WO2024241264A1 - Object comprising a mark and method for obtaining the mark - Google Patents

Abstract

The invention relates to a substrate with a mark consisting of microscopic metallurgical structures (3) arranged randomly on the surface of the substrate and having at least one physical and/or chemical property different from the rest of the substrate. At least one structure comprises an element such that exposing the mark to radiation or to an external electrical or magnetic field or to a chemical attack or to mechanical, thermal or electrical stress induces a temporary or permanent change of at least one physical or chemical property of the structure. The structures may be a different first alloy (31) and second alloy (32). The alloy 31 changes colour in a stable and definitive manner after exposure to laser radiation while the alloy 32 has a high reflectivity and is therefore stable to laser exposure.

Description

Object comprising a mark and method for obtaining the mark

The present invention relates to an object comprising a metal substrate and on the metal substrate at least one mark consisting of randomly arranged microscopic metallurgical structures. The present invention also relates to a method for obtaining such a mark on the substrate of an object.

Many industries use product marking to ensure their authentication and traceability. Thanks to recent micromachining processes, it is possible to mark a product without altering it. Traceability is particularly important in the medical field or spare parts, while luxury sectors such as watchmaking or jewelry seek to guarantee authenticity. The marking is then intended to be robust, difficult to reproduce, discreet or even aesthetic but also easily readable.

Most of the known micromachining marking techniques make it possible to produce marks whose properties (pattern, color, etc.) are fixed as soon as the mark is obtained. In the field of valuable paper (banknotes), it is common to use optical devices to produce marks whose properties (pattern, color, etc.) change depending on the viewing angle. It would be interesting to be able to obtain marks on metal substrates using micromachining techniques whose properties would change even after they have been machined.

The present invention therefore aims to propose an alternative to existing markings by offering a mark which can be affixed to a metal substrate of an object for aesthetic purposes or to identify the object, which is robust and which allows a wide variety of patterns and functional or physical properties, these not being completely fixed after machining of the mark. The present invention relates to an object according to claim 1, a method of marking an object according to claim 7 or a method of identifying an object according to claim 8.

The attached figures illustrate an object according to the invention.

Figure 1a illustrates a cross-sectional view of the substrate of an object before the affixing of a mark according to the invention.

Figure 1b illustrates the substrate of Figure 1a after affixing a mark according to the invention.

Figure 1c illustrates the substrate of Figure 1b subjected to radiation, including laser radiation.

Figure 1d illustrates the object and mark of Figure 1b after application of radiation.

Figure 2 illustrates an example of a random pattern obtained in a portion of the mark of Figure 1b.

In the following, the term "microscopic" describes that which is smaller than 0.1 millimeter in size and therefore also covers that which is on the scale of a micrometer or nanometer or even smaller. The term "structure" is used to highlight the fact that the type of marking considered in the present invention requires a certain chemical and/or physical transformation at the location of the metal substrate which is marked and the creation of a new element or new structure distinct from the metal substrate.

The present invention relates in particular to an object comprising a metal substrate 1 on which is affixed a mark 2 consisting of microscopic metallurgical structures 3 arranged randomly on the surface of the metal substrate 1. Figure 2 illustrates the random dispersion of the microscopic metallurgical structures on a portion of the mark 2. The object can be of any nature: finished product on which the mark is directly applied or support bearing the mark which will then be fixed on a product. The present invention applies particularly to an object of the component type watchmaker, timepiece, jewelry item, medical or dental device or instrument including prosthesis or implant, tools, automobile or aeronautical spare part, etc.

The brand and in particular its metallurgical structures 3 have physical (optical, magnetic, etc.) and/or chemical properties different from the metal substrate 1.

Preferably, the mark 2 is obtained by a surface treatment method as described in document WO2008/010044. Electrical discharges are applied between a metal tip acting as an anode and the surface of the metal substrate 1 acting as a cathode (or vice versa). A gap of a few microns separates the tip from the substrate and is entirely occupied by a composite dielectric medium. The micro-discharge that occurs in the dielectric medium forms a conductive ionized plasma channel between the tip and the substrate. An electric current from the discharge of a current source can pass through the ionized plasma. The energy thus provided contributes to the formation of a confined micro-plasma at very high temperatures and pressures. The mass of the plasma, surrounded by a gas envelope or gas bubble, grows during the discharge. But the radial expansion of the plasma is strongly restricted by the presence of the dielectric medium, and the energy of the discharge is concentrated in a very small volume. The ultra-hot plasma radiates energy towards the electrode surface causing the melting of the substrate metal. The plasma mass is in fact composed of molecules of the composite dielectric medium, pulverized and dissociated by the energy of the discharge. The high temperature of the plasma causes the melting of a disk-shaped substrate surface. However, the high pressure of the plasma limits the evaporation of molten material from the electrodes. This mechanism results in the formation of quasi-circular imprints of molten metal at the roots of the arc. The size of the molten metal disk is a direct function of the discharge duration. These quasi-circular imprints form metallurgical structures microscopic, alloys of the metal substrate and the constituent elements of the composite dielectric medium that have been pulverized by the discharge. These microscopic metallurgical structures are dispersed in a completely random manner on the surface of the metal substrate, in the manner illustrated in Figure 2. Once the arc is established, the tip can be moved in the plane to make elongated marks or even lines or other more complex trajectories, without extinguishing the current in the manner of a micro-torch. By controlling the energy of the discharge, its duration, the breakdown distance and/or the gap, and especially the chemical composition and additives present in the dielectric medium, the discharge plasma is used as a microreactor to produce marks formed of microscopic structures of molten metal with chemical compositions other than in the basic metal substrate 1.

Alternatively, any suitable method could be used to produce on a portion of the surface of the metal substrate of an object a mark 2 consisting of microscopic metallurgical structures 3 randomly distributed on said surface of the metal substrate 1. For example, the mark can be obtained on a metal substrate by heating said substrate to a temperature slightly below its melting point, then bombarding said substrate with a high-speed gas flow containing solid particles which are therefore implanted on the quasi-molten surface of the substrate to form microscopic metallurgical structures randomly dispersed on the surface of the metal substrate. Other plasma jet, plasma coating or additive manufacturing methods are also conceivable.

With either of the above methods, whether particles A, B, C, etc. are added to the dielectric or to the gas flow, it is not possible to predict which microscopic metallurgical structures will form where and in what proportion. In particular, it is not possible to determine in advance that at a particular point on the mark, the microscopic metallurgical structure will have as its constituent element A, B, or C, etc. The distribution of the type of microscopic metallurgical structures and the dispersion of these structures are therefore totally random.

The mark 2 thus obtained already forms a very robust identification device in view of the random nature of the dispersion of the microscopic metallurgical structures 3 composing it: it is possible to observe a precise portion of the mark 2 such as the square illustrated in figure 2 and to associate with the object the unique pattern of the microscopic metallurgical structures observed in this portion, for a future comparison and a sure identification.

In addition, mark 2 may have an aesthetic character due to its shape and its outline but also due to its composition which may give it interesting properties in terms of color, in particular depending on the elements added to the metal substrate during the creation of mark 2.

The present invention goes even further in that the mark 2 formed on the metal substrate 1 contains at least one alloy distinct from that of the metal substrate 1 and of which at least one physical or chemical property can be altered temporarily or permanently by exposure to radiation or application of an external field or chemical attack or by electrical or mechanical stress. By radiation, we mean laser, UV or infrared radiation. Similarly, by external field, we mean either a magnetic field or an electric field. By electrical stress, we mean the application of an electric current directly into the metal substrate 1. By mechanical stress, we mean any mechanical stress applied to the substrate such as tension, torsion or pressure or temperature.

In the example of figures 1a to 1d, a mark 2 is therefore produced on the metal substrate 1 by any suitable method. Preferably, the method described in document WO2008/010044 is used: to do this, at least two distinct elements are chosen and added to the dielectric medium that is applied to the metal substrate 1. A micro-discharge is generated in the dielectric medium between the tip and the substrate and forms an ionized plasma channel. conductor. An electric current from the discharge of a current source can pass through the ionized plasma. Quasi-circular imprints of molten metal are formed at the roots of the electric arc. This produces a mark 2 formed of microscopic metallurgical structures 3 which are alloys formed from the metal substrate 1 and a mixture of the distinct elements added to the dielectric medium. A wide variety of alloys can be obtained depending on the ratios between each constituent (substrate and dielectric elements. To simplify, it is considered that among the microscopic metallurgical structures 3 at least one first alloy 31 and one second alloy 32 with different physical properties are obtained, in particular with different behavior upon exposure to laser radiation (thermal reactivity, reflectivity, optical absorptivity, etc.). In this example, alloy 31 changes color in a stable and definitive manner after exposure to laser radiation, while alloy 32 has a high reflectivity and is therefore stable upon exposure to laser radiation. Thus, when mark 2 is exposed to laser radiation 4 as shown schematically in FIG. 1c, the microscopic metallurgical structures comprising alloy 31 will change color (as illustrated in FIG. 1d). A new, completely random color pattern is then obtained since the microscopic metallurgical structures comprising alloy 31 are randomly distributed during the production of the brand 2.

For this application using laser radiation, the marking process used can be arranged to produce a mark 2 whose constituent elements are compounds with high reflectivity such as aluminum, copper or silver or ZrN compounds: these compounds will therefore not change color after exposure to laser radiation. They are combined with non-stoichiometric and thermosensitive compounds (TiNx) which will change color after exposure to laser radiation. By combining these two types of constituent elements to form the mark 2 (for example by adding them to a dielectric medium before implementing the method according to WO2008/010044), It is possible, after laser radiation, to form a random color pattern following selective absorption of the laser energy.

For example, for an object identification application, a mark 2 is first applied to the metal substrate of the object made of randomly arranged microscopic metallurgical structures, said structures comprising at least one constituent element sensitive to laser radiation. The metal substrate 1 is then laser engraved at the location of the mark 2 to obtain a final QR code with a completely random coloring, thus offering a higher level of security and traceability.

In another example, mark 2 could be a decorative pattern whose outline is formed by a multitude of microscopic metallurgical structures arranged randomly in the pattern and at least part of which comprises as a constituent element a laser-sensitive compound, changing color after exposure to the laser. The decorative pattern then becomes unique after exposure to laser radiation due to its completely random color distribution. Depending on the method used, alloys offering different laser sensitivities can be inserted into mark 2 along a particular outline and/or in different proportions along the outline to create truly unique decorative patterns. This aspect is particularly interesting in the field of jewelry or watchmaking. It is in particular possible to produce complex and unique decorative patterns, which can also be used to identify the object and which are obtained by micromachining processes which do not distort the object apart from the mark and which, in particular, do not alter the mechanical properties of the object. It is therefore possible to decorate or mark any type of watch or jewelry component, even the most delicate and precise.

In the example above, the constituents of the microscopic metallurgical structures 3 of mark 2 are chosen for their reaction to laser radiation and in particular for their color which changes or not after exposure to laser radiation. In another example, the mark 2 comprises microscopic metallurgical structures 3 whose constituents are chosen for their reactivity to an external electric or magnetic field. By exposing the mark 2 to such an external magnetic field for example, it is possible to cause a selective magnetization of certain microscopic metallurgical structures 3 to create in the mark 2 a random mosaic of magnetized regions. This mosaic mark can then be read by suitable instrumentation for the purpose of identifying, tracing or authenticating the mark and the object bearing it.

In another case, exposure to an external electric field can induce an electric polarization in certain grains or domains. It is thus possible to develop surfaces with particular functional properties (sensitive surfaces, piezo- or magneto-active and usable in actuator type devices).

In the above examples, the changes induced in mark 2 by the radiation or the external field are permanent and, after exposure, a new mosaic mark is obtained. In other variants, the changes could be temporary, for the duration of a reading or observation of mark 2 in particular. For example, the mark may consist of microscopic metallurgical structures whose constituent elements are metals or alloys having very different optical properties (reflectivity, absorptivity, etc.). In this case, by exposing mark 2 and its randomly arranged microscopic metallurgical structures to UV or infrared radiation, it is possible to temporarily create a new random mosaic to enable the identification or authentication of the object bearing the mark. An object bearing such a mark can then be identified using a UV lamp by observing the mosaic revealed by the UV radiation.

In yet another example, a new mosaic is created after chemically etching the first mark. For example, a mark is formed consisting of tungsten and aluminum. Chemically etching this mark in using hydrochloric acid will leave a new porous tungsten-based mosaic on the metal surface of the substrate.

Finally, in other examples, either an electric current passing through the substrate or the application of a mechanical or thermal stress is used to induce a temporary or permanent physical and/or chemical change in the microscopic metallurgical structures of the first mark 2 to obtain a new mark. For example, if by forming the first mark 2, microscopic metallurgical structures are obtained which are shape memory alloys (Ni-Ti, Cu-Zn-Al alloys, etc.), by applying a mechanical stress which causes a change in temperature, the roughness of the surface of the first mark changes. Thus, an imprint could become visible by heating the surface of the first mark 2 comprising microscopic metallurgical structures in shape memory alloy. It is thus possible to control in real time properties of the surface of the first mark such as its wettability. More generally, this makes it possible to construct a surface with a controllable and reversible morphology.

It is noted that if the subsequent treatment is of a reactive nature (such as acid etching), one or more of the microscopic metallurgical structures may become non-metallic. A selective CVD type treatment on a specific material can lead to this result. This would also be the case for a mosaic consisting of gold or platinum structures and another metal, subjected to a strongly oxidizing treatment.

As seen above, the first mark made on the metal substrate consists of randomly arranged microscopic metallurgical structures. This random arrangement makes the final mark after treatment by radiation, chemical attack or magnetic or electric field also random. It is nevertheless possible to control and modulate the structure of the mark at the macroscopic level: this modulation results from the controlled dosage of the ratios between the component(s) grafted into the metal substrate to form microscopic metallurgical structures with physical (optical, magnetic, etc.) and/or chemical properties different from the substrate. It is indeed possible to control the proportions of the element(s) to be grafted to the substrate during the preparation of the mark (preparation of the composite dielectric or the gas flow).

For example, by adjusting the ratio between reflective particles A and less reflective particles B, the macroscopic reflectivity of the mark after laser exposure can be modulated. The same applies to the magnetic or piezoelectric response of the mark: it is possible to dilute/modulate this response by combining magnetic or piezoelectric elements with neutral elements during the formation of the mark. It is also possible to adjust the thermal expansion (in the manner of borosilicate glass).

It is also possible to combine several constituent elements to form microscopic metallurgical structures with distinct reactions to radiation or to the electric/magnetic field: hybrid mosaics can thus be produced with different magnetic/piezoelectric, superconductor/metal properties, etc.

In terms of colour, some tonal adjustments are possible by varying the proportion of certain constituent elements during the formation of the mark: for example, if the 100% TiN alloy gives an intense blue colour after laser treatment, the addition of a neutral reagent such as tungsten carbide WC (which tends towards silver grey after laser treatment) will make it possible to obtain shades of blue from intense blue to sky blue. The macroscopic impression is that of a dot colonisation (pointillism).

Furthermore, it is noted that the first mark made on the metal substrate may have a sufficiently small size such that it can be concealed in a secret place on the substrate or the object or applied to small objects in a discreet manner. Due to the small size of the structures microscopic metallurgical, it is thus possible to hide the first mark in another, clearly visible (macroscopic) identification element, to add an additional level of protection.

The fields of application of the present invention are multiple. The mark according to the invention can have an aesthetic purpose as well as a technical and functional one, can serve as decoration or as an identification and security device.

For example, in the medical field, it is possible to make a mark on an instrument or device that combines copper or silver-based alloys with high laser reflectance and other alloys that are more sensitive to laser radiation. Copper or silver also have a strong antibacterial, antimicrobial and antiviral effect. Thus, a mark comprising a copper compound as a constituent element is a particularly suitable site for laser engraving instrument identification information. Indeed, laser engraving areas are often the site of dirt accumulation. Furthermore, by first creating a copper-charged mark that is then engraved, two antibacterial mechanisms are combined for a potentially multiplied antibacterial effect: first, the ionic effect in which OH- ions are produced by contact between the copper surface and water and secondly, a purely mechanical effect since the spikes obtained after engraving the surface of the mark cause a rupture of the cell wall of the bacteria. Finally, using in particular the method according to WO2008/010044, a mark 2 can be formed on the metal substrate of a medical instrument whose microscopic metallurgical structures comprise as constituent elements an antibacterial element such as copper and another element more attractive to bacteria such as titanium. Since the "attractive" or "antibacterial" microscopic metallurgical structures are infinitely close, a bacteria "trap" is constructed at the location of the mark 2. Thus, with the invention, it is possible to obtain a marking of a medical instrument or device that is both robust since the dispersion of the microscopic metallurgical structures and their change after passage of the laser are totally random and non-reproducible and furthermore carried out on an antibacterial and biocompatible surface.

In general, the present invention relates to an object comprising a metal substrate and on this metal substrate a mark consisting of microscopic metallurgical structures arranged randomly on the surface of the metal substrate. Said microscopic metallurgical structures have physical and/or chemical properties different from the rest of the metal substrate. According to the invention, at least one microscopic metallurgical structure comprises a constituent element distinct from the metal substrate and such that the exposure of the mark to radiation or to an external electric or magnetic field or to a mechanical, thermal or electrical stress induces at least one temporary or permanent change in at least one physical or chemical property of said at least one microscopic structure.

By change is meant an alteration of a physical or chemical property of a metallurgical microscopic structure without destruction of the structure or the substrate, such as for example a change in color, polarization, roughness, wettability, etc.

Preferably, the radiation is laser, UV or infrared radiation. Preferably, exposure to the radiation or external field induces a temporary or permanent change in color, electrical polarization or magnetization of said at least one microscopic metallurgical structure.

Preferably, the mark is part of or constitutes a decorative motif or an identification device of the object. The present invention also relates to a method of marking an object for decorative purposes or for identifying the object, comprising the following steps:

• provide an object comprising a metal substrate;

• choosing at least one reactive element distinct from those constituting the metal substrate, said reactive element being chosen for its particular reactivity to at least one first treatment such as exposure to radiation or to an external electric or magnetic field or to a chemical attack or to a mechanical, thermal or electrical stress;

• producing on the metal substrate a first mark consisting of microscopic metallurgical structures arranged randomly on the surface of the metal substrate and having at least one physical and/or chemical property distinct from said metal substrate, at least one of said microscopic metallurgical structures comprising said at least one reactive element as a constituent element;

• exposing the first mark to said first treatment to induce a permanent or temporary change in at least one physical or chemical property of said at least one microscopic structure to obtain a second mark distinct from the first.

With this process, we can obtain random mosaics of colors, magnetization, electrical polarization as in the examples above.

The present invention also relates to a method for identifying an object comprising the following steps: providing an object comprising a metal substrate; • choosing at least one reactive element distinct from those constituting the metal substrate, said reactive element being chosen for its particular reactivity to at least one first treatment such as exposure to radiation or to an external electric or magnetic field or to a chemical attack or to a mechanical, thermal or electrical stress;

• producing on the metal substrate a first mark consisting of microscopic metallurgical structures arranged randomly on the surface of the metal substrate and having at least one physical and/or chemical property distinct from said metal substrate, at least one of said microscopic metallurgical structures comprising said at least one reactive element as a constituent element;

• exposing the first mark to said first treatment to induce a permanent or temporary change in at least one physical or chemical property of said at least one microscopic structure to obtain a second mark distinct from the first;

• read/observe/acquire the second mark and associate it with the object for its identification.

Thus, the present invention makes it possible to mark an object for aesthetic or identification purposes and offers a wide variety of results in the properties of the final mark (color, functional characteristic, magnetization, polarization, etc.). This diversity and the random nature of the result obtained are assets in the field of identification, authentication and traceability of objects: in fact, the marks according to the invention are robust and non-reproducible. In addition, according to certain embodiments, in particular in the case of using UV radiation, the mark is very easily readable by simple tools for strong but easy identification of the object (identification of a luxury object directly by a reseller without resorting to specialized tools or an expensive procedure).

As indicated above, the invention relates to any object comprising a metal substrate on which a mark consisting of microscopic metallurgical structures arranged randomly on the surface of the metal substrate and having at least one physical and/or chemical property distinct from said substrate can be applied. In particular, the object may be a watch component, a piece of jewelry, a medical or dental device, a replacement component or spare part intended for automobiles or aeronautics.

Claims

Claims 1. Object comprising a metal substrate and on this metal substrate a mark consisting of microscopic metallurgical structures arranged randomly on the surface of the metal substrate, said structures comprising at least one constituent element distinct from those constituting the metal substrate and said structures having at least one physical and/or chemical property different from the rest of the metal substrate, characterized in that at least one of said microscopic metallurgical structures comprises a reactive constituent element such that exposure of the mark to radiation or to an external electric or magnetic field or to a chemical attack or to a mechanical, thermal or electrical stress induces at least one temporary or permanent change in at least one physical or chemical property of said at least one microscopic metallurgical structure. 2. Object according to claim 1, characterized in that the radiation is laser, UV or infrared radiation. 3. Object according to claim 2, characterized in that the temporary or permanent change of at least one physical or chemical property of said at least one microscopic metallurgical structure is a change in color of said at least one microscopic metallurgical structure. 4. Object according to claim 1, characterized in that at least one of said microscopic metallurgical structures comprises a reactive constituent element such that exposure of the mark to an external electric or magnetic field induces respectively a change in electrical polarization or a magnetization of said at least one microscopic metallurgical structure. 5. Object according to claim 1, characterized in that at least one of said microscopic metallurgical structures comprises a reactive constituent element such that said microscopic metallurgical structure is a shape memory alloy so that exposure of the mark to mechanical, thermal or electrical stress induces a change in roughness or wettability of said at least one microscopic metallurgical structure. 6. Object according to one of the preceding claims, characterized in that the mark is part of or constitutes a decorative motif or a device for identifying the object. 7. Method for obtaining a permanent or temporary mark on an object for decorative purposes or for identifying the object, comprising the following steps: o providing an object comprising a metal substrate; o choosing at least one reactive element distinct from those constituting the metal substrate, said reactive element being chosen for its particular reactivity to at least one first treatment such as exposure to radiation or to an external electric or magnetic field or to a chemical attack or to a mechanical, thermal or electrical stress; o producing on the metal substrate a first mark such that said first mark consists of microscopic metallurgical structures arranged randomly on the surface of the metal substrate and having at least one physical and/or chemical property distinct from said substrate, at least one of said structures comprising as a constituent element said at least one reactive element; o exposing the first mark to said first treatment such as to induce a temporary or permanent change in said at least one microscopic metallurgical structure comprising said reactive element to obtain a second temporary or permanent mark distinct from the first. 8. A method for identifying an object comprising the following steps: o providing an object comprising a metal substrate; o choosing at least one reactive element distinct from those constituting the metal substrate, said reactive element being chosen for its particular reactivity to at least one first treatment such as exposure to radiation or to an external electric or magnetic field or to a chemical attack or to a mechanical, thermal or electrical stress; o producing on the metal substrate a first mark such that said first mark consists of microscopic metallurgical structures arranged randomly on the surface of the metal substrate and having at least one physical and/or chemical property distinct from said substrate, at least one of said structures comprising as a constituent element said at least one reactive element; applying the first mark to said first treatment so as to induce a temporary or permanent change in said at least one microscopic metallurgical structure comprising said reactive element to obtain a second temporary or permanent mark distinct from the first; reading/observing/acquiring the second mark and associating it with the object for the identification of said object.