VISIBLE PERMANENT WRITING PROCESS ON OPTICAL ARTICLES AND MARKED ARTICLES

Description

[0001] The present invention relates to the general field of visible permanent marking of optical articles, typically ophthalmic lenses, coated with a multi-layer interference coating.

[0002] It is known that ophthalmic lenses, such as spectacle lenses, undergo different manufacturing stages. One of these stages includes the marking, called permanent, of the ophthalmic lens on one of its faces. The technical permanent marking is formed by engraving, or micro-engraving, representing dots or crosses and identifying a particular point (for example the optical center of the ophthalmic lens or the prism reference point for a progressive lens), or axis lines (for example to indicate the horizontal axis along which astigmatism is corrected), or shapes limiting a particular area (for example, the near vision area or the distance vision area in the case of a progressive lens).

[0003] These permanent markings, whether technical or commercial, are often made on one side, either the front or the back, of ophthalmic lenses, some markings being on the front and others on the back. By "back" or "inner side" (usually concave) of the substrate is meant the side which, when the article is in use, is closest to the wearer's eye. Conversely, by "front" or "outer side" (usually convex) of the substrate is meant the side which, when the article is in use, is furthest from the wearer's eye.

[0004] The most common methods of marking optical articles today are ink marking and laser (beam) marking.

[0005] Ink marking has the disadvantages that it is difficult to find a permanent ink compatible with any type of ophthalmic lens surface, and that this type of marking is not only visible to an outside observer but also to the wearer of the ophthalmic lens.

[0006] Jax Holdings Inc.'s US 2004 / 0095645 and EP 0677764 each describe a method for constructing an interference coating by successively depositing layers on a transparent substrate, in which a patterned mask is printed on a base layer before subsequent layers are deposited. The mask is printed with an ink configured to be cleaned with a solvent. The mask is removed after subsequent layers are deposited so that the interference coating has a reduced thickness in the portions previously occupied by the mask. The coating has different reflective properties depending on its thickness, making the pattern visible. Such a technique is time-consuming and expensive, and requires the use of complex machinery.

[0007] Laser marking can also be achieved by ablation (i.e. removal of a quantity of material) forming an engraving of the surface. Thus, the marking is generally formed by a series of points called marking points (also called "spots"), each marking point being produced by one or more laser pulses. In this case, the marking has a visibility which depends on the depth and width of the marking points, as well as the thickness and nature of the ablated layer(s). This marking must also be positioned outside the field of vision of the ophthalmic lens wearer so as not to disturb their vision.

[0008] Document US 2014 / 0016083 describes an improvement of this latter technique, according to which a marking can be carried out by laser beam on the convex surface of an ophthalmic lens after vacuum deposition of a coating of thin oxide layers. These thin layers are applied in a certain order, and are then successively exposed to the laser beam, and therefore successively ablated. The treated surface therefore has a different visibility compared to the untreated surface. This makes it possible to produce a marking visible to an external observer, because different colors are visible to an external observer in the case of irradiation with white light.

[0009] However, this ablative solution using a laser beam has the major problem that the marking is not easily controllable, mainly in depth. Consequently, the marking points made by repeating a marking step at different points belonging to the same pixel are generally not contiguous, which implies that the marking is not continuous. According to this document, a succession of multiple partial ablations in the same pixel makes it possible to avoid the problem of an engraving carried out in an excessively large manner (i.e. too much laser beam in a given location), which could lead to the undesired effect that a coating of the ophthalmic lens, such as an anti-reflective coating or an anti-abrasion coating, is attacked, in part or in full, by the laser beam.

[0010] Document JP 2016 007612 A has optical marking.

[0011] One of the objects of the invention is to provide a method for marking an optical article which overcomes the drawbacks of the state of the art, in particular the problems of unwanted removal of all or part of a coating of the optical article.

[0012] The invention thus relates, in a first aspect, to a method for marking an optical article comprising at least one step of using a marking machine on an optical article: The marking machine being an electromagnetic beam marking machine, preferably a laser beam, comprising an electromagnetic source, preferably a laser source, configured to emit a beam having a determined radiation wavelength called the marking wavelength; The optical article being an optical article comprising a substrate having a main face coated with an interference coating, said interference coating comprising at least two superimposed layers called the inner layer and the outer layer, the inner layer being located between the substrate and the outer layer, the interference coating being such that it has a reflection coefficient Re in the visible range (380-780 nm);The use comprising the exposure of at least the inner layer at a given point called the marking point, by means of the laser beam at the marking wavelength, so as to ablate, at the marking point, the inner layer over at least part of its thickness, and any layer located between the electromagnetic source and the inner layer; and being such that the ablated zone has a reflection coefficient Rm in the visible range (380-780 nm), Rm being different from Re by at least 3%; The inner layer absorbing the marking wavelength more significantly than any layer located between the electromagnetic source and the inner layer. ;

[0013] The invention also relates, in a second aspect, to an optical article comprising a substrate coated with an interference coating comprising two superimposed layers of materials called the inner layer and the outer layer, the inner layer being located between the substrate and the outer layer, the interference coating being such that it has a reflection coefficient Re in the visible range (380-780 nm);

[0014] Said article comprising a marking pattern on the surface of the interference coating, the marking pattern being formed by a plurality of substantially identical marking points, each marking point corresponding to the localized absence of the inner layer and of any layer located between said surface and the inner layer, the ablated zone having a reflection coefficient Rm in the visible range (380-780 nm) such that Re is different from Rm by at least 3%, the marking pattern preferably being continuous. Preferably, such an optical article is obtained by the marking method according to the invention.

[0015] The invention is described in more detail below.

[0016] The method according to the invention therefore makes it possible to carry out at a marking point a direct localized ablation of at least part of the inner layer and indirect ablation of the layers located between the electromagnetic source and the inner layer.

[0017] The invention therefore advantageously allows the marking process to be controlled, in particular the depth of the engraving, which is very advantageous compared to the processes of the prior art. Without wishing to be bound by any theory, the applicant believes that this is mainly due to the fact that the electromagnetic beam manages to insolate the inner layer which is made of a material that is highly absorbent at the wavelength of the radiation compared to the other layers present.

[0018] Indeed, according to the invention, each of the layers of material between the electromagnetic source and the inner layer is at least partially transparent to the marking wavelength, that is to say that it does not absorb at least in part at this marking wavelength. Preferably, this layer is at least semi-transparent at this marking wavelength, that is to say that it allows more than half of the energy of this marking wavelength to pass through.

[0019] Therefore, upon exposure to the electromagnetic beam, this inner layer receives most of the transmitted energy and is therefore selectively degraded. Since the layers between the inner layer and the electromagnetic source are generally very thin oxide layers, the degradation, or even sublimation of the inner layer, actually separates these layers, which can then be removed.

[0020] Thus, the electromagnetic beam advantageously aims to ablate the inner layer, and indirectly allows the ablation, most often by detachment, of any layer located between the electromagnetic source and the inner layer, and therefore in particular of the outer layer. In other words, the inner layer is destroyed (partially or totally) by the beam, the layers between the beam and the inner layer being destroyed / removed by collateral effect of the destruction of the inner layer.

[0021] The ablation is such that the resulting single marking point generally has a substantially cylindrical shape with an axis substantially perpendicular to the surface of the inner layer furthest from the substrate before it is ablated.

[0022] It is noted that when the invention is applied to an ophthalmic lens having an anti-reflective coating, not only are the reflection intensity values ​​between the ablated area and the non-ablated area different, but in a further embodiment, the chroma, presented in an L, a*, b* system, is different between the two areas. The non-ablated area may thus have a pale green residual reflection color, for example for the lens having a Crizal Forte ® coating, with a reflection value of about 0.8%, and the ablated area has a rather pale blue reflection color.

[0023] More generally, the marking method according to the invention is advantageously such that the reflection at the marking point has a color, in saturation (hue: h*) and / or in tint (Chroma: C*), different from that of the reflection of the non-ablated zone.

[0024] Thus, the contrast between the ablated area and the non-ablated area allowing the pattern to be observed, which is mainly based on a difference in reflection intensity, can be improved by a difference in reflection color. The optical article according to the invention is not necessarily a low-transmittance article such as a solar glass. It can also be almost transparent.

[0025] It should be noted, however, that the laser focal point is not necessarily located in the inner layer of the interference coating. It is even most often outside of it, typically 1 to 2 mm outside of it, for example 2 mm above the optical article. This is for example described in the applicant's patent application WO 2015 / 040338.

[0026] By "element between A and B" is meant, unless otherwise specified, that the element is located between A and B but is neither A nor B.

[0027] By "element within an interval from A to B" or "element from A to B" is meant, unless otherwise specified, that the element is located between A and B and can be either A or B. By "set of elements from A to B" is meant, unless otherwise specified, the set formed by A, B and any element located between A and B.

[0028] According to the invention, "to insolate" means to expose to an electromagnetic beam. This leads to the removal of material, i.e. to ablation. Insolation is carried out according to the invention by means of the marking machine.

[0029] According to the invention, the term "non-ablated zone" means any part of the main face which has not been exposed to sunlight and therefore has not been ablated.

[0030] For the purposes of the invention, the term "interference coating" (also called interference filter or dichroic filter) means any coating of at least two layers whose indices and thicknesses lead to attenuating and / or amplifying the reflection coefficient of a surface of the optical article by an interference mechanism, constructive or destructive, on all or part of the wavelengths included in the visible, that is to say in the interval (380 nm-780 nm). This reflection filter is therefore made up of a succession of thin layers, the operating principle of which is based on the interference of successive reflections on each of the diopters encountered. The interference can, depending on the thickness of the layers and the wavelength, be constructive or destructive. The part that is not transmitted is reflected. In the case of anti-reflective coatings, the various reflections interfere to strongly attenuate each other.Conversely, when all reflections are in phase, we obtain mirror interference coatings with a very high reflection factor.

[0031] An "antireflective coating" is defined as a coating deposited on the surface of an optical article, which improves the anti-reflective properties of the article ready for use. It reduces the reflection of light at the article-air interface over a relatively broad portion of the visible spectrum.

[0032] Anti-reflective coatings are well known in the art and particular examples are described in application US2008 / 0206470. The anti-reflective coating of the present invention may include any layer or coating of layers that enhances the anti-reflective properties of the final optical article, over at least a portion of the visible spectrum, so as to increase light transmission and reduce surface reflectance at the air-optical article interface.

[0033] As explained above, the invention also relates to a mirror-type interference coating.

[0034] The interference coating, whether anti-reflective coating or not, of the optical article according to the invention comprises the interference coating according to the invention as defined above.

[0035] In particular, for the purposes of the invention, the “interference coating” does not include any anti-fouling and / or anti-fog and / or anti-rain and / or hydrophobic and / or oleophobic and / or hydrophilic coating which generally has a thickness less than or equal to 2 nm and only contributes negligibly to attenuating or amplifying the reflection. Thus, any layer of the interference coating has an effect on the interference mechanism.

[0036] According to the invention, "inner" refers to the side closest to the substrate and "outer" refers to the side furthest from the substrate. Therefore, "inner layer" and "outer layer" respectively mean, unless explicitly stated otherwise, "the layer of the interference coating closest to the substrate among the layers of the interference coating" and "the layer of the interference coating furthest from the substrate among the layers of the interference coating".

[0037] The "outer layer" may be covered with a possible additional anti-fouling or anti-rain or anti-fog layer, or even with a temporary layer intended to increase adhesion, for example for a trimming step, and intended to be removed for use of the optical article by an end user. Such an additional layer is usually known as a "topcoat", and does not belong, as explained above, to the interference coating within the meaning of the invention.

[0038] By "the inner layer absorbing the marking wavelength more significantly than any layer located between the electromagnetic source and the inner layer", it is meant according to the invention that the absorption coefficient at the marking wavelength of the inner layer is at least 10%, preferably at least 20%, higher than the absorption coefficient at the marking wavelength of any other layer, located between the electromagnetic source and the inner layer.

[0039] The "absorption coefficient" represents the absorption at a wavelength of the visible spectrum, and is defined according to the invention as the ratio between the absorbance A and the optical path L (= A / L) for an electromagnetic beam of given wavelength (here in the visible range) in a given medium. This ratio is expressed in m -1< or cm -1< , in particular according to the ISO / CD 11551 standard.

[0040] By "more significantly" is meant according to the invention in a manner discernible by a person skilled in the art, to suit the purpose sought by the invention.

[0041] By "reflection coefficient" (Re or Rm according to the invention), within the meaning of the invention, is meant the rate of light reflected by the surface of an optical article, illuminated by an illuminant covering at least the entire visible spectrum, for example solar illuminant or illuminant D65. The reflection rate is preferably measured with a ray of light incident on the surface with an angle of 2° or 10°. When this is not specified, the reflection coefficient only takes into account visible light, i.e. light having a wavelength between 380 nm and 780 nm.

[0042] The "transmission factor", or "transmittance" T v (tau index v) corresponds to the fraction of luminous flux which passes through an optical article, as a function of the wavelength, illuminated by an illuminant covering at least the entire visible spectrum, for example the solar illuminant or the illuminant D65. The factor τ v corresponds to an international standard definition (standard ISO 13966:1998) and is measured in accordance with standard ISO 8980-3. It is defined in the wavelength range from 380 to 780 nm.

[0043] By "transparent" is meant according to the invention not absorbing at a visible wavelength [380-700 nm], that is, in other words, that an image observed through the product described as transparent is perceived without significant loss of contrast or quality.

[0044] The inner layer is the layer of the interference coating closest to the substrate. It is located between the substrate and the outer layer of the interference coating, but is not necessarily in contact with the substrate or the outer layer. Thus, one or more layers of one or more intermediate coatings may be arranged between the substrate and the inner layer, and between the inner layer and the outer layer. In addition, the inner layer does not necessarily completely cover the substrate, although it preferably does.

[0045] Any possible layer located between the substrate and the inner layer is at least partially transparent to the marking wavelength, i.e. it does not absorb at least in part at this marking wavelength. Preferably, this layer is at least semi-transparent to this marking wavelength, i.e. it allows more than half of the energy of this marking wavelength to pass through.

[0046] Similarly, the outer layer is not necessarily in contact with the inner layer. In addition, one or more additional layers may be arranged above the outer layer, as indicated above. In other words, the outer layer is not necessarily the layer of the optical article furthest from the substrate. These additional layers are, for example, temporary layers used in the context of manufacturing but not intended to be present on the optical article that will be used by an end user. This may be, for example, in the case of ophthalmic lenses, a coating used to allow the trimming of the lenses so that they can be shaped into a frame, said additional layers being removed after this shaping.

[0047] Although the optical article according to the invention may be any article, such as a screen, glazing, protective glass usable in particular in a work environment, or a mirror, it is preferably an ophthalmic glass, and even better an ophthalmic lens, for spectacles, or an ophthalmic lens blank such as a semi-finished optical lens, in particular a spectacle lens. The lens may be a clear, polarized, colored lens or a photochromic lens, or be added to an active element such as an augmented reality device, an electrochromic or electrofocal device. The lens may be a lens without optical power, with optical power, simple or complex, or even be a progressive or bi or multifocal lens.

[0048] An optical article generally has, on the side of the outer layer furthest from the substrate, an interference coating, preferably an anti-reflective coating, as is known to those skilled in the art, so as to prevent the formation of parasitic reflections which are annoying for the wearer of the ophthalmic lens and those with whom he is speaking. It is this interference coating which is marked by the marking method according to the invention.

[0049] Thus, typically, an ophthalmic lens is most often provided with a single- or multi-layer anti-reflective coating, generally made of mineral material. Such an interference coating may be, without limitation, an anti-reflective coating, a reflective (mirror) coating, an infrared filter or an ultraviolet filter or an interference coating functioning as an anti-reflective coating on a portion of the light spectrum and functioning as a partial mirror around one or more wavelength ranges, preferably an anti-reflective coating.

[0050] The substrate is transparent to visible wavelengths [380-780nm], and has main front and back faces.

[0051] The substrate according to the invention is preferably an organic glass, for example made of thermoplastic or thermosetting plastic material. Before depositing the interference coating on the substrate optionally coated, for example with at least one layer of abrasion-resistant and / or scratch-resistant coating, it is common practice to subject the surface of said optionally coated substrate to a physicochemical activation treatment, intended to increase the adhesion of the interference coating.

[0052] The interference coating according to the invention may be present on the surface of at least one of the main faces of the bare, i.e. uncoated, substrate, or on at least one of the main faces of a substrate already coated with at least one layer of functional coating. But it may also be present on the surface of the two main faces of the substrate of the optical article.

[0053] By "functional coating", we mean, within the meaning of the invention, at least one coating chosen from a non-exhaustive list including anti-scratch coatings, anti-shock coatings or coatings improving adhesion, tinted, anti-static or other coatings, films or coatings comprising a polarized function, or a photochromic function, or structures allowing an active function, for example electrochromic.

[0054] As is well known, interference coatings, preferably antireflective coatings, are typically multilayer coatings usually comprising high refractive index (HI) layers and low refractive index (LI) layers.

[0055] HI layers are well known in the art. They generally comprise one or more inorganic oxides such as, without limitation, zirconia (ZrO 2 ), titanium oxide (TiO 2 ), tantalum pentoxide (Ta 2 O 5 ), neodymium oxide (Nd2O5), hafnium oxide (HfO 2 ), praseodymium oxide (PrTiO 3 ), La 2 O 3 , Nb 2 O 5 , Y 2 O 4 , indium oxide In 2 O 3 or tin oxide SnO 2 . Preferred materials are TiO 2 , Ta 2 O 5 , PrTiO 3 , ZrO 2 , SnO 2 , In 2 O 3 and mixtures thereof.

[0056] BI layers are also well known and may include, without limitation, SiO 2 , MgF 2 , SrF 4 , alumina (Al 2 O 3 ) in small proportion, AlF 3 , and mixtures thereof, preferably SiO 2 .

[0057] At least one of these layers may be electrically conductive. This thus makes the optical article antistatic. By "antistatic" is meant the property of not retaining and / or developing an appreciable electrostatic charge. An optical article is generally considered to have acceptable antistatic properties when it does not attract or fix dust and small particles after one of these surfaces has been rubbed with a suitable cloth. The electrically conductive layer may be located at different points of interference coating, provided that the interference properties of the optical article, for example anti-reflective, are not disturbed. It must be sufficiently thin so as not to alter the quasi-transparency of the interference coating.Generally, its thickness varies between 0 and 100 nm, preferably in a range of 2 to 25 nm, even more preferably in a range of 4 to 15 nm. The electrically conductive layer, which is part of the interference coating, preferably comprises a metal oxide chosen from indium, tin, zinc oxides and mixtures thereof. Indium-tin oxide (In 2 O 3 :Sn, tin-doped indium oxide) and indium oxide (In 2 O 3 ), as well as tin oxide SnO 2 , are preferred.

[0058] For example, the applicant's French patent application FR 2943798 describes an optical article with antistatic and antireflective or reflective properties, comprising a substrate having at least one main surface coated with an antireflective or reflective coating, said coating comprising at least one electrically conductive layer based on tin oxide, i.e. comprising at least 30% by mass of tin oxide relative to the total mass of the electrically conductive layer. Such an optical article can advantageously be marked by the marking method according to the invention, the electrically conductive layer being particularly suitable for being the inner layer according to the invention at certain marking wavelengths.

[0059] The interference coating may also comprise an undercoat (i.e. a coating of relatively significant thickness), with the aim of improving the abrasion and / or scratch resistance of said coating and / or promoting its adhesion to the substrate or the underlying coating. Such an undercoat, which is part of the interference coating, generally has a thickness of 100 to 200 nm. It is generally of an exclusively mineral nature, for example consisting of silica dioxide SiO 2 .

[0060] Typically, a HI layer is 10-120 nm thick, and a BI layer is 10-100 nm thick.

[0061] Preferably according to the invention, the total thickness of the interference coating is less than 1 µm, better still less than or equal to 780 nm, even better still less than or equal to 500 nm. The total thickness of the interference coating is generally greater than 100 nm, preferably greater than 150 nm.

[0062] The marking machine is for example as described in the applicant's patent application WO 2015 / 040338, which describes in particular the use of an Nd-YAG laser at application wavelengths of 230 to 290 nm, preferably around 266 nm.

[0063] For example, an Nd-YAG laser can be used according to the invention, at 266 nm with 1 ns pulses, a pulse energy of 3 µJ and a marking spot area of ​​10 µm in diameter.

[0064] This type of setting of the marking laser advantageously makes it possible to target a SnO 2 layer and to remove at least partially the SnO 2 layer when exposed, without crossing the substrate, but also to remove, during the ablation of the part of the SnO 2 layer, the layer(s) present above the SnO 2 layer. This will be demonstrated in the examples below.

[0065] In the case where the interference coating is an anti-reflective coating, its reflection coefficient Re is preferably less than 1.4% and even more preferably less than 0.85%.

[0066] The marking method according to the invention advantageously makes it possible to obtain a marking pattern that is very visible to an external observer and little, preferably not at all, visible to the wearer of the optical article. In practice, a 2% difference in reflection coefficient between Re and Rm (Rm-Re = 0.02) corresponds to a local increase in reflection of approximately 200 to 300% depending on the angle of reflection, the perceived increase in reflection being as follows: (Rm-Re) / Re.

[0067] In the case where the interference coating is an anti-reflective coating, the perceived increase in reflection is for example about 0.02 / 0.0085 [i.e. (Rm-Re) / Re], or 235%.

[0068] As claimed, the difference between Rm and Re is, in absolute value, greater than 3%, even more preferably greater than 5% (in quantity relative to the same incident light). In general, the difference between Rm and Re is less than 50% of the reflection coefficient Re, except when the interference coating is a mirror.

[0069] According to one embodiment, the difference between Rm and Re is, in absolute value, between 5% and 25%, preferably between 7% and 20%.

[0070] According to one embodiment of the invention, the exposure step is followed by a cleaning step to remove any trace of the layers ablated during the exposure step.

[0071] According to a preferred embodiment of the invention, the electromagnetic beam is emitted by pulse, and has an energy per pulse comprised in a range of 0.1 to 10 µJ, for example equal to 0.5 µJ, 1 µJ, 2 µJ or 5 µJ, preferably comprised in a range of 0.1 to 3 µJ, for example equal to 0.5 µJ, 1 µJ, 2 µJ or 3 µJ.

[0072] Preferably, the insolation step is carried out by emitting a focused beam of pulsed ultraviolet laser radiation having at least the following parameters: a radiation wavelength in the range of 200 to 400 nm, preferably 200 to 300 nm, a pulse duration in the range of 0.5 to 5 ns, and an energy per pulse in the range of 0.1 to 10 µJ, preferably in the range of 0.5 to 3 µJ, as well as, at the marking point, a beam diameter in the range of 5 to 50 µm.

[0073] In a preferred embodiment of the invention, when the radiation wavelength of the pulsed ultraviolet laser radiation beam performing the insolation step is in the range of 200 to 300 nm, the inner layer is based on, preferably consisting essentially of, tin, preferably tin oxide, even more preferably tin dioxide SnO 2 .

[0074] “Based” means for the purposes of the invention that the inner layer comprises at least 50%, by mass, of the compound relative to the total mass of the inner layer.

[0075] “Consisting essentially” means for the purposes of the invention that the proportion of the compound in said inner layer is greater than or equal to one of the following values: 70%, 75%, 80%, 90%, 95%, 97%, 99%, 99.5%, 99.9%, 99.95%. Ideally, said inner layer consists of a layer of tin dioxide SnO 2 .

[0076] The inventors have in particular noted that the tin-based layers, in particular tin oxide, especially tin dioxide, react selectively upon illumination by means of a laser beam having a wavelength of between 200 and 300 nm, when they are present in an interference coating otherwise comprising only silica- or zirconia-based layers. In this configuration, the silica- or zirconia-based layers are substantially transparent at the wavelength while the tin-based layers absorb energy at this wavelength in sufficient quantity to generate destruction, or even local ablation of this layer, over at least part of its thickness.

[0077] The inner layer may contain other constituents, including metal oxides, particularly electrically conductive metal oxides which are preferably transparent. It may in particular comprise titanium oxide and / or zinc oxide. Preferably, the inner layer does not contain indium, whether in oxide form or in any other form.

[0078] Preferably, the inner layer has a thickness in the range of 1 to 100 nm, preferably 2 to 25 nm, even more preferably 4 to 15 nm, the sum of the thicknesses of the inner and outer layers being in the range of 5 to 300 nm, preferably 45 to 175 nm.

[0079] The outer layer is generally based on, preferably consisting essentially of, silicon, preferably silicon oxide, even more preferably silicon dioxide SiO 2 .

[0080] According to a particular embodiment of the invention, the transmission in the visible of the optionally coated interference coating and the transmission in the visible of all the layers going from the substrate to the outer layer are substantially identical. This is generally achieved by the fact that the absorbance, in the visible, is substantially identical (i.e. to within 0.1 or 0.2%), whether or not the ablated layers are present. Thus, in general, the difference in the quantity of light transmitted between the ablated zone (i.e. marked zone, comprising at least one marking point or even a marking pattern, produced by the marking method according to the invention) and the non-ablated zone (or non-marked, i.e. not comprising such a marking pattern) depends mainly, to the first order, on the difference in reflection between these zones.For a clear ophthalmic lens with an anti-reflective coating, the rate of visible light transmitted is generally greater than 85%, or even 90% or even 95%. In particular, the transmission, in the visible, of the interference coating is close to (0.99-Rm), where Rm is the reflection coefficient of this coating. In this case, a difference in reflection between the two zones, between 1% and 8%, leads to a rate of light passing through the interference coating at the ablated zone between 0.92 times and 0.99 times the rate of light passing through the coating in the non-ablated zone. It is this small difference that makes the marking pattern barely or not visible to the wearer.

[0081] According to a preferred embodiment of the invention, at least one absorbing layer (i.e. one that at least partially absorbs visible light) is present in the interference coating of the invention, and is locally removed, directly or indirectly, during the ablation of the inner layer by the electromagnetic beam. In this case, preferably, all the layers from the inner layer to the outer layer have an absorption of at least 0.5% of the transmitted visible light, for example at least 1% of the transmitted light and, preferably, the absorbing layer has an absorption ("Abs") (or in other words an absorption coefficient) in a range of 0.5 to 1.5 times, preferably 0.9 to 1.1 times, the absolute value of the difference between Re and Rm. This is achieved by the parameters of the thickness and the absorption coefficient of the absorbing layer.

[0082] The absorbing layer is a layer of the interference coating and contributes to the reflection properties of the interference coating. It can be the inner layer, the outer layer, or another layer positioned between these two layers.

[0083] According to this embodiment, the rate of light transmitted through the interference coating no longer depends solely on the reflection coefficient of the interference coating, but also on the intrinsic absorption of the absorbing layer. Thus, the rate of light transmitted through the interference coating in the non-ablated area corresponds approximately to [1 - Re - Abs] with Abs representing the absorption of light by the absorbing layer. For comparison, the rate of light transmitted through the interference coating in the ablated area, in which the absorbing layer has been locally removed (directly or indirectly) during insolation, corresponds approximately to [1 - Rm]. Indeed, the absorption of the layers of the interference coating other than the absorbing layer is considered to be zero at first order.

[0084] Thus, the difference in reflection between the two zones remains [Re-Rm]; on the other hand, the difference in the rate of light transmitted between the two zones is then [Rm-Re-Abs].

[0085] On the other hand, the difference in the rate of light transmitted between the ablated zone and the non-ablated zone is reduced. It is preferably between - 0.5x(Rm-Re) and 0.5x(Rm-Re), it being understood that (Rm-Re) represents the absolute value of the difference between Re and Rm. This value depends on the absorption value of the absorbing layer. In such a case, the perception in transmission of the ablated zone, by the wearer of glasses, is reduced at least by half.

[0086] In a particular case, the thickness and absorption coefficient of the absorbing layer are determined so that the light absorption by the absorbing layer is close to the reflection difference and is between 0.9 and 1.1 times the absolute value of (Re-Rm). In this case, it is possible to consider that the ablated area is invisible in transmission.

[0087] According to one embodiment of the invention, the interference coating is an anti-reflective coating. In this case, the anti-reflective coating preferably comprises, from the surface of the optionally coated substrate outwards, a layer of ZrO 2 , 5 to 40 nm thick, a layer of SiO 2 , 10 to 55 nm thick, a layer of ZrO 2 , 20 to 150 nm thick, an inner layer of SnO 2 , 4 to 15 nm thick, and an outer layer of SiO 2 , 50 to 120 nm thick.

[0088] In one embodiment of the invention, the interference coating is itself coated (on the face furthest from the substrate) with a coating of protective material, such as an anti-rain coating, an anti-fog coating and / or an anti-fouling coating, said marking method then generally being followed in this case by a deprotection step subsequent to said marking method, said deprotection step comprising the removal of this coating of protective material.

[0089] According to a particular embodiment according to the invention, the insolation step is carried out at as many marking points as necessary so as to locally mark a region of the main surface of the substrate of the optical article by means of multiple marking points, said region forming a predefined pattern called a marking pattern. In such a case, there is preferably continuity between the marking points which define the region forming the marking pattern. Such a marking region preferably comprises less than 1% of surface residues of the ablated layers (by direct or indirect insolation). Such a state can be obtained directly at the end of the marking process, or require an additional brushing and removal step, accessible to those skilled in the art. This differs notably and advantageously from the embodiments of the prior art.

[0090] In such a case, preferably, the marking is carried out at a step of dimension less than or equal to the dimensions of the marking point, that is to say less than or equal to the average diameter of an ablated zone in a single marking point, so that the marking points show a partial overlap. For example, the marking step is between 0.5 and 1 times the marking diameter of a pulse of the beam when the beam emits by pulse. If the pulse is reproduced identically each time by the electromagnetic source, a particular embodiment is such that the marking step is equal to the marking diameter. This particularly and advantageously makes it possible, according to the invention, to be able to carry out a continuous marking method which consumes the least possible amount of electromagnetic energy.This is particularly effective when the electromagnetic beam is emitted in a pulse, and has an energy per pulse in the range of 0.1 to 3 µJ, for example equal to 0.5 µJ, 1 µJ, 2 µJ or 3 µJ.

[0091] According to the invention, the term "step" means the minimum distance between the centers of two marking points made successively.

[0092] Preferably, only one pulse is required per marking point.

[0093] The invention also relates to an optical article comprising a substrate having a main face coated with a multi-layer interference coating, said interference coating comprising at least two superimposed layers of materials called inner layer and outer layer, the inner layer being located between the substrate and the outer layer, said article comprising a marking pattern on the surface of the interference coating, the marking pattern being formed by a plurality of substantially identical marking points, each marking point corresponding to the localized absence of at least part of the thickness of the inner layer and of the entirety of any layer located between said surface and the inner layer, the marking pattern preferably being continuous.

[0094] Preferably, such an optical article is obtained by the marking method according to the invention, in which the exposure step is repeated several times.

[0095] The marking area is formed from a plurality of marking points, each marking point being obtained by insolation carrying out the ablation by electromagnetic beam of at least part of the thickness of the inner layer.

[0096] By "on the surface of the interference coating" is meant on the surface of the interference coating if it is not itself coated with at least one coating layer and on the surface of the most distant coating layer on the substrate if it is itself coated with at least one coating layer.

[0097] By "continuous marking pattern" is meant according to the invention that any marking pattern is formed of multiple contiguous marking points, the pitch between two contiguous marking points being of a dimension less than or equal to the smallest of the dimensions of these two marking points.

[0098] The characteristics of the interference coating, in particular of the inner and outer layers, are as described above for the marking method according to the invention.

[0099] Preferably, the optical article according to the invention does not absorb in the visible or absorbs little in the visible. This means, within the meaning of the present application, that its transmission factor τ v in the visible, also called relative transmission factor in the visible, is greater than 90%, preferably greater than 95%, more preferably greater than 97% and even more preferably greater than 99%.

[0100] Particularly preferably, the light absorption of the optical article according to the invention is less than or equal to 1.

[0101] Alternatively, the optical article may be a tinted lens, known as a solar lens, having for example a transmission of between 5% and 50% depending on its classification on the international sunglasses classification scale.

[0102] The invention will be better understood from the attached drawings in which: THE Figures 1 to 3 schematically represent a first example of embodiment of the marking method according to the invention, the Figure 1 schematically representing in sectional plan the principle of the marking process before its realization, the Figure 2 schematically representing in sectional plan the marking process in progress, and the Figure 3 schematically representing in sectional plan the marking process at the end of production; and The Figures 4 and 5 illustrate the results obtained in reflection (R) and in transmission (T) for the ophthalmic glass (1) obtained according to the first example of realization of the Figures 1 to 3, in the area of ​​the marking point (25) and in other areas of the surface of the ophthalmic lens; and The Figures 6 to 9 schematically represent a second example of embodiment of the marking method according to the invention, the Figures 6 and 7 representing the ophthalmic glass before the marking process is carried out and the Figures 8 and 9 representing the ophthalmic glass after the marking process has been carried out, more precisely the Figure 6 representing the ophthalmic glass in overall view before carrying out the marking process, the Figure 7 representing in perspective a section of the layers present on the ophthalmic glass before carrying out the marking process, the Figure 8 representing the ophthalmic lens in overall view after the marking process has been carried out, and the Figure 9 representing in perspective a section of the layers present on the ophthalmic glass after the marking process has been carried out.

[0103] The invention will be better understood from the following exemplary embodiments, with reference to the appended drawings as indicated above. Figures 1 to 9 are explained in the examples below. EXAMPLES

[0104] The following examples illustrate the invention without limiting its scope.

[0105] In the following two embodiments, the inner layer consists of tin dioxide SnO 2 ; the outer layer consists of silica oxide, namely either silica monoxide SiO or silica dioxide SiO 2 ; and the electromagnetic beam is a 266 nm (UV) laser beam. The marking wavelength is therefore 266 nm. Example 1 : marking of an ophthalmic lens consisting of a substrate, a first chrome layer (“Cr1”), an inner layer SnO 2 , of a second absorbing chromium layer (“Cr2”), and an outer SiO2 layer

[0106] The ophthalmic lens (1) consists of a substrate (6) on which have been successively superimposed a first layer (5) of metal (chromium, "Cr1"), an inner layer (4) of tin dioxide SnO 2 , a second layer (3) of metal (chromium, "Cr2"), or absorbent layer, and an outer layer (2) of silica monoxide SiO. The substrate (6) is here a polarized or tinted substrate comprising an anti-scratch coating of the Mithril ® brand.

[0107] Such a substrate-metal-dielectric-metal-dielectric structure is similar to that of glass which is marked according to the state of the art US 2004 / 0095645, except that, according to the invention, a layer of SnO 2 has been added between the Cr1 layer and the Cr2 layer.

[0108] The layers (2) SiO / (3) Cr2 / (4) SnO 2 / (5) Cr1 are of such a nature and thickness that the coating they constitute creates an interference effect increasing the reflections so as to create a mirror with reflection. This coating has an average reflection coefficient of about 12 to 15%, with a stronger reflection in the violet.

[0109] The layer (5) chrome Cr2 absorbing very slightly in the visible significantly reduces the overall transmission of the system, which does not pose a problem in the case of the ophthalmic glass (1) used which here is a solar glass.

[0110] The nature and physical and optical characteristics of the layers are indicated in the following table: Layer number from substrate / Layer reference (illustration) Layer material Layer thickness (± 2 nm) 1 / (5) Cr 15 nm 2 / (4) SnO 2 6 nm 3 / (3) Cr 5 nm 4 / (2) SiO 65 nm

[0111] The marking method according to the invention was carried out using a pulsed laser emitting a beam at the wavelength of 266 nm with pulses of duration 1 ns, an energy per pulse of 3 µJ and a marking spot surface of approximately 10 µm in diameter.

[0112] THE Figures 1 to 3 schematically illustrate this first example of embodiment of the marking method according to the invention. The laser beam 23 is represented very symbolically by a flash which focuses on the inner layer 4.

[0113] There Figure 1 schematically represents in sectional plan the principle of the marking process before its realization on the ophthalmic glass 1. It shows the substrate (6), on which the first layer (5) of chromium Cr1 has been deposited, on which are superimposed the inner layer (4) of tin dioxide SnO 2 , then the layer (3) of chromium Cr2, and finally the outer layer (2) of silica monoxide SiO.

[0114] There Figure 2 schematically represents in sectional plan the marking process in progress by local removal of the layers (4), (3) and (2) by the electromagnetic beam (23) which insulates the inner layer (4) in SnO 2 and destroys it, causing the removal of the layers (3) and (2) indirectly during the destruction of the layer (4). We can distinguish the part (24) of the layers (4), (3) and (2) in the process of removal, which will become the marking point (25) of the Figure 3 . On this section plane, layer (4) splits into two parts (4') and (4"), layer (3) splits into two parts (3') and (3") and layer (2) splits into two parts (2') and (2"). The ophthalmic lens (1') on which the marking begins also includes layer (5) on the substrate (6).

[0115] There Figure 3schematically represents in sectional plane the marking process at the end of production. On this sectional plane, the layers (4), (3) and (2) have been ablated following exposure by the electromagnetic beam (23), splitting respectively into two parts (4') and (4"), into two parts (3') and (3") and into two parts (2') and (2"). An engraved ophthalmic lens (10) is thus obtained.

[0116] The realization thus schematized made it possible to make a marking point (25). The repetition of the insolation step of the method of the invention makes it possible to make several marking points thus forming a marking pattern, such as a logo.

[0117] Advantageously, the chromium layer (5) Cr1, between the inner layer (4) and the substrate, absorbs little or very little of the light emitted at the wavelength of the laser (266 nm), which makes it practically insensitive to the electromagnetic marking beam. It is therefore not destroyed by insolation by the electromagnetic marking beam. It is therefore possible to superimpose the marking points without risk of over-etching at the intersection between two marking points. Consequently, the method according to the invention advantageously makes it possible to produce a continuous marking on the surface of the ophthalmic lens (1), such as a large, homogeneous logo, without a “pointillist” effect.

[0118] On the contrary, state-of-the-art technologies wishing to carry out residue-free marking by laser ablation must produce marking points in partial superposition, which implies greater local over-etching of two contiguous marking points compared to the rest of the pattern, which could lead, for example, to the local ablation of at least one additional layer, here the Cr1 layer (5).

[0119] There Figure 4 illustrates the results obtained in reflection (R) for the ophthalmic glass (1) obtained according to the first example of realization of the Figures 1 to 3 , in the ablated area of ​​the marking point (25): R m and in the non-ablated area of ​​the ophthalmic lens surface (1): R e .

[0120] We see that the interference coating (2, 3, 4, 5) is characterized by a specific reflection spectrum R e , illustrated in Figure 4, and that in the unablated area the average reflection spectrum Ref2, which is about 12 to 15%, reflects slightly more in the violet. We also see that the layer (5) Cr1, alone, present on the anti-scratch material, leads the lens to locally have a reflection coefficient Ref1 of about 33% (which is higher than Ref2), and relatively homogeneous according to the visible wavelengths.

[0121] Thus, when the ophthalmic lens (1) is observed, the observer perceives an additional reflection in the area of ​​the marking, in contrast to the reflection of the surrounding points.

[0122] The difference in reflection coefficient between the marking point (25) and the other (non-ablated) areas of the surface of the ophthalmic lens (1) is therefore approximately 18% on average, which makes it possible to form patterns by difference in reflection intensity but also in tint and Chroma (respectively "hue" and "Chroma" in English) in reflection on the surface of the ophthalmic lens. There is in fact a factor of up to approximately two and a half in the central wavelengths of the visible spectrum, between the reflection coefficient R m of the pattern formed by the ablated area of ​​the marking point (25) and the reflection coefficient of the non-ablated area of ​​the surface of the ophthalmic lens (1).

[0123] This variation in hue and chroma can also be achieved by means of the invention with interference coatings other than that of example 1.

[0124] Furthermore, as appears from the above data, the tint of the reflection and the intensity of this tint varies between the ablated area of ​​the marking point (25) and the non-ablated area of ​​the surface of the ophthalmic lens (1). The marking point (25) has a substantially homogeneous reflection over the visible light spectrum, which gives a substantially white reflection, or in any case with a low tint intensity. On the other hand, the non-ablated area of ​​the surface of the ophthalmic lens (1) reflects violet more particularly, giving a rather violet overall tint to the ophthalmic lens (1).

[0125] Preferably, the absorbance A2 of the Cr2 layer (3) in the visible is such that the following equation is verified or approximated: Ref2 + A2 = Ref1. In this case, the transmission of the light passing through the ophthalmic lens (1) in the ablated area of ​​the marking point (25) is substantially identical to the transmission outside the marking, in the non-ablated area of ​​the surface of the ophthalmic lens (1). This allows the ophthalmic lens wearer to perceive practically no difference or even no difference in transmission at the marking point (25). This is therefore visible to an external observer and invisible to the wearer of the ophthalmic lens (1).

[0126] Thus, according to this embodiment, the absorbance, in the visible (380-780 nm) of the layer (3) Cr2 is such that it is equivalent to the reduction in the efficiency of the interference coating devoid of the layers (2) SiO 2 , (3) Cr2, and (4) SnO 2 .

[0127] There Figure 5shows the transmission (T) measured as a function of the wavelength, through the ophthalmic glass (1) obtained according to the first example of embodiment of the Figures 1 to 3 , in the area of ​​the marking point (25): T m and in the unablated area of ​​the ophthalmic lens surface (1): T e .

[0128] It can be seen that, when ablation of at least part of the thickness of the inner layer (4), the Cr2 layer (3) is also removed and no longer participates, in the ablated area of ​​the marking point (25), in absorbing light. Consequently, as can be seen on the curve of the Figure 5 , the transmission is substantially identical for the ablated area of ​​the marking point (25) (curve T m ) and for the non-ablated area of ​​the surface of the ophthalmic lens (1) (curve T e ).

[0129] Thus, the reduction in the rate of light passing through the ophthalmic lens (1) caused by the absorption of the chromium (3) Cr2 layer in the unablated area of ​​the surface of the ophthalmic lens (1) is approximately equivalent to the reduction in the rate of light passing through the ophthalmic lens (1) caused by the presence of a greater reflection coefficient in the ablated area of ​​the marking point (25).

[0130] Different variants of this first example of embodiment can be envisaged, all within the reach of those skilled in the art. Some of these variants are explained below.

[0131] Thus, the Cr1 layer (5) can be replaced by a coating of layers each having the property of not absorbing too much at the marking wavelength.

[0132] Similarly, the SiO layer (2) and the Cr2 layer (3) can be replaced by another coating of similar layers.

[0133] Finally, it is possible that the Cr2 layer (3) is not absorbent, even slightly, in the visible (380-700 nm), or is not present. This is particularly the case when the inner layer (4) is itself chosen from a material absorbing in the visible wavelength range. Example 2: marking of an ophthalmic lens consisting of a substrate, a layer ZrO 2 , of a layer SiO 2 , of a layer ZrO 2 , of an inner layer SnO 2 , of an outer layer SiO 2 , of a DSX layer and a temporary double layer

[0134] The ophthalmic lens (20) consists of a substrate (21) which is a 1.5 index lens from Essilor International ®< comprising a Mithril ®< brand anti-scratch coating, on which is superimposed an interference coating consisting of a coating comprising successively, starting from the varnish present on the substrate, a first layer (18) of zirconium oxide ZrO 2 , a first layer (17) of silica dioxide SiO 2 , a second layer (16) of zirconium dioxide ZrO 2 , a layer (15) of tin dioxide SnO 2 , or inner layer, a second layer (14) of silica dioxide SiO 2 , or outer layer, an anti-fouling (hydrophobic and / or oleophobic) layer (13), a layer (12) of magnesium difluoride MgF 2 with a thickness of 37 nm and a layer (11) of oxide of magnesium MgO a few nanometers thick.

[0135] All of the layers (14, 15, 16, 17, 18), without taking into account the respective layers 12 and 11 MgF 2 and MgO which are temporary layers, produce an interference coating which is here an anti-reflective coating, having layer thicknesses calculated by means of software known to those skilled in the art (which takes into consideration the nature of these layers) in order to present a total reflection coefficient (Re) of less than 1%, for example 0.7 or 0.8% depending on the samples measured.

[0136] The nature and physical and optical characteristics of the layers of the interference coating are indicated in the following table: Layer number from substrate / Layer reference (illustration) Layer material Optical index of the layer Layer thickness (± 3 nm) 1 / (18) ZrO 2 2,0038 30 nm 2 / (17) SiO 2 1,4741 40 nm 3 / (16) ZrO 2 2,0038 60 nm 4 / (15) SnO 2 1,8432 6 nm 5 / (14) SiO 2 1,4741 110 nm

[0137] Carrying out the method according to the invention results in a local ablation of the outer SiO 2 layer 14, of the layers 13, 12 and 11, external to the outer SiO 2 layer, as well as an at least partial ablation of the inner layer 15, in SnO 2 . At this marking point (P), the value of the reflection measured in the ablated zone (Rm) is approximately 8.5%, or approximately 10 times more than Re.

[0138] THE Figures 6 to 9 schematically illustrate this second example of embodiment of the marking method according to the invention.

[0139] THE Figures 6 and 7 represent the ophthalmic glass before the marking process is carried out and the Figures 8 and 9 represent the ophthalmic glass after the marking process has been carried out.

[0140] There Figure 6 schematically represents the ophthalmic lens (20) in overall view before carrying out the marking process.

[0141] There Figure 8schematically represents the ophthalmic lens (30) in overall view after the marking process has been carried out. It shows the marking or engraving (22) in a marking pattern forming the word “Essilor”.

[0142] There Figure 7 schematically represents in perspective a section of the layers present on the ophthalmic glass (20), before carrying out the marking process.

[0143] We see the substrate (21), on which have been successively deposited a layer (19) of UV filter “UL”, a first layer (18) of ZrO 2 , a first layer (17) of SiO 2 , a second layer (16) of ZrO 2 , an inner layer (15) of SnO 2 , a second layer of SiO 2 , outer, (14), a layer (13) of DSX coating, a layer (12) of MgF 2 and a layer (11) of MgO.

[0144] There Figure 9schematically represents in perspective a section of the layers present on the ophthalmic glass (20) after carrying out the marking process.

[0145] The layers (11), (12), (13), (14) and (15) have been ablated at a marking point (P) (here shown schematically in two dimensions while it is in reality, as explained further on, substantially a cylinder which, by repeating the insolation step of the method of the invention, is part of the marking (22), which led to the obtaining of the layers (11'), (12'), (13'), (14') and (15'). An engraved ophthalmic lens (30) is thus obtained.

[0146] In practice, at the bottom of the marking point (P), it has been observed that there is a slight marking (25) (here shown schematically in two dimensions whereas it is in reality substantially a cylinder) in the layers (16) and (17) immediately present under the layer (15). The zirconium dioxide ZrO 2 of the layer (16) and the silica dioxide SiO 2 of the layer (17) therefore slightly absorb the marking wavelength. The absorption being relatively low, as could be observed on the resulting marking, this is compatible with the performance of the marking method according to the invention because the visibility of the marking is not affected. Example 3 : marking of an ophthalmic lens consisting of a substrate, an underlayer SiO 2 , of a layer ZrO 2 , of a layer SiO 2 , of a layer ZrO 2 , of an inner layer SnO 2 , of an outer layer SiO 2 , of a DSX layer and a temporary double layer

[0147] THE Figures 6 to 9 schematically illustrate this third example of embodiment of the marking method according to the invention, only the nature of the layer (19) being modified compared to the second example of embodiment.

[0148] The ophthalmic lens (20) consists of a substrate (21) which is a 1.5 index lens from Essilor International ®< comprising an anti-scratch coating of the Mithril ®< brand, and comprising on top an interference coating comprising successively, starting from the varnish present on the substrate: a thick layer (19) of SiO 2 , a first layer (18) of zirconium oxide ZrO 2 , a first layer (17) of silica dioxide SiO 2 , a second layer (16) of zirconium dioxide ZrO 2 , a layer (15) of tin dioxide SnO 2 , or inner layer, a second layer (14) of silica dioxide SiO 2 , or outer layer, a layer (13) of anti-fouling coating (hydrophobic and / or oleophobic), a layer (12) of magnesium difluoride MgF 2 of thickness 37 nm and a layer (11) of magnesium oxide MgO a few nanometers thick.

[0149] All of the layers (14, 15, 16, 17 and 18), without taking into account the respective layers 12 and 11 MgF 2 and MgO which are temporary layers, produce an interference coating which is here an anti-reflective coating, having layer thicknesses calculated by means of software known to those skilled in the art (which takes into consideration the nature of these layers) in order to present a total reflection coefficient of less than 1%, for example 0.7% or 0.8% depending on the samples measured.

[0150] The nature and physical and optical characteristics of the layers are indicated in the following table: Layer number from substrate / Layer reference (illustration) Layer material Optical index of the layer Layer thickness (±3 nm) 1 / (19) SiO 2 1,4658 150 nm 2 / (18) ZrO 2 2,0038 20 nm 3 / (17) SiO 2 1,4741 20 nm 4 / (16) ZrO 2 2,0038 100 nm 5 / (15) SnO 2 1,8432 6 nm 6 / (14) SiO 2 1,4741 75 nm

[0151] Carrying out the method according to the invention, according to the operating conditions of example 1 and in the same way as in example 2, creates a pattern on the surface of the ophthalmic lens by local ablation of the outer SiO 2 layer 14, of the layers 13, 12 and 11, external to the outer SiO 2 layer 14, as well as at least partial ablation of the inner layer 15, made of SnO 2 , which is the inner layer ablated by the electromagnetic beam. At this marking point (P), the value of the reflection measured in the ablated zone (Rm) is close to 10%, more precisely between 9.5% and 10.5% depending on the samples, i.e. approximately 12 times more than Re.

Claims

1. Method for marking an optical article (1, 20), said method including at least one step of use of a marking machine on an optical article (1, 20): the marking machine being a marking machine that marks with an electromagnetic beam (23), preferably with a laser beam, said marking machine including an electromagnetic source, preferably a laser source, configured to emit a beam having a set radiation wavelength called the marking wavelength; the optical article being an optical article (1, 20) including a substrate (6, 21) having a main face coated with an interference coating (2, 3, 4, 5; 14, 15, 16, 17, 18, 19), said interference coating comprising at least two superposed layers called the interior layer (4, 15) and the exterior layer (2, 14), the interior layer being located between the substrate and the exterior layer, the interference coating being such that it has a reflection coefficient Re in the visible domain (380-780 nm); the use comprising irradiating at least the interior layer (4, 15) in a given spot called the marking spot (25, P), by means of the laser beam at the marking wavelength, so as to ablate, in the marking spot, the interior layer, over at least one portion of its thickness, and any layer located between the electromagnetic source and the interior layer; and being such that the ablated zone has a reflection coefficient Rm in the visible domain (380-780 nm), Rm being different from Re, in absolute value, by at least 3% and even more preferably more than 5%, and the reflection coefficient Rm of the ablated zone being greater than the reflection coefficient Re of the interference coating; the interior layer absorbing the marking wavelength more greatly than any layer located between the electromagnetic source and the interior layer.

2. Marking method according to Claim 1, such that the irradiating step is carried out by emitting a focused beam of pulsed ultraviolet laser radiation having at least the following parameters: - a radiation wavelength comprised in an interval of 200 to 400 nm and preferably of 200 to 300 nm, and - a pulse duration comprised in an interval of 0.1 to 5 ns, and - an energy per pulse comprised in an interval of 0.1 to 10 µJ and preferably comprised in an interval of 0.5 to 3 µJ, and, in the marking spot (24, P), a beam diameter comprised in an interval of 5 to 50 µm.

3. Marking method according to either of Claims 1 and 2, such that, when the radiation wavelength of the beam of pulsed ultraviolet laser radiation performing the irradiating step is comprised in an interval of 200 to 300 nm, the interior layer (4, 15) is based on, and preferably essentially consists of, tin, preferably tin oxide and even more preferably tin dioxide SnO2.

4. Marking method according to one of Claims 1 to 3, such that the interior layer (4, 15) has a thickness comprised in an interval of 1 to 100 nm, preferably of 2 to 25 nm and even more preferably of 4 to 15 nm, the sum of the thicknesses of the interior layer (4, 15) and of the exterior layer (2, 14) being comprised between 5 and 300 nm and preferably between 45 and 175 nm.

5. Marking method according to one of Claims 1 to 4, such that the interference coating (2, 3, 4, 5) includes at least one absorbent layer (3).

6. Marking method according to Claim 5, such that all the layers counted from the interior layer to the exterior layer together absorb at least 0.5% of the transmitted visible light and, preferably, have an absorption comprised in an interval of 0.5 to 1.5 times and preferably 0.9 to 1.1 times the absolute value of the difference between Re and Rm.

7. Marking method according to one of Claims 1 to 6, such that the difference between the amount of light transmitted by the ablated zone and by the unablated zone is comprised between - 0.5x(Rm-Re) and 0.5x(Rm-Re), (Rm-Re) being understood to represent the absolute value of the difference between Re and Rm.

8. Marking method according to one of Claims 1 to 7, such that the interference coating is an antireflection coating (14, 15, 16, 17, 18) and comprises, from the surface of the substrate or of a varnish present on the substrate, to the exterior, a layer (18) of ZrO2, of 5 to 40 nm thickness, a layer (17) of SiO2, of 10 to 55 nm thickness, a layer (16) of ZrO2, of 20 to 150 nm thickness, an interior layer (15) of SnO2, of 4 to 15 nm thickness, and an exterior layer (14) of SiO2, of 50 to 120 nm thickness.

9. Marking method according to one of Claims 1 to 8, such that the interference coating is itself coated with a surface coating (13, 12, 11), such as a rain-repellent coating, an anti-fog coating, an anti-fouling coating and / or at least one layer of protective material.

10. Marking method according to one of Claims 1 to 9, such that the irradiating step is carried out in as many marking spots as necessary so as to locally mark a region of the main surface of the substrate of the optical article by means of multiple marking spots, said region forming a predefined pattern (22) called the marking pattern.

11. Marking method according to Claim 10, such that there is a continuity between the marking spots that define the region forming the marking pattern, said region preferably including less than 1% per unit area of residues from the ablated layers.

12. Marking method according to either of Claims 10 and 11, such that the marking is carried out with a pitch of dimension smaller than or equal to the dimensions of the marking spot.

13. Marking method according to one of Claims 1 to 12, such that the reflection at the marking spot has a colour, in saturation and / or in hue, different from that of the reflection of the unablated zone.

14. Optical article (30) including a substrate (21) having a main face coated with an interference coating (14, 15, 16, 17, 18), said interference coating comprising at least two superposed layers of materials called the interior layer (15) and the exterior layer (14), the interior layer being located between the substrate and the exterior layer, the interference coating being an antireflection coating (14, 15, 16, 17, 18) and comprising, from a surface of the substrate or of a varnish present on the substrate, to the exterior, a layer (18) of ZrO2, of 5 to 40 nm thickness, a layer (17) of SiO2, of 10 to 55 nm thickness, a layer (16) of ZrO2, of 20 to 150 nm thickness, the interior layer (15) being of SnO2, of 4 to 15 nm thickness, and the exterior layer (14) being of SiO2, of 50 to 120 nm thickness, the interference coating being such that it has a reflection coefficient Re in the visible domain (380-780 nm); said article (30) comprising a marking pattern (22) on the surface of the interference coating, the marking pattern (22) being formed by a plurality of substantially identical marking spots (P), each marking spot corresponding to the localized absence of at least one portion of the thickness of the interior layer (15) and of any layer (14, 13, 12, 11) located between said surface and the interior layer, the ablated zone having a reflection coefficient Rm in the visible domain (380-780 nm) such that Re is different from Rm by at least 3% and even more preferably more than 5%, and the reflection coefficient Rm of the ablated zone being greater than the reflection coefficient Re of the interference coating, the reflection coefficients Re and Rm corresponding to the amount of light reflected by the surface of an optical article, illuminated by illuminant D65, the marking pattern (22) preferably being continuous.