Optical security component

Abstract

The invention relates to a security optical component (100), comprising an assembly 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 influences the reflection, diffraction or diffusion of an incident electromagnetic wave, in particular visible light. It is essentially characterized in that: It comprises at least one zone of said assembly 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.

Description

Title of the invention: Optical security component

[0001] The present invention relates to the field of optical security components.

[0002] Optical security components are typically implemented on security documents, which may be governmental or private and which are valuable documents.

[0003] For example, a security document is a passport, a driving license, a banknote, a countermark, etc.

[0004] The securing of security documents is generally implemented by a plurality of security means, including the securing of an optical security component with said security document.

[0005] For the purposes of the present invention, an optical security component comprises a reflective dielectric layer, which allows particular optical effects.

[0006] Typically, a security optical component exhibits color variation effects by changing its viewing angle.

[0007] 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).

[0008] Other examples of implementation of the present invention are described later.

[0009] 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 under the same observation angle.

[0010] 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,

[0011] The optical component (100) comprising a set of at least one zone in which the optical component (100) locally comprises a stack of:

[0012] • An adhesive layer (110),

[0013] • A reflective layer of dielectric (120),

[0014] • A support layer (130) on which the reflective layer of di is deposited electric (120) and which is:

[0015] i. smooth (131) or

[0016] ii. structured (132), and which influences the reflection, diffraction or diffusion of an incident electromagnetic wave, in particular visible light.

[0017] It is essentially characterized in that:

[0018] the optical component (100) comprises at least one zone of said assembly 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.

[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 along 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:

[0023] • a set of at least one optical network whose pitch is constant;

[0024] • a set of at least one optical network whose pitch is not constant.

[0025] It can be provided that the assembly 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.

[0026] 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).

[0027] 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.

[0028] It can be provided that the support layer (130) is smooth (131) and / or structured (132), the optical component (100) further comprising:

[0029] • A first metallic layer (141) in contact with one face of the reflective layer of dielectric (120); and

[0030] • a second metal layer (142) in contact with the other face of the re- layer 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).

[0031] According to another of its objects, the invention also relates to a security document (200), identity or fiduciary document, 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 enlarged for ease of understanding.

[0034] DESCRIPTION OF THE DRAWINGS

[0035] [Fig. 1] illustrates a cross-section of an embodiment of an optical component according to the invention, arranged on a security document,

[0036] [Fig.2] illustrates a cross-section of an embodiment of an optical component according to the invention, arranged on a security document,

[0037] [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

[0038] [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,

[0039] [Fig.5] illustrates a cross-section of the principle of an optical component according to the prior art,

[0040] [Fig.6] illustrates a cross-section of the principle of an optical component according to the invention,

[0041] [Fig.7] illustrates a top view of the optical component of [Fig.6],

[0042] [Fig.8] illustrates a cross-section of an embodiment of an optical component according to the invention,

[0043] [Fig.9A] illustrates an embodiment of an optical component according to the prior art,

[0044] [Fig.9B] illustrates an optical component according to the invention, reproducing the same pattern than that of [Fig.9A],

[0045] [Fig. 10] illustrates an embodiment of an optical component according to the invention.

[0046] As explained at the beginning of the description, and illustrated in [Fig.5], a component optical 100 according to the prior art comprises a reflective layer of dielectric 120 deposited on a support, for example an adhesive layer 110 on [Fig.5].

[0047] According to the prior art, the deposited reflective dielectric layer 120 has a uniform thickness.

[0048] The thickness of the reflective dielectric layer 120 imparts a color to the optical component 100.

[0049] The present invention cleverly uses this feature.

[0050] 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.

[0051] 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 under the same observation angle, that is to say that the same reflective layer of dielectric 120 presents different colors under the same observation angle.

[0052] 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 [Fig.6] show different embodiments of an optical component 100 according to the invention, seen in cross-section, along the Z axis.

[0053] The optical component 100 comprises a set of at least one zone in which it locally comprises a stack of:

[0054] • An adhesive layer 110,

[0055] • A reflective layer of dielectric 120, and

[0056] • A support layer 130.

[0057] 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 obligatory.

[0058] 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 FIGS. 1 to 4 in addition to the optical component 100.

[0059] 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 [Fig.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.

[0060] It is also possible to provide, as illustrated in [Fig.4], that the support layer 130 comprises a smooth part 131 and a structured part 132. [Fig.4] illustrates a smooth part 131 and a structured part 132 adjacent, they can of course be distant from each other.

[0061] The smooth part 131 or the structured part 132 of the support layer 130 of the component optical layer 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 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.

[0062] In the particular case of [Fig.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.

[0063] The effects of an optical component according to [Fig.4] are illustrated in [Fig.10]. In [Fig. 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.

[0064] 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.

[0065] The variation in thickness of the reflective layer is illustrated in [Fig.6], compared to the prior art illustrated in [Fig.5].

[0066] In [Fig.6], it is clearly seen that the reflective dielectric layer 120 can be discontinuous.

[0067] In [Fig.6], 3 zones Z1, Z2 and Z3 are illustrated, for which the thickness of the reflective dielectric layer 120 is locally variable.

[0068] In each of these zones, the 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.

[0069] In this case, the zone Zl has a first gradient Gl_l for example in a direction - Y, the zone Z2 has a first gradient G2_l for example also in a direction - Y, and the zone Z3 has a first gradient G3_l for example also in a direction - Y.

[0070] It can 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.

[0071] In this case, the zone ZI has a second gradient Gl_2 for example in a Y direction, the zone Z2 has a second gradient G2_2 for example also in a Y direction. In this case the zone Z3 does not have a second gradient in a Y direction.

[0072] It should also be noted that: - the value of the first gradient or the second gradient of a zone can 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 zone ZI is different from the first gradient G2_l of zone Z2. - for a given zone, the value of the second gradient can be different from that of the first gradient. For example, as illustrated in [Fig.6], the first gradient G2_l of zone Z2 is equal to the second gradient G2_2 of zone Z2, but the first gradient Gl_l of zone ZI is different from the second gradient Gl_2 of zone Zl. - the maximum thickness of the reflective dielectric layer 120 of one area may be different from the maximum thickness of the reflective dielectric layer 120 of another area. 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.

[0073] [Fig. 7] illustrates the zones Z1 and Z2 of [Fig. 6] in a top view. In [Fig. 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.

[0074] The optical component 100 may comprise a set of at least one optical network. 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 network whose pitch is constant.

[0075] 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.

[0076] In this case, as illustrated in [Fig.l], 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.

[0077] The optical component 100 may comprise a plurality of optical networks, for example 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 and for example orthogonal thereto.

[0078] 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 pattern visible 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.

[0079] 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.

[0080] However, thanks to the invention, the first optical network RI has a first zone ZI 1 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.

[0081] 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.

[0082] Thus, the first optical network RI has a blue color in the part framed in dotted lines in [Fig.9A], degrading towards the green of the first zone Z11 and the second zone Z12. And the second optical network R2 has a yellow color in the part framed in dotted lines in [Fig.9A], degrading towards the red of the first zone Z21 and the second zone Z22.

[0083] 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.

[0084] 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.

[0085] In a second variant illustrated in [Fig.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 metallic layer 141), a reflective dielectric layer 120 whose thickness is locally variable, and an adhesive layer 110.

[0086] 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 under the same angle of incidence and the same angle of observation.

[0087] Thus, an optical component 100 according to the invention may be free of pigments or free of colored varnish.

[0088] 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.

[0089] In particular, the embodiments illustrated in [Fig.l] and in [Fig.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.

[0090] 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.

[0091] Nomenclature

[0092] 100 Optical component

[0093] 110 adhesive layer

[0094] 120 reflective layer of dielectric

[0095] 130 support layer

[0096] 131 smooth support layer

[0097] 132 structured support layer 32

[0098] 141 first metal layer

[0099] 142 second metal layer

[0100] 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 in which the optical component (100) locally comprises a stack of: • An adhesive layer (110), • A reflective dielectric layer (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, the diffraction or the diffusion of an incident electromagnetic wave, in particular visible light, Characterized in that: the optical component (100) comprises at least one zone of said assembly 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.

2. Optical component (100) according to claim 1, wherein: 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).

3. Optical component (100) according to claim 2, wherein: for at least one zone for which the thickness of the reflective dielectric layer (120) is locally variable, said 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, the value of the second gradient may be different from that of the first gradient.

4. An optical component (100) according to any preceding claim, wherein said optical component (100) is free of pigments or free of colored varnish.

5. 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 whose pitch is constant; • a set of at least one optical network whose pitch is not constant.

6. An 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 elongation axis and a second optical network having a second elongation axis, intersecting with the first elongation axis.

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

8. 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.

9. An 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 metal 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), such that the reflective dielectric layer (120) is sandwiched between the first metal layer (141) and the second metal layer (142).

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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