FR2965752A1 - SECURITY STRUCTURE INCORPORATING MICROPERFORATIONS - Google Patents

Abstract

The present invention relates to a security structure (10) comprising at least: a first set (Gi) of microperforations all making a first angle (α) with the normal to the structure, and defining a first visible pattern when observed in an observation direction coinciding with the axis of the microperforations of the first set, and - a second set (G) of microperforations all forming a second angle (α) with the normal to the structure, different from the first angle, this second set defining a second visible pattern when observed in an observation direction coinciding with the axis of the microperforations of the second set.

Description

The present invention relates to the field of security documents. It is known, including Swiss banknotes, perforations perpendicular to the plane of the paper to secure it. The visual effect obtained is the only observation in light transmitted perforations.

The patent application EP 1 525 100 describes a security document through which a plurality of perforations of ellipsoidal section, oriented according to the normal to the document, extends. The application WO 00/43216 describes a security element against forgery, comprising non-through perforations, resulting in different depths, which may include oblique perforations. The perforations are visible in the form of a gray gradient when the structure is observed in transmission. WO 02/33652 discloses a security element having conical perforations oriented perpendicularly to the element, through or not, to form a multi-tone image.

There is a need to further enhance security and improve authentication processes of security documents, in particular to increase the difficulty of forging these documents. The invention thus has, according to one of its aspects, a safety structure comprising at least: a first set of microperforations, all of which make a first angle with the normal to the structure, and defining a first visible pattern at the less when observed in an observation direction coinciding with the axis of the microperforations, and - a second set of microperforations all forming a second angle with the normal to the structure, different from the first angle, this second set defining a second pattern visible at least when observed in an observation direction coinciding with the axis of the microperforations of the second set. An "assembly" of microperforations consists of at least two microperforations, and preferably at least ten microperforations. By "microperforation" is meant a hole optionally filled with a non-opaque material having a greater transverse dimension of millimeter or micrometer size, especially between 5 microns and 200 microns, better between 10 and 50 microns. The transverse dimension is measured perpendicularly to the axis of the microperforation. The cross section of the microperforation is less than or equal to 0.1 mm 2, better still 0.002 mm 2. The microperforations preferably each have a larger cross-sectional area of less than or equal to 0.1 mm 2. A microperforation has the advantage of being easily detectable only under certain observation conditions, and is thus not easily visible to the naked eye if these observation conditions are not respected. When the first pattern is observed along the axis of the microperforations of the first set, the second pattern is not visible or is visible with a lower contrast than when the microperforations of the second set are observed along their axis. A microperforation may be of constant cross section or not. It may be circular or non-circular, in particular polygonal, in particular polygonal regular or non-regular, oblong, in particular elliptical. The micro-perforations may be carried out using a laser, which is preferred, or using micro-needles or by water jet. By "oblique" microperforation is meant a microperforation extending in the structure in a direction at a non-zero angle to the normal to the structure. The angle of a microperforation relative to the normal to the structure is oriented, a negative value meaning that it is oriented to the left and positive to the right. The structure may comprise at least a third set of 25 microperforations making the same third angle with the normal to the structure and defining a third visible pattern when observed in a direction of observation coinciding with the axis of the microperforations of the third set. According to an exemplary implementation of the invention, the first, second and third angles can define a strictly increasing sequence, so that, when the direction of observation of the structure is continuously varied, an impression of movement is imparted to the observer, the corresponding patterns successively passing through a maximum observation contrast with their environment.

The second set can be located between the first and the third set. The first and second sets of microperforations may be adjacent and the angular difference (in absolute value) between the first and second angles may be between 5 ° and 90 °, preferably between 5 and 50 ° so that the observation of the first and the second set does not require an amplitude of inclination of the document too important to perform by the observer. The second and third sets of microperforations may be adjacent and the angular difference (in absolute value) between the second and third angles may be between 5 ° and 90 °.

The first and third angles may be opposite values and the second angle may be zero. The variation of the angle between the sets of microperforations can be done in a plane, which is for example parallel to the long side or the short side of a document incorporating the structure.

This variation can also be done along two axes perpendicular to each other. This may allow an observer to observe different sets of microperforations by varying the viewing angle from left to right and also to observe different sets of microperforations by varying the angle from bottom to top. At least one microperforation of the first set and at least one microperforation of the second set can meet at a common end and have opposite ends disjoint. Such an arrangement is quite difficult to reproduce for a counterfeiter. At least one microperforation of the first set, at least one micro-perforation of the second set and at least one micro-perforation of the third set can meet at one common end and have opposite ends disjoint. Patterns can be visible in transmitted light. The microperforations can thus appear brighter than the rest of the structure when observed along their axis. To do this, the microperforations can be through to let the light through them. In this case, the structure can be opaque except microperforations. Alternatively, the microperforations may be non-through and result in at least one layer of the non-opaque structure, consisting of a varnish, a transparent film or a paper made transparent or translucent. Alternatively, the patterns may be visible in reflected light. To do this, the microperforations can lead to a reflective layer, including a metal layer, of the structure. In a variant, the microperforations can lead to or in an inner layer of the structure comprising a "waveguide", which makes it possible to guide the light to micro-perforations. The structure may thus comprise an input surface of the light, other than a microperforation, for example defined by an aperture ending in the waveguide. The micro-perforations can still lead to a luminescent layer. The structure may be monolayer or multilayer. The structure may comprise at least one recto layer and a backside layer, adjacent or not. The structure may further comprise at least one inner layer located between the front and back layers. The structure may in particular comprise at least two inner layers located between the front and back layers. Each inner layer may have a different color than the others. This may allow, when the microperforations allow to observe the color of said inner layers, to create a color effect in addition to the aforementioned motion effect. The structure may comprise a translucent or transparent protective layer, for example a varnish, covering the microperforations at one end. Thus, the microperforations are protected from a risk of clogging by dirt. The structure may comprise a polarized filter comprising at least one of the first, second and third sets of microperforations, so that it can be observed, for an orientation of the polarized filter relative to an external light source placed behind the filter relative to to the observer, an extinction of the transmitted light and a contrast between said set of microperforations and its environment. The polarized filter can be incorporated in a through window of the structure.

The polarized filter may be visible only on one side of the structure, the light arriving at the filter through one or more layers that do not allow direct observation. The polarized filter can be attached to one or more other layers of the structure. At least one or even more than one microperforation, preferably all the microperforations of at least one set, or even all sets of microperforations, may be through, and in particular may lead to the outside of the security structure.

At least one microperforation of an assembly, or even several microperforations, in particular all the microperforations of at least one set, or even all sets of microperforations, may be non-through, in particular may open into a layer of the structure, preferably a non-opaque layer and preferably still transparent.

At least one of the sets, or all sets of microperforations, may be oblique (s), the microperforations of said set (s) all forming a non-zero angle with the normal to the structure. Preferably, the structure comprises at least one, more preferably a plurality of oblique through microperforations. Preferably, all the microperforations defining the sets of microperforations as defined previously are oblique through. The thickness e of the structure can be chosen such that all the oblique through microperforations respect the condition: di / sin (0 ~) <e and 0, 0 where 0i denotes the angle that the axis of a traversing microperforation oblique with the normal to the multilayer structure and di denotes the largest transverse dimension of the orifices through which said microperforation opens on the outer faces of the structure, d; being measured perpendicular to the axis of the orifice. This avoids that we can see through the structure, via microperforations through, normal incidence.

According to another of its aspects, the invention relates to a security article, in particular a wire, a foil or a patch, comprising a security structure according to the invention.

According to yet another of its aspects, the invention relates to a security document comprising a security article or a security structure according to the invention, being chosen in particular from a means of payment, such as a bank note, a check or a restaurant ticket, an identity document such as an identity card or a visa or a passport or a driving license, a title deed, a diploma, a lottery ticket, a ticket or a entrance ticket to cultural or sporting events. According to another of its aspects, the invention relates to a method for authenticating a security element or a security document incorporating a security structure according to the invention, comprising the following steps: - observing the article or the security document by continuously varying the direction of observation, - determining, based on at least the images generated by the appearance and disappearance of microperforations, the authenticity of the article or security document. According to another of its aspects, the subject of the invention is a safety structure which comprises microperforations made through at least one polarized filter. According to this aspect of the invention, the structure may comprise only one set of microperforations all having the same axis. The additional features defined above apply to this object of the invention. The invention relates to a method for authenticating a security article or security document incorporating a security structure comprising a polarized filter, as defined above, in which the external light source emits polarized light, in particular is a liquid crystal display, said method comprising the steps of: arranging the article or security document in front of the light source; modifying, to vary the degree of extinction of the light transmitted by the light structure; safety, the orientation of the article or safety document with respect to the source, - determine, on the basis of at least one variation in the contrast between the microperforation and its environment, the authenticity of the article or document. security document.

The invention will be better understood on reading the following detailed description, nonlimiting exemplary embodiments thereof, and on examining the appended drawing, in which: FIG. FIG. 2a, 2b, 2c, 2d, 2e, 2f show the security structure of FIG. 1 observed in different directions, FIGS. 2a, 2c and 2e being views of FIG. 2b, 2d, 2f cross-sections along II of Figures 2a, 2c and 2e. FIG. 3 is an enlarged sectional view of a microperforation, FIGS. 4 and 5 illustrate alternative structures of the invention, in section, FIGS. 6a, 6b, 6c, 6d, 6e, 6f and 6h. represent the structure of FIG. 5 observed in different viewing directions, FIGS. 6a, 6c, 6e, 6g being front views of the structure and FIGS. 6b, 6d, 6f, 6h of cross-sections along II-II of FIG. FIG. 6a, - FIG. 7 represents an alternative embodiment, - FIGS. 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h partially represent a variant of security structure observed in different observation directions, FIGS. 8a, 8c, 8e being front views of the structure and Figures 8b, 8c, 8d, 8f, 8h cross sections along III-III of Figure 8a; FIGS. 9, 10, 11, 12, 13, 14, 15, 16, 17 are diagrammatic and partial sections of alternative embodiments of structures according to the invention, FIGS. 20 to 26 show examples of security documents. according to the invention, FIG. 24 being a sectional view along XXIV-XXIV of FIG. 23, and FIGS. 27 and 28 show document variants comprising polarized filters. In the figures, the actual proportions of the various elements represented have not always been respected, for the sake of clarity of the drawing. For the same reason, the micro-perforations have been represented in one and the same plane of section, but they can extend in different planes, in particular parallel to one another.

Identical or similar elements found in separate embodiments have been designated in the figures by the same reference numeral. FIG. 1 shows an exemplary structure 10 according to the invention, comprising two sets G1 and Gz of pi and pz microperforations, the microperforations being, for example, through, obliquely crossing the structure from one side to the other. In a general manner, each set Gi comprises microperforations pi extending parallel in the same direction Xi. The directions Xi, Xz of the two sets G1, Gz with respect to the normal are distinct from each other. For example, the first set Gi may comprise a plurality of microperforations pi extending parallel to a direction Xi making an angle ai with the normal N to the structure and opening through orifices oi on an outer face 11 of the structure and the second set Gz may comprise a plurality of microperforations pz extending parallel to a direction Xz making an angle az with the normal N and opening through orifices oz on the outer face 11 of the structure, with ai az.

The angle α1 can be understood as an absolute variant between 30 ° and 60 °, being for example equal to 45 °. The angle a2 may be included as an absolute variant between 30 ° and 60 °, being for example equal to 45 °. The angular difference lai-azl can be between 5 ° and 30 °. These different inclinations can, during the observation of the transvision structure and by continuously varying the angle of the observation direction at least in the interval [ai, az], to create an impression of movement, because the maximum light intensity from the microperforations passes successively from one set to another when the viewing angle changes. This structure thus offers first-level security to the user. FIGS. 2a-2f show an example of implementation of such a structure, observed according to different directions of observations. The sets G1, Gz of microperforations are for example arranged to form two adjacent patterns, in this case the letters AW. FIGS. 2a and 2b correspond to an observation in transvision, placing the structure in front of a light source, in a first direction of observation substantially coinciding with the direction Xi of the first set of microperforations. The pattern A formed by the pi microperforations of the first set Gi thus appears bright while the pattern W formed by the microperforations pz of the second set Gz remains relatively obscure. The structure 10 is represented in FIGS. 2c and 2d observed in transvision along a second normal observation direction N at the structure, different from the directions XI, X2. The two AW patterns then appear obscure, as illustrated in Figure 2c. Finally, when the structure 10 is observed in transvision along a third direction of observation substantially corresponding to the direction Xz of the second set Gz of microperforations, as illustrated in FIG. 2f, the pattern A formed by the microperforations pi of the first set G1 appears dark and that W formed by the microperforations pz of the second set Gz appears bright, as shown in Figure 2e. Thus, when the direction of observation is varied by continuously scanning at least the interval [ai, az], the letters A and W appear alternately luminous and then obscure, giving the observer the impression of a movement. There is shown in Figure 3 a structure according to the invention, traversed from one side by an oblique microperforation p. This figure illustrates the limiting case where the thickness of the structure is equal to the minimum thickness which makes it possible to prevent viewing through the microperforation under normal observation. This minimum thickness is calculated according to the largest transverse dimension d; o orifices; by which said microperforation opens on the outer faces 11, 12 of the structure, it seems to us that the measurement is not perpendicular to the axis, please check this point, and the angle 0; what does this microperforation do with the local normal. The total thickness of the structure is preferably greater than or equal to em ,,,, where in,; ,, = d; / sin (0;) (with 0; 0).

The invention is not limited to a structure comprising two sets of microperforations. FIG. 4 shows a structure having a plurality of sets G1, G2,... G 'of oblique crossing microperforations pi ... p ,,. Each set G; has microperforations p; extending parallel in the same direction X ;.

The directions X1, X2,... X 'of the n sets G1,... G' with respect to the normal are preferably distinct from each other, as illustrated.

For example, the first set G1 may comprise at least three microperforations pi extending in a direction forming a bi angle with the normal, the second set Gz may comprise at least three microperforations pz extending in a direction making an angle 82 with the normal, and the uth set G 'may comprise at least three microperforations p' extending in a direction at an angle 8n with the normal. The angles 8i, 82,... Sn are advantageously chosen while respecting the relation bi <bi <... <8 ,,, with the different sets G1, ... G 'succeeding one another in a direction, for example on the left on the right in the example of FIG. 4. This scheduling can make it possible, during the observation of the structure in transvision and by continuously varying the angle of the observation direction, to create an impression of movement, because the Maximum light intensity from the microperforations successively passes through the different sets when the viewing angle changes. FIGS. 5 and 6 show an example of implementation of such a structure, observed in different viewing directions. The structure here comprises three sets G1, Gz and G3 of microperforations, these sets being for example arranged so as to form three adjacent patterns, in this case the letters AWS. In the example considered, the second set of microperforations is located between the first and third sets.

As can be seen in FIG. 5, the set Gi comprises microperforations pi extending in parallel along the same direction Xi making an angle α with the normal, and opening through orifices oi on an external face 11 of the structure 10. The assembly Gz comprises microperforations pz extending parallel in the same direction Xz forming an angle az with the normal, and opening through orifices oz on the outer face 11. The assembly G3 comprises microperforations p3 extending in parallel in the same direction X3 making an angle a3 with the normal, and opening through orifices o3 on the outer face 11. The angles ai, az, a3 are chosen such that 0 (i <OE2 <a3. the? -a; +11 may be between 5 ° and 90 ° preferably between 5 and 50 °.

FIGS. 6a and 6b correspond to an observation in transvision, according to a first direction of observation substantially coinciding with the direction Xi of the first set Gi of microperforations. The pattern A formed by the microperforations pi of the first set G1 thus appears bright whereas the patterns W and S formed by the microperforations pz, p3 of the second and third sets Gz and G3 appear relatively obscure, as illustrated in FIG. 6a. FIGS. 6c and 6d illustrate the observation in transvision along a different direction of observation of the directions X 1, X 2, X 3 of the three sets, for example according to the normal N to the structure. The three AWS patterns appear dark, as shown in Figure 6c. When the structure 10 is observed in transvision along an observation direction substantially corresponding to the direction Xz of the second set G2, as illustrated in FIG. 6f, the patterns A and S formed by the microperforations pi, p3 of the first and third sets G1 , G3 appear relatively obscure and that W formed by microperforations pz of the second set Gz appears brighter, as shown in Figure 6e. Finally, when the structure 10 is observed in transvision along an observation direction corresponding substantially to the direction X3 of the third set G3 of microperforations, as illustrated in FIG. 6h, the patterns A and W formed by the microperforations pi, pz of the first and second sets G1, Gz appear relatively obscure and the pattern S formed by microperforations p3 of the third set G3 appears brighter, as illustrated in Figure 6g.

Thus, when the direction of observation is varied by continuously scanning at least the interval [ai, a3], the letters AWS appear alternately luminous and then obscure, giving the observer an impression of a movement. In the examples described above, the microperforations have been represented oblique, but it may be otherwise. For example, one of the sets of microperforations may have microperforations oriented perpendicular to the structure. FIG. 7 shows a structure in which microperforations pz of the second set Gz extend perpendicular to the plane of the structure.

Motion printing can be created within a set of microperforations defining a basic pattern such as a letter. To obtain this result, the structure may comprise at least two sets of microperforations, or even at least three sets of microperforations as previously described, with the difference that they together define the same pattern instead of defining respective distinct patterns. In the example illustrated in FIGS. 8a to 8h, there is shown a structure on which extends an elementary pattern, in this case the letter A, formed by a plurality of microperforations passing right through the structure and composed of three sets G1, G2, G3. The assembly G1 comprises four through microperforations pii ... p14 extending in parallel planes, in the same direction Xi making an angle with the normal to the structure. The assembly G2 comprises two through microperforations fold, p22 extending parallel, for example following the normal N to the structure. The assembly G3 comprises four p3i ... p34 traversing microperforations extending in parallel planes, along the same direction X3 forming for example an angle a3 = -ai with the normal to the structure.

FIGS. 8b, 8c and 8d show various possible arrangements of microperforations of one set relative to another, while maintaining the same orientation. FIG. 8d illustrates the variant in which the microperforation p12 of the first set G1, the microperforation p22 of the second set G2 and the microperforation p32 of the third set G3 are disjoint.

In FIG. 8c, the microperforation p22 of the second set and the microperforation p32 of the third set meet at a common end, opening on one face 12 of the structure, and have respective opposite ends disjoint opening on the other face 11 of the structure, the microperforation p12 remaining separate from the other two microperforations.

Alternatively, a microperforation of the first set and a microperforation of the second set can meet at a common end and have respective opposite ends disjoint, and a microperforation of the third set can extend independently of the other two microperforations. In FIGS. 8b, 8f and 8h, the microperforation p12 of the first set G1, the microperforation p22 of the second set G2 and the microperforation p32 of the third set G3 meet at a common end opening on the face 12 of the structure and have ends respective disjoint opposing opening on the face 11 of the structure. The presence of microperforations which meet at a common end may advantageously make it possible to create different patterns respectively on the front and the back of the structure. The reduction in the number of orifices visible on the front or the back can also make it possible to reinforce the security of the structure, making the microperforations more difficult to detect. FIGS. 8b and 8a correspond to an observation in transvision, according to a first direction of observation substantially coinciding with the direction Xi of the first set G1 of microperforations. The microperforations pii ... p14 of the first set G1 thus appear bright while the microperforations p21, p22 and p31 ... p34 of the second and third sets G2 and G3 appear relatively obscure. Figures 8e and 8f correspond to an observation in transvision following a second direction of observation, for example according to the normal N to the structure. The microperforations pzi, pzz of the second set G2 thus appear bright while the microperforations pii ... p14 and p31 ... p34 of the first and third sets G1 and G3 appear relatively obscure. When the structure 10 is observed in transvision along a third direction of observation corresponding substantially to the direction X3 of the third set G3 of microperforations, as illustrated in FIG. 8h, the microperforations p31 ... p34 of the third set G3 appear bright while the microperforations pl 1 ... p14 and p21, p22 of the first and second sets G1, G2 appear relatively obscure. It is possible to arrange the structure so that the microperforations open onto a reflective material, for example metal, in order to be able to perceive the effect of movement by observation in reflected light. In this case, it is preferable for the first and third sets of microperforations to be symmetrical with respect to the normal, so that when observed in a direction corresponding to the axis of the microperforations of the first set, a light can be observed. reflected from the third set of microperforations. FIG. 9 thus shows a structure comprising microperforations p12, p22 and p32 such as those described in the preceding example, and further comprising a reflective opaque layer 20 covering the common end of the microperforations. The figure also illustrates the possibility of covering the opposite orifices of the microperforations with a layer 21 of translucent or transparent material, for example a varnish. In the example considered, the layers 20 and 21 completely cover the two faces of the structure 10. In a variant, the layers can only partially cover the structure, in the vicinity of the orifices of the microperforations, so as to close them. The presence of a translucent or transparent protective layer is not specifically related to this embodiment and such a layer may cover the microperforations of any of the previously described examples, or illustrated thereafter. At least one set of microperforations may comprise at least one non-through microperforation, as shown in FIG. 10. In this case, the structure is advantageously at least partially translucent, at least in the region comprising the non-through microperforation (s). In this way, when the structure is observed in transvision, the non-crossing microperforation (s) appear (ssen) t brighter than the support. Furthermore, the invention is not limited to a monolayer structure. As illustrated in particular in Figure 11, the structure may comprise at least a first layer 31 and a second layer 32 at least partially superimposed, especially in the region comprising the microperforations. This figure also illustrates the possibility for the different layers to be, in plan view, of different dimensions. For example, the layer 32 may belong to a fibrous substrate and the layer 31 to an insert element on this fibrous substrate, such as a patch, a foil or a security thread. The different layers of the structure may for example be of different colors. This can make it possible to observe, besides the effect of movement according to the angle of observation, a color effect.

By "color" is meant a color observed under an illuminant which may be visible light, especially daylight, or non-visible light, especially UV or IR light. In an example where the structure comprises at least two layers, the first layer may be made of fibrous material, for example paper, or synthetic material, for example polyester, having for example a first color in visible light. It may have a thickness of between 20 microns and 70 microns. The second layer may be made of fibrous material, for example paper, or of synthetic material, for example polyester, having for example a second color different from the first. It may have a thickness ez of between 20 microns and 70 microns. In general, the color difference 4E under illuminant D65 between the colors of the layers is, for example, greater than or equal to 2. The color of one of the layers is, for example, achromatic, such as white or black. In a variant, at least one of the layers is luminescent, for example phosphorescent or fluorescent. The layers can have different colors of luminescence. The structure illustrated in FIG. 12 differs from that of the preceding figure in that the structure comprises, in addition to two inner layers 31 and 32, a recto layer 41 and a backside layer 42, the first and second layers 31 and 32 extending between the front and back layers. The stack is traversed from one side by microperforations p, parallel axes, belonging to a set of microperforations according to the invention. The layers 41 and 42 are preferably opaque, at least at the portion through which the microperforations pass. The layers 41 and 42 may be formed by impressions or by an added or coated coating on the rest of the structure. These layers can still be constituted by a metallization or a laminated film on the rest of the structure. The presence of the front 41 and back 42 layers can be advantageous for masking the inner layers 31 and 32, for example to make respective colors different from these inner layers visible only through the microperforations, under certain observation conditions. The user can for example observe, in addition to the effect of movement following the arrangement of sets of microperforations, at least one first color at the microperforations by observing the front of the article or security document that incorporates the structure and at least a second color, different from the first, by observing the back of the article or document. The first color may be different from the color of the outer face 11 of the recto layer 41, at least in the non-transparent region where the microperforations are located, so that the microperforations are detectable by the difference in color that appears between microperforations and said region. The same is true for the second color, which is preferably different from the color of the outer face 12 of the backing layer 42, at least at the level of the region in which the microperforations are located.

In the example considered, the front 11 and back 12 layers appear homogeneous and completely cover the underlying layers, but in a variant the front and back layers can cover only a part of the underlying layers, being for example absent or transparent in places. A structure according to the invention may further comprise only one inner layer 33 located between the front and back layers 41 and 42, as illustrated in FIG. 13. The example of FIG. 14 shows the structure of FIG. 12, the first and second inner layers 31 and 32 each having a waveguide type light collecting material, for example a polycarbonate-based luminescent film marketed by the company BAYER under the name USA®. In this figure, the possibility that the structure comprises one or more intermediate layers extending between the first and second inner layers 31 and 32, for example a single intermediate layer 36 adjacent thereto, is further illustrated. The intermediate layer 36 is for example reflective. The recto 41 and back 42 layers comprise one or more openings, distinct microperforations, defining entry surfaces 37 of the light. The light entering through the entry surfaces 37 is propagated in the layers 31 and 32 and emerges through the microperforations. Thus, during the implementation of the authentication method, the user illuminates the input surfaces 37 and observes the light emerging from the microperforations. The presence of a "waveguide" material is advantageous in that it can make it possible to better distinguish the colors returned by the first and second inner layers 31 and 32 through the microperforations. The waveguide material of the inner layers may optionally comprise luminescent materials. The layers 41 and 42 may be reflective, in order to accentuate the "waveguide" effect. The microperforations can be successful (it is necessary to penetrate into the waveguide so that light can be emitted by this exit point) in a layer comprising a waveguide film, as illustrated in FIG. 14b. In this figure, there is illustrated an opaque layer 51 contiguous to a reflective layer 52 underlying, said layers being traversed from one side by a first set of microperforations Gi and a second set of microperforations Gz as previously defined.

The structure also comprises a waveguide layer 53 extending under the reflective layer 53 and on a reflecting layer 54, the microperforations opening onto the layer 53. The structure also has a surface 56 for entering the light, defined by an opening 57 through the opaque layer 51 and the underlying reflective layer 52, allowing the light to propagate in the layer 53 and out through the microperforations. Thus, the optical effect associated with microperforations can be observed in reflected light. In the exemplary embodiment illustrated in FIG. 15, the structure comprises a plurality of superimposed layers and a plurality of non-through microperforations, defining several distinct sets of microperforations G1, G2,..., G ', six in number in each case. the illustrated example. Micro-perforations of the same set G; are oriented at the same inclination Si relative to the normal N to the structure. The inclination specific to each set of microperforations makes it possible to obtain color effects that vary according to the angle of observation of the microperforations, when the different layers where the microperforations end up have different colors. In the example under consideration, when the structure is viewed from the front, the sets G1, G2, G3 are shifted and are not superimposed on the sets G4, G5, G6. This may make it possible to prevent the pattern or patterns drawn by the sets G1, G2, G3 from interfering with the pattern (s) drawn by the sets G4, G5, G6 and vice versa, especially when the structure is observed in transvision and does not present not enough opacity to prevent the detection of the presence of a microperforation opening on one side by observing the opposite side.

Within the same set G ,, at least two or all micro-perforations can lead into separate layers. In an exemplary embodiment illustrated in FIG. 16, the structure 10 comprises several sets of microperforations, all the microperforations p; of the same set G; having the same inclination Si and resulting in the same inner layer 1 ,, all pi microperforations of at least one other set Si inclination Si different from that of all other sets, resulting in internal layers respective ones. Thus, when the inner layers are of different colors, a color change can be observed when the viewing angle changes. In general, as illustrated in FIG. 17, at least one of the sets of microperforations may comprise at least one microperforation filled with a material or a fluid other than air, translucent or transparent, for example a transparent resin, a surface treatment as described in EP1319104 or a varnish. According to the variant illustrated in Figures 18 and 19, the security structure comprises a polarized filter 70, preferably linearly, comprising at least one of the first, second and third sets of microperforations. In the example considered, only one set has been represented, for example drawing an AW pattern.

In FIG. 18a, the filter 70 is illuminated with light transmitted by an external light source 80 of polarized light, with an orientation of the filter with respect to the source for which the filter is translucent and passes light. The light also passes through the microperforations. In this way, the contrast between the microperforations and the filter is relatively low.

In Fig. 18b, the polarized filter 70 is oriented relative to the light source 80 so as to observe an extinction of the transmitted light. Under these conditions, the filter appears obscure, and microperforations that let in the light appear brighter. The external light source 80 of polarized light may be a liquid crystal display (LCD), as shown in Figs. 19a and 19b.

In FIG. 19a, the polarized filter 70 of the security structure is backlit by the LCD screen with an orientation such that the light is transmitted uniformly through the filter and the microperforations. In Fig. 19b, the structure 10 is oriented relative to the LCD screen so as to cause an extinction of the light transmitted by the screen. FIGS. 20 to 26 show exemplary embodiments of security documents according to the invention, comprising a security structure 10 according to the invention. In FIG. 20, the security structure 10 according to the invention is directly integrated into a security document 90, for example a banknote. The microperforations draw for example a pattern on it. In FIG. 21, the document 90 comprises a security thread or a foil 92 defining with the remainder of the document a security structure 10 according to the invention. The wire or foil 92 may appear integrally on the surface of the document 90 and extend across the width / document between two opposite edges. The width of the wire or foil 92 may be between 0.5 mm and 30 mm. The structure according to the invention 10 may be formed in part by a layer of the document 90 such as a fibrous or thermoplastic substrate and the rest of the structure may be defined by the wire or foil 92. It is advantageous in this case that the micro-perforations 20 are made after incorporation of the wire or foil to the document 90. In the variant of FIG. 22, the structure 10 according to the invention is a thread 92 integrated in windows, called "window thread", and the microperforations appear in one or several windows 94. It is interesting to provide windows on the two opposite sides of the document, so as to allow microperforations to be observed on both sides of the document. In FIG. 23, the document comprises a window 94, in which is integrated a security structure 10 according to the invention. FIG. 24 shows a sectional view illustrating the case where the security structure 10 is sandwiched between two paper jets 96, 97 of the document 90. According to a variant not shown, the window can be defined by a transparent area of the document.

In general, the structure 10 according to the invention and / or the security document 90 which incorporates such a structure may comprise additional security elements, as defined below. Among the additional security features, some are detectable by eye, daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level. Other types of additional security elements are detectable only with a relatively simple apparatus, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, boards, strips, wires or particles. These security elements may be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting in a wavelength of 365 nm. These security elements are said to be second level. Other types of additional security elements require for their detection a more sophisticated detection device. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level.

The additional security element or elements present in the security document, or the security structure that it comprises, may have first, second or third level security features. In FIGS. 25 and 26, the security document 90 according to the invention comprises a security structure 10 comprising a polarized filter 70 as described with reference to FIGS. 18a and 18b. The presence of the polarized filter and its orientation may be indicated by a reference 71, for example an arrow directed in the direction of polarization of the filter.

The security structure comprising the polarized filter 70 can be incorporated in the security document 90 in the form of a security thread 92, as shown in FIG. 25, or a patch 98 within a window. 94, as shown in Fig. 26. Fig. 27 shows an example of a document that incorporates two windows containing polarized filters 100 and 101 having cross polarization directions, arranged so that both filters can be superimposed by folding the document. , for example according to a median fold line 102. One of the filters 100 and 101 comprises microperforations, for example as defined above. Once the filters are superimposed, almost no light passes except where there are microperforations.

FIG. 28 represents a variant where the filter 100 is in a through window and the other filter 101 is incorporated in "windows thread", that is to say that the filter appears in windows 103 alternating with regions 104 where the filter is hidden by a paper jet of the document. The perforations are present on one of the filters.

Of course, the invention can not be limited to the embodiments described. In particular, the number of microperforations per set, their spacing, the shape of the cross section of the microperforations, their size, the number of microperforation sets can be modified according to the desired optical effect. The characteristics of the various embodiments can be combined with each other within non-illustrated variants. The expression "having one" shall be understood as being synonymous with "having at least one", unless the opposite is specified.

Claims (22)

REVENDICATIONS1. Safety structure (10) comprising at least: - a first set (GO of microperforations all of which have a same angle (a1) with the normal to the structure, and defining a first visible pattern when observed in a coinciding observation direction with the axis of the microperforations of the first set, and - a second set (G2) of microperforations all making the same second angle (o2) with the normal to the structure, different from the first angle, this second set defining a second visible pattern when observed in a direction of observation coinciding with the axis of microperforations of the second set. 2. Safety structure according to the preceding claim, further comprising at least a third set (G3) of microperforations making the same third angle (a3) with the normal to the structure and defining a third visible pattern when observed in a direction d observation coinciding with the axis of the microperforations of the third set, and ai <~ z <a3 so that, when the direction of observation of the structure is continuously varied, an impression of movement is imparted to the observer. 3. Safety structure according to claim 1 or 2, the patterns being visible in transmitted light. 4. Security structure according to claim 2, the second set (G2) being located between the first set (GO and the third set (G3). 5. Safety structure according to any one of the preceding claims, the first set (GO and second set (G2) microperforations being adjacent and the angular difference lai-a2l being between 5 ° and 50 °. 6. Safety structure according to any one of claims 2 to 5, the second set (G2) and third set (G3) of microperforations being adjacent and the angular difference 1 OE2-a31 being between 5 ° and 50 °. 30 7. Safety structure according to any one of the preceding claims, at least one microperforation of the first set (GO and at least one microperforation of the second set (G2) joining at a common end and having opposite ends disjoint. 8. Safety structure according to any one of claims 2 to 7, at least one microperforation of the first set (GO, at least one microperforation of the second set (G2) and at least one microperforation of the third set (G3) joining at a common end and having opposite ends disjointed. The security structure of any of claims 2 to 8, wherein a2 = 0 and a1 = -3. 10. Safety structure according to any one of the preceding claims, comprising a polarized filter (70) having at least one of the first, second and third sets of microperforations, so that it can be observed, for an orientation of the filter polarized with respect to an external light source (80), an extinction of transmitted light and a contrast between said set of microperforations and its environment. 11. Safety structure according to the preceding claim, the polarized filter (70) being incorporated in a window (94) through the structure. 12. Safety structure according to claim 10, the polarized filter (70) being only visible on one face of the structure. 13. Safety structure according to any one of the preceding claims, at least one of the microperforations being filled with a material or a fluid other than air, transparent or translucent. 14. Safety structure according to any one of the preceding claims, all the microperforations being through, in particular opening out of the security structure. 25 15. Safety structure according to any one of claims 1 to 13, at least one set of microperforations comprising at least one non-through microperforation. 16. Security structure according to any one of the preceding claims, at least one of the sets, or all sets of microperforations, being oblique, the microperforations of said set (s) all being at an angle no one with the normal to the structure. 17. Safety structure according to any one of the preceding claims, comprising a layer (21) of translucent or transparent protection, including a varnish, covering one end of the microperforations. 18. Security structure according to any one of the preceding claims, the microperforations each having a larger section of the range less than or equal to 0.1 mm 2. 19. Security article, in particular a wire, a foil or a patch, comprising a security structure (10) according to any one of the preceding claims. 20. Security document (90) comprising a security article according to the preceding claim or a security structure (10) according to any one of claims 1 to 18, being in particular selected from a means of payment, such as a banknote, a check or restaurant ticket, an identity document such as an identity card or a visa or a passport or a driving license, a title deed, a diploma, a lottery ticket, a transport ticket or a ticket to 15 cultural or sporting events. 21. A method of authenticating a security article or security document (90) incorporating a security structure (10) as defined in any one of claims 1 to 18, comprising the following steps: observing the article or security document by continuously varying the direction of observation, - determining, on the basis at least of the images generated by the appearance and disappearance of microperforations, the authenticity of the article or the security document. 22. A method of authenticating a security article or security document (90) incorporating a security structure (10) as defined in any one of claims 10 to 12 or as defined in any one of claims 13 to 18 according to claim 10, wherein the external light source emits polarized light, in particular is a liquid crystal screen, said method comprising the steps of: - arranging the article or the security document in front of the light source, modifying, in order to vary the degree of extinction of the light transmitted by the security structure, the orientation of the article or security document with respect to the source, - determining, on the basis of at least a variation of the contrast between the microperforation and its environment, the authenticity of the article or the security document.