CH703994B1 - Optically variable devices and method of manufacture. - Google Patents

Abstract

A variable optical effect device comprising a plurality of groups of raised surface elements. The groups are interlaced and / or stacked. A first group of relief elements is characterized by a first height or depth and produces a first type of optical and / or electromagnetic effect. A second group of raised elements is characterized by a second height or depth that is different from the first height or depth. The second group produces a second type of optical and / or electromagnetic effect different from that produced by the first group.

Description

Field of the invention

The present invention relates to safety devices capable of producing multiple variable optical effects on security documents or security tokens incorporating such devices and methods of manufacturing such devices.

Definitions

[0002] Security document or token

As used in the present application, the term security document includes all types of documents and valuable tokens as well as identification documents among which, but not limited to: monetary items such as banknotes and coins, credit cards, checks, passports, identity cards, securities and certificates of market value, driver's licenses, deeds, travel documents such as banknotes air and train tickets, admission cards and entrance tickets, birth, death and marriage certificates, as well as academic titles.

The invention is particularly, but not exclusively, applicable to security documents or tokens, such as banknotes, or identification documents such as identity cards or passports, made from a substrate on which an impression is deposited in one or more layers.

Substrate

As used in the present invention, the term substrate refers to the base material from which the security document or token is formed. The base material may be paper or other fibrous materials such as cellulose; a plastic or polymeric material including but not limited to polypropylene (PP), polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene terephthalate (PET); or a composite material consisting of two or more materials, such as a paper-based laminate and at least one plastic, or two or more polymeric materials.

The use of plastics or polymers in the manufacture of security documents launched for the first time in Australia has been a great success because the polymeric type of banknotes are more durable than their paper equivalents and that they can also incorporate new devices and safety features. One of the security features particularly appreciated in polymer bank notes manufactured for Australia and other countries has been the creation of a transparent area called "window".

[0008] Transparent windows and half-windows

[0009] As used hereinafter the term "window" refers to a transparent or translucent area in the security document, as compared to a substantially opaque region on which printing is applied. The window may be entirely transparent so that it allows substantially unaltered light transmission, or it may be partially transparent or partially translucent allowing partial transmission of light but without allowing objects to be clearly seen at through the window area. A window area may be formed in a polymeric security document having at least one layer of transparent polymeric material and one or more opacifying layers deposited on at least one side of a transparent polymeric substrate, omitting at least one opacifying layer in the region forming the window area. If opacifying layers are deposited on both sides of a transparent substrate a fully transparent window may be formed by omitting the opacifying layers on both sides of the transparent substrate in the window area.

[0010] A partially transparent or translucent zone, hereinafter referred to as a "half-window", may be formed in a polymeric security document having opacifying layers on both sides by omitting the opacifying layers on one side only the security document in the window area so that the "half-window" is not totally transparent, but allows a certain amount of light to pass without allowing the objects to be clearly distinguished through the half-window .

Alternatively, it is possible for the substrates to be formed of a substantially opaque material, such as paper or fibrous material, with a transparent plastic insert inserted in a blank, or a recess in the paper substrate. or fibrous material to form a transparent window area or a translucent half-window area.

[0012] Opacifying layers

The opacifying layers deposited on a transparent substrate may comprise one or more kinds of many opacifying coatings. For example, the opacifying coatings may comprise a pigment, such as titanium dioxide, dispersed in a binder or a heat-activated crosslinkable polymeric material carrier. Alternatively, a substrate of transparent plastics material may be sandwiched between opacifying layers of paper or other partially or substantially opaque material on which indicia may then be printed or otherwise applied.

[0014] Element or security feature

As used in the present invention, the term security element or feature includes any one of a plurality of important devices, elements, or security features for protecting the security document or token. counterfeiting, copying, alteration or forgery.

The devices or security features may be provided in or on the security document substrate or in one or on one or more layers applied to the base substrate, and may take a wide variety of shapes, such as wires. security features embedded in layers of the security document; security inks such as fluorescent, luminescent and phosphorescent inks, metallic inks, iridescent, photochromic, thermochromic, hydrochromic or piezochromic inks; printed or embossed features, including relief structures; interferential layers; liquid crystal devices; lentils and lenticular structures; variable optical effect devices (OVDs) such as diffractive devices including diffraction gratings, holograms and diffractive optical elements (DOEs).

Diffractive optical elements (DOEs)

As used in the present invention, the term diffractive optical element refers to a digital diffractive optical element (DOE). Digital diffractive optical elements (DOEs) are based on the mapping of complex data that reconstruct a two-dimensional intensity pattern in the far field (or reconstruction field). Thus, when the substantially collimated light, e.g. from a point light source or a laser, is incident on the DOE, an interference pattern is generated which produces a projected image in the reconstruction plane which is visible when an appropriate viewing surface is located in the reconstruction plane, or when the DOE is viewed in transmission in the reconstruction plane. The transformation between the two planes can be approximated by a Fast Fourier Transform (FFT). Thus, complex data including amplitude and phase information must be physically encoded in the DOE microstructure. These DOE data can be calculated by performing an inverse FFT Fourier transform of the desired reconstruction (i.e., the desired intensity pattern in the far field).

The DOEs are sometimes referred to as computer-generated holograms, but they differ from other types of holograms, such as rainbow-type holograms, Fresnel holograms, and reflection holograms. of volume.

Technological background

The use of diffractive devices with variable optical effect on security documents and other valuable items is known as a security feature. These are usually provided as a portion or metal strip that is affixed to the document or security article by hot stamping. Since the image on the portion or the band varies with the viewing angle or the illumination angle, the image can not be reproduced using scanning or printing techniques using computers. Many bank notes around the world are now using variable optical effect (OVD) diffractive-image devices as protection against counterfeiting.

Examples of OVD technologies include the diffractive device with variable optical effect (DOVD) described in US patents US 5,825,547 and US 6,088,161, and the DOVD described in European patents EP 330,738 and EP 1,059,099. These devices are examples of sheet-based diffractive structures that have proved to be highly effective deterrents against counterfeiting of official documents.

Although a single diffractive security device can discourage or prevent the counterfeiting of a security document, it is desirable to provide multiple separate optical effects in the same security device to increase recognition and security. efficiency of device security.

Any discussion of documents, acts, materials, devices, articles or the like included in the present description is only intended to provide a contextual framework for the present invention. It should not be considered admitted that some or all of these subjects are part of the prior art or part of the general common knowledge in the field of the present invention as it existed in Australia, or elsewhere, prior to the date of publication. priority of each claim appended to this application.

Summary of the invention

In a first aspect, the present invention provides a variable optical effect device comprising a transparent, translucent or reflective substrate comprising a plurality of groups of raised surface elements, the groups being intertwined and / or stacked, and in which wherein a first of said groups is characterized by a first height or depth and produces a first type of optical and / or electromagnetic effect, and a second one of said groups is characterized by a second height or depth which are different from the first height or depth, the second group producing a second type of optical and / or electromagnetic effect different from that produced by the first group.

By applying the elements in relief such that they are interlaced and / or stacked, it is possible to produce a composite structure that has an optical effect when viewed under certain conditions, and a second distinct optical effect, visible in substantially the same area of the device, when the device is viewed under different conditions. For example, the first optical effect may be observable in transmission, while the second is visible in reflection.

In a second aspect of the present invention, there is provided a method for producing a variable optical effect device comprising a plurality of groups of raised surface elements, the method comprising the steps of: applying a first one of said groups of raised surface elements to a substrate, the first group being characterized by a first height or depth and producing a first type of optical and / or electromagnetic effect, and applying a second one of said groups of raised surface elements which are interlaced and / or stacked with the first group, the second group being characterized by a second height or depth which differs from the first height or depth, wherein the second group produces a second type of optical and / or electromagnetic effect different from that produced by the first group.

Preferably, the groups of raised surface elements are formed in a radiation curing material applied to the substrate.

In a particularly preferred embodiment, the first and second groups are formed in a radiation-curing material applied to a substrate.

Preferably, the first type of optical and / or electromagnetic effect is a non-diffractive effect and the second type of optical and / or electromagnetic effect is a diffractive effect with variable optical effect.

In a preferred embodiment, the first type of optical and / or electromagnetic effect consists of one or more of the following effects: reflection, refraction, scattered diffusion, electrical. Advantageously, this substantially reduces or eliminates the optical interference between the optical effects produced by the device, since the diffractive effect is mainly observable in higher diffraction orders whereas the reflection, refraction or scattered scattering effect is observable. only in zero order.

Preferably, a third group of raised surface elements is interwoven and / or stacked with the first and second groups. The raised elements of the third group may be formed in one surface of the raised elements of the first group or the second group. Alternatively, the raised elements of the third group may be interwoven with the raised elements of the first group or the second group.

The first type of optical and / or electromagnetic effect may be a gray level on the optically invariable image. In this embodiment, the grayscale image may be visible in reflection from a first side of the device, and a negative version of the grayscale image visible in transmission from the first side of the device. The gray levels of the grayscale image can be determined by the surface density of the raised elements of the first group in the plane of the device. Alternatively, the gray levels can be determined by the depth of the relief elements of the first group.

[0033] Preferably, the first height or depth is at least five times larger, and more preferably at least ten times greater than the second height or depth.

The height or the minimum depth of the relief elements of the first group is preferably greater than about 5 microns, and the maximum height or depth is preferably less than about 120 microns.

The raised elements of the second group preferably have a height or a maximum depth which is less than about 4 microns. The minimum height or depth of the relief elements of the second group is preferably greater than about 0.1 μm.

By having two groups of relief elements that differ significantly in terms of scale, it is possible to ensure that the optical effects generated by the two groups are visibly distinct.

The raised elements of the second group may be formed at least partially in an upper or lower surface of the relief elements of the first group. In a particularly preferred embodiment, the raised element of the second group is formed in upper surfaces of the raised elements of the first group. This allows, if desired, to preferentially coat the second group, shallower, with a layer of a patterned material, such as a metallic ink, so that the pattern is in perfect adequacy with the second group.

The first and / or the second groups may be metallized. For example, at least some of the relief elements of the second group may be metallized, such that the second group produces a variable optical diffraction effect in reflection, while the first group produces a diffraction or non-diffractive effect in transmission. Alternatively, at least some of the raised elements of the first group and the second group may be metallized so that both effects are observable in reflection.

If a third group of relief elements is present, the third group may alternatively be metallized.

The second group may be metallized in a pattern that forms at least one passive electrical component. Preferably, the second group is metallized in a pattern that forms a passive radio frequency antenna, for example an RFID tag. Another non-optical authentication means may thus be incorporated into the security device.

In another embodiment of the invention, the relief elements in the second group are preferably spaced from each other at a distance that is sufficiently small that the light transmitted or reflected by the second group is polarized. . The separation of the relief elements of the second group is preferably in the range of 100 nm to 300 nm. In this embodiment, the second height or depth is preferably in the range of 5 microns to 10 microns.

The device may further comprise a layer or coating applied to the first and / or second group and, where appropriate, the third group. The layer or coating may be a protective or coating layer. Preferably, the refractive index of the coating layer is different from the refractive index of the material in which the relief elements are formed. If the layer or coating is applied to both groups of relief elements, each of the optical effects may be visible in transmitted light.

Preferably, the first group comprises micro prisms having a lower surface, an upper surface and at least one inclined sidewall. In one embodiment, the first group comprises two or more sets of micro prisms, and each set of micro prisms is characterized by an angle of inclination different from that of the inclined lateral side, whereby the images or different regions of an image can be seen through each set of micro prisms of the variable optical effect device.

The device may comprise an image layer carrying an image composed of two or more interlaced sub-images, with each set of micro prisms displaying one of the sub-images. The interlaced sub-images may be arranged in strips or slats. The image layer is preferably a printed layer.

Each of the micro-prisms can correspond to a pixel of a gray-scale bitmap image, the zone of each micro-prism being linked to the gray level of the corresponding pixel.

The device may further comprise a spacer layer between the first and second group of relief elements. Preferably, the spacer layer has a refractive index which is substantially different from the refractive index of the material in which the relief elements are formed.

In a preferred embodiment, the first group comprises microlenses. Preferably, the device further comprises a micro-printing layer, the micro-printing being visible through the microlenses to produce the first optical effect.

The second group of elements in relief can at least partly take the form of micrographic elements, in which the micro impression is visible through the microlenses from a position on the axis and the micrographic elements are as for them visible through the microlenses from an off-axis position.

The device may further comprise a transparent or translucent substrate. If the relief elements are formed in a radiation curing material applied to the substrate, the radiation curing material is preferably applied by printing.

In a particularly preferred embodiment of the method of the present invention, the first and second groups of relief elements are applied simultaneously.

The method may further comprise the step of applying a second layer of radiation curing material covering the first group of raised elements, so that the second group of raised elements is formed in the second layer. radiation-hardening material. The second layer of radiation-curing material is preferably applied by printing.

In a particularly preferred embodiment, the layer or layers of radiation-curing material are embossed to form the first and second groups of relief elements and the radiation-curing material is substantially cured at the same time as the embossing step. Such an embossing process is described in WO 2008/031170, the contents of which are incorporated herein by reference.

The curing step is preferably carried out by means of actinic radiation, as selected from the group consisting of X-ray irradiation, electron beam and UV radiation.

The method preferably further comprises the step of applying the radiation curing material, for example by a printing process, to a transparent or translucent substrate.

According to a third aspect of the invention, there is provided a security element, comprising the variable optical effect device according to the first aspect, or manufactured according to the second aspect of the invention.

According to a fourth aspect of the invention, there is provided a security document, comprising the security element of the third aspect of the invention.

In a particularly preferred embodiment, the variable optical device is provided in a window or half-window area of the security document.

According to a fifth aspect of the invention, there is provided an embossing tool comprising a plurality of groups of elements in relief or recesses on the surface, the groups being intertwined and / or stacked, in which a first said groups is characterized by a first height or depth and a second of said groups is characterized by a second height or depth which is different from the first height or depth, and wherein when a transparent, translucent or reflective material is embossed by means of the embossing tool, the raised areas obtained with the first group of relief elements produce a first type of optical effect, and the raised areas obtained with the second group of relief elements produce a second type of optical effect different from the first type of optical effect.

The embossing tool may further comprise a third group of raised elements or surface recesses intertwined with the first group or the second group, whereby the embossed areas with the third group produce a third type of optical effect.

According to a sixth aspect of the invention, there is provided a method of creating an embossing tool for applying a plurality of groups of elements in relief to the surface to a transparent, translucent or reflective material, the method comprising the steps of: embossing a first group of raised surface elements on a substrate, the first group being characterized by a first height or depth to produce a first type of optical effect; embossing a second group of raised surface elements on the substrate such that the first and second groups are intertwined and / or stacked, the second group being characterized by a second height or depth which is different from the first height or depth to produce a second type of different optical effect; and a step of electroplating or electroplating a replica of the embossed substrate to form the embossing tool.

If the material is transparent or translucent, it may be a polymer substrate or a radiation-curing transparent material applied to a substrate. The reflective material may comprise a metallized layer applied to a substrate.

In a seventh aspect of the present invention, there is provided an embossing tool manufactured according to the sixth aspect of the invention.

In an eighth aspect, the present invention relates to a method of creating an embossing tool for applying a plurality of groups of raised surface elements to a transparent, translucent or reflective material, the method comprising: a substitution procedure comprising a first group of raised surface elements, the first group being characterized by a first height or depth to produce a first type of optical effect; applying a second group of sacrificial material embossed surface elements to the first group, the second group having a second height or depth that is different from the first height or depth; applying a third group of raised surface elements in an upper surface of the second group of raised surface elements; depositing a metal layer on the first, second and third groups by electrodeposition or electroplating, and remove the sacrificial material.

The sacrificial material may be photoresist. If so, the second group of raised surface elements can be formed by irradiating the photosensitive resin through a mask. The mask may include apertures with a surface density corresponding to gray levels of an input image in grayscale.

Brief description of the figures

Some preferred embodiments of the invention will now be described, with reference to the accompanying drawings in which: <tb> Figs. 1 (A) to 1 (B) and 2 (A) to 2 (C) <SEP> show sectional views through various embodiments of the variable optical device; <tb> fig. 3 <SEP> schematically illustrates the generation of two optically variable effects by the device illustrated in FIG. 2 (C); <tb> figs. 4 (A) and 4 (B) <SEP> show a selective metallization of a group of relief elements in an example of a device with variable optical effect; <tb> figs. 5 (A) to 5 (C) <SEP> illustrate the formation of a variable optical effect device, in which both optical effects are visible in reflection; <tb> fig. <SEP> is a sectional view of a variable optical effect device, including a printed layer; <tb> fig. SEP illustrates one embodiment of the invention in which microlenses are used to produce one of the optical effects; <tb> fig. 8 <SEP> shows a modification of the embodiment of FIG. 7; <tb> fig. 9 <SEP> illustrates the generation of two different different optical effects by the device of FIG. 8; <tb> figs. 10 (A) and 10 (B) <SEP> illustrate embodiments of the invention, including a wire grid polarizer; <tb> figs. 11 (A) and 11 (B) <SEP> show an alternative in which groups of relief elements are stacked to produce a variable optical effect device; <tb> fig. [SEP] shows yet another embodiment with an interlace and stacked arrangement of groups of relief elements; <tb> figs. 13 (A) to 13 (C) and 14 <SEP> schematically represent two preferred embodiments of a method of creating an embossing tool; <tb> fig. <SEP> is a schematic sectional view in a security document incorporating a variable optical effect device according to the invention; <tb> fig. <SEP> shows another embodiment of a method for creating an embossing tool; <tb> fig. <SEP> represents a method of manufacturing a variable optical effect device using the embossing tool of FIG. 16; and <tb> fig. 18 <SEP> shows a person looking at the device of FIG. 17.

Detailed description of the figures

Referring now to FIG. 1 (A), there is shown a variable optical effect device 100 comprising a first group of relief elements in the form of micro prisms 110, shown in section, each having an inclined side wall 112.

A second group of elements in relief is formed by a set of microstructures 120 which are formed in the upper surface of the micro prisms 110, thus forming a composite structure 130 in which two different groups of relief elements having different depths. d and D are intertwined to produce two different variable optical effects.

The depth of the first group is indicated in FIG. 1 (A) by D, and that of the second group by d. D is generally greater than an order of magnitude or more at d, and is preferably in a range from about 5 μm to about 120 μm and more preferably from about 10 μm to about 40 μm.

The depth d is preferably in the range from about 0.1 μm to about 4 μm and more preferably from about 0.2 μm to about 2 μm.

The two groups of relief elements 110, 120 may be formed such that the first group 110 produces mainly a refractive effect, while the second group 120 produces mainly a diffractive effect. The second group may, for example, take the form of a diffraction grating, a hologram or a diffractive optical element (DOE).

The composite structure 130 is formed on a transparent substrate 200, and is such that both the diffractive and refractive effects with variable optical effect can be seen in transmission from each of the faces of the device.

A variable optical refraction effect can be produced by structuring the microphones prisms such that the slopes of the lateral flanks of the micro prisms vary. The first group of relief elements 110 thus constitutes two or more subgroups of relief elements interwoven in the form of micro-prism networks, each network being characterized by a given slope. Each micro-prism array will refract the light in a particular range of angles, so that different regions of an input image would be visible in transmission at different angles of view of the light source or different viewing angles. relative to the normal to the plane of the transparent substrate 200.

Alternatively, an image switch can be created in the transmission, if two groups of intertwined prismatic regions have been made with an opposite slope, with the set of prisms of a group corresponding to a first input image. , and the set of prisms of opposite slope corresponding to a second input image. When the transmitted angle of view or the angle of the light source changes from one side of the normal to the surface to the other, an image switching effect will be observed.

A third type of effect in refractive image transmission mode could be observed if the micro prisms all had the same slope, but varied in the area region region, according to the gray value of the corresponding region of the region. an input grayscale image, such as an image of a human face portrait.

For each of the above three cases of variable refractive optical effects of the image, the overall behavior of the optical device would be a hybrid of a variable optical diffraction effect observed from the collective behavior of the second group of elements. in relief 120 which is formed in the upper surfaces of the micro prisms 110, together with a variable optical refraction effect, both effects being observed in transmission.

The variable optical effect device in the form of a two-level microstructure 130 is formed in a radiation-curing material by an embossing method. For example, a UV-curing clearcoat is first applied to the polymeric substrate 200 by any suitable method, such as a printing process. The varnish can then be embossed hot and under pressure (hot embossing) with a wedge carrying the relief structures 110, 120 and cured by UV radiation to simultaneously form the elements in relief in the varnish.

Alternatively, the relief elements 110,120 can be embossed in the varnish while it is still soft, and then cured by UV radiation while the embossing wedge is still in contact with the varnish (soft embossing) . The embossing and curing steps can be performed substantially simultaneously.

It is also possible to form the structure shown in FIG. 1 (A) in two separate steps. In a first step, the relief elements 110 are formed in the UV-curing lacquer, either by the soft embossing or soft embossing methods described above, using an embossing shim bearing only the first group relief elements 110. A new layer of UV-curing lacquer is then formed on the upper surfaces of the first relief elements 110, and the other layer is then embossed, in relation to the first group of relief elements, with a separate shim bearing only the second raised elements 120.

The device may optionally comprise a protective layer 210, as shown in FIG. 1 (B). The protective layer must have a refractive index which is sufficiently different from that of the radiation-curing material, the protective layer, comprising for example a transparent ink having a high refractive index, so as not to cancel the optically variable effects produced. by the two groups of relief elements.

The main visual difference between the optically variable diffraction and refraction effects generated by this type of device is the appearance of multiple orders and diffraction color effects in the case of diffractive images with a variable optical effect. The refractive images with variable optical effect generated by the intertwined networks of micro prisms will be achromatic in color and only the zero order effect will be active. This means that the images generated by the refractive elements will not interfere or "mix" with the variable optical effect images generated by the diffractive elements. A particular advantage offered by this dual transmission effect is the ability to design variable optical effect images in which the diffractive and refractive elements produce different components of the same variable optical effect image. For example, since the refractive effect is achromatic and occurs only in the zero order, and the diffractive effects are polychromatic and occur only in nonzero orders, it is possible to design images with variable optical effect. in which an achromatic central picture element is surrounded by polychromatic picture elements with the different elements of the composite picture by switching on and off according to whether the viewing angle or the transmission illumination angle is amended.

Referring now to FIGS. 2 (A) to 2 (C), there is shown a modification of the variable optical effect device of FIG. 1. An interleaved two-level microstructure 130 is formed as before (Fig. 2 (A)). The microstructure 130 is then selectively metallized in the diffractive regions 120 with a metal ink 125 using, for example, a rotogravure printing process, which results in the selectively reflective diffraction regions 120 illustrated in FIG. fig. 2 (B). The resulting microstructure is then overprinted with a clear ink or lacquer 135 of refractive index different from the UV cured lacquer (Fig. 2 (C)). The device is then capable of producing a variable optical diffractive effect observable in reflection, and a refractive or diffractive variable optical effect observable in transmission.

Note that in FIG. The different regions are not scaled and there could be a large number of grooves 122 within each metal region 120, depending on the resolution required for the optically variable image component.

For example, for diffractive and refractive images each having a smaller pixel (or image element) of the size of 30 μm, the diffractive elements would each contain from 10 to 50 grooves, depending on the diffraction angle necessary for the diffraction effect.

A ten-groove element would be diffracting at a much smaller angle than an element with fifty grooves. Note that because the primary primary structure (for example used for embossing 2 (A)) is generated by precision micro-fabrication processes, such as electron beam lithography, size and positioning of diffractive elements and individual refractories can be produced with almost unlimited precision - for example up to a fraction of a micron if necessary.

[0085] Referring now to FIG. 3, the two observation modes of the device of FIG. 2 are represented. In the first mode, a diffractive diffractive image 310 with a higher order diffraction maximum corresponding to the angles θ1, θR is observed in reflection from the metallized diffractive regions 120. The variable diffractive optical effect may include image switching, motion effects, portrait effects, and so on. The shape, position and angle of view of the images generated by diffraction of one of the regions 120 depend on the spacings (spatial frequency) and orientation of the grooves in that region.

In the second mode of operation of the device, a refractive variable optical effect can be observed in transmission by looking at a light source 320 placed behind the substrate 200. The second variable optical effect is produced by refraction from the micro-prism gratings. 110 to generate the optically variable image. The shape, location and viewing angle of the refractive images of the regions 110 depend on the angles and orientation of the local micro-prisms in each region.

Due to the fact that each diffractive region 120 and the refractive region 110 is small (generally having a maximum dimension of between about 30 and 60 μm), the different individual optical zones 110, 120 are not noticeable. to the naked eye, and it is the collective behavior of a large number of these elementary regions 110, 120, which contributes to the observed macroscopic images, and which appears to an observer to occupy substantially the same spatial region of the substrate 200 .

In FIG. 4, we see a sketch of the selective metallization process. In fig. (A) a two-level microstructure 130 is printed with a metal ink 125 using a printing plate 400 uniformly coated with the metallic ink at a very shallow depth d, which is approximately equal to or greater than the depth d of the relief structure 120, but much less than the depth D of relief structure 110. Because the deep regions 110 of the microstructure are much deeper than the thickness of the ink on the printing plate, these regions do not take any ink.

Only relatively shallow diffractive regions 120 of the microstructure will accept ink and become reflective (Fig. 3 (B)). The metallized regions 120 are thus automatically related to the second group of relief elements, thus avoiding the known problem with selective metallization process in which there is a lack of precise relationship between the printing process and the preferred regions. of the microstructure that must be metallized. The method described here is therefore much more precise and has a much higher intrinsic resolution because its limits are determined by the accuracy and resolution of the microstructure itself and not by that of the printing process.

The metal layer can be configured by use of a suitable patterned printing plate. In one embodiment, it is possible to create variable optical effect devices with integrated electronic or electromagnetic capability. Examples of such effects include passive RFID antenna responses, wherein the metallized diffractive regions of the variable optical effect device have antenna patterns of the type images that act as conductive tracks, producing a unique electromagnetic return signature in response to an electromagnetic interrogation wave. Since the metallized regions are also diffractive, and therefore can carry optically variable image information, the RFID tag and the optically variable diffractive effect provide a composite security device in which optical and non-optical security features are combined in a single device. The surrounding regions are non-metallized refractive regions or diffuse scattering regions which can further provide an optically variable effect visible in transmission.

Other printed electronic substrate components can also be made by integrating a two-level metallized differential microstructure into a polymer film. For example, the microstructure may be embossed directly into the film under heat and pressure conditions, or formed by gently embossing a polymer precursor and curing the embossed precursor, and then selectively metallizing the microstructure as it has been. has been described above. The back of the film may also have metallized regions printed such that the resulting sandwich structure produces capacitive effects between the upper and lower surfaces of the conductive electrodes. Similarly, the resistive components and patterns can be created using metal inks with variable resistance properties determined by the nature of the constituent particles of the ink.

In FIG. 5, there is shown an alternative embodiment in which the two groups of relief elements are metallized. Beginning again with an interleaved two-level microstructure 130 (Fig. 5 (A)), a much thicker layer of metallic ink 125, having a depth D equal to or greater than the depth D of the deep relief elements 110 , is applied to the printing plate. The two types of relief patterns are then reflective (Fig. 5 (B)) and the hybrid optically variable effect is produced by a combination of reflecting diffractive elements 120 and reflective micro-reflecting elements (micro mirror elements). . A protective layer 136 of an opaque or transparent material may optionally be applied (Fig. 5 (C)).

Referring now to FIG. 6, there is shown an alternating variable optical effect device 600 in which an optically invariable image 610 is printed on one side of the substrate 200 adjacent to a high refractive index film layer 210. By appropriate arrangement or microstructuring of the deep embossed reliefs 110, it can then be shown that the printed information 610 on the backplane of the substrate 200 can be made to appear only at certain viewing angles determined by the shape of the deep phase refractive elements 110. The Differentially metallized diffraction grating regions 120 produce a variable diffractive optical effect image, and refraction and diffuse scattering from the combined refractive effect of the combined printed characteristics 110, 610 produce a second optically variable effect whose color is a function of the colors used in the printed image 610. If the refractive elements 110 are shaped in the form of longitudinal prisms then printed information 610 is in the form of thin strips, the axis of the strip being parallel to the longitudinal axis of micro prisms 110.

When it is observed and illuminated through the transparent polymer film 200 and the UV curable lacquer layer 115, an optically hybrid effect of switching is observed through the interaction of a diffractive optical switch from metallized regions. 120 and a refractive lenticular image switch from the high refractive index transparent regions 110 to the printed background 610. In its simplest form, the printed background 610 may consist of a background uniformly metallized obtained, for example, through printing with metallic inks. Alternatively, the printed layer 610 may consist of variable printed information, in which case the device represents an OVD ultra-high resolution diffractive optically variable diffractive device. In this case, it is not necessary to have a difference in refractive index between the protective film and the lacquer layers, since the different parts of the variable printed information 610 may be observable in the non-metallized regions. 114 when the viewing angle is changed.

In another embodiment of the variable optical effect device according to the present invention, the first group of raised elements may include one or more microlens arrays. Referring to FIG. 7, the deep level microstructures incorporate partially cylindrical or partially spherical refractive lenses 712 adjacent to shallow diffractive elements 722 in the grooved sections 720. Each grooved section 720 has a width preferably of between 30 and 60 μm, the microlenses 712 being dimensioned similarly to the grooved sections 720. The grooved diffraction regions 720 may be coated with a metal layer 725 using the differential metallization printing method described above, or may remain non-metallized.

The microslentilles 712 can be used as magnifying elements for micro text or micro graphics 735 printed on the opposite face 730 of the polymer film 200. The hybrid effect OVD therefore consists of an optically variable effect or a switching effect diffractive due to diffractive regions 720 superimposed on micro text or printed magnified graphics that vary with the angle of the distance variation between the microlenses 712 and the micro text or the micro graphic 735 when the viewing angle is exchange.

In yet another embodiment, illustrated in FIG. 8, at least some of the diffractive regions 721 may be shaped as micrographic elements 723. In this embodiment, the optical magnification of the micrographic elements 723 is observed when viewed through the lenses 712 from a position off-axis 801, in addition to the magnification of the micro text or various micrographic elements 735 seen through the lenses 712 from a position on the axis 802 (Fig 9). It should be noted that the magnification of the off-axis magnification is much greater than that observed from the position on the axis 802 due to the fact that the optical precision is determined solely by the process of creating the microstructure 720, 721, and not by a subsequent micro-printing process on the top layer of the substrate 730, or above the high refractive index (HRI) protective film layer 210.

According to FIG. 9, it can be seen that the magnification of the micro-print 735 occurs on the axis, so that little or no interference should take place between the magnification of the micrographic elements 723 off the axis and the magnification of the elements. printed microphone 735 on the axis.

Other embodiments of the invention are shown schematically in FIGS. 10 (A) and 10 (B), wherein regions of relatively deep relief elements 860 having a high spatial frequency are interleaved with relatively shallow relief regions 850 having a lower spatial frequency. The embossed elements are embossed in, for example, a UV-sensitive lacquer layer 880 applied to the substrate 900, the lacquer then being cured. The two regions 850 and 860 can be coated with metallic ink 855, as shown in FIG. 10 (A). If the spacing between adjacent relief elements in regions 860 is smaller than the wavelength at which the safety device is observed, and in particular of the order of half the wavelength, the light which is incident on regions 860 will be selectively absorbed in one direction so that regions 860 form a polarization structure, sometimes known as a wire grid polarizer.

The 850 regions diffract the incident light and thus produce a variable optical diffraction effect which is visible mainly in first and second diffraction orders.

The device of FIG. 10 (B) is similar to that shown in FIG. (A), except that the diffractive regions 850 remain unmetallized when the thin layer of the metallic ink 855 is applied.

The device of one of FIGS. 10 (A) or 10 (B) is a two-channel variable optical effect device, wherein the first group of raised elements 860 produces a polarization-dependent image which is observed in zero order, while the second group 850 produces an optically variable diffractive image that is observed in the first and second orders of diffractive propagation. Advantageously, an optically variable effect can therefore be observed both under uniformly diffused lighting conditions, in which the normal variable optical effect devices show little or no normal variation, and also under the illumination of normal light sources. finite measurement, conditions in which ordinary diffractive optical devices can be observed.

[0103] In FIG. 11 (A), there is shown another embodiment of the present invention, in which a matrix 920 of micro prism structures having a relatively high surface relief has been stacked on a diffractive structure having a relatively low surface relief 910 for form a combination of bi-level microstructure. In this case the diffraction microstructure 910 is first gently embossed and then is UV-cured on a polymer film 900 and then coated with a high refractive index transparent film 915 using, for example, a rotogravure printing process. A UV-curing lacquer layer 917 is then applied, preferably by printing, to the top of the high refractive index film 915 and then gently embossed with a microstructure of micro-prisms in a 920 matrix and cured. again to UV. Finally, a second high refractive index layer 925 is applied to the top of the micro-prism microstructure in a matrix to protect the matrix of micro prisms. The doubly embossed diffractive and refractive structure shown in FIG. 11 (A) will produce optically variable zero-order refractive effects from the micro prism arrays 920, in combination with diffractive optically variable effects in non-zero diffraction orders from the diffraction grooved matrix 910. The combination diffractive variable optical effect and the refractive variable optical effect is generated from the same area of the multilayer film, which increases the difficulty when an infringer seeks to perform "reverse engineering" and rebuild the device.

[0104] In FIG. 11 (B), there is shown a variant of the two-level microstructure of FIG. 11 (A). In fig. 11 (B) the refractive component comprises pairs of micro prisms, 920, 920 respectively having inclined lateral flanks 922, 922 of opposite slope. An image switching effect is produced in the zero order of the transmitted beam due to the image components of an image refracted from the left inclined pitch micro-prisms 920 and the second image components which are generated by the micro prisms 920 slope inclined right.

Optionally, the diffractive layer 910 may also be designed as a matrix or track structure interleaved with two different spatial frequencies so that the image switching with different illustrations could also be generated from this layer. In this case, the overall effect of the combination of refractive and diffractive layers would be that of a four-channel image switching device, the switches of the inner diffractive image being colored (as a result of the dependence of the wavelength at the diffraction orders), and the external image switches being colorless (or achromatic) that result from the refractive mechanism.

In yet another embodiment, shown in FIG. 12, micro prisms 1120 are also stacked on top of the diffractive regions 1110, but in this case are also interlace with the diffractive regions since the side walls of the prisms 1124 cover non-diffractive regions 1111 which separate the diffractive regions 1110. Those skilled in the art will also appreciate that the set of each micro prism 1120 could cover each of the corresponding non-diffractive regions 1111.

[0107] Referring now to FIGS. 13 and 14, there is shown schematically a method of manufacturing an embossing tool which can be used to form a variable optical effect device according to the present invention.

First, two separate and complementary embossing tools 1210, 1220 are produced (steps 1310, 1320). The respective relief structures are written in a photo-resistant material using electron beam lithography, for example, or by a combination of electron beam lithography and photolithography, depending on the size of the relief structures and therefore the resolution required to produce said structures. Each embossing tool or wedge is then produced by electroforming or electroplating on the respective embossed embossed structures.

A polymeric substrate, for example comprising Perspex, is prepared and is then embossed (under high temperature and pressure conditions) with the first embossing tool 1210 to form the relief structure 110 in the polymer substrate (FIG. 13 (A) and step 1322). A thin layer (eg 2 micron thick) 1215 of UV curing lacquer is then applied (step 1330) to the top of the embossed structure 110 using, for example, a rotogravure printing plate, uniformly coated with the lacquer to produce the structure 1217 shown in FIG. 13 (B). The second relief structure 120 is then obtained by soft embossing (step 1340) in relation to the top of the first microstructure, for example by a nano-printing method, and cured (step 1350) by UV radiation 1250 as shown in FIG. fig. 13 (C). The resulting bi-level microstructure 130 is then formed in the final bi-level embossing tool by an electroforming or electroplating technique (step 1360).

Alternatively, the two-level microstructure 130 could be created in a single step using direct electron beam lithography writing techniques, for example using two-electron beam etching methods. In yet another alternative, the bi-level structure 130 could be created using a thick electron beam embossing method followed by a direct write process for the diffractive relief structure.

In yet another alternative, the bi-level microstructure can be created using the first embossing tool 1210 to form the relief structure 110 in a layer of a UV curing lacquer (step 1325), and the hardening of the lacquer (step 1327). This is followed by a soft embossing, in connection with a thin layer of UV curing varnish applied to the relief structure 110 by the second embossing tool 1220 as before.

[0112] Referring now to FIG. 15, there is shown a cross-section through a portion of a security document, indicated generally at 1400, comprising a security device in the form of a two-level interleaved microstructure 100 substantially as shown in FIG. 2 (C). The security document comprises a transparent substrate 200 on which the security device 100 comprising refractive elements 110 and metallized diffractive relief structures 120 is formed. A material of high refractive index 210 is applied to the microstructure 100. The security document comprises at least one opacifying coating 1410 applied on one or both sides, outside the window areas 1420a 1420b in which the s) opacifying coating (s) 1410 is (are) omitted. An observer looking at the window area 1420b of the security document 1400 will see a combination of a refractive effect due to relief elements 110 and a diffractive effect due to diffractive metallized structures in relief 120.

[0113] Turning now to FIG. 16, there is shown a substrate 1500 in which a first group of raised surface elements 1510 is formed. The raised surface elements 1510 may be embossed directly into the substrate 1500, or the substrate 1500 may be a preformed structure, such as the embossing wedge 1220 shown in FIG. 13.

The substrate 1500 is then coated with a relatively thick layer (for example, 30 microns thick) of photosensitive resin 1520. The photosensitive resin 1520 is then exposed through a mask 1530 having openings 1531 formed at the same time. inside. The radiation source 1525 may be any suitable source for exposing the photoresist 1520, for example, a source of UV radiation.

The exposure step leaves a second group of relief elements in the form of photosensitive resin pillars 1542 which cover the first group of raised surface elements 1510. The vertices of the pillars 1542 are then embossed with a second embossing wedge 1550, which can carry a raised surface structure which is the same as or different from the embossed surface structure 1510 carried by the substrate or the embossing wedge 1510. This step leaves photoresist embossed pillars 1552 having a third group of raised surface elements 1543 formed in their upper surface.

The photosensitive resin is then made passive by coating with a metal layer 1560, for example a nickel coating which is sprayed on the photoresist. This is followed by electrodeposition of a thick layer of nickel, after which the photosensitive resin is dissolved to keep the composite embossing wedge 1600. The embossing wedge 1600 comprises a first group 1601, a second group 1602, and a third group 1603 of relief surface structures.

[0117] FIG. 17 shows the manufacture of a variable optical effect device using the wedge 1600 of FIG. 16. The shim 1600 is brought into contact with the embossing support 1710 (e.g., embossable and radiation curing ink) to create the groups of the first, second and third embossed surface structures 1701, 1702 and 1703. A cylinder of Printing with a thin layer of metal ink 1710 is then brought into contact with the tops of the pillars 1702 to create metallized relief surface structures 1713 which can be observed in reflection. The raised surface structures are then coated with a transparent lacquer 1720 having a refractive index different from that of the embossable support 1710.

In use, as illustrated in FIG. 18, a person 1800 looking at the device 1700 from a first side 1810 will see a variable optical effect image from the metallized regions 1713 of the device 1700. If the light source 1805 is placed on the opposite side 1820 of the first side 1810, the observer 1800 sees in transmission a second variable optical effect image from the regions 1701 of the device 1700.

In the embodiments shown in FIGS. 16 to 18, the apertures 1531 of the photomask 1520 may advantageously be arranged to have a surface density corresponding to the gray levels of an input image in gray levels. The observer 1800 will then see in reflection a grayscale image (for example, a raster portrait), corresponding to the configuration of the second group of relief surface elements 1702, while, in transmission, a negative version of the image. grayscale image will appear to observer 1800.

It is understood that for a qualified person, many combinations, variations and modifications of the methods and devices presented above are possible using the information disclosed in this application, without departing from the spirit and scope of the invention as defined in the appended claims. For example, the security document shown in FIG. It may have an impression or other elements comprising additional security features applied to one or other of the opacifying coatings. The coating on the upper surface can be applied over the entire surface of the security document, so that omitted region 1420b forms a half-window area. In addition, the security document of FIG. 15 may include any of the different types of security device described herein.

Claims (56)

A variable optical effect device (100, 600), comprising a transparent, translucent or reflecting substrate comprising a plurality of groups of raised surface elements (1601, 1602, 1701, 1702), the groups being interwoven and / or in which a first one of said groups (1601, 1701) is characterized by a first height and produces a first type of optical and / or electromagnetic effect, and a second one of said groups (1602, 1702) is characterized by a second height which is different from the first height, the second group (1602, 1702) producing a second type of optical and / or electromagnetic effect different from that produced by the first group (1601, 1701). The variable optical effect device (100, 600) according to claim 1, wherein the plurality of groups of raised surface elements (1601, 1602, 1701, 1702) are formed in a radiation-curing material applied to the substrate. (200, 900, 1500). The variable optical effect device (100, 600) according to claim 2, wherein the radiation-curing material is applied to the substrate (200, 900, 1500) by printing. 4. Variable optical effect device (100, 600) according to one of claims 1 to 3, wherein the first type of optical and / or electromagnetic effect is a non-diffractive effect and the second type of optical effect and / or electromagnetic is a diffractive optical effect variable. The variable optical effect device (100, 600) according to claim 4, wherein the first type of optical and / or electromagnetic effect is one or more of one of the following effects: reflection, refraction, diffuse scattering. The variable optical effect device (100, 600) according to one of claims 1 to 5, wherein a third group of raised surface elements (1603, 1703) is interwoven and / or stacked with the first and / or or second groups (1601, 1701, 1602, 1702). The variable optical effect device (100, 600) according to claim 6, wherein the raised surface elements of the third group (1603, 1703) are formed in a surface of the raised surface elements of the first group (1601, 1701) or the second group (1602, 1702). The variable optical effect device (100, 600) according to one of claims 4 to 7, wherein the elements of the first group of surface elements are arranged to produce an optically variable greyscale image (310). The variable optical effect device (100, 600) according to claim 8, wherein the grayscale image (310) is visible in reflection from a first side (1810) of the device (100, 600). , and a negative version of the grayscale image (310) is visible in transmission from the first side (1810) of the device (100, 600). The variable optical effect device (100, 600) according to claim 8 or claim 9, wherein the gray levels of the greyscale image (310) are determined by the surface density of the surface elements by relief of the first group (1601, 1701) in a plane of the device (100, 600). The variable optical effect device (100, 600) according to one of claims 8 to 10, wherein the gray levels of the gray scale image (310) are determined by the height of the raised surface elements. of the first group (1601, 1701). 12. Variable optical effect device (100, 600) according to one of claims 1 to 11, wherein the first height is at least five times greater than the second height. The variable optical effect device (100, 600) according to claim 12, wherein the first height is at least ten times greater than the second height. The variable optical effect device (100, 600) according to one of the preceding claims, wherein the height of the raised surface elements of the first group (1601, 1701) is greater than about 5 μm. 15. Variable optical effect device (100, 600) according to one of the preceding claims, wherein the height of the raised surface elements of the first group (1601, 1701) is less than about 120 microns. 16. Variable optical effect device (100, 600) according to one of the preceding claims, wherein the height of the raised surface elements of the second group (1602, 1702) is less than about 4 microns. The variable optical effect device (100, 600) according to one of the preceding claims, wherein the height of the raised surface elements of the second group (1602, 1702) is greater than about 0.1 μm. The variable optical effect device (100, 600) according to one of the preceding claims, wherein the raised surface elements of the second group (1602, 1702) are at least partially formed in an upper or lower surface of the elements of relief surface of the first group (1601, 1701). The variable optical effect device (100, 600) according to one of the preceding claims, wherein a layer or a coating is applied to the first group and / or to the second group of relief elements (1601, 1701; 1602, 1702), and / or, where appropriate, the third group of relief elements (1603, 1703). The variable optical effect device (100, 600) according to claim 19, wherein the layer or coating comprises a reflective metal layer (725, 1560). The variable optical effect device (100, 600) according to claim 20, wherein the reflective metal layer (725, 1560) has a thickness which is equal to or greater than the maximum height of the raised surface elements of the second group ( 1602, 1702), but less than the minimum height of the raised surface elements of the first group (1601, 1701) and in which only the second group (1602, 1702) is made reflective. The variable optical effect device (100, 600) according to claim 20 or claim 21, wherein the reflective metal layer (725, 1560) is applied in a pattern. The variable optical effect device (100, 600) according to claim 22, wherein the pattern forms at least one passive electrical component. The variable optical effect device (100, 600) of claim 22, wherein the pattern forms a passive radio frequency antenna. The variable optical effect device (100,600) of claim 24, wherein the passive radio frequency antenna is part of an RFID tag. The variable optical effect device (100, 600) according to one of claims 20 to 22, wherein the raised surface elements in the second group (1602, 1702) are spaced apart from one another by a distance of is small enough that the light transmitted or reflected by the second group (1602, 1702) is polarized. The variable optical effect device (100, 600) according to one of claims 19 to 26, wherein the layer or coating is a protective coating (136, 210). 28. Variable optical effect device (100, 600) according to one of claims 19 to 27, wherein the refractive index of the layer or coating is different from the refractive index of the material in which the plurality of groups relief surface elements (1601, 1602, 1603, 1701, 1702, 1703) are formed. 29. A variable optical effect device (100, 600) according to one of the preceding claims, wherein the first group of relief elements (1601, 1701) comprises micro prisms (110, 1120) having a lower surface, a upper surface and at least one inclined lateral flank (112). The variable optical effect device (100, 600) according to claim 29, wherein the first group (1601, 1701) comprises two or more sets of micro prisms (110, 1120), and each set of micro prisms (110, 1120) is characterized by a different inclination angle of the lateral flank (112), whereby different images or regions of an image can be viewed through each set of micro-prisms (110, 1120) of the effect device variable optics (100, 600). The variable optical effect device (100, 600) according to claim 30, wherein the device (100, 600) comprises an image layer (310, 610) carrying an image composed of two or more interlaced sub-images, and each set of micro prisms (110, 1120) sees one of the sub-images. The variable optical effect device (100, 600) according to claim 31, wherein the interlaced sub-images are arranged in strips or lamellae. The variable optical effect device (100, 600) according to claim 31 or claim 32, wherein the image layer (310, 610) is a printed layer. The variable optical effect device (100, 600) according to one of claims 29 to 31, wherein each micro-prism (110, 1120) corresponds to a pixel of a gray-scale bitmap and the region of each micro prism (110, 1120) is related to the gray level of the corresponding pixel. The variable optical effect device (100, 600) according to one of the preceding claims, wherein a spacer layer is applied between the first and second groups of relief elements (1610, 1602, 1701, 1702). The variable optical effect device (100, 600) according to claim 35, wherein the spacer layer has a refractive index which is different from the refractive index of the material in which the raised surface elements are formed. . 37. The variable optical effect device (100, 600) according to one of claims 1 to 28, 35 or 36, wherein the first group of raised surface elements (1601, 1701) comprises microlenses (712). 38. A variable optical effect device (100, 600) according to claim 37, further comprising a micro-printing layer (735) (100, 600), and the micro-printing layer (735) is visible through the microlenses (712). ) to produce a first type of optical effect. 39. A variable optical effect device (100, 600) according to claim 38, wherein one or more regions of micrographic elements is or are applied in the context of the second group (1602, 1702), whereby the micro-printing ( 735) is visible through the microlenses from a position on an axis (802) and the region or regions of the micrographic elements is or is visible through the microlenses from an off-axis position (801). 40. Security document (1400), comprising a variable optical effect device (100, 600) according to one of claims 1 to 39. 41. The security document (1400) of claim 40, wherein the variable optical effect device is provided in a window or half-window of an area of the document (1400). A method of producing a variable optical effect device (100, 600) comprising a plurality of raised surface element groups (1601, 1602, 1701, 1702), the method comprising the steps of: forming a first group of said raised surface elements (1601, 1701) on a transparent, translucent or reflective substrate (200, 900, 1500) by an embossing process, the first group (1601, 1701) being characterized by a first height and producing a first type of optical and / or electromagnetic effect, and forming a second group of said raised surface elements (1602, 1702) by an embossing process, said second group of raised surface elements (1602, 1702) being intertwined and / or stacked with the first group (1601, 1701), the second group (1602, 1702) being characterized by a second height which is different from the first height, wherein the second group (1602, 1702) produces a second type of optical and / or electromagnetic effect different from that produced by the first group (1601, 1701). The method of claim 42, wherein the first and second groups of raised surface elements (1601, 1602, 1701, 1702) and, if appropriate, the third group (1603, 1703) are applied simultaneously. The method of one of claims 42 to 43, further comprising the step of applying a layer of radiation curing material overlying the first group of raised surface elements (1601, 1701) so that the second group of raised surface elements (1602, 1702) is formed in the layer of radiation-curing material. The method of claim 44, wherein the layer of radiation curing material is applied by printing. The method according to one of claims 44 to 45, wherein the layer of radiation-curing material is embossed to form the first and second groups of raised surface elements (1601, 1602, 1701, 1702) and the material. radiation curing is cured substantially at the same time as the embossing step. 47. The method according to one of claims 44 to 46, wherein the radiation-curing material is cured by actinic radiation. 48. The method of claim 47, wherein the actinic radiation is selected from the group consisting of X-rays, an electron beam, and ultraviolet UV radiation (1250). 49. An embossing tool (1210) having a plurality of groups of raised surface elements or recesses (1601, 1602, 1701, 1702), the groups being intertwined and / or stacked, wherein a first one of said groups ( 1601, 1701) is characterized by a first height and a second of said groups is characterized by a second height which is different from the first height, so that when a transparent, translucent or reflective material is embossed with the embossing tool (1210), the zones embossed with the first group of relief elements (1601, 1701) produce a first type of optical and / or electromagnetic effect and the embossed areas embossed with the second group of relief surface elements ( 1602, 1702) produce a second type of different optical and / or electromagnetic effect. The embossing tool of claim 49, further comprising a third group of raised surface elements or recesses (1603, 1703) interwoven with the first group or with the second group (1601, 1602, 1701, 1702). ), in which embossed areas embossed with the third group (1603, 1703) produce a third type of optical effect. A method of manufacturing an embossing tool (1210) according to one of claims 49 or 50 for applying a plurality of groups of relief surface elements (1601, 1602, 1701, 1702) to a transparent substrate. , translucent or reflective, the method comprising the steps of: embossing a first group of raised surface elements (1601, 1701) on a substrate (900, 1500), the first group being characterized by a first height to produce a first type of optical effect; embossing a second group of raised surface elements (1601, 1701) on the substrate (200, 900, 1500) so that the first and second groups (1601, 1602, 1701, 1702) are intertwined and / or stacked the second group (1602, 1702) being characterized by a second height which is different from the first height to produce a second type of optical effect different from the first type produced by the first group; and electroplating or electroplating a replica of the embossed substrate (200, 900, 1500) to form the embossing tool (1210). 52. The method of claim 51, wherein the first group of raised surface elements (1601, 1701) is embossed directly into the substrate (200, 900, 1500). A method of manufacturing an embossing tool according to one of claims 49 or 50 for applying a plurality of groups of relief surface elements (1601, 1602, 1701, 1702) to a transparent, translucent material or reflecting, the method comprising the steps of: providing a substrate (200, 900, 1500) comprising a first group of raised surface elements (1601, 1701), the first group characterized by a first height to produce a first type of optical effect; depositing a sacrificial material on the first group (1601, 1701); forming a second group of raised surface elements (1602, 1702) on the sacrificial material, the second group (1602, 1702) having a second height which is different from the first height; forming a third group of surface relief surface elements (1603, 1703) at an upper surface of the second group of raised surface elements (1602, 1702); depositing by electrodeposition or electroplating a metal layer (725, 1560) on the first, second and third groups (1601, 1602, 1603, 1701, 1702, 1703); and remove the rest of the sacrificial material. The method of claim 53, wherein the sacrificial material is a photoresist (1520). The method of claim 54, wherein the second group of raised surface elements (1602, 1702) is formed by irradiating the photosensitive resin (1520) through a mask (1530). The method of claim 55, wherein the mask (1530) comprises apertures (1531) having a greyscale surface density of a grayscale input image.