Method for fixing a marking composition onto a substrate

Abstract

The invention relates to a method (100) for fixing a marking composition onto a substrate, said marking composition comprising at least one pigment, said method comprising the following steps: - deposition (102) of the marking composition onto at least a portion of the substrate; - fixing (104) a portion of the marking composition by laser irradiation via a laser beam, said laser irradiation being carried out by moving the laser beam over the substrate; - removal (106) of the marking composition not irradiated in the fixing step (104), the laser beam having a power density of between 60 W / mm² and 5 kW / mm² in contact with at least a portion of the irradiated marking composition, and the scanning is carried out at a scanning speed of between 0.1 and 9.0 meters per second. Figure for the abstract: Fig. 5

Description

Description Title of the invention: Method for fixing a composition of marking on a substrate Technical field of the invention

[0001] — The present invention relates generally to a laser fixing method of a marking composition on a substrate.

[0002] = It relates more particularly to a method of fixing a composition of marking on a fragile substrate such as an organic substrate of origin plant, an organic substrate of animal origin, a substrate of synthetic origin, a substrate made from cellulose such as cardboard or paper.

[0003] — The invention also relates to a marking composition intended to be placed implemented within the framework of this process. State of the art

[0004] — Hot stamping processes are known which are used to mark substrates in leather. These processes use iron systems that are pressed onto the leather at mark. These processes are functional but do not allow you to obtain a marking with pigments. In addition, in these processes, the substrates are en- damaged locally, which may affect their properties such as their com- behavior towards water, hydrophilia or phobia. Finally, these processes do not allow not to easily customize patterns on substrates.

[0005] — Laser marking processes on hard substrates are also known, for example se- selected from a metal, a plastic, ceramic, glass. These processes are functional, but are not usable for soft or flexible substrates that are could be described as fragile due to their susceptibility to being easily scratched. effect, in these processes, the characteristics of the laser beam used to irradiate the substrate produce heating greater than 500°C due to light interaction material between the laser beam and the substrate. Such a characteristic is suitable for the hard substrate such as metal, plastic, ceramic or glass but is not suitable for more fragile substrates such as leather, textiles, cardboard because the heating of material induced in this process would cause damage to these substrates by a pyrography phenomenon inducing local carbonization of the substrate. Such local carbonization is incompatible with the realization of marking in colors other than black and induces a substantial local alteration of the properties of the substrate, in particular its behavior in water.

[0006] — The invention aims to remedy at least one of the aforementioned drawbacks for propose a fixing method which is suitable for marking a composition of marking on fragile substrates, particularly those of organic origin. Presentation of the invention To this end, the invention provides a method for fixing by laser irradiation a marking composition on a substrate, the marking composition comprising at least one pigment, method comprising the following steps: - depositing the marking composition on at least a portion of the substrate; - fixing a part of the marking composition by laser irradiation, or a laser beam on the substrate, - removal of non-irradiated marking composition at the fixation stage. According to the invention, the laser beam has a power density of between 60 W / mm? and 5 kW / mm? in contact with the irradiated marking composition and the displacement of the laser beam is carried out at a speed, measured relative to the substrate, of between 0.1 and 9.0 meters per second (ms"). In the context of the invention, the displacement speed corresponds to the displacement speed relative to the substrate of the spot or spot of the laser beam on the substrate. Power density is the amount of power that passes through a surface per unit of that surface. It therefore quantifies the power received over a portion (area) of the surface. Thanks to the invention, it is possible to fix pigments of various colors on fragile substrates without altering them, unlike hot stamping techniques. Such a process is also easy to implement and allows for the creation of personalized patterns more easily. It should be noted that the combination of power density and scanning speed, according to the invention, makes it possible to limit the amount of power, per unit area, received by the substrate during its irradiation. Surprisingly and contrary to what might have been expected, this limitation of irradiation does not prevent optimal fixing of the marking composition on fragile substrates. In this disclosure, laser beam means a light beam emitted by a laser. In one embodiment, the movement of the laser beam is carried out at a speed of between 0.6 and 9.0 meters per second. Such a feature further reduces the exposure of the substrate to the laser beam, and therefore limits the risk of damaging the substrate without affecting the quality of the fixation. Within the scope of the invention, the displacement of the laser beam relative to the substrate can be carried out in any suitable manner and for example by at least one of the de- following investments: - movement of the laser beam (i.e., laser scanning), - displacement of the substrate, - combination of laser beam displacement and substrate displacement. In one embodiment, the laser is coupled with a focusing device having a focal length for focusing the laser beam into a focal point. The substrate is then located at a distance from the focal point of less than 5 cm and preferably less than 1 cm. The combination of the beam power and speed characteristics with such focusing makes the fixing effective even on substrates having a planar shape or a non-planar shape. A non-planar substrate is understood to mean in particular a substrate whose face to be marked is curved or a substrate whose face to be marked has planar parts and non-planar parts and / or an irregular surface such as a substrate having concave and convex areas for example. Furthermore, working outside the focal point allows the laser power density to be reduced when in contact with the substrate. Therefore, these characteristics offer an easy-to-implement solution for fixing pigments on very fragile substrates without the need to flatten the surface to be marked. According to the invention, the laser used in the fixing step is continuous or pulsed. In one embodiment, the laser used is a Y AG laser emitting a laser beam at an emission wavelength of 1064 nanometers. In another embodiment, the laser used is a CO laser, emitting a laser beam at an emission wavelength of 10600 nanometers. In yet another embodiment, the laser used is a triple YAG fiber laser emitting a laser beam at an emission wavelength of 355 nanometers. The method according to the invention therefore works with commonly used and widely commercially available lasers, improving the ease of implementation of the method at a reasonable cost. In one embodiment, the beam has a minimum diameter of between 70 micrometers and 120 micrometers, for example when the laser beam is in contact with the substrate. In one embodiment, the marking composition comprises: - an aqueous base; - at least one pigment in the form of particles suspended in the aqueous base. In one embodiment, each pigment is in the form of particles between 10 nm and 0.1 mm in size. In one embodiment, the aqueous base is 50% to 84% by weight in the marking composition. In one embodiment, the pigment is at a rate of 16% to 50% in the marking composition. In one embodiment, the aqueous base is liquid. Using such an aqueous liquid base as a vehicle for the pigments and particles constituting the marking composition provides a solution that improves the ergonomics of the implementation as well as the safety of the process. Indeed, in a liquid base, the pigment particles are dispersed. In one embodiment, the aqueous base comprises water with a short chain alcohol or acrylic binder mixed with a surfactant. Such a formulation of the marking composition makes it possible, on the one hand, to increase the homogeneity and stability of the suspension constituting the marking composition and, on the other hand, to improve the fixation of the pigments on the substrate. The quality of the marking as well as its longevity are therefore improved. Binder means an emulsion of water and acrylic resin. In one embodiment, the aqueous base does not include an organic solvent. It is thus possible to avoid the use of organic solvents which are flammable and toxic to humans and the environment. In one embodiment, the aqueous base comprises an organic solvent. In a variant of this embodiment, said pigment is in the form of particles of size between 10 and 50 micrometers. These characteristics improve the fixation of the pigment in the fixation stage. In addition, such a particle size is less dangerous for humans (in case of inhalation or ingestion). In one embodiment, the at least one pigment is arranged not to change color after the fixing step. In one embodiment, the pigment in the form of particles is chosen from: - a metal oxide; - a metal; - a metal alloy; - a metal alloy oxide; - inorganic material; or mixtures thereof. Using an inorganic pigment allows for very good color quality. In addition, this type of pigment has ecological advantages. In one embodiment, the metal particles are selected from particles of bronze, gold, silver, copper, aluminum, or mixtures thereof. Thus, the process according to the invention works with noble metals such as gold and silver or bronze-type alloys, which makes it possible to obtain high-quality and precious marked objects. In addition, these metal particles allow the substrate to be pigmented in different colors. In one embodiment, the marking composition comprises as pigment particles of at least one metal oxide. For example, the particles of at least one metal oxide are selected from the following transition metal oxides: - titanium oxide; - iron oxide; - tin dioxide. These compositions allow you to obtain different marking colors In one embodiment, the pigment further comprises mica comprised at 38% to 74% by weight in the pigment composition. Such pigments are environmentally friendly and inexpensive. In addition, mica particles improve the pigment's adhesion to the substrate and absorb some of the beam's energy. Thus, mica particles limit substrate heating while increasing heat transfer to the pigment particles, which contributes to the quality of the marking. In one embodiment, the mica is in the form of particles having at least one of the following characteristics: - a particle size k times 10* greater than the size of the other particles in the pigment composition, with k an integer ranging from 1 to 9, - a particle size between 3.0 um and 80 um. In one embodiment, the marking composition is deposited on the substrate in a layer having a thickness of between 10 nanometers and 0.1 millimeters. In one embodiment, the substrate comprises at least one of the following materials: - an organic material of plant origin; - an organic material of animal origin; - a material of synthetic origin, for example comprising polyurethane; - a cellulose-based material such as cardboard or paper - a woven or non-woven material at least partly of an organic nature. For the purposes of the invention, the organic nature of a material corresponds to the fact that at least part of its components or constituents are produced by a living organism, animal or plant. Therefore, the process works perfectly with fragile substrates such as, for example, leather goods made of natural, vegetable or synthetic leather. In one embodiment, after the removal step, the marking composition covers at least ninety percent of the irradiated substrate. In one embodiment, the surface of the substrate has a roughness of between 0 micrometers and 2 millimeters. Thus the process works on different types of substrate, smooth or rough. In one embodiment, the substrate is planar or curved. In one embodiment, the method comprises a step of air drying the marking composition before the irradiation step, said drying step preferably being of a duration of less than 2 minutes. The invention also relates to a marking composition intended to be fixed on a substrate by laser irradiation comprising: - an aqueous base comprising water and a stabilizing agent, said aqueous base being present in a proportion of 50% to 84% by weight in the marking composition, - at least one pigment in the form of particles suspended in the aqueous base at a rate of 16% to 50% by weight in the marking composition. A water-based base means a liquid base or a base in paste form. In one embodiment, the stabilizing agent comprises a short-chain alcohol or acrylic resin and a surfactant. In one embodiment, the aqueous base comprises an organic solvent. In one embodiment, each pigment is in the form of particles between 10 nm and 0.1 mm in size. In one embodiment, the pigment in the form of particles is chosen from: - a metal oxide; - a metal; - a metal alloy; - a metal alloy oxide; - inorganic material; or mixtures thereof. In one embodiment, the pigment further comprises mica comprised at 38% to 74% by weight in the pigment composition. In one embodiment, the mica is in the form of particles having at least one of the following characteristics: - a particle size k times 10° greater than the size of the other particles in the pigment composition, - a particle size between 3.0 um and 80 um. Of course, the different characteristics, variants and embodiments of the invention may be combined with each other in various combinations provided that they are not incompatible or mutually exclusive. The invention also relates to a marking composition comprising at least one pigment and an aqueous base. Detailed description of the invention The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented. On the attached drawings: [Fig.1] is a schematic representation of an embodiment of a system for fixing a marking composition according to the present invention; [Fig.2] is an example of a deposition device included in a system for fixing a marking composition according to the invention; [Fig.3] is a first example of a fixing device included in a system for fixing a marking composition according to the invention; [Fig.4] is a second example of a fixing device included in a system for fixing a marking composition according to the invention; [Fig.5] is an example of a method of attaching a marking composition to a substrate according to the present disclosure; [Fig.6] is a front view of a planar substrate irradiated by a fixing device of a system for fixing a marking composition; and [Fig.7] is an example of a curved substrate marked with a marking composition by the fixing method according to the invention. System [Fig. 1] illustrates a system S for fixing a marking composition 2 on a substrate 4. The system S comprises a control unit 50 and a fixing device 10. Optionally, the system S also comprises a deposition device 20 as well as a cleaning device 60 and a synchronization device 90. As illustrated in [Fig.1] and [Fig.3], the fixing device 10 comprises a frame 11, a laser device 30 and a support 40. This fixing device 10 is connected to the control unit 50 which is configured to control the fixing device 10. The control unit 50 is a computer or any other electronic element making it possible to implement a succession of commands and / or calculations. The control unit 50 typically comprises a processor, a memory and various input and output interfaces. Thanks to its input and output interfaces, the control unit 50 is suitable for receive input data, for example adjustment data, a pattern to be produced, the type of substrate used, etc. For this, the control unit 50 is typically connected to a human-machine interface allowing a user to enter the input data which will be used by the fixing device 10 to fix a marking composition 2 on the substrate 4. The output data are the commands sent to the different elements of the system S. For the fixing device 10, in particular for the laser device 30, these commands comprise, for example, adjustment data for the laser device 30 (for example, an operating mode, a power, a scanning speed, etc.). For the support 40, these data comprise, for example, a distance from a focusing plane of the laser beam. As illustrated in [Fig.3], the frame 11 holds the laser device 30 as well as the support 40. In this example, the laser device 30 comprises a laser 31 configured to irradiate the marking composition 2 positioned on the substrate 4, a scanning device 32 and a focusing device 33 comprising at least one focusing lens 34. The laser 31 is arranged to emit a monochromatic beam 35 towards the substrate 4 in a propagation direction oriented towards the substrate 4. In [Fig.3], the laser beam 35 passes into the scanning device 32 which directs the laser beam 35 onto the substrate 4. The scanning device 32 is configured to move the laser beam 35 on a surface 3 of the substrate 4 in two directions x, y transverse to the propagation direction of the laser beam 35. Thus, a laser scan is performed by means of the scanning device 32. Typically, the scanning device 32 consists of at least two movable mirrors for directing the laser beam 35 on the substrate 4 so as to perform a spatial scan of the portion of substrate to be irradiated, the portion of substrate to be irradiated being defined via input data transmitted to the control unit 50. In the present disclosure, the scanning device is typically a high-speed scanning head, such as a galvo scanner. Thus, in this embodiment, the movement of the laser beam 35 is performed by means of the scanning device 32 configured to move the laser beam on the surface 3 of the substrate 4. Typically, the scanning is carried out in a linear manner by scanning each portion of the surface of the substrate to be irradiated along a (fictitious) line defined on the substrate aligned along the x axis and then moving the laser beam 35 on another line by a movement along the y axis so as to carry out a two-dimensional scan. (xy) of the portion of substrate to be irradiated. Of course, other modes of movement can be configured such as for example a line scan along the y axis then a movement along the x axis to carry out the scan in two dimensions (x, y) or vector scans known to those skilled in the art. The movement of the laser beam 35 on the surface of the substrate 4 controlled by the scanning device 32 makes it possible to create multiple patterns, shapes, symbols, designs, letters on the surface of the substrate 4. Typically, the desired patterns are previously entered into the control unit 50 which will control the scanning device 32 to produce the desired shapes. At the output of the scanning device 32, the laser beam 35 is focused onto the substrate A via the focusing device 33. Here, the focusing device 33 thus has a focal distance for focusing the laser beam 35 onto a focal point included in a focusing plane. The substrate 4 illustrated in [Fig. 3] is positioned on the support 40. The support makes it possible to hold the substrate 4 in the fixing device 10. Typically, the substrate 4 can be positioned on a flat support 40. In one embodiment, the support 40 and the frame 11 are formed from a single piece. In a variant, the support 40 is not flat, it can have claws which are fixed to a part of the substrate to hold the substrate 4. As illustrated in [Fig.3], a distance d separates the surface 3 of the substrate 4 from the focusing device 33. The distance d is defined between a point of the surface 3 (here positioned in a plane PL1) of the substrate and a plane PL2 of the parallel focusing device 33. Typically, the plane PL1 can be located in the focusing plane or in a plane parallel to the focusing plane and spaced up to 5 cm from the focusing plane, the plane PL2 being parallel to the focusing plane. In one embodiment, the support 40 is movable. In this case, the support 40 is arranged to move in at least one spatial direction. In the example illustrated in [Fig. 3], the support 40 is arranged to move the substrate 4 along a z axis parallel to the propagation direction of the laser beam 35. Such an arrangement makes it possible to adjust the position of the substrate 4 relative to the focusing point of the laser beam 35. In this example, the distance d is adjusted by moving the support 40. As explained above, the substrate 4 can be offset up to 5 centimeters from the focusing plane (depending on the focusing device 33). The position of the substrate 4 relative to the focal point of the laser beam 35 can be adjusted before the emission of the laser beam 35 or during the irradiation. Of course, in another embodiment, the support 40 can also be arranged to move the substrate 4 in three spatial dimensions x, y, z. In this case, the displacement of the laser beam 35 relative to the substrate 4 can be the combination of the displacement of the laser beam 35 via the scanning device 32 and displacement of the substrate 4 by movement of the substrate 4 via the support 40. For this purpose, the support 40 can be equipped with an electric motor (not shown) or the position of the support 40 can be adjusted via adjusting rings to position the support 40 in the correct position. The laser 31 used in the laser device 30 is a continuous laser 31 or a pulsed laser. In a first embodiment, the laser 31 is a yttrium Aluminum Garnet laser known as an Nd:YAG laser emitting a laser beam at an emission wavelength of 1064 nanometers. In this embodiment, very good results are obtained, for example on leather, when the laser beam has a power density of 1.9 kW / mm? to 3.8 kW / mm?. The emitted laser beam 35 is pulsed at a pulse rate ranging from 1 kHz to 50 kHz. The power of the emitted laser beam to fix the marking composition 2 on the substrate 4 is between 7.5 and 15 Watts. In this embodiment, the laser beam 35 is configured to scan the surface of the substrate 4 at a scanning speed of between 3 m / s and 4.5 m / s. In this embodiment, the laser beam 35 typically has a laser power density of between 1.9 W / mm? and 3.8 kW / mm? in contact with the marking composition which is irradiated by the laser beam 35. In another embodiment, laser 31 is a CO laser, emitting an infrared laser beam at an emission wavelength of 10600 nanometers. Preferably, the CO laser 31 operates in pulsed mode and emits a laser beam at a power less than or equal to 25 Watts, preferably between 3 and 25 Watts. The laser beam 35 has a pulse rate ranging from 1 kHz to 50 kHz. In this embodiment, very good results are obtained when the laser beam 35 has a power density of between 60 W / mm? and 1.89 kW / mm? In this embodiment, the laser beam 35 is configured to scan the surface of the substrate 4 at a scanning speed of between 0.1 m / s and 9 m / s and has a laser power density of between 60 W / mm? and 5 kW / mm? in contact with the marking composition which is irradiated by the laser beam 35. In another embodiment, laser 31 is a tripled Yttrium Aluminum Garnet doped Ytterbium laser known as a Yd:YAG laser emitting a laser beam at an emission wavelength of 355 nanometers. In this embodiment, very good results are obtained when the laser beam has a power density of between 5.0 W / mm? and 60 W / mm?. The emitted laser beam 35 is pulsed at a pulse rate ranging from 1 kHz to 50 kHz. The power of the emitted laser beam is between 3 and 8 Watts, it is typically 5 Watts. In this embodiment, the laser beam 35 is configured to scan the surface of the substrate at a scanning speed of between 10 mm / s and 150 mm / s and typically has a laser power density of between 60 W / mm? and 5 kW / mm? in contact with the marking composition which is irradiated by the laser beam 35. The laser beam 35 has a diameter of between 50 and 120 micrometers in contact with the surface 3 of the substrate 4 covered with the marking composition. The laser beam 35 of the system S thus irradiates the marking composition 2 to fix the marking composition 2 to the substrate 4. In system S, the non-irradiated portions of the marking composition 2 are then removed by cleaning the non-irradiated portions. In the system S, these non-irradiated parts can be cleaned manually using wipes or a sponge moistened with an aqueous composition or by the cleaning device 60 controlled by the control unit 50. The aqueous solution can comprise an alcohol or a composition of water and soap. In another variant, the non-irradiated marking composition 2 can be removed by means of an adhesive, for example with an adhesive roller. The cleaning device 60 may comprise an ultrasonic system arranged to emit sound waves to remove portions of the marking composition 2 not irradiated by the laser beam 35. In another example, the cleaning device 60 consists of a movable arm provided with a tool, for example a moistened sponge or a brush or a spray device or a wipe for removing the marking composition not irradiated by the laser beam 35 with an aqueous solution. According to the present disclosure, different substrates 4 can be marked by the system S described above. In particular, the 4-marked substrates are fragile substrates. Typically, fragile substrates include polyurethane, plasticized leather, artificial leather, organic substrates of animal origin such as leather (smooth, grained). Organic substrates also include pressed or dried substrates of plant origin such as cardboard, paper, imitation leathers derived from plants, called vegetable leathers or vegetable skins such as pineapple leather, mango leather, mushroom leather, tomato leather, etc. In some applications, the substrate may be plastic or include plastic. The substrates used can also be of different thicknesses. Furthermore, these substrates can be of various shapes. Typically, the substrates used can be flat or curved. The substrates according to the present disclosure may have a roughness of between 0 micrometers and 2 centimeters. The roughness depends on the substrate 4 to be marked on which the marking composition 2 is deposited. Substrates marked by the 100 method have a Shore A hardness between 50 and 90. In the present disclosure, the marking composition 2 comprises: - an aqueous base at a rate of 50% to 84% by weight in the marking composition, - at least one pigment in the form of particles suspended in the aqueous base at a rate of 16% to 50% by weight in the marking composition. Each pigment of marking composition 2 is in the form of particles with a size between 10 nm and 0.1 mm. The aqueous base serves as the application vector for the marking composition 2. The aqueous base includes water and a stabilizing agent. Typically, the stabilizing agent comprises a short-chain water-soluble alcohol or mixed acrylic resin and a surfactant. When using alcohol, such an aqueous base helps to reduce the "pigment / water - substrate" surface tension. The alcohol's role is, in particular, to accelerate the drying of the marking composition on the surface of the substrate. In one embodiment, the stabilizing agent may comprise an organic solvent. Typically, the organic solvent is selected from acetone, petroleum ether, cyclohexane, dioxane, dichloromethane. Of course, other organic solvents may be used. In a preferred embodiment, the aqueous base, in particular the stabilizing agent, does not comprise an organic solvent. For example, when the stabilizing agent is a water-soluble short-chain alcohol, the short-chain alcohol may comprise a C;-C; base or may be methanol. When the stabilizing agent is an acrylic resin and a surfactant, the acrylic resin mixed with water intervenes in the pigment fixing process. In this case, the surfactant can be selected from anionic surfactants, cationic surfactants, non-ionic surfactants such as esters, zwitterionic surfactants, polymeric surfactants, bio-sourced surfactants belonging to one of the preceding categories. The surfactant used depends on the pigment that will be used in the marking composition. The pigment in the form of particles is chosen from: - a metal oxide; - a metal; - a metal alloy; - a metal alloy oxide; - an inorganic material or may be mixtures of the pigments listed above. When the pigment includes particles of at least one metal, these particles are selected from Bronze, Gold, Silver. As described above, the pigment can be a mixture of several distinct element particles. For this purpose, in one embodiment, the pigment further comprises mica comprised at 38% to 74% by weight in the composition of the pigment. Typically, the mica particles may be coated with particles of one or more metal oxides. The particles of at least one metal oxide are selected from the following transition metal oxides: - titanium oxide; - iron oxide; - tin dioxide. The detailed examples below describe different pigments of marking composition 2 used in method 100. Example | In this example, the pigment comprises bronze particles made from an alloy of copper and tin known to those skilled in the art. The bronze particles have a particle size of between 10 nanometers and 20 μm. The bronze particles are mixed in the aqueous base comprising water and a short-chain alcohol but remain insoluble. For example, the bronze particles are present at 16.6% by weight in the marking composition 2, the isopropanol of the aqueous base is present at 16.6% by weight in the marking composition 2 and the water of the aqueous base is present at 66.6% by weight in the marking composition 2. This composition is then applied to the substrate manually or via the deposition device 20. The color obtained by this marking composition is typically the color GOLD. Example 2: In this example, the pigment comprises carbon particles and iron oxide (Fe203) particles. The carbon particles have a particle size between 10 nanometers and 100 um. Such a pigment produces a black color. The iron oxide particles are mixed in the aqueous base comprising water and a short-chain alcohol but remain insoluble. For example, the pigment is present at 16.6% by weight in the composition of marking 2, the isopropanol of the aqueous base is present at 16.6% by weight in the marking composition 2 and the water of the aqueous base is present at 66.6% by weight in the marking composition 2. This composition is then applied to the substrate manually or via the deposition device 20. Example 3 In this example, the pigment comprises synthetic or natural mica particles combined (here coated) with particles of a noble metal selected from Gold to obtain a gold / golden color or Silver to obtain a silver color. In this embodiment, the mica particles are a thousand times larger than the silver or gold particles. Typically, the mica particles have a size of the order of a micrometer while the gold or silver particles have a size of the order of tens / hundreds of nanometers. The mica particles are present at a rate of 80 to 99% by weight in the composition of the pigment. These particles are mixed with the aqueous base as described above. For example, the pigment is present at 16.6% by weight in the marking composition 2, the isopropanol of the aqueous base is present at 16.6% by weight in the marking composition 2 and the water of the aqueous base is present at 66.6% by weight in the marking composition 2. This composition is then applied to the substrate manually or via the deposition device 20. Example 4 In this example, the aqueous base comprises an acrylic binder and a surfactant. Typically, in this embodiment, the pigment is 30% by weight in the marking composition 2, the acrylic binder is 64% by weight in the marking composition 2 and the surfactant is 66.6% by weight in the marking composition 2. The surfactant may comprise Sodium lauryl sulfoacetate. The pigment consists of synthetic or natural mica particles mixed with metal oxide particles. The mica particles are present in a proportion of 38 to 74% by weight in the pigment composition. The remainder of the pigment composition is composed of particles of at least one metal oxide. In this example, the mica particles have a size of between 3.8 μm and 74 μm. Different pigment compositions can be considered. Case 1: The pigment of the marking composition comprises mica particles, titanium dioxide (TiO3) particles, tin dioxide (SnO3) particles and iron oxide (Fe203) particles each having a particle size between 10 micrometers and 60 micrometers. For example, mica particles are present at 66% to 74% by weight in the pigment composition, the TiOz particles are present at 15% to 19% by weight in the pigment composition, the Fe,O particles are present at 11% to 15% by weight in the pigment composition and the SnO particles are present at less than 1% by weight in the pigment composition. This pigment is mixed with the aqueous base as described above to obtain the marking composition 2. According to this example, the marking composition 2 irradiated on the substrate is gold / golden in color. Case 2: The pigment of the marking composition comprises, in this example, mica particles, titanium dioxide (TiOz) particles and iron oxide (FeO4) particles each having a particle size of between 10 micrometers and 60 micrometers. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is gold / golden in color. Case 3: The pigment of the marking composition comprises in this example mica particles, iron oxide particles (Fe,O3) having a particle size between 5 micrometers and 23 micrometers. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is gold / golden in color. Case 4: The pigment of the marking composition comprises in this example mica particles, titanium dioxide (TiOz) particles having a particle size between 10 micrometers and 60 micrometers. This pigment is mixed in the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is white in color. Case 5: The pigment of the marking composition comprises mica particles and iron III oxide (Fe:04) particles. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is green in color. Case 6: The pigment of the marking composition comprises mica particles present at 69% to 73% by weight in the pigment composition and titanium dioxide particles at 26% to 30% by weight in the pigment composition. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is gray in color. Case 7: The pigment of the marking composition comprises mica particles, iron oxide particles and tin dioxide (SnO;) particles. This pigment is mixed with the aqueous base as described above to obtain the composition of marking 2. Following this example, the marking composition 2 irradiated on the substrate is yellow in color. Case 8: The pigment of the marking composition comprises mica particles, iron oxide particles and titanium dioxide (TiOz) particles. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is orange in color. Case 9: The pigment of the marking composition comprises mica particles, SnO particles, and TiO particles. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is purple in color. Case 10: The pigment of the marking composition comprises mica particles, TiO particles; and Fe,O4 particles. This pigment is mixed with the aqueous base as described above to obtain the marking composition 2. According to this example, the marking composition 2 irradiated on the substrate is black in color. Case 11: The pigment of the marking composition comprises mica particles, and Fe,O particles. This pigment is mixed with the aqueous base as described above to obtain marking composition 2. According to this example, marking composition 2 irradiated on the substrate is red in color. Although the pigments of this example are shown mixed with an aqueous composition comprising an acrylic binder and a surfactant, in an alternative embodiment, the pigment may be mixed in an aqueous base comprising a short-chain alcohol as shown in the previous examples. Example 5 In one embodiment, the pigment comprises at least one of the following particles: - ceramic enamel particles composed of silica, - fondant particles, - alumina particles, or mixtures thereof. Such a pigment is a gray color. Typically, the pigment is 16.6% by weight in the marking composition 2, the isopropanol of the aqueous base is 16.6% by weight in the marking composition 2, and the water of the aqueous base is present at 66.6% by weight in the marking composition 2. Example 6 In this example, the pigment comprises aluminum oxide particles coated with titanium dioxide and also comprises tin oxide. The pigment particles are in this example between 5 μm and 60 μm, here from Sum to 30 μm. Such a pigment makes it possible to obtain a blue color. The aluminum oxide particles are mixed in the aqueous base comprising an acrylic binder and a surfactant. For example, the pigment is at a rate of 30% by weight in the marking composition 2, the aqueous base is at a rate of 66% by weight of the marking composition. In this example, the aqueous base comprises an acrylic binder at a rate of 60% by weight in the marking composition 2 and the surfactant is at a rate of 6% by weight in the marking composition 2. This composition is then applied to the substrate manually or via the deposition device 20. In order to carry out the marking according to the invention, the marking composition 2 must be deposited on a surface 3 of the substrate which will be positioned facing the laser beam 35, this deposition can be carried out in various ways. In the present disclosure, the marking composition 2 may be deposited manually on the substrate 4, for example using a brush. In this case, the deposited marking composition 2 may have a thickness of less than 1 mm, preferably between 0.01 mm and 0.1 mm. In one variant, the marking composition can be deposited automatically via the deposition device 20. For this purpose, the deposition device 20 is controlled by the control unit 50. Typically, the deposition device 20 may comprise a movable arm provided with a tool, for example a brush arranged to deposit the marking composition on the surface 3 of the substrate 4. The deposition of the marking composition 2 is preferably carried out in a linear manner on the substrate 4. In a variant illustrated in [Fig. 2], the deposition device 20 uses an application rod according to a technique known under the English name of Rod Coater. As illustrated in [Fig. 2], the deposition device 20 comprises in this example a movable cylindrical rod 21 covered with a wire 22 wound around the rod 21 so as to form a coil. In [Fig. 2], the substrate 4 is positioned on the support 40. A portion of the marking composition 2 is deposited on the surface 3 of the substrate 4 at a given position P, for example by spraying. A rotation (movement) of the rod 21 in a direction 6 allows the deposition of the marking composition 2 on the substrate 4 in the direction 6. The thickness of the marking composition 2 depends on the thickness of the wire 22 used. The speed of movement of the rod 21 is controlled by the control unit 50. It typically varies between 2 and 15 m / min. In the present disclosure, the deposition device 20 is configured such that the marking composition 2 has a thickness of between 10 μm and 20 mm, for example between 10 μm and 100 μm. [Fig.4] illustrates a second example in a fixing device 70. Only the differences with [Fig.3] will be described. In this example, the fixing device 70 comprises a frame 11, a laser device 30 comprising a laser 31 emitting a laser beam 35, a focusing device 33 comprising the focusing lens 34 as well as a support 40. In this example, the fixing device 70 does not include a scanning device. Here, the support 40 is a mobile support 40 arranged to move in three spatial directions x, y, z as explained in the previous example. Therefore, in this embodiment, the movement of the laser 35 is achieved by means of the movement of the substrate 4. First, the distance between the substrate 4 and the focusing device 33 is adjusted by moving the support 40 along the z axis so as to position the substrate at the desired distance from the focusing point of the focusing device. This distance can be adjusted before the emission of the laser beam 35 or adjusted during the irradiation of the laser. Then, the laser beam 35 at the output of the focusing device 33 moves on the substrate 4 via the movable support 40 which will move in the two spatial directions x, y. Typically the movement of the support 40 is linear. The support 40 moves on a (fictitious) line along the x axis then passes to another line by a movement along the y axis so as to obtain a relative movement of the laser beam 35 with respect to the substrate 4. By the movement in two dimensions (x, y) of the support 40, the laser beam 35 irradiates the portion of substrate to be irradiated to obtain the desired pattern. For this purpose, the fixing device 70 may comprise a synchronization device 90 for synchronizing the movement of the substrate 4 relative to the laser beam 35. In this case, the synchronization device 90 is controlled by the control unit 50. Process A method 100 of fixing a marking composition to a substrate will be described using Figures 5 to 8. The process illustrated in [Fig.5] is implemented by the system S illustrated in [Fig.1]. The method 100 comprises a step 102 of depositing the marking composition 2 on at least a portion of the substrate 4. In this example, the substrate 4 is grained polyurethane having an average particle size of 35 μm. As explained above, this deposition on the substrate 4 can be carried out manually, for example using a brush, or automatically via the deposition device 20 as explained above. When the marking composition 2 is deposited on the substrate, here in particular, on the surface 3 of the substrate, the method 100 comprises a step 103 of drying the marking composition 2. The drying step 103 depends on the marking composition 2 used. Typically, the drying step 103 is carried out in the open air. The drying time depends on the marking composition 2 and the material of the substrate 4. In the example presented, the drying time is less than two minutes. The method 100 then comprises a step 104 of fixing a portion of the marking composition 2 by laser irradiation. The fixing step 104 is carried out by the fixing device 10 illustrated in [Fig. 3] or the fixing device 70 illustrated in [Fig. 4], in particular by the laser device 30 of the fixing device 10, 70 which will emit the laser beam 35. As illustrated in [Fig. 5], the laser beam 35 irradiates the substrate 4 at a point or spot 36. Here, the laser beam 35 has a diameter at the surface 3 of the substrate 4 of 90 μm. The laser beam 35 is then moved over the surface 3 of the substrate 4 to obtain a desired pattern on the surface 3 of the substrate 4. As explained above, the movement of the laser beam 35 can be carried out using the scanning device 32 as illustrated in [Fig. 3] or by a movement of the substrate 4 by means of a movable support 40 or by a combination of the two aforementioned movements. The scanning device 32 and / or the movement of the substrate 4 along the x, y axes makes it possible to orient the laser beam 35 at the desired positions on the surface 3 of the substrate 4. In the present disclosure, the color of the pigment remains the same (before and after laser fixation). The method 100 then comprises a step 106 of removing the marking composition which has not been irradiated in the fixing step 104. Typically, the removal step 106 may be performed manually or via the cleaning device 60 as described above. The removal step 106 makes it possible to remove the parts of the marking composition 2 which were not irradiated by the laser beam 35 in the fixing step 104. It can be seen that the substrate 4 illustrated in [Fig.5] obtained following the removal step 106 is marked by a gold-colored marking. In this example, nine gold patterns 16 of 3 millimeters by 3 millimeters have been marked on the substrate 4. Apart from the patterns 16, the substrate 4 has portions 17 which have not been marked. This means that these portions 17 have not been irradiated by the laser beam 35 during the fixing step 104. The marking composition 2 irradiated by the laser beam 35 has not changed from color (pigmentation) between the deposition step 102 and the fixing step 104. [Fig.7] illustrates an example of a substrate 4 obtained following the application of the method 100 to the substrate 4. The substrate 4 illustrated in [Fig.6] is a grained leather having an average roughness of 35 Hum and has two parts, a first part 14 which has not been covered with marking composition and a second part 15 which has been covered with marking composition 2 in the deposition step 102. In this example, the first part 14 of the substrate 4 and the second part 15 of the substrate 4 were irradiated in the fixing step 104 by a CO2 laser beam as described above (the irradiations on the first and second parts were carried out with the same laser parameters). Here, the laser beam 35 irradiated the portions P1, P2, P3 and P4 of the first part 14 and the portions P5, P6, P7 and P8 of the second part 15 of the substrate 4. As illustrated in [Fig.6], the substrate 4 does not have any marks on the portions P1, P2, P3 and P4 whereas on the portions P5, P6, P7 and P8, 18 square patterns of 5 mm by 5 mm of gold color have been marked on the surface 3 of the substrate 4. In the second part 15, all the portions PS, P6, P7 and P8 of the substrate 4 are covered by the marking composition 2, this marking composition 2 being fixed to the substrate 4. Thus, the laser beam 35 has not marked or damaged the first part 14 of the substrate 4 which has nevertheless been irradiated. Typically, the marking composition 2 in the portions P5, P6, P7 and P8 covers at least ninety percent of the irradiated portions P5, P6, P7 and P8 of the substrate 4. By coverage rate, we mean the ratio between the effective marked surface (i.e. pigmented, here the surface of the marking composition fixed on the substrate 4) following the method 100 on the effective irradiated surface. In this example, each portion P5, P6, P7 and P8 corresponds to an effective irradiated surface in the second part 15 of the substrate 4. Here for each portion PS5, P6, P7 and P8, the effective marked surface is obtained by comparing the effective irradiated surface (here the surface of the portions P5, P6, P7 and P8) to the shares of the non-irradiated substrate in each portion P5, P6, P7 and P8. [Fig.7] illustrates an example of a bottle or flask B made of synthetic leather or artificial leather (polyurethane) having a cylindrical shape. As illustrated in [Fig.7], a pattern M of golden color is marked on the surface 3 of the substrate 4 of the box B. This pattern M was marked by the use of the method 100 described above. Typically, in the method 100, the box M has been positioned with respect to the focusing device 33 before the fixing step 104, here following or during the drying step 103. The distance d separating the surface of the substrate 4 of the box B and the focusing device- lization 33 was adapted to the shape of the box B. Since the method 100 can mark substrates positioned up to 5 cm from the focusing plane, it was not necessary to adapt the distance d during the fixing step 104 even though the substrate is curved. Indeed, these 5 cm make it possible to encompass the shapes and curvatures of the substrate to be marked during the fixing step. Variants The present invention is in no way limited to the embodiments described and shown, but those skilled in the art will be able to provide any variation in accordance with the invention.

Claims

Claims

1. Method of fixing by laser irradiation a marking composition (2) on a substrate (4), the marking composition (2) comprising at least less one pigment, the method comprising the following steps: - depositing (102) the marking composition (2) on at least one portion of the substrate (4); - fixing (104) of a part of the marking composition (2) by de- placing a laser beam (35) to irradiate at least part of the marking composition deposited on the substrate (4), - elimination (106) of the non-irradiated marking composition (2) at the fixing step (104), characterized in that the laser beam (35) has a density of power between 60 W / mm? and 5 kW / mm? in contact with the com- irradiated marking position (2) and in that the displacement of the laser beam is produced at a speed, measured relative to the substrate, between 0.1 and 9.0 ms-!.

2. Method according to claim !, characterized in that the laser (31) is coupled with a focusing device (33) having a distance focal point for focusing the laser beam (35) into a focal point, the substrate (4) being located at a distance from the focal point less than or equal to 5 cm.

3. Method according to any one of claims 1 to 2, characterized in that the laser beam (31) is generated by a pulsed laser.

4. Method according to any one of claims 1 to 3, characterized in that the laser (31) used comprises at least one of the following lasers: - a YAG laser emitting a laser beam at a wavelength 1064 nanometer emission, - a CO2 laser emitting a laser beam at a wavelength 10600 nanometer emission, - a tripled YAG fiber laser emitting a laser beam at a wavelength emission wave of 355 nanometers.

5. Method according to any one of claims 1 to 4, characterized in that the substrate (4) comprises at least one of the following materials: - an organic material of plant origin; - an organic material of animal origin; - a synthetic material; - a cellulosic material; - a mixture or assembly of several of the preceding materials.

6. Method according to any one of claims | to 5, characterized in that after the elimination step (106), the marking composition (2) covers at least ninety percent of the irradiated substrate (4).

7. Method according to any one of claims 1 to 6, characterized in that the substrate (4) has a roughness of between 0 mi- centimeters and 2 centimeters.

8. Method according to any one of claims 1 to 7, characterized in what the marking composition includes: - an aqueous base, - at least one pigment in the form of particles suspended in the water-based.

9. Method according to one of Claim 8, characterized in that the base aqueous comprises water with a short-chain alcohol or binder acrylic mixed with a surfactant.

10. Method according to any one of claims 1 to 9, characterized in that the pigment in the form of particles is chosen from: - a metal oxide; - a metal; - a metal alloy; - a metal alloy oxide; - inorganic material; or mixtures thereof.

11. | Method according to claim 10, characterized in that the pigment further includes mica included at a rate of 38% to 74% in the pigment composition.

12. Method according to claim 11, characterized in that the mica is under particle shape exhibiting at least one of the characteristics following: - a particle size k times 10* greater than the size of the others particles of the pigment composition, with k an integer ranging from 1 to 9, - a particle size between 3.0 um and 80 um.

13. Method according to any one of claims 1 to 13, characterized in that the marking composition (2) [fixed on said substrate (4) has a thickness of between 10 nanometers and 0.1 millimeters.

14. | Marking composition intended to be fixed on a substrate by ir- laser radiation according to the method defined according to any one of the res- indications 1 to 7 including: - an aqueous base comprising water and a stabilizing agent, said aqueous base being present at a rate of 50% to 84% by weight in the composition marking, - at least one pigment in the form of particles suspended in the aqueous base at a rate of 16% to 50% by weight in the composition of marking, each pigment being in the form of particles of size between 10 nm and 0.1 mm.

15. Marking composition according to claim 14, characterized in that that the stabilizing agent comprises a short-chain water-soluble alcohol or an acrylic resin and a surfactant.

16. A marking composition according to any one of claims 14 to 16, characterized in that the pigment in the form of particles is chosen from: - a metal oxide; - a metal; - a metal alloy; - a metal alloy oxide; - inorganic material; or mixtures thereof,

17. Marking composition according to claim 16, characterized in that that the pigment further comprises mica included at a rate of 38% to 74% by weight in the pigment composition.

18. Marking composition according to claim 17, characterized in that that the mica is in the form of particles having at least one of the ca- following characteristics: - a particle size k times 10° greater than the size of the others particles of the pigment composition, - a particle size between 3.0 um and 80 um.