WO2024256675A1 - 3d marking method - Google Patents

Abstract

The present application relates to a stamping-type marking method comprising the preparation of 3D patterns which are based on photo-luminescent nanoparticles in a photo-crosslinkable resin, and are applicable directly on the surface without a transfer step.

Description

DESCRIPTION

3D MARKING PROCESS

The present invention relates to the marking of products, in particular for the purposes of combating counterfeiting, the traceability and authentication of said products.

Typically, it is possible to achieve this type of marking by producing a label that is then transferred/deferred onto the product of interest. This is the case, for example, using the technique of assembling photoluminescent nanoparticles by nanoxerography (EP2964564 and FR3022043). However, the presence of the transferred label can facilitate the detection and localization of the marker on the product and potentially restrict the range of products to be labeled.

Other commercially available direct marking technologies such as laser, inkjet printing and pyrography nevertheless have drawbacks resulting in degradation of the surface of the product and its possible coating, are not chemically resistant and can be costly and time-consuming.

In order to overcome these drawbacks, the so-called “Stamping” process, relating to this invention, proposes a method of manufacturing 3D patterns based on photoluminescent nanoparticles, applicable directly to the surface without a transfer step.

Platel et al Applied Nanomaterials 201, 4, 3537-3544 describes the production of 3D patterns in epoxy resin, with specific geometry, in which colloidal quantum dots are incorporated.

However, depending on the nature of the substrate, the nature of the composite used for marking and the preparation conditions, the marking proved unsatisfactory.

However, it remains to make available new marking processes compatible with various substrates, and in particular substrates subjected to very drastic conditions, particularly in terms of UV or other radiation, and/or variations in temperature and/or humidity which can, for example, lead to detachment, and/or compatible with environmental requirements.

According to a first object, the present invention therefore aims at a method of 3D marking of a substrate, said method comprising: The application to a surface of said substrate of a polymeric bonding layer by means of a first photocrosslinkable resin, and the crosslinking of this resin;

Application of a photocrosslinkable marker resin;

Applying a flexible and transparent stamp comprising at least one topographically structured pattern on said resin applied to the substrate, generating a 3D pattern;

UV crosslinking of the generated 3D pattern.

According to another object, the present invention also aims at a method of 3D marking of a substrate, said method comprising:

The application of a photocrosslinkable marker resin to a surface of said substrate;

Applying a flexible and transparent stamp comprising at least one topographically structured pattern on said resin applied to the substrate, generating a 3D pattern;

UV crosslinking of the generated 3D pattern.

According to the invention, the patterns produced by the method can address different types of geometry and surface nature (curved/flat, metal, glass, fibers, polymer, etc.). It has been demonstrated, among other things, that an increase in the height of the microstructured patterns results in an increase in the overall photoluminescence signal, which can also make it possible to use nanoparticles with low quantum yield. The method according to the invention makes it possible to generate an interpenetrating network of polymers (IPNs) whose networks are formed according to the same polymerization mechanism or even IPNs combining two entangled networks of polymers of the same nature or of a different nature, preferably of the same nature, whose properties are different from those of the simple network and the same polymer.

The substrate

According to the invention, the nature of the substrate is not limited. It may in particular be chosen from metals, their alloys and their oxides, such as aluminum, steel, indium-tin oxide; cellulose derivatives such as paper; cardboard, whether or not comprising fillers, sizing, bleaching agents); silicon; fabrics; glasses; ceramics; polymers formulated in particular in the form of plastics, paints, or varnishes and such as polyethylene terephthalate (PET) or the cyclic olefin-polyethylene copolymer, of formula, respectively:

It is understood that the substrate may optionally be covered with a surface coating layer, such as paint and/or varnish, a protective layer such as an anti-corrosion protective coating; and/or a bonding layer, such as the layers resulting from chemical treatments (cleaning, degreasing, pickling, passivation, etc.), electrochemical treatments (such as chromic anodic oxidation (OAC), sulfuric anodic oxidation (OAS), hard anodic oxidation (OAD), deposits of zinc, nickel, chromium, tin, precious metals, etc.; galvanization, etc.), and combinations thereof.

The resin

The term "photocurable" refers to the ability of the resin to crosslink when exposed to light, visible or UV. Thus, a photocurable resin is a photosensitive resin that changes state and transforms into material under the action of visible or UV light.

The photocrosslinkable resins according to the invention are therefore typically chosen from photosensitive resins which must remain transparent at the emission wavelength of the photoluminescent nanoparticles used.

These resins are generally polymers (also called polymer matrix), preferably chosen from epoxy resins due to their good inherent adhesion, mechanical and thermal resistance properties.

Many polymers are commercially available:

Thus, we can cite the glues, resins or films that can be crosslinked with UV, used for example in optical adhesion and/or protection processes such as the OG type 147, 116, 317 lllumabond ranges, the NOA, NVA, UVS ranges offered by Epoxy Technologies or the CN SR range offered by STARTOMER/Arkema; the resins or films photosensitive materials used in microelectronics such as the SU8 - SU8 2000 - SU8 3000, KMPR, KMSF ranges, offered by KAYAKU, the AZ and Ordyl ranges offered by Microchemicals, the DF range from Dupont; polymers used in LIV 3D / SLA printing by manufacturers such as Buckdown, Anycubic.

Particular mention may be made of epoxy type resins, such as the S1813EPO-TEK OG142-87 resin marketed by Epoxy Technology Inc.

According to the invention, the resins are markers.

The term "marker" as used herein refers to the property that allows it to be identified and traced by photoluminescence. The term "marker" therefore refers here to a photoluminescent agent (ie) its ability to be detectable by photoluminescence.

The term "photoluminescence" refers to the phenomenon of light emission such as fluorescence or phosphorescence following the reaction of said resin subject to "excitation" by exposure to ultraviolet (UV), visible or infrared optical radiation.

Photocurable resins may be intrinsically labeling or, alternatively, loaded with a label. Photocurable resins may also be intrinsically labeling and loaded with a label.

Thus, according to a first alternative, photocrosslinkable resins are intrinsically markers in that they are detectable by photoluminescence without the addition of an exogenous marker agent.

Preferably, the resins are photocrosslinkable in the UV, thus rendering photoluminescence in the visible. Thus, as photocrosslinkable photoluminescent resin the resins mentioned above. We can also more particularly mention biosourced photocrosslinkable photoluminescent resins, such as resins derived from plants and more particularly from soybean oil, such as for example linoleic acid derivatives, such as EcoUV type resins marketed by Anycubic. Biosourced resins can also be derived from monomers or oligomers of the (methyl)acrylate family with a biorenewable carbon (or BRC) content, such as the family of biosourced methyl acrylates of the Sarbio type marketed by Arkema, or even epoxies. According to one embodiment, the photocrosslinkable marker resin is a photoluminescent bio-based resin.

According to a second alternative, the photocrosslinkable resins are loaded with a marker agent. The marker-loaded photocrosslinkable resin is then referred to as a “nanocomposite” comprising a crosslinkable resin in which a marker is integrated, such as a photoluminescent nanoparticle or a quantum dot for example.

Thus, according to one embodiment, the photocrosslinkable marker resin is loaded in that it comprises such a marker.

According to one embodiment, the first resin and/or the photocrosslinkable marker resin is chosen from resins with ester functions.

The marker

A marker is any photoluminescent agent.

According to one embodiment, the marker consists of marker nanoparticles, such as photoluminescent nanoparticles.

Depending on the intended applications, several types of nanoparticles may be suitable. Typically, nanoparticles suitable for the invention may be chosen from photoluminescent nanoparticles that are dispersible and stable in the solvent used to dilute/dissolve the resin. Nanoparticles in powder form may also be used if they can be redispersed in this medium.

Multiple photoluminescent nanoparticles are commercially available such as semiconductor quantum dots ZnCdS/CdZnS, ZnCdSe/CdZnS and CdSe/CdS/CdZnS, CdSe/ZnS, CdSe@CdS, PbS, InP, carbon dots; lantanide ion-doped nanoparticles; perovskite-type nanoparticles, etc.

The choice of the marker can be adjusted according to their nature, i.e. the elements composing them (classically Cd, Se, Pb, Si, C, Ce, In, S, Zn, Cu, perovskite, etc.) according to the level of acceptable safety or toxicity; their quantum yield, it being understood that a low quantum yield, a guarantee of a higher level of safety, may imply a more powerful excitation source and a more sensitive detection device; their absorption and emission wavelengths corresponding to the excitation sources and to the desired detection sensor; their photostability to temperature and humidity, depending on the expected operating ranges.

Such nanoparticles are commercially available, for example from Nanowerk and AZNano including Nanopartz, Cd-bioparticles, Quantum solutions, Sigma Aldrich, Merck, Ossila, American Elements, Nanoshel, Quantum Nanotech, ACS Material, Nexdot, Nano N.O.M., etc.

As quantum dots, we can notably cite lnP@ZnS, (Tessier et al Chemical matters 2018, 30, 6877-6883) or CdSe@CdS.

Markers can also be bio-based, such as carbon-based quantum dots.

When the resin includes marker nanoparticles, it is hereinafter referred to as a nanocomposite.

Thus, in this case, the method further comprises the step of preparing the photocrosslinkable marker resin by mixing said marker nanoparticles with said photocrosslinkable resin, prior to the step of applying said photocrosslinkable marker resin thus obtained.

More particularly, said nanocomposite can be prepared from a suspension of said marker nanoparticles in a solvent, by mixing the suspension in said photocrosslinkable resin, and evaporating said solvent.

Alternatively, said nanocomposite can be prepared from a suspension of said marker nanoparticles in a solvent, then evaporation of the solvent and dispersion of the nanoparticles in the resin.

The solvent is chosen from solvents also allowing solubilization/dilution of the resin. According to one embodiment, the method may further comprise, prior to the step of mixing the nanoparticles with said resin, dispersing said nanoparticles in an organic solvent, such as in particular chosen from chloroform, xylene, acetone, preferably xylene.

Typically, the suspension comprises less than 20% by mass, preferably less than 10% by mass of nanoparticles to maintain the crosslinking of the nanocomposite. To obtain a viscosity compatible with subsequent structuring, drying is preferably carried out until a viscosity close to the viscosity of the resin is obtained: this drying can be carried out by evaporation of the solvent, in particular by natural evaporation.

Application of the polymeric bonding layer

The process involves the creation of an interpenetrating polymer network (IPN).

Interpenetrating polymer networks (IPNs) are defined as a combination of two or more polymer networks synthesized and crosslinked in juxtaposition. The entanglements of the two crosslinked polymers give rise to a “forced miscibility” compared to polymer blends, which are usually incompatible. As a result of the crosslinking of each component, this structuring has good dimensional stability over time. These polymer associations are generally carried out in order to develop materials with better mechanical properties, increased resistance to degradation while blurring the defects of each of the two polymers.

RIPs can be obtained by two synthesis routes: sequential synthesis and in situ synthesis, preferably by sequential synthesis, by application and/or adaptation of the method described by Sperling et al. Advances in chemistry series 1994, 239, 3.

Thus, the method according to the invention comprises the creation of a crosslinked polymeric bonding layer. Thus, the method further comprises, prior to the application of said photocrosslinkable marker resin: the application of a polymeric bonding layer, typically a layer of a photocrosslinkable resin,

- the crosslinking of this resin.

The stamp

A "stamp" or "stamp" is a topographically structured element that is transparent to UV, shapeable/structurable and inert with respect to the resin or nanocomposite. It can be made of silicone such as PDMS or thermoplastic polymer such as PET, or glass for example. It is preferably flexible. It can be implemented by different techniques: micromolding on a master mold containing the structures/patterns of interest (itself produced by photolithography, microfabrication or AM processes), by thermal nanoimprinting, AM, electron beam lithography (EBL), two-photon photopolymerization, inkjet printing, etc.

In the classic case of a PDMS stamp, the microstructures of the master mold can be produced by UV photolithography processes on SU8 type photosensitive resins or laminated dry films. The mold can then be silanized by liquid or gaseous means in order to facilitate the subsequent demolding of the PDMS stamp. PDMS can then be cast on the master mold and thermally crosslinked before being cut to size.

Furthermore, concerning the production of the master mold, it was found that mechanical integrity can be advantageously ensured for reasons of lateral resolution greater than 8 pm.

After printing the stamp on the nanocomposite, there may remain a residual thickness of a few pm of nanocomposite which will cover the entire surface. The height of the stamp patterns is advantageously greater than the residual thickness, typically greater than 5 pm of the residual thickness.

The 3D pattern

The 3D printed pattern can be of any shape, geometry, including any type of coding or their combination including alphanumeric text, logo, drawing, data matrix, bar code, QR code, bleam, etc., of size from mm to pm and can in fact include a significant density of stored information.

Different levels of security can be possible through:

- The shape and size of the pattern that allows topographic marking; like QR codes, it allows the storage of information, identification and topographic authentication of the product.

- The unique light signature of the pattern (due to the random distribution of particles in the volume) which allows authentication by light signature of the product. The pattern can be integrated directly into the surface of a final product, downstream of its manufacture, including on a curved substrate and for variable dimensions (nanometric to centimetric).

The pattern may be detectable or undetectable to the naked eye, and is compatible with different reading means depending on the size of the pattern, such as an atomic force microscope, a camera or photo device equipping an optical microscope, the camera of a smartphone equipped or not with clip-on lenses, etc.

The process

According to the invention, it comprises the following steps:

Application of a polymeric bonding layer;

Application of the marking resin to be marked;

Application of the transparent stamp with topographically structured patterns on the resin layer;

This application can be assisted by any means, such as a laminator, press, etc.

Crosslinking of the resin under UV.

Typically, exposure can be carried out for a variable duration, depending in particular on the power of the UV lamp. As an illustration, exposure of the order of a minute may be suitable, it being understood that the more powerful the lamp, the shorter the duration.

Typically, the method may further comprise any of the following steps, as well as any combination thereof:

Possible prior preparation of the substrate

This step includes one or more pre-treatments of the substrate chosen from among in particular: chemical pre-treatments such as cleaning, degreasing, stripping, passivation etc., for example in order to improve its hydrophilicity, electrochemical pre-treatments such as anodic oxidation pre-treatments with or without sealing: chromic anodic oxidation (OAC), sulfuric anodic oxidation (OAS), hard anodic oxidation (OAD), TSA; passivations; chemical conversions for example to trivalent chromium: surtec 650, TCS PACS, lanthanum or to hexavalent chromium: alodine; electrodeposition of deposits of zinc, nickel, cadmium, chromium, tin, precious metals, etc.; galvanization; their combinations.

Advantageously, if the substrate is porous (fabric for example), this step can also include the application of transparent photocrosslinkable resin, in order to saturate the pores of the substrate (the photocrosslinkable marker resin which will be structured by the buffer will then be applied to this saturated surface of the substrate);

Removal of the buffer after the crosslinking step.

This can be done by peeling, taking care not to tear it off. If the crosslinking is complete, there is generally no nanocomposite residue left in the pad. The latter can be cleaned if necessary by mechanical rubbing using a swab soaked in ethanol, for example, with a view to its reuse.

The method according to the invention can also include a step of encapsulating the pattern thus created:

Although optional, depositing an encapsulation layer can have the following advantages: o Physical protection of the created 3D pattern; o Planarization of the layer.

According to one embodiment, the encapsulation layer is advantageously transparent to the emission of the marker and/or has a thickness allowing the marker to be read: typically, the thickness of the encapsulation layer is greater than twice the height of the pattern created.

According to a more particular embodiment, the method according to the invention comprises the steps of: - the application of a polymeric bonding layer to a surface of the substrate by means of a first photocrosslinkable resin and the crosslinking of this resin;

- Integration of photoluminescent nanoparticles into a UV-crosslinkable resin;

- Deposition of the resin loaded with nanoparticles on the crosslinked resin;

- Application of a flexible and UV-transparent stamp (e.g. silicone) with topographically structured patterns;

- UV crosslinking of the 3D pattern obtained;

- Deposit of a planarizing varnish completely covering the 3D pattern;

The preferred embodiments of the invention may be cited:

When the substrate is aluminum, the process preferably comprises the following steps:

Optionally, pre-treatment of the substrate by sulfuric anodic oxidation, application of a crosslinked polymeric bonding layer; prior to the step of mixing photoluminescent particles with the photocrosslinkable resin, dispersing said photoluminescent nanoparticles in xylene.

When the substrate is steel, the method preferably comprises the following steps: optionally pre-treatment of the substrate by electrodeposition of cadmium or zinc-nickel or silver plating, prior to the step of mixing photoluminescent particles with the photocrosslinkable resin, dispersing said photoluminescent nanoparticles in xylene or chloroform.

According to another object, the present invention also aims at a method for detecting an object comprising a substrate marked by a method according to the invention, said detection method comprising: reading the marked substrate; comparing the read 3D pattern with the marked 3D pattern. The reading of the 3D pattern produced can be done according to one or more of the 3 reading/security levels: visible to the naked eye, detectable using a simple optical reader for example and/or detectable in the laboratory using a dedicated optical bench/expert equipment.

Figures

[Fig 1] Figure 1 schematizes the development of a micro-structuring marking of an interpenetrating polymer network (IPN) by UV-assisted nano-imprint on a substrate.

[Fig 2] Figure 2 illustrates a sequential synthesis of RIP of OG-142 epoxy (2) and bio-based resin (3) with or without QD on a support (1).

[Fig 3] Figure 3 is a snapshot of a 2024 aluminum alloy test piece treated with a tag.

[Fig 4] Figure 4A and Figure 4B are photos of the RIP OG-142 tags + bio-based resin before (A) and after (B) the salt spray test for 168h under UVA (315-400 nm) - ALU 2024 support treated by TCS PACS chemical conversion

Examples

In the examples, when the term “tag” is used, it will correspond to the term “pattern” or “3D pattern” of the invention.

The tests are carried out on: 2024 aluminum test pieces treated with OAS fine sealing TCS PACS (chromium III) or treated by chemical conversion with trivalent chromium TCS PACS supplied by Aéroprotec (Example 1), and

- steel test pieces having undergone cadmium plating or zinc-nickel (Zn-Ni) treatment with or without finishing after treatment (Example 2).

1. Formulation and structuring of the nano-composite when a bonding layer is implemented (RIP) The RIP was prepared by sequential sequence, illustrated by Figures 1 and 2: the first network formed (2), here the virgin OG-142 epoxy resin, was obtained by depositing on the substrate (1) a few drops of the latter using a FISNAR SL101 N fluid dispenser (with a pressure of 1.5 bar and a deposition time of 0.1 second). The OG-142 epoxy is spread manually by a mold (4) in transparent unstructured poly (dimethyl-siloxane) (PDMS) then crosslinked (6) for 5 min under UV radiation (λ = 365, 385, 395, 405 nm). This preliminary step improves the adhesion between the support and the product to be marked.

For the preparation of nano-composites (3) 5 g of bio-sourced resin Anycubic Plant-based UV Resin+ were mixed with 300 μl of CdSe@CdS quantum dots dispersed in chloroform or xylene synthesized in the laboratory. The concentration of the colloidal dispersion is previously adapted according to the mass percentage of QD desired in the final nano-composite, i.e. between 1 -5% of the total mass.

A drop of bio-based nano-composite (3) or photoluminescent bio-based resin (3) (m drop— 10.2 mg) (3) is then deposited to be able to swell the first network and make a second layer, this time using the structured part of the PDMS mold (4) presenting the chosen label designs (QR code, alphanumeric code or bleam). The assembly is directly pressed manually by applying a support with a mass equal to 225 g on the mold (4) and exposing it (7) (5 minutes, at a height of 86 mm) using a UV torch with a power of 200 mW/cm ² and a wavelength of 365 or 385 or 395 or 405 nm. Finally, the PDMS mold (4) is peeled off from the surface, leaving photoluminescent nano-composite structures (3) as labels on the surface (1).

This technique makes it possible to prepare RIPs whose networks are formed according to the same polymerization mechanism or RIPs combining two entangled networks of polymers of the same nature, whose properties are different from those of the simple network and the same polymer.

2. Aging

The samples were aged in a climatic chamber:

• 3-day cycle at 90°C - 65% HR (relative humidity)

• 3-day cycle at 20°C - 65% HR (relative humidity) These different tests listed below were carried out in order to know the evolution of the durability of the tags in a given environment:

- Tape adhesion test,

- Water jet adhesion test,

- Thickness monitoring by profilometer,

- Resistance to solvents,

- Neutral salt spray,

- Fourier transformed infrared analysis,

- Photoluminescence,

- Solid/liquid extraction,

- Differential scanning calorimetry (DSC).

3. Solvent resistance

In the aeronautics industry, many solvents, such as ethanol, butanone, salt water, acidified water and COMORAL DXP solution can be used for cleaning metal parts. The solvent resistance of the tags is studied here. For this, the materials are rubbed for 30 s then immersed for 30 min in solvents of different polarity and solubility parameters (ethanol, butanone, salt water and acidified water). They are then wiped and dried for 15 min under a hood at room temperature.

The experimental conditions applied during these tests are deliberately severe in order to more easily observe the effect of the different solvents on the materials, the test pieces not being, of course, intended to be immersed in a solvent during normal use. o CO MO R AL DXP Solution

In relation to the resistance test for the COMORAL DXP solution, the product usage temperature must be between 60°- 80°C with a pH of 12.

The marked test pieces are immersed for 5 min in a beaker containing the COMORAL solution with mechanical stirring when the temperature is 70°C. They are then washed with distilled water and dried for 15 min under a host at room temperature.

4. Neutral salt spray

It is a way to check the quality of a metallic material with a protective coating against corrosion. The test is carried out in a corrosion chamber using the NSS test standard (NF ISO 9227) and ASTM B 117. Test characteristics

• The sodium chloride concentration in the prepared solution should be 50 gL ¹ ± 5 g.L' ¹ .

• The density of this solution is between 1.029 and 1.036 at 25°C.

• The temperature of the salt spray chamber must be 35±2°C.

• Samples are placed in the chamber according to the test standard (20° inclination according to the standard)

• No sample obscures other samples; droplets from one sample cannot fall on other samples.

5. FTIR spectroscopies

An FTIR spectroscopic study was performed using a Thermo-SCIENTIFIC FTIR spectrometer. Each spectrum was obtained by performing 32 scans between 4000 and 650 cm' ¹ with a resolution of 2 cm' ¹ . The obtained spectrum was then processed using ORIGIN software.

6. Solid/liquid extraction

In order to study the soluble parts of the materials studied, a solid-liquid extraction was carried out using a cellulosic cartridge of the "Soxhlet" type containing the product. The Soxhlet extraction was carried out at a temperature of 60 ° C using dichloromethane (CH2CI2) as solvent in three cycles for 2 g of product ground and dried for 24 h under vacuum.

7. ¹ H NMR spectroscopy

In order to characterize the chemical composition of the extractables, nuclear magnetic resonance spectroscopy (NMR) analysis was carried out using a Bruker NMR spectrometer with a frequency of 400 MHz. The products are dissolved in deuterated chloroform (CDCh). Note that NMR only allows the extracted part of the resin to be obtained.

8. Photoluminescence or Optical microscope

A fluorescence optical microscopy setup is used taking into account the photoluminescence characteristics of CdSe@CdS QDs.

The excitation source is a light-emitting diode with a narrow emission band centered around 460 nm. A dichroic mirror with a cut-off wavelength of 505 nm is used to reflect this excitation source towards the CdSe@CdS QDs-based marker. In response, the latter emits a signal centered around the red (622-780 nm). o Digital USB microscope The labels obtained can also be excited optically by a simple blue LED and observed using a digital USB microscope of the brand (Dino-Lite) at high magnification (250x) and with a resolution of 1.3 Megapixels the response obtained is retransmitted using a camera that will allow taking photos or videos. o Using a smartphone

The obtained labels can also be observed by a smartphone equipped with a Lens Clip (magnification) after excitation by a blue LED. The reading is simple and is visible through a smartphone camera although the camera resolution and magnification may fluctuate depending on the quality of the smartphone camera, autofocus and digital zoom functions.

9. Tape adhesion test

This technique is carried out according to the ISO 2409 standard (without grid).

Test characteristics

• Using 3M 2525 Scotch Tape, cut a strip of at least 75 mm and apply the centre of the tape to the surface to be checked. Be careful not to touch the working area of the tape (adhesive side).

• Smooth the tape over 50 mm then rub firmly with your fingertip to remove air bubbles.

• Remove the tape with a sharp pull at an angle of around 60°.

• No trace of the deposit on the tape and no detachment on the part should be observed.

10. DSC: Differential Scanning Calorimetry

Differential scanning calorimetry aims to determine, when possible, the glass transition temperatures of amorphous phases and the melting temperatures of crystalline phases. The aim is to obtain information on the composition of the phases, particularly in the case of partial miscibility.

Test characteristics • Temperature rise following three passages:

The first pass was carried out with a speed of 10°C.min ^-1 up to 130°C.

The second pass was carried out at a speed of 10°C.min ^-1 up to 25°C. And finally the third pass was carried out at a speed of 10°C.min ^-1 up to 130°C.

• Cross-linked nano-composite mass between 10 to 20 mg

I. Results

1. Adhesion test o Adhesion to tape:

The adhesion of the tag to the treated metal support depends on the exposure time, which allows the formation of the tag, to avoid any detachment of the tag when using 3M 2525 tape to be able to carry out this test. Thus, to be able to test their adhesion to the metal support used, the tags studied were obtained for exposure times of 3 min and 5 min. For an exposure time greater than or equal to 5 minutes (per layer), good adhesion was observed and reading the bleam is always possible. o Adhesion by water jet:

All the specimens used were marked with an exposure time of 5 min per layer before water jet projection. Thus a fine water jet with high pressure hits the surface of a part at high speed for 1 min and no modification of the surface of the label is observed.

2. Macroscopic observations of RIPs aged in the climatic chamber for 3 days at 90°C and 65% relative humidity

A first observation of the different aged samples shows a detachment of the tag in the case where the RI P is made of the epoxy OG-142 and the bio-sourced nano-composite (CdSe@CdS) surely due to a mechanical degradation caused by the dispersion solvent of the CdSe@CdS QDs, namely chloroform which will lead to a lack of cohesion between the matrix of the photoluminescent bio-sourced resin and the CdSe@CdS QDs. On the other hand, the reading of the bleam is done on all the samples before and after aging.

3. Solvent resistance When the RIP is made of OG-142 resin ( ^1st layer) and bio-based resin without QD ( ^2nd layer) a slight variation in the residual surface of the tag is observed, not preventing the reading of the latter when butanone is used.

Thus, there is a complementarity of the properties of the two resins and the reading of the QR code is even possible after 30 minutes of immersion in the different solvents.

In the case where the RI P is made of OG-142 epoxy and bio-sourced nano-composite (CdSe@CdS), a low alteration of the surface is observed with solvents such as ethanol, salt water or acidified water. On the other hand, with butanone, a strong degradation of the surface is observed with the tag leaving in certain areas.

Reading the bleam is no longer possible after rubbing with butanone. o CO MO R AL DXP Solution

After the solvent resistance test with COMORAL DXP solution, no surface modification is observed and the reading of the QR code is still possible for any type of RI P used with or without QDs.

4. Chemical evolution of Interpenetrating Polymer Networks (IPNs): OG-142 resin and bio-sourced resin

Infrared spectroscopy was used to better understand the different mechanisms that can take place within the RIP before and after aging.

There is a lack of miscibility between the two faces during their polymerizations. The chloroform that is part of the nano-composite has an absorption band characteristic of the C-CI bond present on the surface of the OG-142 epoxy. The chloroform therefore swelled the surface of the crosslinked OG-142 epoxy before polymerization of the bio-sourced nano-composite.

Due to the immiscibility of the two faces to be able to characterize the chemical modification within the RIP, a solid/liquid extraction of the materials was carried out. The evolution of the extractable rates of the materials was determined. The initial sample of the RIP consisting of OG-142 ( ^1st layer) and bio-sourced resin ( ^2nd layer) has an extractable rate of 0.09% which highlights the good crosslinking of the material; and when the latter is aged the extractable rate obtained is so low that it cannot be quantified. This decrease is perhaps the origin of the increase in the rigidity of the material during aging.

The RIP consisting of OG-142 epoxy ( ^1st layer) and bio-sourced nano-composite ( ^2nd layer) has an extractable rate equal to 0.2% in the initial state and 0.15% when aged at 90°C and 65% relative humidity for 3 days. ¹ H NMR analysis revealed the presence of chloroform in the extractable, confirming that the solvent is not completely evaporated during the process.

From a macroscopic point of view, a swelling reaction of the OG-142 epoxy by the bio-sourced nano-composite will lead to a decrease in the rigidity of the RIP consisting of OG-142 ( ^1st layer) and bio-sourced nano-composite ( ^2nd layer). These effects are partly reversible. In the long term, the reversibility of these "physical" phenomena can be altered by chemical reactions that may be caused by chloroform. However, the decrease in the extractable rate seems to indicate that the crosslinking of the material continues beyond the process.

5. Salt spray or TCS PACS treatment

In the case where the 2024 aluminum specimens are treated by chemical conversion with TCS PACS process, they will be placed in a corrosion chamber for 168 hours with an inclination angle of 20° and a pH of 7.07. The photos obtained after salt spray treatment for the RIPs made of OG-142 epoxy ( ^1st layer) and bio-based resin ( ^2nd layer) demonstrate that no priming or pitting at the level of the specimen or tags and the reading of the QR code is still possible. Thus the TCS PACS treatment has no influence on the tag of the RIP made of virgin OG-142 epoxy and bio-based resin. The tag of the RIP made of OG-142 epoxy ( ^1st layer) and bio-based resin ( ^2nd layer) does not present any chemical or visual modification after the salt spray tests.

The presence of pitting corrosion at the tag level only is observed. These pits are induced by the bio-sourced nano-composite (composed of chloroform and CdSe@CdS QDs). Pitting corrosion occurs when aluminum is brought into contact with an aqueous solution containing halide ions, most frequently chloride ions. Indeed, the study of infrared spectroscopy in the initial state has shown that there is a diffusion of the chloroform solution contained in the bio-sourced nanocomposite within the OG-142 epoxy. From this result, 3 hypotheses are put in place:

• The chloride ions contained in the chloroform will migrate towards the surface of the aluminum and destabilize the protective film (TCS PACS treatment);

• The underlying aluminum then dissolves to form Al ³⁺ ions, which hydrolyze on contact with the electrolyte;

2

• The combined action of environmental conditions (chlorides/temperature/humidity) and stresses develops cracking and the stress corrosion mechanism.

The study of the chemical modification after salt spray of the RI P tag made up of OG-142 epoxy and bio-sourced nano-composite revealed two areas of degradation:

Zone 1: we observe a strong absorption of water which will correspond to a dilution of the different chemical functions which constitute the RIP with disappearance of certain characteristic bands. In addition, the absorption band at 3466 cm ^-1 due to the elongation vibrations of the OH groups becomes increasingly wider with an increase in intensity; this may correspond to an absorption of water or to an accumulation of degradation products.

Zone 2: The band at 1724 cm' ¹ , relating to the elongation vibrations of the carbonyl groups of the ester (R-(C=O)-O-R'), decreases sharply. Indeed, the water molecules interact with the carbonyl groups by hydrogen bonding leading to a retro-esterification with a formation of the corresponding acid and alcohol. And the more the quantity of water absorbed increases, within the polymer matrix, the more the free carbonyl groups decrease in favor of the bound carbonyl groups. Thus, the degradation of the C=O groups takes place over time.

The degradation of the material could be observed using a scanning electron microscope (SEM) coupled with EDX.

In the initial state, the RIP matrix is made up of the elements C, O and the different metallic particles that constitute aluminum. After salt spray, the presence of black intermetallic particles of irregular shape precipitated on the surface of the tag made up of silicon (Si) and magnesium (Mg) is observed. From these results, two hypotheses were developed:

• The aluminum specimen consists of Mg and Si in the initial state which can combine to give magnesium silicide (Mg ₂ Si) at the grain boundaries.

• But the presence of an aggressive environment dissolves this phase leaving behind a cavity, which can act as a site for nucleation of corrosion pits. The results of this study of the resistance to salt spray corrosion for an example of a tag (RIP OG-142 + bio-based resin) on a 2024 aluminum specimen treated in chemical conversion (TCS PACS) are illustrated in Figure 4, where Figure 4A represents a photo of the tag before the salt spray test, and photo 4B after the salt spray test (168h).

6. Balance sheet

When the RI P is made up of OG-142 epoxy and bio-sourced resin, we see an improvement in all properties:

First of all, the adhesion between the support and the tag; the tag becomes increasingly difficult to remove.

The tag is resistant to solvents such as ethanol, butanone, salt water, acidified water and COMORAL solution: there is therefore complementary property between OG-142 epoxy and bio-sourced resin.

- No chemical or visual changes of the tag were observed after salt spray tests for TCS/PACS treated specimens.

On the other hand, if the RI P is made up of the epoxy OG-142 and the bio-sourced nano-composite (CdSe@CdS), we observed:

Tag peeling off during aging at 90°C and 65% relative humidity.

- With the solvent resistance test, an improvement in properties was observed except in the case of butanone where a significant degradation of the surface was observed with the tag disappearing in certain areas.

- After the salt spray test for the specimens treated with TCS/PACS, a very marked modification of the chemical structure is observed with the presence of certain corrosion markers on the surface of the tag.

From its various results during the study of the interpenetrating network of polymers (RI P) consisting of epoxy OG-142 and bio-sourced resin, it was observed an excellent adhesion between the marking and the substrate for any support used (treated aluminum, treated steel, glass, paper, polymer, etc.) for the marking. In addition, a strong overall improvement in the mechanical and chemical resistance of the marking is also noted.

The results are summarized below for both substrate types. Example 1: Aluminum substrate

Example 1.1: OG-142(5°) + CdSe@CdS dispersed in chloroform

Example 1.2: OG-142(5°) + Chloroform

Example 1.3: OG-142(5°) + CdSe@CdS Example 1.4: RIP: OG-142 + biosourced nano-composite CdSe@CdS (2 layers)

Example 1.5: Bio-sourced resin + CdSe@CdS dispersed in chloroform

Example 1.6: Bio-sourced resin

Example 1.7: OG-142 (25°) + xylene

Example 1.8: OG-142 (25°) + CdSe@CdS dispersed in xylene Example 1.9: RIP: OG-142 + bio-based R. (2 layers)

Example 1.10: R. Biosourced + Carbon

Example 1.11: R. Biosourced + Graphene

The results are detailed in Table 1: [Table 1]

PL: Photoluminescence

Example 2: Aluminum substrate

Example 2.1: OG-142(5°) + CdSe@CdS dispersed in chloroform Example 2.2: OG-142(5°) + Chloroform

Example 2.3: OG-142(5°) + CdSe@CdS

Example 2.4: RIP: OG-142 + bio-sourced nano-composite CdSe@CdS (2 layers)

Example 2.5: Bio-based resin + CdSe@CdS dispersed in chloroform

Example 2.6: Bio-based resin Example 2.7: OG-142 (25°) + xylene

Example 2.8: OG-142 (25°) + CdSe@CdS dispersed in xylene

Example 2.9: RIP: OG-142 + biosourced R. (2 layers)

Example 2.10: R. Biosourced + Carbon

Example 2.11: R. Biosourced + Graphene

The results are detailed in Table 2:

[Table 2]

Exemple 3 : Différentes réalisations de motifs ont été effectuées :

Example 3: Different patterns were created:

Implementation 1: production of a test piece in 2024 aluminum alloy treated with a tag according to the invention (Figure 3).

Achievement 2: production of RIP OG-142 tags + biosourced resin before (Figure 4 A) and after (Figure 4 B) the salt spray test for 168 hours under UVA (315-400 nm) - ALU 2024 support treated by TCS PACS chemical conversion.

Claims

1. Method for 3D marking of a substrate, said method comprising: The application to a surface of said substrate of a polymeric bonding layer by means of a first photocrosslinkable resin, and the crosslinking of this first resin; Application of a photocrosslinkable marker resin; Applying a flexible and transparent stamp comprising at least one topographically structured pattern on said resin applied to the substrate, generating a 3D pattern; UV crosslinking of the generated 3D pattern. 2. Method according to claim 1 such that the photocrosslinkable marker resin is a photoluminescent bio-sourced resin. 3. Method according to claim 1 such that the photocrosslinkable marker resin is loaded in that it comprises, in addition to a photocrosslinkable resin, marker nanoparticles. 4. Method according to claim 3 such that the method comprises the step of preparing the photocrosslinkable marker resin by mixing said marker nanoparticles with said photocrosslinkable resin, prior to the step of applying said photocrosslinkable marker resin thus obtained. 5. Method according to claim 4 such that it comprises, prior to the mixing step, dispersing said nanoparticles in an organic solvent chosen from chloroform, xylene, preferably xylene. 6. Method according to any one of the preceding claims such that the substrate is chosen from metals, their alloys and their oxides; cellulose derivatives; silicon; fabrics; glasses; ceramics; polymers. 7. Method according to claims 5 and 6, such that the substrate is aluminum, and the solvent is xylene. 8. A method according to claims 5 and 6, such that the substrate is steel and the solvent is xylene or chloroform. 9. A method according to claim 6, such that the substrate is cardboard. 10. Method according to any one of the preceding claims, such that the first resin and/or the photocrosslinkable marker resin is chosen from resins with ester functions.