Safety optical component

Abstract

The invention relates to a safety 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. textured (132), and which influences the reflection, diffraction, or scattering 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) resulting in a corresponding variation in color when said optical component (100) is observed at the same angle of incidence and the same viewing angle.

Description

Title of the invention: Safety optical component

[0001] The present invention relates to the field of optical safety 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 driver's license, a banknote, a voucher, etc.

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

[0005] In the context of the present invention, a safety optical component includes a reflective layer of dielectric, which enables particular optical effects.

[0006] Typically, a safety optical component exhibits color variation effects when its viewing angle is changed.

[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 safety components, the present invention makes it possible to obtain, in a completely innovative way, a variability of colors of an optical safety component under the same angle of observation.

[0010] In this context, the present invention relates, according to a first of its objects, to a safety optical component (100), the optical component (100) being planar and extending along two orthogonal XY directions and having a thickness along an axis Z,

[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 dielectric layer (120),

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

[0015] i. smooth (131) or

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

[0017] It is essentially characterized in that:

[0018] the optical component (100) includes at least one area 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) allowing a corresponding variation in color to be obtained when observing said optical component (100) under the same angle of incidence and the same angle of observation.

[0019] It can be predicted that for at least one area 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 foreseen that for at least one area for which the thickness of the reflective dielectric layer (120) is locally variable, said reflective dielectric layer (120) further exhibits a set of at least a 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 being able to be 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 foreseen that the support layer (130) is structured (132) and comprises at least one of the following:

[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 foreseen 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.

[0026] It can be predicted that the contours of the whole of at least one optical network draw a pattern visible when observing said optical component (100).

[0027] It can be foreseen 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 structured support layer (130) (132) or on the metallization layer.

[0028] The support layer (130) may be provided to be 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 metallic layer (142) in contact with the other face of the layer reflective dielectric (120), so that the reflective dielectric layer (120) is sandwiched between the first metallic layer (141) and the second metallic 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 features and advantages of the present invention will become more apparent from the following description given by way of illustrative and non-limiting example and made with reference to the accompanying figures.

[0033] The figures are not necessarily to scale. Some details may have been omitted and others amplified to facilitate 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 safety document,

[0036] [Fig.2] illustrates a cross-section of an embodiment of an optical component according to the invention, arranged on a safety 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 safety 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 safety 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 stated at the beginning of the description, and illustrated in [Fig.5], an optical component 100 according to the prior art comprises a reflective layer of dielectric 120 deposited on a support, for example an adhesive layer 110 in [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 gives a color to the optical component 100.

[0049] The present invention cleverly uses this feature.

[0050] Indeed, it is planned here to locally modify the color of the optical component 100 by locally modifying the thickness of the reflective layer of dielectric 120.

[0051] Thus, whereas according to the prior art it is necessary to modify the angle of observation 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 angle of observation, that is to say that the same reflective layer of dielectric 120 presents different colors under the same angle of observation.

[0052] An optical component 100 according to the invention is planar and extends along two 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 mandatory.

[0058] The adhesive layer 110 allows the optical component 100 and a safety document 200 to be joined together. The safety document 200 is shown in Figures 1 to 4 in addition to the optical component 100.

[0059] The support layer 130 allows the reflective dielectric layer 120 to be deposited on it, either 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 textured 132, depending on the desired optical effects. It influences the reflection, diffraction, or scattering of an incident electromagnetic wave, in particular visible light.

[0060] It can also be foreseen, 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 optical component 100 illustrated in [Fig.4] allows for different color effects: with a smooth support layer 130, the color effects are due solely to variations in the 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 structured support layer 130 132 or smooth 131, a first metallic layer 141, a reflective dielectric layer 120 whose thickness is locally variable, a second metallic layer 142, so that the reflective dielectric layer 120 is sandwiched between the first metallic layer 141 and the second metallic 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 metallic 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 area framed by dotted lines which corresponds to a zone 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 area 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] On [Fig.6], it is clearly seen that the reflective layer of dielectric 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, zone Zl has a first gradient Gl_l, for example, along a direction -Y, and zone Z2 has a first gradient G2_l, for example, also along a direction - Y, and the zone Z3 presents a first gradient G3_l for example also along a direction -Y.

[0070] It can be foreseen that the reflective layer of dielectric 120 also has a set of at least a second thickness gradient along a second predetermined direction included in the XY plane and opposite to the first direction.

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

[0072] It should also be noted that: - The value of the first or second gradient of one zone may be different from the value of the first or second gradient of another zone. For example, as illustrated in [Fig. 6], the first gradient Gl_l of zone Z1 is different from the first gradient G2_l of 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 zone Z2 is equal to the second gradient G2_2 of zone Z2, but the first gradient Gl_l of zone Z1 is different from the second gradient Gl_2 of zone Z1. - The maximum thickness of the dielectric reflective layer 120 in one zone may differ from the maximum thickness of the dielectric reflective layer 120 in another zone. For example, as illustrated in [Fig. 6], the maximum thickness of the dielectric reflective layer 120 in zone Z1 and zone Z2 is identical, but less than the maximum thickness of the dielectric reflective layer 120 in zone Z3.

[0073] Figure 7 illustrates the Z1 and Z2 zones of Figure 6 in top view. In Figure 7, the thickness gradient of the reflective dielectric layer 120 is illustrated by a gradient of gray, and the direction of the first and second gradients is illustrated by a double arrow.

[0074] The optical component 100 may comprise an assembly 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 an assembly of at least one optical grating whose pitch is constant.

[0075] Alternatively or combinatorially, and not illustrated, it may also be provided 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.1], the optical component 100 comprises a stack of a support layer 130, in this case structured 132, a reflective dielectric layer 120 whose thickness is locally variable, and an adhesive layer 110.

[0077] The optical component 100 can comprise a plurality of optical gratings, for example at least a first optical grating having a first elongation axis and a second optical grating having a second elongation axis, intersecting with the first elongation axis and for example orthogonal to it.

[0078] An example of an optical component 100 comprising a plurality of optical gratings according to the prior art is illustrated in [Fig. 9A]. The two optical gratings RI and R2 form a pattern visible when observing said optical component 100. For example, the first optical grating RI displays a green color and the second optical grating R2 displays a red color.

[0079] An optical component 100 according to the invention reproducing the same pattern is illustrated in [Fig. 9B]. The first optical grating RI mainly exhibits a green color and the second optical grating R2 mainly exhibits a red color.

[0080] However, thanks to the invention, the first optical grating RI has a first zone Z1 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 grating 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 allows a corresponding variation in color to be obtained when observing said optical component 100 under the same angle of incidence and the same angle of observation.

[0082] Thus, the first optical grating RI exhibits a blue color in the area outlined in dotted lines on [Fig.9A], fading to green in the first zone ZI 1 and the second zone Z12. And the second optical grating R2 exhibits a yellow color in the area outlined in dotted lines on [Fig.9A], fading to red in 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 layer of dielectric 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 metallic 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 previously stated, the variation in thickness of the reflective layer of dielectric 120 makes it possible to obtain a corresponding variation in 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 can be free of pigments or free of colored varnish.

[0088] An optical component 100 according to the invention is advantageously attached 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. 1] and [Fig. 4] can be implemented on identity documents. The present invention can be implemented even for identity documents that include at least one layer of polycarbonate, for example, smart card-format identity cards, also known as "ID1" cards, personal data pages in passports, driver's licenses, etc.

[0090] According to the invention, the reflective layer of dielectric 120 can 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 dielectric layer

[0095] 130 support layer

[0096] 131 smooth support layer

[0097] 132 structured support layer 32

[0098]

[0099]

[0100] 141 first metallic layer 142 second metallic layer 200 safety document

Claims

1.

2. Demands Optical safety component (100), the optical component (100) being planar and extending along two 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 stacking 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 scattering 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) allowing a corresponding variation in color to be obtained 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 by the fact that: for at least one zone (Z1, Z3) the value of the second gradient is different from that of the first linear gradient. Optical component (100) according to claim 1, wherein: the maximum thickness of the dielectric reflective layer (120) of one zone (Zl, Z2, Z3) is different from the maximum thickness of the dielectric reflective 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: • an assembly of at least one optical grating having a constant pitch; • an assembly of at least one optical grating having a non-constant pitch.

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

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

7. Optical component (100) according to any one of the preceding claims, wherein 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 support layer (130) or on the metallization layer.

8. 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 metallic layer (141) in contact with one face of the reflective dielectric layer (120); and • a second metallic layer (142) in contact with the other face of the reflective dielectric layer (120), such that the reflective dielectric layer (120) is taken into

9.

10. sandwich between the first metallic layer (141) and the second metallic layer (142). Optical component (100) according to any one of the preceding claims, wherein the reflective dielectric layer (120) is discontinuous. Security document (200), identity or fiduciary document, in particular a banknote, comprising an optical component (100) according to any one of claims 1 to 9.

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