Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/30—Identification or security features, e.g. for preventing forgery
  • B42D25/324—Reliefs
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
  • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
  • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
  • B42D25/30—Identification or security features, e.g. for preventing forgery
  • B42D25/328—Diffraction gratings; Holograms

Definitions

• This description relates to the field of security marking. More particularly, it relates to optical security components visible in reflection to verify G the authenticity of a document, to a method of manufacturing such a component and to a secure document equipped with such a document.
• An optical security component described in the aforementioned application has a visible effect in reflection.
• the optical security component comprises a diffractive structure etched on a layer of a dielectric material.
• the structure has a first pattern comprising a bas-relief with a first set of facets whose shapes are determined to simulate a series of concave or convex cylindrical optical elements, visible in reflection, this first pattern being modulated by a second pattern forming a sub-wavelength grating.
• Such an optical security component has a dynamic visual effect of luminous bands of different colors and scrolling in opposite directions when it undergoes a rotation in tilt around an axis parallel to one of the main directions of the cylindrical elements.
• the security optical component described in [Ref. 2] comprises a first layer of dielectric material and a diffractive structure etched on the first layer.
• the diffractive structure comprises a first pattern with a set of modules arranged side by side, according to a given direction of arrangement, a maximum width of each module, defined in the direction of arrangement, being less than 300 ⁇ m.
• Each module comprises a bas-relief with a first set of facets whose shapes are determined to simulate an optical element visible in reflection, with at least one convex or concave region, said optical element having a profile with a continuously variable slope along a single direction, called the direction of variation of the slope, perpendicular to the direction of arrangement.
• the slope along at least one line parallel to the direction of arrangement is different between said two modules.
• the minimum number of modules is determined by the maximum width of the modules, such that the diffractive structure is visible to the naked eye.
• Such an optical security component has, in reflection and under the effect of a tilt movement around an axis parallel to said arrangement direction, a dynamic visual effect comprising the movement of one or more complex graphic elements, depending on the arrangement of said modules, and allows, compared to simple horizontal scroll bars, a more secure authentication and a stronger technological barrier, due to the design and manufacture of the modules necessary to obtain the visual effect described above.
• the first pattern can be modulated by a second pattern forming a periodic grating of sub-wavelength period, determined to produce, after deposition of a second layer having a spectral band of reflection in the visible, a resonant filter in a given spectral band, making it possible to combine the dynamic visual effect with a color effect of order 0.
• This application describes an optical security component with an original structure not only allowing access to complex dynamic visual effects or "animations" as described in [Ref. 2] but also allowing to switch continuously from an achromatic, white animation, to the same iridescent animation, by a simple tilt movement of the optical security component over a wider angular range, ensuring even greater authentication robust, by simple visual inspection and without specific equipment.
• the term “include” means the same as “include”, “contain”, and is inclusive or open and does not exclude other elements not described or represented. Furthermore, in the present description, the term “approximately” or “substantially” means the same as “presenting a margin lower and/or higher than 10%, for example 5%", of the respective value.
• the invention relates to an optical security component configured to be observed in reflection, with the naked eye, along at least one first observation face, in a direction of observation making a given angle of observation with a given direction of illumination, the component comprising: a first layer of dielectric material, transparent in the visible; at least one first diffractive structure etched on said first layer; and a second layer, at least partly covering said first structure, and having a spectral band of reflection in the visible; and in which: said first diffractive structure comprises a first pattern consisting of a set of parallel facets, having variable slopes along a direction of variation of the slope, said slopes comprising angular values comprised in absolute value between a minimum angular value and a maximum angular value, said facets comprising a given maximum height, said set of facets being arranged to produce, when the component is illuminated in white light along said axis of illumination, a dynamic visual effect observable in reflection under the effect of a tilt movement along an axis substantially perpen
• a transparent layer in the visible is defined as a layer having a transmission of at least 70%, preferably at least 80% for a wavelength included in the visible, that is to say a wavelength between about 400 nm and about 800 nm.
• a layer thus transparent makes it possible to observe the layers located under the transparent layer with the naked eye.
• a set of “parallel” facets means a set of facets presenting a variation of the slope in one and the same direction, called “direction of variation of the slope”.
• the slope of the facets can however vary in this direction, in opposite directions.
• tilt movement of the component generally refers to a rotation of the component along an axis contained in the plane of the component.
• the specular reflection corresponds in the present description to the position of the component which allows a reflection of the incident light with a reflection angle of measurement opposite to that of the incident angle.
• the normal to the plane of the component separates the angle of observation in two angular sectors of the same measure.
• the observation angle is for example defined with respect to a vertical lighting direction. According to one or more exemplary embodiments, the viewing angle is between approximately 30° and approximately 60°. For example, the observation angle is equal to approximately 45°, which corresponds, for vertical lighting, to a conventional observation position for an observer.
• said minimum angular value of the slopes is equal to 0°.
• said maximum angular value of the slopes is between about 7° and about 15°.
• the positive direction for the measurement of the angular values of the slopes of the facets is the clockwise (or anti-trigonometric) direction.
• the facets have a dimension in the direction of the slope (or “width”) greater than or equal to approximately 4 times, advantageously greater than or equal to approximately 8 times, said grating period.
• the minimum dimension can therefore be chosen according to the period of the grating. For example, a minimum dimension of the width of the facets is equal to about 2 ⁇ m.
• the widths of the facets are between about 2 ⁇ m and about 100 ⁇ m, advantageously between about 2 ⁇ m and about 80 ⁇ m, advantageously about 4 ⁇ m and about 80 ⁇ m.
• the facets have a substantially rectangular shape and have a "length" measured in a direction perpendicular to the direction of the slope.
• the length is for example less than about 100 ⁇ m.
• all of the facets have a substantially identical height.
• the height of the facets is for example less than 2 microns, advantageously less than 1 micron.
• the facets of the set of facets have different heights.
• the facets have a maximum height. Said maximum height is for example less than 2 microns, advantageously less than 1 micron.
• At least some of the facets of the set of facets are arranged with variable slopes, the variation of which is increasing, respectively decreasing, in order to simulate a reflective element with a convex region, respectively concave.
• a dynamic effect of the type "half-wave” the visual effect resulting from such an arrangement of facets when the slopes of the facets have angular values whose variation is increasing or decreasing, but which are of the same sign.
• a “wave” type dynamic effect the visual effect resulting from such an arrangement of facets when the slopes of the facets have angular values whose variation is increasing or decreasing, and for which at least one change of sign.
• a dynamic effect of the "wave” or "half-wave” type appears for an observer, during a tilt movement of the component, as a continuous scrolling of a line of white light.
• the set of facets comprises one or more subsets of facets each configured to produce a dynamic “wave” type effect.
• said period of the diffraction grating, said maximum angular value of the slopes, measured in absolute value, and said observation angle are determined such that said first part of the angular range of tilt comprises an angular superposition (overlap) with the second part of the angular tilt range comprised between approximately 1° and approximately 10°, preferably between approximately 3° and approximately 8°, for example equal to approximately 5°, on both sides other than the first part of the angular range.
• said period of the diffraction grating, said maximum angular value of the slopes, measured in absolute value, and said observation angle are determined such that the angular range of tilt is between approximately 45 ° and about 120° (measured in air).
• said period of the diffraction grating, said maximum angular value of the slopes, measured in absolute value, and said observation angle are determined such that the first part of the tilt angular range is comprised between approximately 15° and approximately 50° (measured in air), advantageously between approximately 20° and approximately 35° (measured in air).
• said period of the diffraction grating, said maximum angular value of the slopes, measured in absolute value, and said observation angle are determined such that the second part of the tilt angular range (measured in the air) is comprised, on either side of the first angular range of tilt, between about 30° and about 70°, advantageously between about 40° and about 60°.
• said one-dimensional diffraction grating is a diffraction grating with a sinusoidal profile.
• a sinusoidal profile grating is advantageous in that it allows symmetry of diffraction efficiencies at +1 and -1 orders and hence symmetry in terms of visual efficiencies for iridescent animation on either side achromatic animation.
• grating profiles are possible, such as, for example, and without limitation, a diffraction grating with a pseudo-sinusoidal profile, defined as a sum of sinusoids with amplitudes and phases that can be adjusted according to the expected profile, a rectangular profile diffraction grating, or any other advantageously symmetrical profile grating to have a similar visual efficiency for the iridescent animation on either side of the achromatic animation.
• a pseudo-sinusoidal profile defined as a sum of sinusoids with amplitudes and phases that can be adjusted according to the expected profile
• a rectangular profile diffraction grating or any other advantageously symmetrical profile grating to have a similar visual efficiency for the iridescent animation on either side of the achromatic animation.
• a depth of the diffraction grating is determined so as to optimize a diffraction efficiency of the grating at order 1 and at order -1 at at least one wavelength of the visible spectrum, for example at a central wavelength of the visible spectrum, for example around 550 nm.
• the second layer comprises a metallic material.
• the metallic material comprises one of the materials or an alloy of materials chosen from: Aluminum (Al), Silver (Ag), Chromium (Cr), Gold (Au), Copper (Cu).
• a thickness of the layer of metallic material is greater than about 2 to 3 times the thickness of the skin of the metal or alloy from which it is formed in the visible frequency range; for example, a thickness of the layer of metallic material is between about 20 nm and about 60 nm for aluminum.
• the dielectric material of the first layer has a first refractive index and the second layer comprises a dielectric material having a second refractive index such that the difference between the second refractive index and the first index of refraction is greater than or equal to approximately 0.3, advantageously greater than or equal to approximately 0.5.
• said second layer comprises a material chosen from: zinc sulphide (ZnS), titanium dioxide (TiCh) silicon nitride (S13N4).
• a minimum dimension of the first structure is greater than 300 ⁇ m, preferably greater than 1 mm, preferably greater than 2 mm, preferably greater than 5 mm. Such a minimum dimension makes it possible to make the structure visible to the naked eye.
• said first structure has an outline forming, seen from the observation face, a recognizable graphic shape.
• the optical security component according to the first aspect comprises at least one second structure etched on said first layer, said second layer at least partially covering said second structure.
• the second structure is configured to form, for example and in a non-limiting manner, a diffusing structure, a holographic structure, a diffracting structure making it possible to produce a so-called Alphagram® effect developed by the applicant.
• the components can be juxtaposed, each with recognizable shapes.
• said first pattern has an outline forming, seen from the observation face, a recognizable graphic shape.
• said first pattern is interrupted in regions forming, seen from the observation face, a recognizable graphic object visible during the achromatic animation and during the iridescent animation.
• said first pattern is not modulated or is modulated by a third pattern forming a periodic lattice different from said second pattern, said second region forming, seen from the face of observation, a recognizable graphical object visible only during iridescent animation.
• the optical security component according to the first aspect comprises one or more additional layers depending on the needs of the application, without this or these additional layers contributing to the desired visual effect.
• the optical security component is configured for securing an object, for example a document or a product, and further comprises, on the face opposite the observation face, a diaper suitable for transfer of the component to the document or the product, for example an adhesive layer or a reactivatable adhesive layer.
• the optical security component further comprises, on the side of the first observation face, a support film intended to be detached after transfer of the component to the document or the product.
• the optical security component is configured for the manufacture of a security track for securing banknotes, and comprises on the side of the first observation face and/or on the opposite face on the first observation face, one or more protective layers.
• the present description relates to a secure object, for example a secure document of value, comprising a substrate and an optical security component according to the first aspect, deposited on said substrate or on one of the layers of said substrate in the case of a multi-layered substrate.
• Such a secure object is for example, and without limitation: a banknote, an identity or travel document, on a paper or polymer substrate.
• the present description relates to methods of manufacturing optical security components according to the first aspect.
• the present description relates to a method of manufacturing an optical security component intended to be observed in reflection, with the naked eye, according to at least one first observation face, the method comprising: the deposition on a support film a first layer of dielectric material, transparent in the visible; the formation on said first layer of at least a first diffractive structure, such that: said first diffractive structure comprises a first pattern consisting of a set of parallel facets, presenting variable slopes according to a direction of variation of the slope, said slopes comprising angular values comprised in absolute value between a minimum angular value and a maximum angular value, said facets comprising a given maximum height, said set of facets being arranged to produce, when the component is illuminated in white light along said axis of illumination , a dynamic visual effect observable in reflection under the effect of a tilt movement along a tilt axis substantially perpendicular to the direction of variation of the slope, and in a given tilt angular range; in at least a first region, said first pattern
• FIG. 1A schematically illustrates a (partial) sectional view of an embodiment of a component according to the present description.
• FIG. IB schematically illustrates a (partial) sectional view of another embodiment of a component according to this description.
• FIG. 2 diagrams illustrating parameters of a diffractive structure in a security component according to the present description.
• FIG. 3 a diagram illustrating the sequence of iridescent animations and achromatic animation, during a tilt movement of an optical security component according to the present description.
• FIG. 4A diagrams illustrating according to an example, a first iridescent animation in an optical security component according to the present description, as a function of the tilt angle of the component, in a first part of the angular tilt range.
• FIG. 4B diagrams illustrating, in an optical security component identical to that of FIG. 4 A, an achromatic animation depending on the tilt angle of the component, in a second part of the angular tilt range, the achromatic animation following on from the first iridescent animation.
• FIG. 4C diagrams illustrating, in an optical security component identical to that of FIG. 4 A, a second iridescent animation as a function of the tilt angle of the component, in a third part of the angular tilt range, the second iridescent animation linking up with the achromatic animation and presenting an inversion of the colors vis-à-vis -vis the first iridescent animation.
• FIG. 5A curves illustrating respectively: an example of spatial distribution of the widths of the facets, for a given height, in an arrangement of facets configured to produce a dynamic effect of the “half-wave” type; angular values of facet slopes (in degrees) as a function of facet widths, for two facet heights, in an arrangement of facets configured to produce a “half-wave” type dynamic effect; angular values of facet slopes (in degrees) as a function of facet widths, for two facet heights, in an arrangement of facets configured to produce a dynamic “wave” type effect.
• FIG. 5B a diagram illustrating an example of distribution of the facets to form “pixels”.
• FIG. 5C curves illustrating the effect of the slopes of the facets for three component tilt angles located in the first part of the angular tilt range.
• FIG. 6 a curve illustrating the effect of the slopes of the facets and of the grating, as a function of the tilt angle of the component, in the second part of the angular tilt range, on either side of the first part of the tilt angular range.
• FIG. 7 curves showing the efficiency at order +1 or -1 of a diffraction grating with a sinusoidal profile, as a function of the depth of the grating, for a wavelength of 550 nm.
• FIG. 8 an example of an optical security component according to the present description, with a “patch” type format.
• FIG. 9A a diagram illustrating an example of a valuable document, for example a banknote, secured with an optical security component according to the present description.
• FIG. 9B a diagram showing an enlargement of the secure document illustrated in FIG. 9A.
• FIG. 10A diagrams respectively illustrating designs of a first pattern and of a second pattern in an example of an optical security component according to the present description.
• FIG. 10B diagrams illustrating, according to a given visual scenario, achromatic and iridescent visual animations, based on the patterns as schematized in FIG. 10A.
• FIG. 1A and FIG. 1B show schematically and according to (partial) sectional views two examples of optical security components according to the present description.
• the optical security component 101 shown in FIG. 1 A represents for example an optical security component intended to be transferred onto a document or a product with a view to securing it.
• it comprises a support film 111, for example a film of polymeric material, for example a film of polyethylene terephthalate (PET) of a few tens of micrometers, typically 15 to 100 ⁇ m, as well as a detachment layer 112, for example in natural or synthetic wax.
• PET polyethylene terephthalate
• the detachment layer makes it possible to remove the polymer support film 111 after transfer of the optical component to the product or document to be secured.
• the optical security component 101 also comprises a first layer 113 of dielectric material, having a first refractive index ni and at least one first diffractive structure S, comprising a first pattern Mi, modulated by a second pattern M2 forming a periodic grating, stamped on said first layer 113 and which will be described in more detail later.
• the optical security component 101 also comprises a second layer 114 at least partially covering said first structure S, and having a spectral band of reflection in the visible.
• the second layer 114 is for example a metallic layer or a so-called index variation layer having a refractive index different from that of the first, the difference in index between the layers 113 and 114 having a value at least equal to 0 .3, advantageously a value at least equal to 0.5.
• the layer 114 makes it possible to ensure the reflection of the incident light.
• the optical security component also comprises one or more optional layers, optically non-functional but adapted to the application.
• the optical security component further comprises a layer of adhesive 117, for example a heat-activated adhesive layer, for transferring the optical security component to the product or document.
• a layer of adhesive 117 for example a heat-activated adhesive layer
• the optical security component can be manufactured by stacking the layers on the support film 111, then the component is transferred onto a document/product to be secured using the adhesive layer 117.
• the support film 111 can then be detached, for example by means of the detachment layer 112.
• the main observation face 100 of the optical security component is thus located on the side of the first layer 113 opposite to the etched face of layer 113.
• the optical security component 102 shown in FIG. IB represents for example a optical security component intended for securing banknotes; it is for example a part of a security thread intended to be integrated into the paper during the manufacture of the note or a laminated track covering a window in the paper or a patch.
• the component 102 comprises as previously a support film 111 (12 to 25 ⁇ m) which will also serve as a protective film for the security thread, and, as in the example of FIG.
• the optical security component 102 also comprises, in the example of FIG. IB, a set of optional layers 115, 116, 118.
• the layer 115 is for example a layer of dielectric material 115, for example a transparent layer; layer 116 (optional) is for example a security layer 116, for example a discontinuous layer with a specific pattern printed locally with UV ink to produce additional marking that can be checked by eye or by machine; and the layer 118 (optional) is for example a protective layer, for example a second polymer film or a varnish.
• layer 118 may be an adhesive layer.
• manufacturing can be performed by stacking the layers on the support film 111.
• the dielectric layer 115 and the security layer 116 can form a single layer.
• the protective layer (or adhesive layer) 118 and the layer 115 can also form only one and the same layer.
• the optical security component may be visible from both sides, with an inversion of the curvatures of the optical elements generated.
• FIG. 2 illustrates in more detail the parameters of a diffractive structure S (diagram 23) according to the present description.
• the structure S is formed of a first pattern Mi comprising a set of facets Fi (diagram 22), said pattern being at least partially modulated by a second pattern M2 defined by the projection of a diffraction grating in one direction referenced G ( diagram 21) and defined in a plane p parallel to the plane of the component (and therefore parallel to viewing face 100).
• All the facets Fi are parallel, i.e. they present a variation of the slope in one and the same direction, referenced ⁇ in the example of FIG. 2. They are characterized by a height /?, defined by the distance between a lowest level of the facet and a highest level, the distance being measured along an axis perpendicular to the plane p parallel to the plane of the component, namely along the z axis in the example of FIG. 2.
• the facets all have the same height /?, said height being less than about 2 ⁇ m, advantageously less than about 1 ⁇ m, for example between about 0.5 ⁇ m and about 1 m.
• the facets are also characterized by a width A, defined by the dimension according to the direction of variation of the slope, the width generally being for example between about 2 ⁇ m and about 100 ⁇ m, for example between about 2 ⁇ m and about 80 ⁇ m , for example about 4 ⁇ m and about 80 ⁇ m.
• a minimum width of the facets will be greater than approximately 4 times, advantageously greater than approximately 8 times, the grating period.
• the facets generally have a substantially rectangular shape.
• the dimension of the facets along the x axis included in an xy plane (plane p) parallel to the plane of the component and perpendicular to the axis defines the width of a pixel, i.e. that is, an elementary region of the structure which reflects light in the same direction.
• the facets Fi comprise slopes whose angular values a i are included, in absolute value, between a minimum angular value, for example 0° and a maximum angular value, for example between about 7° and about 15°.
• the positive direction chosen for the measurement of the angular values of the slopes is the clockwise or anti-trigonometric direction.
• the diffraction grating G is a one-directional diffraction grating, characterized by a pitch or period d and a depth t.
• d pitch or period
• t depth
• the structure S resulting from the modulation of the first pattern comprising all the facets by the diffraction grating G comprises a set of facets Fi each supporting a one-dimensional diffraction grating Gi.
• the facets Fi each have with respect to the plane p parallel to the plane of the component an angle a i.
• the projection on each facet Fi of a diffraction grating G of constant pitch d and whose grating vector has a direction collinear with the direction of variation of the slope can result in a projected grating Gi of variable pitch, referenced Î/ M on diagram 23. Since the slopes of the facets have low angular values, typically less than 15° in absolute value, the effect of these variations in grating pitch on the different facets can be neglected in most embodiments.
• the first-order G diffraction grating presents a sinusoidal profile.
• Other profiles are possible, such as, for example, a quasi-sinusoidal profile, defined as a sum of sinusoids with adjustable amplitudes and phases depending on the expected profile, or a rectangular profile.
• Such profiles symmetrical, have the advantage of presenting a diffraction efficiency similar to the order + 1 and to the order -1.
• symmetrical network profile we understand a network whose profile has a central symmetry (relative to a point).
• the method of recording the structure can be carried out with a view to the manufacture of the optical security components, as will be described in more detail later.
• the period d of the diffraction grating, the maximum angular value a of the slopes, measured in absolute value, and the viewing angle are determined to observe an achromatic animation in a first part of the angular range of tilt around the specular reflection, and to observe the same animation, iridescent, in a second part of the angular range of tilt, the iridescent animation being linked with the achromatic animation on either side of said first part of the tilt angular range.
• FIG. 3 shows a diagram illustrating the desired sequence of iridescent animations and achromatic animation, during a tilt movement of an optical security component 40 according to the present description.
• a L the lighting axis, for example vertical lighting corresponding to natural light
• Do the observation axis corresponding to the direction of observation by an observer (symbolized by an eye in FIG. 3)
• 0 Obs the angle of observation between the axes A L and Do.
• 0 Obs is assimilated to the absolute value of the angular measurement of the observation angle.
• tilt a rotation
• the tilt axis is therefore substantially parallel to the x axis (FIG. 2).
• the directions of illumination and observation are fixed and the tilt movement of the component results in a variation of the angle of incidence 0i of the incident light on the component, defined with respect to an axis D N normal to the plane of the component.
• the positive direction of the angle of incidence is the narrow trigonomic direction.
• the diffraction angle 0 O is thus defined by the angle between the normal to the component and the direction of observation Do.
• the positive direction of the diffraction angle is, as for the angle of incidence, the trigonometric direction.
• the second part of the tilt angular range comprises an angular range A0R. and an angular range A0R+ corresponding respectively, from the point of view of an observer, to a tilt of the optical safety component towards the rear or towards the front.
• the iridescent animation is a "rainbow" animation in which an observer sees the colors of the rainbow scrolling.
• the iridescent animation is a "rainbow" animation in which an observer sees the colors of the rainbow scrolling.
• 4 colors of the rainbow are represented, symbolized by textures, namely red (texture 311), yellow (texture 312), green (texture 313), blue (texture 314 ).
• FIGS 4A - 4C illustrate in more detail an example of visual dynamic effect obtained with an optical security component according to the present description.
• the optical security component comprises in this example two diffractive structures according to the present description, a structure 401 forming a number “2” and a structure 402 forming a number “5”.
• the diffractive structures have delimited contours for example thanks to a demetallization, or more generally thanks to the localized suppression of the reflective layer or in other exemplary embodiments, due to a delimitation of the structure itself.
• FIG. 4B illustrates the achromatic animation effect in the first angular tilt range referenced DQ B in FIG. 3. More specifically, diagram 44 corresponds to the position of the optical security component 40 referenced 4 in FIG. 3, diagram 45 corresponds to the position of the optical security component 40 referenced 5 in FIG. 3 (central position corresponding to the specular reflection), diagram 46 corresponds to the position of the optical security component 40 referenced 6 in FIG. 3.
• the achromatic animation comprises for example a displacement of circular white lines on a black background.
• FIG. 4A illustrates the iridescent animation effect in the second part of the tilt angular range referenced A0R+ in FIG. 3 and which corresponds, from the point of view of the observer, to a forward tilt movement of the component. More precisely, diagram 41 corresponds to the position of the optical security component 40 referenced 1 in FIG. 3, diagram 42 corresponds to the position of the optical security component 40 referenced 2 in FIG. 3, diagram 43 corresponds to the position of the optical security component 40 referenced 3 in FIG. 3. In FIG. 4A, each color is illustrated by a texture similar to that used in FIG. 3.
• FIG. 4C illustrates the iridescent animation effect in the second part of the tilt angular range referenced A0R. in FIG. 3 and which corresponds, from the point of view of the observer, to a tilt movement of the component backwards. More precisely, diagram 47 corresponds to the position of the optical security component 40 referenced 7 in FIG. 3, diagram 48 corresponds to the position of the optical security component 40 referenced 8 in FIG. 3, diagram 49 corresponds to the position of the optical security component 40 referenced 9 in FIG. 3. In FIG. 4C, each color is illustrated by a texture similar to that used in FIG. 3.
• an achromatic dynamic visual effect is observed around the specular reflection which, as explained in more detail below, results from the arrangement of the facets forming the first pattern and on both sides we observe the same dynamic but iridescent visual effect, with a parade of rainbow-like colors.
• the iridescent effect results from the diffraction at orders +1 and -1 of the grating (respectively for the angular ranges of tilt Dqk- and Dqk-) which modulates the facets.
• the iridescent animation is chained on either side of the chromatic animation.
• FIGS 4A - 4C it is thus possible to define two particular angles of incidence, respectively 0G (diagrams 43 and 44) and 0 / (diagrams 46 and 47) which correspond to the transition angles of incidence between respectively l achromatic animation and iridescent animation at order +1 and achromatic animation and iridescent animation at order -1.
• one begins by determining the structure of the first pattern, that is to say the positions of the facets, their dimensions and the slopes of the facets to obtain the achromatic animation sought in the first part of the tilt angular range (DQ B in FIG. 3).
• FIG. 5 A shows an example of the spatial distribution of the widths of facets making it possible to produce a dynamic effect (diagram 51) as well as diagrams illustrating the angular values of the slopes of the facets as a function of the width, as a tool for designing the first pattern in a component safety optics according to the present description to construct the desired animation.
• diagram 51 represents a curve 510 illustrating, in a first arrangement of facets configured to produce a dynamic effect, the spatial distribution of the widths of the facets along F axis y of variation of the slope (see FIG. 2).
• the variation of the widths is decreasing, which translates at constant height h of the facets into a continuous and increasing variation of the angular values of the slopes, with the aim of simulating a concave reflective element.
• diagram 51 illustrates a continuous decreasing variation which follows a mathematical curve which can be written as + b, where a and b are the adjustment parameters of the function. Note that other functions can be used.
• the variation of the widths and angles of the facets comprises discrete values chosen according to the size of the diffractive structure. Thus, for example, if it is sought to produce a “wave” type effect in a region of given size, it will be possible to choose a greater number of facets in a larger region and the dynamic effect will be more fluid and continuous.
• Diagram 52 thus represents angular values of slopes (in degrees) of the facets as a function of the facet widths, for two facet heights, namely 1 ⁇ m (curve 521) and 0.5 ⁇ m (curve 522), for an arrangement of facets configured to form a dynamic effect equivalent to that of a concave optical element.
• the width of the facets is decreasing, which results, at constant height, in an increasing variation in the angular value of the slope of the facets.
• diagram 53 represents angular values of slopes (in degrees) of the facets according to the widths of the facets, for two heights of the facets, namely 1 ⁇ m (curve 531) and 0.5 ⁇ m (curve 532) , for an arrangement of facets configured to form a dynamic wave-like (convex) effect.
• the width of the facets is increasing then decreasing, which results, at constant height, in a decreasing variation in the angular value of the slope of the facets, then increasing.
• variable angle and width facets as depicted in FIG. 5 A are exploited to design the first pattern of the structure which will make it possible to generate the achromatic animation in the first angular range of tilt DQ B .
• each of the facets considered makes it possible to return the light towards a given direction according to the slope of the facet and according to a precise angular distribution.
• the facets participating in the movement (“active” facets) are those whose response allows energy to be returned in the direction D 0 (i.e. towards the observer handling the document ).
• the "active" facets will appear white (on) while the other facets will appear black (off).
• the observation angle 0 O bs equal to the absolute value of the angle between the direction of illumination AL, for example a direction of vertical illumination, and the direction of observation Do.
• the viewing angle 0 O bs is between about 30° and about 60° in air.
• the observation angle is equal to approximately 45° in the air.
• the first part of the angular range measured in the air AQ B is equal to 21.5°.
• the optical response of each of the facets is studied for a given illumination defined by the tilt of the sample.
• the optical response of a facet of width A and depth h is obtained by calculating the Fourier transform TF of the phase shift Df undergone by a light ray incident on the optical security component with an angle
• the phase shift Df is expressed by:
• l is a central working length of the visible range, for example 550 nm
• // / is the index of the first layer of dielectric material (113, FIG. 1 A and FIG. IB)
• h is the height of the facets .
• the optical response of the facet is thus expressed by:
• u is the spatial frequency given by: [Math 3]
• the optical response of the facets with slope a L corresponds to a diffractive lobe obtained by considering the envelope of the amplitude of the diffracted orders for wavelengths ranging from 400 nm to 800 nm.
• FIG. 5B Examples of diffractive lobes are shown in FIG. 5B where three scenarios have been modeled. Each of the cases corresponds to a different tilt of the document.
• the angle of incidence e L (angle defined between the direction D N normal to the plane of the component and the direction of illumination of the light source A L ) is therefore also distinct. This angle takes the value of 7.68° (diagram 57), 15° (diagram 58), and 21.8° (diagram 59).
• the diffractive lobes of three facets are represented: Two opposite facets with angles -7.1° and 7.1° corresponding to a width of 8 ⁇ m and a depth of 1 ⁇ m (curves 502 and 503 respectively) and a central facet with a substantially zero angle (curve 501) corresponding to a width of 80 ⁇ m and a depth of 1 ⁇ m.
• the facets with an angle of substantially zero slope that allow the light to be returned to the eye (specular reflection), the direction of observation by an observer handling the document being symbolized by an eye in diagram 58 (curve 501).
• the facets of substantially zero slope angle will appear "active".
• the diffractive lobes 502 and 503 return energy outside the axis of observation, the corresponding facets will appear extinguished.
• the angle is modified and the diffractive lobes are translated by a value of A6 L corresponding to the variation of the angle undergone following a tilt of the sample.
• tilt angles of the sample and the angle of incidence are distinct due to the refraction of the light undergone following the change of interface of index air/ .
• Diagram 57 corresponds to lighting with an angle of incidence of 7.68°, in this case the facet which participates in the achromatic animation is the one whose diffractive lobe is returned towards the direction A 0.
• the facet participating in the The visual effect in figure 57 is the -7.1° angle facet (curve 502).
• the direction of observation by an observer is symbolized by an eye.
• the first pattern can therefore be designed by a spatial arrangement of facets with variable slopes, the facets being determined to return the light energy in the direction of the observer, for a given angle of incidence which corresponds to a given angle of tilt .
• FIG. 5C shows a diagram of an arrangement of facets Fi in a region of the structure used to form the number "2" (FIG. 4A - 4C).
• “Pixels” Pi can be defined as being spatial regions containing one facet or several adjacent facets of the same width and of the same slope angle.
• a pixel can have a rectangular shape with at least one dimension less than 100 ⁇ m, advantageously less than approximately 60 ⁇ m so as not to be visible to the eye. Of course, other shapes of pixels can be envisaged.
• Each "pixel” forms a point of light for a given tilt angle of the component. One can thus create the achromatic animation as illustrated in FIG. 4B.
• the same facets modulated by the G grating generate an iridescent animation in a second part of the tilt angular range.
• the period d of the diffraction grating can be chosen as a function of the maximum angular value a of the slopes, measured in absolute value, and of the angle of observation to observe an achromatic animation in a first part of the angular range of tilt around the specular reflection, and to observe the same animation, iridescent, in a second part of the angular range of tilt, the iridescent animation being linked with the achromatic animation on either side of said first part of the tilt angular range.
• the period d of the grating G advantageously respects the following condition:
• ⁇ _ _ V is _ ni (sin(0 o3 ⁇ 4s,n1 ) - sin(0f Tli - 2 ⁇ a max ⁇ ))
• [Math 5] is the angle of incidence of transition between the achromatic and iridescent animations in the medium of index ni, namely the transition between positions 6 and 7 of the optical security component 40 as referenced in FIG. 3 taking into account the refraction ai r/ni . and: [Math 6]
• Avis is the wavelength with which we want to start the iridescent animation, for example Avis is between about 400 nm and about 450 nm.
• d is chosen equal to 502 nm by applying the equation defined above.
• FIG.6 describes the diffracted wavelengths (+1 and -1 orders) by different facets modulated by the grating G, returned towards the direction A 0 according to the angle of incidence, when the component is illuminated in white light in the direction of illumination A N .
• Curves 61, 62, 63, 64 and 65 correspond respectively to facets with angles ⁇ 7.1°, ⁇ 3.55°, 0°, +3.55° and +7.1°, overmodulated by a grating of period 520 nm.
• the total tilt angular range is divided into 3 angular ranges, an iridescent animation range Dq b _ corresponding to the -1 order diffraction, an achromatic animation range of tilt DQ B around the specular reflection and a second iridescent animation range Dq k+ corresponding to diffraction of order +1.
• each of the facets modulated by the grating G diffracts a different wavelength in the direction of observation. This wavelength depends on the slope specific to each facet.
• the chromatic dispersion generated by the different facets modulated by the grating G follows the same graphic pattern previously defined on the first tilt range.
• curves 70, 71, 72 and 73 illustrate the -1 order grating efficiency curve as a function of grating depth for four grating periods, namely 400 nm, 460 nm, 520 nm, 580 nm respectively for an incident light wavelength corresponding to 550 nm.
• This curve makes it possible to optimize the value of the depth of the diffraction grating G. For example, for a grating G with a period of 520 nm, a depth / of 150 nm can be chosen to have maximum diffraction efficiency at order 1 and -1.
• FIGS. 8 and 9A, 9B Examples of optical security components for securing valuable documents are illustrated by means of FIGS. 8 and 9A, 9B.
• FIG. 8 shows an example of an optical security component of the “patch” or stamp type according to the present description, for example a label, the patch being configured to be fixed for example on a banknote or a product.
• the optical security component comprises a stack of layers, for example a stack of layers as illustrated in FIG. IB, the layer 118 then being able to be an adhesive layer.
• the optical security component comprises a first diffractive structure etched in the first layer (113, FIG. 1B) and delimited by the outline referenced 81 in FIG. 8, this first diffractive structure being in accordance with the present description to generate an effect achromatic dynamic visual in a first angular tilt range and the same dynamic, but iridescent, visual effect in angular tilt ranges on either side of the first angular tilt range.
• the optical security component also comprises other structures delimited by the contours 82, 83 and 84. These may be, for example, diffusing structures, holographic structures or diffracting structures making it possible to produce so-called Alphagram® effects.
• a reflective layer (114, FIG. IB), for example a metallic or high-index layer, can be applied to the whole of the component, the regions 81, 82, 83, 84 being distinguished only by differences in the structure etched in the first layer.
• FIG. 9A shows a diagram illustrating an example of a document of value 900, for example a banknote, secured with an optical security component 91 according to the present description
• FIG. 9B is a diagram showing an enlargement of the secure document illustrated in FIG. 9A.
• the optical security component comprises a stack of layers, for example a stack of layers as illustrated in FIG. 1 A, the layer 117 possibly being, for example, a layer of hot-reactivable adhesive, for the transfer of the optical security component onto the support of the banknote 900.
• the optical security component 91 comprises a first diffractive structure etched in the first layer (113, FIG. 1B) and delimited by the contour in the shape of a “2” referenced 911 in FIG. 9A as well as a second diffractive structure etched in the first layer and delimited by the contour in the shape of a "5" referenced 912.
• These two diffractive structures are diffractive structures in accordance with the present description for generating an achromatic dynamic visual effect in a first tilt angular range and the same dynamic, but iridescent, visual effect in tilt angular ranges on either side of the first tilt angular range.
• the animations resulting from the two diffractive structures may exhibit different patterns.
• the second layer (reflecting) is non-existent locally to reveal regions 915 in which appears the support of the banknote on which the optical security component is fixed.
• the reflective layer (114, FIG. 1 A) does not completely cover the diffractive structure.
• the first pattern forming said diffractive structure may have regions 918 in which there is no modulation with the order 1 grating. These regions will not be perceptible when the optical safety component undergoes a tilt movement in the first angular range (achromatic animation) but will appear black to an observer when the optical safety component undergoes a tilt movement in the tilt angular ranges on both sides other side of the first angular range of tilt. It is thus possible to offer additional protection with a message that only appears at high tilt angles, during the iridescent animation.
• the regions 918 could be modulated by a second grating different from the first grating, for example a second grating of order 1 of pitch and/or orientation different from those of the first grating so as either to cause a spectral shift of the iridescence, or to allow azimuthal control in the case where the orientation is different from the direction of the first grating of order 1 which modulates the rest of the first pattern.
• a second grating different from the first grating for example a second grating of order 1 of pitch and/or orientation different from those of the first grating so as either to cause a spectral shift of the iridescence, or to allow azimuthal control in the case where the orientation is different from the direction of the first grating of order 1 which modulates the rest of the first pattern.
• the optical security component illustrated in FIGS 9A, 9B further comprises another structure delimited by the contour 913. It may be for example a diffractive structure comprising a set of facets as described in the present description but not modulated by a diffraction grating. Thus, region 913 will present an achromatic dynamic visual effect to an observer. It is for example possible to calculate the angular range of tilt of region 913 to observe an achromatic animation over the entire angular range of tilt over which the animations of regions 911 and 912 are visible. In this way, we can simultaneously observe achromatic and iridescent animations in the component.
• FIGS. 10A and 10B illustrate an example of an original "visual scenario", obtained by means of an example of an optical security component according to the present description.
• FIG. 10A thus illustrates diagrams 1001 and 1002 respectively illustrating designs of a first pattern and a second pattern.
• the first pattern 1012 comprises a set of facets arranged according to the present description to produce, when the component is illuminated in white light along the axis of illumination A L , a dynamic visual effect observable in reflection under the effect of a tilt movement and within the given tilt angular range AG t u t.
• the first pattern is delimited in this example by a disc and interrupted in regions 1011, the regions 1011 forming a first recognizable graphic object, here the outline of a bulb and of a base of the bulb.
• the diagram 1002 symbolizes the second pattern 1022, that is to say a network of order 1 (network G, FIG. 2) which modulates the first pattern. It is present over the whole of the first pattern except in regions 1021 which correspond on the one hand to regions 1011 in which there is no first pattern but also to additional regions which form a second recognizable graphic object, in this example a light bulb filament and light rays.
• FIG. 10B shows diagrams illustrating, according to the predefined visual scenario, the achromatic and iridescent visual animations obtained thanks to the patterns as schematized in FIG. 10A.
• an achromatic animation 1003 is observed over the entire component except at the places 1011 in which there is no first pattern . An observer therefore sees the outline of a bulb and the base during the achromatic animation (first graphic object).
• the animation continues in the second part of the angular range of tilt but in an iridescent way thanks to the presence of the first diffractive grating of order 1, except at the places corresponding to the regions 1011 (no first pattern) and 1021 (no first pattern or second pattern).
• An observer thus sees appear during the achromatic animation, in addition to the outline of the bulb and the base, the filament and the rays (second graphic object).
• the resulting structure thus produces a blinking scenario during the tilt between the first and second parts of the tilt angular range.
• the observer perceives a light bulb which "lights up" during the iridescent animation and "goes out” during the achromatic animation, the whole being visible on a disc shaped animated background.
• a first step comprises the design of said at least one first diffractive structure according to the methods described above, and any other structures.
• the optical master is for example an optical support on which the structure(s) are formed.
• the optical master can be formed by electronic or optical lithography methods known from the state of the art.
• the optical master is produced by etching a resin sensitive to electromagnetic radiation using an electron beam.
• the structure having the first pattern modulated by the second pattern can be etched in a single step.
• an optical lithography (or photolithography) technique can be used.
• the optical master is in this example a plate of photosensitive resin and the origination step is carried out by one or more exposures of the plate by projection of masks, of the phase mask type and/or of the amplitude mask type, followed by development in an appropriate chemical solution.
• a first exposure is produced by projection of amplitude masks whose transmission coefficients are adapted so that, after development, a relief corresponding to the first pattern is formed, in the regions in which the first pattern is provided.
• a second global exposure is carried out, according to interference photolithography methods known to those skilled in the art, a diffraction grating (diffraction grating G, FIG.
• a step of matrix duplication of the metal master can be carried out to obtain a large-scale production tool suitable for replicating the structure in industrial quantities.
• the manufacture of the optical security component then comprises a replication step.
• the replication can be carried out by stamping (by hot pressing of the dielectric material in English "hot embossing") of the first layer 113 (FIGS. 1 A, IB) in dielectric material of refractive index m, for example a low index layer, typically a stamping varnish a few microns thick.
• Layer 113 is advantageously carried by support film 111, for example a 12 ⁇ m to 100 ⁇ m film of polymer material, for example PET (polyethylene terephthalate).
• Replication can also be made by molding the layer of stamping varnish before drying and then UV curing (“UV casting”). Replication by UV crosslinking makes it possible in particular to reproduce structures having a large depth amplitude and makes it possible to obtain better fidelity in the replication.
• any other high-resolution replication method known from the prior art can be used in the replication step.
• the deposition on the layer thus embossed of all the other layers for example the reflective layer 114, the layer of dielectric material 115 (optional), the security layer 116 (optional) which can be deposited uniformly or selectively to figure a new pattern and the glue or varnish type layer (117, 118) by a coating process.
• optical security component according to the invention and the method of manufacturing said component comprise various variants, modifications and improvements which will appear obvious to those skilled in the art. , it being understood that these various variants, modifications and improvements form part of the scope of the invention as defined by the following claims.

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