Optical security component

Abstract

The invention relates to an optical security component (100) comprising a set of at least one zone in which it locally comprises a stack of: an adhesive layer (110); a reflective dielectric layer (120); and a support layer (130) on which the reflective dielectric layer (120) is deposited, and which is: i. smooth (131) or ii. structured (132), and which affects the reflection, diffraction, or scattering of an incident electromagnetic wave, in particular visible light. It is essentially characterised in that: it comprises at least one zone of the set in which the thickness of the reflective dielectric layer (120) is locally variable, wherein the variation in thickness of the reflective dielectric layer (120) results in a corresponding variation in colour when the optical component (100) is observed at the same angle of incidence and the same angle of observation.

Description

[0001] Optical security component

[0002] The present invention relates to the field of optical security components.

[0003] Optical security components are typically implemented on security documents, which can be government or private and which are valuable documents.

[0004] For example, a security document is a passport, a driving license, a banknote, a countermark, etc.

[0005] The securing of security documents is generally implemented by a plurality of security means, including the attachment of an optical security component to said security document.

[0006] For the purposes of the present invention, an optical security component comprises a reflective dielectric layer, which allows particular optical effects.

[0007] Typically, a security optical component exhibits color variation effects by changing its viewing angle.

[0008] Holograms are a well-known example of such optical security components. More generally, a hologram produces an optically variable image or visual effect, and is also known as a DOVID (Diffractive Optical Variable Image Device).

[0009] Other examples of implementation of the present invention are described later.

[0010] Unlike currently known optical security components, the present invention makes it possible to obtain, in a completely innovative manner, a variability of colors of an optical security component from the same observation angle.

[0011] In this context, the present invention relates, according to a first of its objects, to an optical security component (100), the optical component (100) being planar and extending in two mutually orthogonal XY directions and having a thickness along a Z axis,

[0012] The optical component (100) comprising a set of at least one zone in which the optical component (100) locally comprises a stack of:

[0013] • An adhesive layer (110),

[0014] • A reflective layer of dielectric (120),

[0015] • A support layer (130) on which the reflective dielectric layer (120) is deposited and which is: i. smooth (131) or ii. structured (132), and which influences the reflection, diffraction or diffusion of an incident electromagnetic wave, in particular visible light; in which the thickness of the reflective dielectric layer (120) is locally variable, the variation in thickness of the reflective dielectric layer (120) making it possible to obtain a corresponding variation in color when observing said optical component (100) under the same angle of incidence and the same angle of observation,

[0016] And in which for at least one zone (Z1, Z2, Z3) for which the thickness of the reflective dielectric layer (120) is locally variable, said reflective dielectric layer (120) has a set of at least one first linear thickness gradient along a first predetermined linear direction included in the XY plane of the optical component (100) and a set of at least one second linear thickness gradient along a second predetermined direction included in the XY plane and opposite to the first direction.

[0017] It is essentially characterized in that: for at least one zone (Zl, Z3) the value of the second gradient is different from that of the first linear gradient.

[0018] It can be provided that the maximum thickness of the reflective dielectric layer (120) of one zone (Zl, Z2, Z3) is different from the maximum thickness of the reflective dielectric layer (120) of another zone (Zl, Z2, Z3).

[0019] It can be provided that for at least one zone for which the thickness of the reflective dielectric layer (120) is locally variable, said reflective dielectric layer (120) has a set of at least one first thickness gradient along a first predetermined linear direction included in the XY plane of the optical component (100).

[0020] It can be provided that for at least one zone for which the thickness of the reflective dielectric layer (120) is locally variable, said reflective dielectric layer (120) also has a set of at least one second thickness gradient in a second predetermined direction included in the XY plane and opposite to the first direction, the value of the second gradient possibly being different from that of the first gradient.

[0021] It can be provided that said optical component (100) is free of pigments or free of colored varnish.

[0022] It can be provided that the support layer (130) is structured (132) and comprises at least one of: a set of at least one optical network whose pitch is constant;

[0023] • a set of at least one optical network whose pitch is not constant.

[0024] It can be provided that the set of at least one optical network comprises at least a first optical network having a first elongation axis and a second optical network having a second elongation axis, intersecting with the first elongation axis.

[0025] It can be provided that the contours of the assembly of at least one optical network draw a visible pattern when observing said optical component (100).

[0026] It can be provided that the support layer (130) is structured (132) by a nanometric plasmonic structure, the optical component (100) further comprising a metallization layer deposited on the reflective dielectric layer (120), itself deposited on the support layer (130) structured (132) or on the metallization layer.

[0027] It can be provided that the support layer (130) is smooth (131) and / or structured (132), the optical component (100) further comprising:

[0028] • A first metal layer (141) in contact with one face of the reflective dielectric layer (120); and

[0029] • a second metal layer (142) in contact with the other face of the reflective dielectric layer (120), such that the reflective dielectric layer (120) is sandwiched between the first metal layer (141) and the second metal layer (142).

[0030] The reflective dielectric layer (120) can be provided to be discontinuous.

[0031] According to another of its objects, the invention also relates to a security document (200), identity or fiduciary, in particular a banknote, comprising an optical component (100) according to the invention.

[0032] Other characteristics and advantages of the present invention will appear more clearly on reading the following description given by way of illustrative and non-limiting example and made with reference to the appended figures.

[0033] Figures are not necessarily to scale. Some details may have been omitted and others magnified for ease of understanding.

[0034] DESCRIPTION OF THE DRAWINGS [Fig. 1] illustrates a cross-section of an embodiment of an optical component according to the invention, arranged on a security document,

[0035] [Fig. 2] illustrates a cross-section of an embodiment of an optical component according to the invention, arranged on a security document,

[0036] [Fig. 3] illustrates a cross-section of a first variant of an embodiment of an optical component according to the invention, arranged on a security document

[0037] [Fig. 4] illustrates a cross-section of a second variant of an embodiment of an optical component according to the invention, arranged on a security document,

[0038] [Fig. 5] illustrates a cross-section of the principle of an optical component according to the prior art,

[0039] [Fig. 6] illustrates a cross-section of the principle of an optical component according to the invention,

[0040] [Fig. 7] illustrates a top view of the optical component of Figure 6,

[0041] [Fig. 8] illustrates a cross-section of an embodiment of an optical component according to the invention,

[0042] [Fig. 9A] illustrates an embodiment of an optical component according to the prior art,

[0043] [Fig. 9B] illustrates an optical component according to the invention, reproducing the same pattern as that of Figure 9A,

[0044] [Fig. 10] illustrates an embodiment of an optical component according to the invention.

[0045] As explained at the start of the description, and illustrated in FIG. 5, an optical component 100 according to the prior art comprises a reflective dielectric layer 120 deposited on a support, for example an adhesive layer 110 in FIG. 5.

[0046] According to the prior art, the deposited reflective dielectric layer 120 has a uniform thickness.

[0047] The thickness of the reflective dielectric layer 120 imparts a color to the optical component 100.

[0048] The present invention cleverly utilizes this feature.

[0049] Indeed, it is provided here to locally modify the color of the optical component 100 by locally modifying the thickness of the reflective dielectric layer 120. Thus, whereas according to the prior art it is appropriate to modify the observation angle or to modify the position of the optical component 100, for example by a rotation of the latter in the plane or around an axis passing through the plane of said optical component 100, according to the invention, the optical component 100 presents different colors when it is observed from the same observation angle, that is to say that the same reflective dielectric layer 120 presents different colors from the same observation angle.

[0050] An optical component 100 according to the invention is planar and extends along two mutually orthogonal XY directions and has a thickness along a Z axis. Figures 1 to 4 and Figure 6 show different embodiments of an optical component 100 according to the invention, seen in cross-section, along the Z axis.

[0051] The optical component 100 comprises a set of at least one zone in which it locally comprises a stack of:

[0052] • An adhesive layer 110,

[0053] • A reflective layer of dielectric 120, and

[0054] • A 130 support layer.

[0055] Preferably, the reflective dielectric layer 120 is in contact with the adhesive layer 110 (Figures 1 and 2). However, as illustrated in Figures 3 and 4, this contact is not mandatory.

[0056] The adhesive layer 110 makes it possible to secure the optical component 100 and a security document 200. The security document 200 is shown in Figures 1 to 4 in addition to the optical component 100.

[0057] The support layer 130 makes it possible to deposit the reflective dielectric layer 120 there, directly (figures 1 to 3) or indirectly in the case of a multilayer component illustrated in figure 4. The support layer 130 can be smooth 131 or structured 132, depending on the desired optical effects. It influences the reflection, diffraction or diffusion of an incident electromagnetic wave, in particular visible light.

[0058] It is also possible, as illustrated in FIG. 4, for the support layer 130 to comprise a smooth part 131 and a structured part 132. FIG. 4 illustrates a smooth part 131 and a structured part 132 adjacent to each other; they can of course be distant from each other.

[0059] The smooth part 131 or the structured part 132 of the support layer 130 of the optical component 100 illustrated in FIG. 4 makes it possible to obtain different color effects: with a smooth support layer 130, the color effects are due solely to the variations in thickness of the reflective dielectric layer 120. With a structured support layer 130 132, carrying optical networks, the color effects are due, in addition, to the structuring of the support layer 130.

[0060] In the particular case of Figure 4, called “metal color” or “multilayer”, the optical component 100 locally comprises a successive stack of: a support layer 130 structured 132 or smooth 131, a first metal layer 141, a reflective dielectric layer 120 whose thickness is locally variable, a second metal layer 142, so that the reflective dielectric layer 120 is sandwiched between the first metal layer 141 and the second metal layer 142, and an adhesive layer 110. In this case, the reflective dielectric layer 120 is “indirectly” in contact with the support layer 130, that is to say that the reflective dielectric layer 120 is directly in contact with the first metal layer 141, itself directly in contact with the support layer 130.

[0061] The effects of an optical component according to Figure 4 are illustrated in Figure 10. In Figure 10, the optical component 100 has a predominantly golden color, except in the part framed in dotted lines which corresponds to an area in which the thickness of the reflective dielectric layer 120 is locally variable and which has a bluish color.

[0062] According to the invention, the optical component 100 comprises at least one zone in which the thickness of the reflective dielectric layer 120 is locally variable.

[0063] The variation in thickness of the reflective layer is illustrated in Figure 6, compared to the prior art illustrated in Figure 5.

[0064] In Figure 6, it is clearly seen that the reflective dielectric layer 120 may be discontinuous.

[0065] In Figure 6, 3 zones Z1, Z2 and Z3 are illustrated, for which the thickness of the reflective dielectric layer 120 is locally variable.

[0066] In each of these zones, the reflective dielectric layer 120 has a set of at least a first thickness gradient along a first predetermined linear direction included in the XY plane of the optical component 100.

[0067] In this case, zone Zl presents a first gradient Gl_l for example in a -Y direction, zone Z2 presents a first gradient G2_l for example also in a -Y direction, and zone Z3 presents a first gradient G3_l for example also in a -Y direction.

[0068] It may be provided that the reflective dielectric layer 120 further has a set of at least one second thickness gradient along a second predetermined direction included in the XY plane and opposite to the first direction. In this case, the zone Z1 has a second gradient Gl_2 for example along a Y direction, the zone Z2 has a second gradient G2_2 for example also along a Y direction. In this case, the zone Z3 does not have a second gradient along a Y direction.

[0069] It will also be noted that: the value of the first gradient or the second gradient of a zone may be different from the value of the first or the second gradient of another zone. For example, as illustrated in FIG. 6, the first gradient Gl_l of the zone Z1 is different from the first gradient G2_l of the zone Z2. For a given zone, the value of the second gradient may be different from that of the first gradient. For example, as illustrated in FIG. 6, the first gradient G2_l of the zone Z2 is equal to the second gradient G2_2 of the zone Z2, but the first gradient Gl_l of the zone Z1 is different from the second gradient Gl_2 of the zone Z1. The maximum thickness of the reflective dielectric layer 120 of a zone may be different from the maximum thickness of the reflective dielectric layer 120 of another zone.For example, as illustrated in FIG. 6, the maximum thickness of the reflective dielectric layer 120 of area Z1 and area Z2 are the same, but less than the maximum thickness of the reflective dielectric layer 120 of area Z3.

[0070] Figure 7 illustrates the zones Z1 and Z2 of Figure 6 in a top view. In Figure 7, the thickness gradient of the reflective dielectric layer 120 is illustrated by a gray gradient, and the direction of the first and second gradients is illustrated by a double arrow.

[0071] The optical component 100 may comprise a set of at least one optical grating. For this purpose, the support layer 130 is structured 132, as illustrated in FIG. 8 which represents a cross-section of an embodiment of an optical component 100 according to the invention in which the thickness of the reflective dielectric layer 120 is locally variable and in which the support layer 130 is structured 132 so as to support a set of at least one optical grating whose pitch is constant.

[0072] Alternatively or in combination, and not illustrated, it is also possible to provide that the optical component 100 according to the invention comprises a set of at least one optical network whose pitch is not constant.

[0073] In this case, as illustrated in FIG. 1, the optical component 100 comprises a stack of a support layer 130, in this case structured 132, of a reflective dielectric layer 120 whose thickness is locally variable, and of an adhesive layer 110. The optical component 100 may comprise a plurality of optical networks, for example at least a first optical network having a first axis of elongation and a second optical network having a second axis of elongation, intersecting with the first axis of elongation and for example orthogonal to it.

[0074] An example of an optical component 100 comprising a plurality of optical networks according to the prior art is illustrated in FIG. 9A. The two optical networks RI and R2 draw a visible pattern when observing said optical component 100. For example, the first optical network RI has a green color and the second optical network R2 has a red color.

[0075] An optical component 100 according to the invention reproducing the same pattern is illustrated in FIG. 9B. The first optical network RI mainly has a green color and the second optical network R2 mainly has a red color.

[0076] However, thanks to the invention, the first optical network RI has a first zone Z11 in which the thickness of the reflective dielectric layer 120 is locally variable and a second zone Z12 in which the thickness of the reflective dielectric layer 120 is locally variable. Similarly, the second optical network R2 has a first zone Z21 in which the thickness of the reflective dielectric layer 120 is locally variable and a second zone Z22 in which the thickness of the reflective dielectric layer 120 is locally variable.

[0077] The variation in thickness of the reflective dielectric layer 120 makes it possible to obtain a corresponding variation in color when observing said optical component 100 under the same angle of incidence and the same angle of observation.

[0078] Thus, the first optical network RI has a blue color in the dotted framed portion in Figure 9A, degrading to the green of the first zone Z11 and the second zone Z12. And the second optical network R2 has a yellow color in the dotted framed portion in Figure 9A, degrading to the red of the first zone Z21 and the second zone Z22.

[0079] The same effect can be obtained when the support layer 130 is structured 132 by a nanometric plasmonic structure. In this case, the optical component 100 further comprises a metallization layer deposited on the reflective dielectric layer 120, itself deposited on the structured support layer 130 132 or on the metallization layer.

[0080] For example, in a first variant illustrated in FIG. 2, the optical component 100 locally comprises a successive stack of: a support layer 130 structured 132 by a nanometric plasmonic structure, a reflective dielectric layer 120 whose thickness is locally variable, a metallization layer (first metal layer 141), and an adhesive layer 110.

[0081] In a second variant illustrated in Figure 3, the optical component 100 locally comprises a successive stack of: a support layer 130 structured 132 by a nanometric plasmonic structure, a metallization layer (first metal layer 141), a reflective dielectric layer 120 whose thickness is locally variable, and an adhesive layer 110.

[0082] As explained previously, the variation in thickness of the reflective dielectric layer 120 makes it possible to obtain a corresponding variation in the color of an optical component 100 according to the invention when it is observed from the same angle of incidence and the same angle of observation.

[0083] Thus, an optical component 100 according to the invention may be free of pigments or free of colored varnish.

[0084] An optical component 100 according to the invention is advantageously secured to a security document 200, identity document or fiduciary document, in particular a banknote, in particular an optical component 100 in which the support layer 130 is structured 132 by a nanometric plasmonic structure.

[0085] In particular, the embodiments illustrated in Figure 1 and Figure 4 can be implemented on identity documents. The present invention can be implemented including for identity documents which comprise at least one layer of polycarbonate, for example identity cards in smart card format, called "ID1", personal data pages in passports, driving licenses, etc.

[0086] According to the invention, the reflective dielectric layer 120 may be high refractive index (HRI), for example ZnS or TiO2, or low refractive index (LRI), for example SiO2.

[0087] Nomenclature

[0088] 100 Optical component

[0089] 110 adhesive layer

[0090] 120 reflective layer of dielectric

[0091] 130 support layer

[0092] 131 smooth support layer

[0093] 132 structured support layer 32

[0094] 141 first metal layer 142 second metal layer

[0095] 200 security document

Claims

Claims 1. Optical security component (100), the optical component (100) being planar and extending in two mutually orthogonal XY directions and having a thickness along a Z axis, The optical component (100) comprising a set of at least one zone (Z1, Z2, Z3) in which the optical component (100) locally comprises a stack of: • An adhesive layer (110), • A reflective layer of dielectric (120), • A support layer (130) on which the reflective dielectric layer (120) is deposited and which is: i. smooth (131) or ii. structured (132), and which influences the reflection, diffraction or diffusion of an incident electromagnetic wave, in particular visible light; wherein the thickness of the reflective dielectric layer (120) is locally variable, the variation in thickness of the reflective dielectric layer (120) making it possible to obtain a corresponding variation in color when observing said optical component (100) under the same angle of incidence and the same angle of observation, And in which for at least one zone (Z1, Z2, Z3) for which the thickness of the reflective dielectric layer (120) is locally variable, said reflective dielectric layer (120) has a set of at least one first linear thickness gradient along a first predetermined linear direction included in the XY plane of the optical component (100) and a set of at least one second linear thickness gradient along a second predetermined direction included in the XY plane and opposite to the first direction, Characterized in that: for at least one zone (Zl, Z3) the value of the second gradient is different from that of the first linear gradient.

2. Optical component (100) according to claim 1, wherein: the maximum thickness of the reflective dielectric layer (120) of one zone (Zl, Z2, Z3) is different from the maximum thickness of the reflective dielectric layer (120) of another zone (Zl, Z2, Z3).

3. Optical component (100) according to any one of the preceding claims, wherein said optical component (100) is free of pigments or free of colored varnish.

4. Optical component (100) according to any one of the preceding claims, wherein the support layer (130) is structured (132) and comprises at least one of: • a set of at least one optical network with a constant pitch; • a set of at least one optical network whose pitch is not constant.

5. Optical component (100) according to claim 5, wherein the set of at least one optical network comprises at least a first optical network having a first axis of elongation and a second optical network having a second axis of elongation, intersecting with the first axis of elongation.

6. Optical component (100) according to claim 5 wherein the contours of the assembly of at least one optical network draw a visible pattern when observing said optical component (100).

7. Optical component (100) according to any one of the preceding claims, in which the support layer (130) is structured (132) by a nanometric plasmonic structure, the optical component (100) further comprising a metallization layer deposited on the reflective dielectric layer (120), itself deposited on the structured (132) support layer (130) or on the metallization layer.

8. Optical component (100) according to any one of claims 1 to 7, wherein the support layer (130) is smooth (131) and / or structured (132), the optical component (100) further comprising: • A first metallic layer (141) in contact with one face of the reflective dielectric layer (120); and • a second metal layer (142) in contact with the other face of the reflective dielectric layer (120), so that the reflective dielectric layer (120) is sandwiched between the first metal layer (141) and the second metal layer (142).

9. Optical component (100) according to any one of the preceding claims, wherein the reflective dielectric layer (120) is discontinuous.

10. Security document (200), identity or fiduciary, in particular a banknote, comprising an optical component (100) according to any one of claims 1 to 9.

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