig. 12-15 show a drawing in the form of a circle 9 layer 2 according to one of the first three options already described.

Circle pattern 9 contains a mixture of active substance based on "4,4-difluoro-4-boro-3a,4a-diaza-s-indacene compound(s)" of the BDPY class with a dye.

The dye has minimal transparency.

According to the first possibility, the dye does not have fluorescent properties and exhibits the effect of changing its own color (on a light background) without changing the color of the fluorescence.

This effect is achieved by adding the color of the dye and the own color of the active substance.

So, for example, if drawing 9 with active substance and without dye has a blue intrinsic color and a red fluorescence color, then drawing 9 containing a mixture of yellow dye and active substance has a green intrinsic color, while the fluorescence color remains red.

Fig. 12 shows Figure 9 with active and no dye on a light background: the color that appears is blue (shaded).

Fig. 13 shows Figure 9 with the active substance and no dye on a dark background: the color that appears is red (shading in the other direction).

Fig. 14 shows figure 9 containing a mixture of active substance and yellow dye on a light background: the color that appears is green (indicated by dots).

Fig. 15 shows figure 9 containing a mixture of active substance and yellow dye on a dark background: the color that appears is red (hatched identically to the shading in fig. 13).

According to another possibility, adding a color (on a light background) to the native color and the dye color can completely hide the native color.

So, for example, if pattern 9 with active and no dye has a pink intrinsic color and a red fluorescence color, then pattern 9 containing a mixture of blue dye and active agent has a blue intrinsic color, while the fluorescence color remains red.

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

In yet another possibility, the dye is a non-BDPY fluorophore and exhibits different excitation and fluorescence emission bands from those of the active substance. In this case, it is possible to change the color emitted by ultraviolet radiation by means of a pattern carrying a mixture of the active substance and the fluorescent dye.

It should be noted that the color on a dark background does not change, since the addition of fluorescence of the added dye is visible only in ultraviolet rays. Under UV illumination, mixing phenomena of the fluorescence color of the active substance (BDPY class) and the color of the added fluorophore dye are observed.

It is possible, for example, to obtain white fluorescence under ultraviolet light by mixing an active substance of its own green color and yellow fluorescence color with a blue fluorescent dye.

According to another possibility, the fluorophore dye allows you to change its own color, as well as the color of the fluorescence. This is possible in case of mixing several compounds of the BDPY class.

Application

The invention also relates to an identity document, fiduciary or administrative document, or a label, including at least one optical marking device 1.

For example, the document can 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 bank note.

The design may be a national or enterprise symbol, or a national logo associated with a brand, or a fixed or variable statement, or a face value.

The marking device 1 occupies the entire document or part of it.

Advantages

From the foregoing description, it is clear that the marking device of the present invention provides the advantage of effective document security, in particular through physico-chemical stimuli such as viewing against a light background followed by viewing against a dark background, or changing the viewing angle.

Any agent will be able to easily and quickly verify the authenticity of a document with a simple movement, sufficient for such verification, without the need for expensive equipment.

Fluorescent compounds of the 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene class and/or the boron difluoride β-diketonate class (BF2bdk) provide a simplified method for creating a labeling device 1 as they readily incorporate into the polymer and display good thermal stability, which also makes it possible to carry out all the steps required to obtain a document in which one or more marking devices 1 are included.

It should be added that the embodiments of the invention described here can be combined with each other, provided that they are not incompatible.

Claims (37)

1. An optical marking device containing at least one first layer (2) and a second layer (3) located at least partially opposite each other, while at least one of the said first and second layers contains an optically variable element (4, 5) showing a color change from a first color to a second color, said first and second colors contrasting with the color of another layer such that when the optically variable element (4, 5) exhibits said first color, the first layer is visible (2) and when the optically variable element (4, 5) exhibits said second color, then the second layer (3) is visible, or when the optically variable element (4, 5) exhibits said first color, then the second layer (3) is visible. ), and when the optically variable element (4, 5) exhibits the specified second color, then the first layer (2) is visible, while the optically variable element (4, 5) contains one or more fluorescent compounds of the 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene class and/or the class of boron difluoride β-diketonates (BF2bdk). 2. The device according to claim 1, in which at least one of the two layers (2, 3) contains a pattern (9, 10) provided with the specified optical variable element (4, 5). 3. An apparatus according to any one of the preceding claims, comprising a substrate (11) bearing at least one of said first and second layers. 4. Device according to any one of the preceding claims, in which two layers (2, 3) are in contact with each other. 5. Device according to any one of the preceding claims, wherein at least one of the two layers (2, 3) at least partly reflects visible light and/or has shades of gray. 6. Device according to any one of the preceding claims, wherein at least one of the two layers (2, 3) at least partially scatters visible light. 7. Device according to any one of the preceding claims, wherein the compound or compounds of the 4,4-difluoro-4-boro-3a,4a-diaza-s-indacene class are selected from compounds of formula I:

, (I) wherein R ¹ is a C1-C6 alkyl group, a C5-C6 cycloalkyl group, a C5-C6 heteroalkyl group, a phenyl group; R ² and R ^2' are independently selected from hydrogen and a C1-C2 alkyl group; R ³ and R ^3' are independently selected from hydrogen, aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, alkynyl; R ⁴ and R ^4' are independently selected from aryl, heteroaryl, cycloalkyl, alkyl, alkenyl; R ⁵ is a C1-C4 alkyl group or a C2-C4 alkenyl group. R ⁶ and R ^6' are independently selected from halogen, C1-C4 alkoxy, C2-C4 alkenyloxy, C1-C4 alkyl, C2-C4 alkenyl, or aryl. 8. The device according to claim 7, in which R ¹ is a phenyl group substituted with one or more groups selected from a C1-C2 alkyl group, hydroxy, R ⁵ COO ^- and halogen; and/or R³ and R^3' chosen from an aryl, heteroaryl, cycloalkyl, alkyl, alkenyl, alkynyl group substituted with one or more groups selected from C1-C4 alkyl group, aryl group, hydroxy group and ferrocene, said aryl group being substituted with one or more groups selected from aryl a group, a C1-C2 alkyl group, a halogen, a hydroxy group, a dimethylamino group, a nitro group, wherein said aryl group is substituted with a C1-C2 alkyl group; and/or R ⁴ and R ^4' are selected from aryl, heteroaryl, cycloalkyl, alkyl and alkenyl groups substituted with one or more groups selected from C1-C3 alkyl, aryl, hydroxy and ferrocene, said aryl group being substituted with one or more groups selected from an aryl group, a C1-C2 alkyl group, a halogen, a hydroxy group, a dimethylamino group, a nitro group, said aryl group being substituted with a C1-C2 alkyl group; and/or R ⁶ and R ^6' are an aryl group substituted with one or more groups selected from a C1-C2 alkyl group, hydroxy, R ⁵ COO- and halogen. 9. Device according to any one of the preceding claims, wherein the compound or compounds of the class of boron difluoride β-diketonates (BF2bdk) are selected from compounds of formula III:

, (III) wherein L ¹ is an unsaturated aliphatic chain or absent, L ² is 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, and R ³ is selected from hydrogen, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group. 10. A device according to any one of the preceding claims containing a polymer comprising an optically variable element (4, 5). 11. Device according to claim 10 wherein the polymer is selected from polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, poly(vinyl chloride), polyamides, polyaramids, ethylene vinyl acetate (EVA), polyurethane, thermoplastic polyurethane (TPU), cyanoacrylate , rosins, pine resins, photopolymerizable resins, or mixtures of the foregoing. 12. An apparatus according to any one of the preceding claims, wherein one of said first and second colors of the layer containing the optically variable element is complementary to the color of the other layer. 13. Device according to any one of the preceding claims, wherein the two layers (2, 3) comprise an optically variable element (4, 5) exhibiting a color change, the two optically variable elements (4, 5) being at least partially superimposed on each other and configured such that only the first layer (2) is visible when the first stimulation of the device (1) is applied and only the second layer (3) is visible when the second stimulation of the device (1) is applied. 14. A device according to any one of the preceding claims, comprising an element configured to polarize light passing through said optical marking device (1). 15. An apparatus according to any of the preceding claims, wherein at least one of said first and second layers (2, 3) comprises a mixture of an optically variable element (4, 5) exhibiting a color change ranging from a first color to a second color, with dye. 16. The device of claim 15 wherein the dye is a fluorophore. 17. Security document containing at least one optical marking device (1) according to any one of the preceding claims. 18. Label containing at least one optical marking device (1) according to any one of paragraphs. 1-16.

Images