EP4729303A1

EP4729303A1 - Laminated micro-optical structures

Info

Publication number: EP4729303A1
Application number: EP24306744.4A
Authority: EP
Inventors: Nicolas KOUTROS; Georgios Tziovaras; Daniel HENTSCHEL; Deivaraj THEIVANAYAGAM; Henri Rosset; Marine GEAUGEY; Philippe Dietemann
Original assignee: Covestro Deutschland AG; Oberthur Fiduciaire SAS; Rolling Optics Innovation AB
Current assignee: Covestro Deutschland AG; Oberthur Fiduciaire SAS; Rolling Optics Innovation AB
Priority date: 2024-10-18
Filing date: 2024-10-18
Publication date: 2026-04-22
Also published as: WO2026082950A1

Abstract

An item (1000) comprising a front face (ff 1000), and a back face (bf1000) and:- A first layer (200), the first layer (200) being at least partly transparent and being made of polycarbonate,- A multilayered structure (500), the multilayered structure (500) being at least partly transparent and including a layer (510) comprising microlenses, and a layer (530) comprising image icons.- A filler material (540), the filler material (540) being transparent and embedding the microlenses, the filler material (540), the microlenses and the image icons cooperating to generate at least one synthetic image visible when observing the front face (ff 1000),- A second layer (700) of polycarbonate,- A first adhesive (300) between the first layer (200) and the multilayered structure (500), said first adhesive (300) being transparent,- A second (layer of) adhesive (600) between the multilayered structure (500) and the second layer (700).

Description

Background

The invention concerns an item comprising microlenses and image icons cooperating to generate at least one synthetic image visible when observing the item, as known from the application published under number WO2011163298 . The synthetic image is for example different depending on the angle between the view direction and the front face of said item.
There is a need for articles comprising such microlenses and such image icons, that would be durable and simple to manufacture and forgery-proof.

Item

The present invention addresses this issue by providing an item (in other words: a flat item, flat means, for example, not thicker than 5 mm) comprising a front face, and a back face opposite to the front face, and sealed together (or in other words: bonded together):

A first layer, the first layer being at least partly transparent and being made of polycarbonate,
A multilayered structure, the multilayered structure being at least partly transparent and including (in other words: comprising) a layer comprising microlenses, and a layer comprising image icons (in other words: micro-images).
A filler material between the microlenses and the fist layer, the filler material being at least partly transparent, embedding the microlenses and forming a planar surface between the layer comprising the microlenses and the first layer, the filler material, the microlenses and the image icons cooperating to generate at least one synthetic image visible when observing (under visible spectrum light, by reflection or transmission, without any optical instrument and/or with a full visual acuity) the front face, (i.e.: said synthetic image being different depending on the angle between the view direction and the front face),
A second layer, the second layer being made of polycarbonate (transparent, translucent or opaque),
A first (layer of) adhesive between the first layer and the multilayered structure (i.e.: sealing the first layer to the multilayered structure), said first adhesive being (at least partly) transparent,
A second (layer of) adhesive between the multilayered structure and the second layer (i.e.: sealing the second layer to the multilayered structure).

Image icons are for example any kind of visual-contrasting patterns forming synthetic optical images when viewed through a layer of microlenses.
The item is thus resistant to wear and delamination. The optical effect provided by the cooperation of the microlenses and the image icons is preserved during the production of the item, by lamination. Indeed, the first adhesive and the second adhesive allow a lamination and a sealing at a relatively low pressure and/or at relatively low temperature which preserves the microlenses and/or image icons during lamination. The lamination is preferably performed at a temperature in a range of ≥ 80 °C to ≤ 220 °C, preferably of ≥ 100 °C to ≤ 180 °C and a pressure of ≥ 2 N/cm² to ≤ 400 N/cm², preferably of ≥ 10 N/cm² to ≤ 300 N/cm² (°C meaning degree Celsius).
The first and/or second adhesive is, for example, selected from the group consisting of an acrylic adhesive, a polyurethane adhesive, a silicon adhesive or a mixture of at least two thereof.
The above layers and the material is, for example, a polymer or consists of at least one polymer.
The item comprises, for example, further layers, in addition to the first layer, the multilayered structure, and the second layer, such as a protective layer covering the front face and the back face of the item or an ink layer.
In an embodiment, the image icons are visible when observing (especially under visible spectrum light, by reflection or transmission, without any optical instrument and/or with a full visual acuity) the front face through the first layer, the first adhesive, the filler material and the layer comprising the microlenses.
The image icons are, for example, visible when observing (especially under visible spectrum light, by reflection or transmission, without any optical instrument and/or with a full visual acuity) the back face through the second layer, and the second adhesive.
In an embodiment, the multilayered structure comprises the filler material, the first adhesive being between the first layer and the filler material, sealing the first layer to the filler material.
As an alternative, the first adhesive is, for example, the filler material. In this case the first adhesive and the filler material are the same material, in particular forming a single layer.
For example, a layer is understood as a solid material of an homogenous composition laid across a direction parallel to the front face and/or to the back face and within the security item.
For example, a layer comprises one or several holes within the material or not.
For example, before to be assembled (in other words: sealed) within the security item, a layer stands alone or is carried by another layer or/and embedded within another layer.
Before to be assembled (in other words: sealed) within the security item, the layer is, for example, solid or liquid. If the layer is a liquid, it comprises, for example, an ink.
For example, a transparent layer or a transparent adhesive or a transparent structure or a transparent item means that respectively the layer or adhesive or structure or item allows light, within the visible spectrum, to pass through and allows objects to be distinctly distinguished respectively through the layer or adhesive or structure or item, for example without any optical instrument and/or with a full visual acuity, and/or with transmitted or reflected light. For example, the material of all layers is translucent or transparent. By transparent it is understood that the material of each layer has a transparency in visible light, from 420 to 780 nm, over the entire spectral range of at least 70 %, for example at least 80 %, for example at least 90 %. For example, the item is translucent or transparent at least in some portions, for example the whole item is transparent. In an embodiment, the item has a transparency in visible light, from 420 to 780 nm, over the entire spectral range of at least 70 %, for example at least 80 %, for example at least 90 % at least in some regions.
The term "Element" is hereafter used to describe a layer or an adhesive or a structure or an item.
In some embodiments, some opaque ink or element covers a transparent layer or is embedded within a transparent element.
For example, the layer comprising the microlenses comprises (or is made of) an ultraviolet curable resin.
For example, the filler material comprises (or is made of) an ultraviolet curable resin or an adhesive.
A transparent element is, for example, colored or not.
For example, an at least partly transparent element means that the layer includes at least a transparent portion and for example also an opaque portion. An at least partly transparent element is, for example, fully transparent.
If a layer of the item comprises a first transparent portion and a first opaque portion, at least another layer, for example all other layers, of the item comprises, for example, a further transparent portion aligned with the first transparent portion. For example, the at least one other layer, preferably all other layer comprise a further opaque portion aligned with the first opaque portion.
Some embodiments of a multilayered structure comprising the filler material are, for example, disclosed in patent application WO2011163298 .
For example, the multilayered structure comprises an at least partly transparent central layer, for example comprising polyethylene terephthalate, which is preferably positioned between the layer comprising the microlenses and the layer comprising the image icons.
For example, the layer comprising the images icons is made of an opaque material, for example an ink (or, alternatively, holographic structures, deposited metal, photo-chromatic projections, laser engravings, UV curable resins with refractive index differences, or diffractive features) for example of a thickness from 1 to 5 micrometers, laid on a surface of the multilayered structure, for example, on a layer, for example in polyethylene terephthalate, for example on a surface of the least partly transparent central layer, or embedded within a layer of the multilayered structure, for example within the second adhesive or the at least partly transparent central layer, forming some patterns whose smallest dimension in a direction d1 parallel to the front face or to the back side is, for example, between 1 and 5 micrometers.
For example, the layer comprising the microlenses and the filler material have different refractive indexes.
For example, the microlenses are concave or convex, and/or have a width of 3 to 30 micrometers, and/or are Fresnel lenses.
For example, the refractive index of the layer comprising the microlenses is higher than the refractive index of the filler material, in case of convex microlenses. In case of concave microlenses, for example, on the contrary, the refractive index of the layer comprising microlenses is lower than the refractive index of the filler material.
For example, the layer comprising the image icons is in a focal plane of the microlenses (i.e. each of the microlenses having the said focal plane). Alternatively, for example, the layer comprising the image icons is positioned at a distance d relative to the layer comprising the microlenses, such that a limited part of the image icons becomes visible when the layer comprising the image icons is viewed through the microlenses, for example, the distance between the microlenses and the image icons is between 60% and 100%, in particular between 60% and 70%, of the focal length of the microlenses.
In an embodiment, the item comprises, for example, a third layer between the first layer and the multilayered structure. In a further embodiment of the item, the item comprises a fourth layer between the multilayered structure and the second layer, for example when the second layer is transparent. For example, the third layer and/or the fourth layer comprises an opaque continuous part, for example, deposited by printing, for example on the first layer on a face opposite to front face. Alternatively, it is a polymeric layer having a transparent window within the opaque continuous part.
In an embodiment, the item is transparent when observing, for example under visible spectrum light, by reflection or transmission, without any optical instrument and or a full visual acuity, through 80% (or 90%) of the area of the front face or/and the back face.
In an embodiment of the item, the microlenses extend over all, preferably over at least 60% of the item, i.e. extend between the entire front face and the entire back face. In another embodiment of the item, the image icons extend over all, (or at least 60% of) the item (in other words extend between the entire front face and the entire back face). For example, the first layer and the second layer have a thickness in a range of from 10 and 50 micrometers, for example between 20 and 40 micrometers. Preferably, the item has a thickness in a range of from 50 to 500 micrometers.
In an embodiment, the first layer, the multilayered structure and the second layer extends over all the item, i.e. between the entire front face and the entire back face.
For example, the microlenses extend over all the multilayered structure or only over a part of the multilayered structure. For example, the image icons extend over all the multilayered structure or only over a part of the multilayered structure.
In an embodiment, the multilayered structure constitutes an insert in an intermediate layer between the first layer and second layer.
In an embodiment, the item is a security item, for example a security document.
As an alternative, the item is, for example, a decorative item for example a gift wrap or an art paper.
For example, the security item is a security device or a security document.
For example, a security document is a mean of payment, for example a bank note, whether made of paper, polymer or their mixtures, a check, a payment card or a restaurant voucher, an identity document such as an identity card, a visa, a passport, a driving license, a lottery ticket, a transport ticket or card, or even an entry ticket to a cultural or sporting event, but also a packaging material for overpackaging, a luxury packaging material and/or a brand protection material.
As an example, the security document has the "ID-1" format according to "ISO 7816" standard or the "TD3" format according to the ICAO (Doc 9303, Part 4).
For example, the security device is a device intended to be integrated into a security document. For example, the security device is an insert, a layer, a patch, a page, for example, intended to be integrated into a passport.
For example, the security item comprises one or more additional, conventional security features, for example, in addition to the personalization data below and/or to the multilayered structure.
Among these additional security features, some are detectable by eye, in daylight or artificial light, without the use of a particular device. These security features include, for example, colored fibers or planchettes, totally or partially printed or metallized security threads, a secure knitted structure, a security film, a watermark, an optically variable device (known as "OVD"), in particular a hologram. These security features are called first-level features.
Other types of additional security features are detectable only using a relatively simple device, such as a lamp emitting in the ultraviolet (UV) or infrared (IR) range. These security features include, for example, fibers, planchettes, strips, threads or particles. For example, these security features are or are not visible to the naked eye, being for example luminescent under the illumination of a Wood lamp emitting in a wavelength of 365 nm. These security features are called second level features.
Other types of additional security features require a more sophisticated detection device for their detection. These security features are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. Automatic detection of the signal makes it possible to authenticate, where appropriate, the document. These security features comprise for example tracers in the form of active materials, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security features are called third level features.
The additional security feature(s), if present within the security item according to the invention, for example, in addition to the personalization data below and/or to the multilayered structure, is(are), for example, a first and/or a second and/or a third level feature(s).
In an embodiment, the adhesive strength between layers of the multilayered structure is lower than the adhesive strength provided by the first adhesive, for example between the first layer and the multilayered structure. The adhesive strength provided by the second adhesive, for example between the second layer and the multilayered structure is, for example, similar to or lower than the adhesive strength of the first adhesive.
In this embodiment, an attempt to delaminate the security item to remove the multilayered structure and reuse it within another item would result into a destruction, or at least an alteration, of the multilayered structure, thus leading to the destruction, or at least alteration, of the synthetic image. This prevents that a forger delaminates the multilayered structure to reuse it in another item. As the multilayer structure is very difficult to reproduce by a forger the delamination of the multilayer structure would be the only way to produce a manipulated security document.
In a preferred embodiment, the security item comprises a markable layer for example between the front face and the multilayered structure, the markable layer being markable by a beam of an infrared laser. The markable layer is for example the first layer.
Such layers are well known in the industry, they are for example made of a polymer material absorbing sufficient energy from the laser beam to burn where exposed by the laser. For example, the item comprises further additives to facilitate laser marking.
In an embodiment, the security item comprises personalization data marked by a beam of an infrared laser within the markable layer.
As an alternative or in addition, the security item comprises, for example, personalization data marked by a beam of an infrared laser within another layer and/or said another layer is, for example, markable by a beam of an infrared laser between the multilayered structure and the back face.
In general, the item is, for example, printed, with for example personalization data, for example, by a beam of an infrared laser or by an ink printer, or not printed.
For example, the personalization data is an information about the holder of card, for example name, address, birthdate, and/or photograph of the holder.
For example, at least a part of the image icons constitutes a background of the personalization data when the front face is observed or an image icon among the image icons is hidden by the personalization data when the front face is observed.
In an embodiment, the security item comprises a blocking material between the first layer and the multilayered structure, said blocking material absorbing light from a laser. For example, the blocking material is made of a material opaque to infrared wavelengths or is a layer comprising infrared blocking particles. Preferably, TiO₂ is used to produce white opaque layers or carbon black is used to produce black opaque layers.
In an embodiment, said blocking material is the first adhesive.
Alternatively, the blocking material is, for example, part of another layer of the security item.
Surprisingly the item according to the invention is compatible with personalization, for example with laser marking. It means for example that personalization, in particular laser marking, of the item do not alter the multilayered structure. Therefore the synthetic image is also not altered.
The invention also relates to a method of manufacturing the item comprising the following steps:

Preparation of a first sheet comprising the first layer, and
Preparation of a second sheet comprising the filler material and the multilayered structure comprising the layer comprising the microlenses and the layer comprising the images icons, and
Preparation of a third sheet comprising the second layer,
Then, lamination of (at least) the first sheet with the second sheet and the third sheet to obtain a lamina, the first adhesive being interposed, prior to the lamination, between the first sheet and the second sheet, and the second adhesive being interposed between the second sheet and the third sheet, prior to the lamination.

Optionally, the method comprises a further step, after the lamination step, of cutting the lamina to get the desired format for the item, for example when the item has, for example, the ID-1 format as mentioned before.
For example, in case the multilayered structure constitutes an insert in an intermediate layer between the first layer and second layer, the second sheet comprises the intermediate layer, and the step of preparation of the second sheet comprises a step of creating a hole in the intermediate layer and a step of inserting the multilayered structure into said hole.
In an embodiment, the second sheet has a thickness of between 10 and 50 micrometers, for example between 20 and 40 micrometers.
Such a thickness allows a symmetrical and thin structure of the security item, comprising layers, e.g. the first layer and/or the second layer, thick enough to be printed by laser.
The invention also relates to a method of personalizing the item comprising a step of marking, into said markable layer, the personalization data, using a beam of an infrared laser.
As an alternative or in addition, the method of personalizing the item comprises, for example, a step of marking said personalization data within another layer, using a beam of an infrared laser.
More generally, the method of personalizing comprises, for example, a step of printing or engraving the item with personalization data, for example by a beam of an infrared laser or by an ink printer.
Although they are not detailed here, the advantages and characteristics of the manufacturing and personalizing methods are identical mutatis mutandis to those of the above item.

Brief description of the drawings

The invention can be better understood on reading the following detailed description of nonlimiting examples, and on examining the appended drawings, in which:

[Fig 1] illustrates an item according to a first embodiment of the invention;
[Fig 2] depicts an item according to a second embodiment of the invention;
[Fig 3] represents the manufacturing steps and the personalizing step of the item in Figure 1 and the item in Figure 2.

Detailed description

Figure 1 shows the identity card 1000 that has a front face ff 1000 and a back face bf1000. The identity card 1000 has an "ID-1" format according to the "ISO 7816" standard.
The identify card 1000 comprise:

A layer 200, fully transparent, for example more than 90 % transparency, and made of polycarbonate,
A multilayered structure 500 including a layer 510 comprising microlenses, a layer 530 comprising image icons, a transparent layer 520 for example in polyethylene terephthalate and a material 540,
A layer 700 fully transparent, for example more than 90 % transparency, and made of polycarbonate,
An adhesive 300 sealing the layer 200 to the multilayered structure 500,
An adhesive 600 sealing the layer 700 to the multilayered structure 500,
The protective layers 100 and 110.

The material 540 is a transparent material embedding the microlenses and forming a planar surface S540 between the layer 510 and the layer 200.
The layer 200 and the layer 700 are markable by a beam of an infrared laser. Personalization data m200 of the holder of the identity card, such as name, address, birthdate, and/or photograph of the holder, is marked by a beam of an infrared laser within the layer 200. Similarly, personalization data m700 of the holder of the identity card is marked within the layer 700.
At least a part of the image icons constitutes a background of the personalization data m200 when the front face ff 1000 is observed.
The adhesive 300 is transparent within the visible spectrum but being opaque with the infrared spectrum to protect the multilayered structure 500 when personalization data is marked by a beam of an infrared laser within the layer 200.
In a way well known by a person skilled in the art, the microlenses and the image icons cooperate to generate at least one synthetic image visible when observing the front face ff 1000, said synthetic image being different depending on an angle A1000 between a view direction and the front face ff 1000.
The layer 200, the multilayered structure 500, and the layer 700 are sealed together by lamination.
The layer 530 comprising the images icons is, for example, made of an ink, laid on a surface of the transparent layer 520, forming some patterns whose smallest dimension in a direction d1 parallel to the front face ff 1000 is 2 micrometers.
The microlenses of layer 510 are convex and have a width of 5 micrometers. The refractive index of the layer 510 is lower than the index of the material 540. The image icons is substantially in a focal plane fp530 of the microlenses.
For example, the item contains a layer 400 and a layer 410, both comprising an opaque continuous part, deposited by printing respectively on the layer 200 and layer 700 and a transparent window within the opaque continuous part.
Alternatively, the layer 400 and the layer 410 are not present. The identity card is then transparent.
For example, the identity card 100 comprises, in addition, an hologram 800.
In one embodiment, the adhesive strength between layers of the multilayered structure 500 is lower than the adhesive strength provided by the adhesive 300 between the layer 200 and the multilayered structure 500 and provided by adhesive 600 between the layer 700 the multilayered structure 500.
Figure 2 shows an identity card 1000' according to a second embodiment of the invention. Figure 2, except for the layer 900', the references with a « ' » at the end designate components similar to those of figure 1 with the same reference without the « ' » at the end.
However, in figure 2, instead of extending all over identity card 1000' as in figure 1 for the identity card 1000, the multilayered structure 500' constitutes an insert in a layer 900' between the first layer 200' and second layer 700'.
The identity card 1000' is transparent when observing through 85% of the surface (in other word : of the area) of the front face ff1000'.
In reference to the figure 3, for the manufacturing of the identity card 1000, at the step S00, a first sheet comprising the layer 100 is prepared (for example, it is cut from a larger sheet commercially available).
At step S10, a second sheet comprising the filler material 540 and the multilayered structure 500 is prepared.
The second sheet has a thickness of 30 micrometers.
A step S20, a third sheet comprising the layer 700 is prepared (for example, it is cut from a larger sheet commercially available).
At step S30, the first sheet, the second sheet and the third sheet are laminated together to produce a lamina.
At step S30, prior to this lamination, the adhesive 300 is interposed, between the first sheet and the second sheet, and the adhesive 600 is interposed between the second sheet and the third sheet.
At step S40, the lamina is cut into ID-1 format cards.
At step S50, using a beam of an infrared laser, the personalization data m200 is marked into layer 100 and the personalization data m700 is marked into layer 700.
The identity card 1000' is produced using the same steps S00 to S50, except the step S20 that comprise in addition a preparation of a hole in the intermediate layer 900' and a step of inserting the multilayered structure 500' into said hole.

Claims

An item (1000, 1000') comprising a front face (ff1000, ff1000'), and a back face (bf1000, bf1000') opposite to the front face (ff 1000, bf1000'), and sealed together:
- A first layer (200, 200'), the first layer (200, 200') being at least partly transparent and being made of polycarbonate,

- A multilayered structure (500, 500'), the multilayered structure (500, 500') being at least partly transparent and including a layer (510, 510') comprising microlenses, and a layer (530, 530') comprising image icons.

- A filler material (540, 540'), between the microlenses and the fist layer (200, 200'), the filler material (540, 540') being at least partly transparent and embedding the microlenses and forming a planar surface between the layer comprising the microlenses (510, 510') and the first layer (200, 200'), the filler material (540, 540'), the microlenses and the image icons cooperating to generate at least one synthetic image visible when observing the front face (ff1000, ff1000'),

- A second layer (700, 700'), the second layer (700, 700') being made of polycarbonate,

- A first adhesive (300, 300') between the first layer (200, 200') and the multilayered structure (500, 500'), said first adhesive (300, 300') being at least partly transparent,

- A second (layer of) adhesive (600, 600') between the multilayered structure (500, 500') and the second layer (700, 700').
The item (1000, 1000') according to the preceding claim wherein:
- The multilayered structure (500) comprises the filler material (540, 540'), and

- The first adhesive (300, 300') is between the first layer (200, 200') and the filler material (540, 540'), and seals the first layer (200, 200') to the filler material (540, 540').
The item (1000, 1000') according to any of the preceding claims, comprising a third layer (400) between the first layer (200) and the multilayered structure (500), the third layer (400) comprising an opaque continuous part and a transparent window within the opaque continuous part.
The item (1000') according to any of the preceding claims, the item (1000') being transparent when observing through 80% of the area of the front face (ff 1000').
The item (1000, 1000') according to any of the preceding claims, wherein the microlenses extend over all the item (1000, 1000') or the image icons extend over all the item (1000, 1000').
The item (1000, 1000') according to any of the preceding claims, wherein the first layer (200), the multilayered structure (500) and the second layer (700) extend over all the item (1000).
The item (1000') according to any of the claims 1 to 4, wherein the multilayered structure (500') constitutes an insert in an intermediate layer (900') between the first layer (200') and the second layer (700).
The item (1000, 1000') according to any of the preceding claims, the item being a security item.
A security item (1000, 1000') according to the preceding claim, wherein the adhesive strength between layers of the multilayered structure (500, 500') is lower than the adhesive strength provided by the first adhesive (300, 300') and than the adhesive strength provided by the second adhesive (300, 300').
The security item (1000, 1000') according to the preceding claim comprising a markable layer between the front face (ff1000, ff1000') and the multilayered structure (500, 500'), the markable layer being markable by a beam of an infrared laser.
The security item according to the preceding claim comprising personalization data (m200, m200') marked by a beam of an infrared laser within said markable layer.
The security item according to the claim 10 or 11, comprising a blocking material between the first layer and the multilayered structure, said blocking material absorbing light from a laser.
The security item according to the preceding claim, said blocking material being the first adhesive (300, 300').
Method of manufacturing the item according to any one of the preceding claims comprising the following steps:
- Preparation of a first sheet (S00) comprising the first layer (200, 200'), and

- Preparation of a second sheet (S10) comprising the filler material (540, 540') and the multilayered structure (500, 500'), and

- Preparation of a third sheet (S20) comprising the second layer (700, 700'),

- Then, lamination (S30) of the first sheet with the second sheet and the third sheet to obtain a lamina, the first adhesive (300, 300') being interposed, prior to the lamination, between the first sheet and the second sheet, and the second adhesive (600, 600') being interposed between the second sheet and the third sheet, prior to the lamination.
Method of manufacturing according to the preceding claim in which the second sheet has a thickness of between 10 and 50 micrometers.
A method of personalizing the item according to any one of claims 1 to 13 comprising a step of marking (S50), into said markable layer, the personalization data (m200, m200'), using a beam of an infrared laser.