EYEGLASS GLASS WITH A REFLECTIVE, ABRASION-RESISTANT, MULTI-LAYER COATING AND METHOD FOR MANUFACTURING THE SOLD GLASS

Description

[0001] The present invention relates to an ophthalmic lens of the type consisting of stacked inorganic layers on a substrate and exhibiting satisfactory abrasion resistance, and its manufacturing process. The invention is particularly applicable to an ophthalmic lens usable for forming a sunglass lens (corrective or non-corrective) and with a reflective front surface.

[0002] As is well known, ophthalmic lenses consist of a thermoplastic or thermosetting substrate covered with at least one multilayer coating, specifically designed to provide the lens with adequate impact and scratch resistance. However, the scratch resistance of these coatings is often insufficient, which is particularly critical for lenses used in sunglasses with reflective front surfaces compared to traditional non-sunglass or anti-reflective lenses. Indeed, scratches on the reflective front surfaces of sunglasses are particularly noticeable both to the wearer, for whom they can cause visual discomfort, and to an observer, for whom these scratched sunglasses are unsightly.

[0003] Document JP-A-2005-292204 discloses an ophthalmic lens whose substrate is coated with an organic abrasion-resistant coating (a "hard-coat layer"), itself covered by a multilayer inorganic coating designed to improve the anti-reflective effect on the back surface of the lens without compromising the reflective effect on its front surface. This inorganic coating consists of a relatively thick stack of at least seven layers, formed by alternating layers of low refractive index (made of SiO₂) and layers of high refractive index (for example, Ta₂O₅), with the optional intercalation of a metallic layer, for example, Cr. It is primarily the abrasion-resistant coating that gives the lens the desired scratch resistance, as explained in §

[0026] ; the multilayer coating on top of it is therefore not designed to minimize the occurrence of scratches on the front surface of the lens.This lens scratch resistance is assessed visually and approximately in this document by means of a so-called steel wool test, with a UA rating of "almost scratch-free" to characterize the abrasion resistance of the lenses tested.

[0004] A major drawback of the lenses presented in this document lies in their potentially very high thickness, for a scratch resistance that is not precisely quantified and may prove insufficient in some cases.

[0005] US patent 7,055,954 B2 discloses a multilayer inorganic, front-facing reflective coating for solar glass, which also consists of alternating layers of low-refractive-index (SiO₂) and high-refractive-index (HfO₂) coatings. This coating is designed to mask existing scratches, not prevent them. The patent does not provide instructions on how to minimize scratching on this front-facing reflective solar glass.

[0006] WO2008 / 107325 A1 and WO 2016 / 060257 A both show an ophthalmic lens comprising a substrate and a coating overlying an abrasion-resistant layer covering the substrate, said substrate comprising alternating layers of high refractive index (ZrO2 or Ta2O5) and layers of low refractive index (SiO2).

[0007] One aim of the present invention is therefore to propose a new ophthalmic lens which remedies at least in part the aforementioned disadvantages, in particular by significantly improving the abrasion resistance of its multilayer inorganic coating while giving it a reduced thickness.

[0008] This goal is achieved in that the Applicant has just discovered, surprisingly, that a particular selection for a multilayer inorganic coating of at least two layers of low refractive index and at least one layer of high refractive index stacked alternately, of determined thicknesses and deposited according to specific processes, makes it possible to obtain for said coating both a sufficiently high average light reflectance factor Rv in the visible, a reduced thickness and a very high Bayer ISTM value of abrasion resistance, this lens being usable to form a solar lens with a reflective front surface.

[0009] More specifically, an ophthalmic lens according to the invention described in claim 1 comprises a substrate having a main front face and a main rear face, the main front face being covered with a multilayer inorganic coating having an average light reflectance factor Rv in the visible range equal to or greater than 4% and consisting of a stack comprising: two or three low refractive index layers, each consisting of a first material with a refractive index less than 1.55, the first material being predominantly or exclusively composed of SiO2, and one to three high refractive index layers, which are consisting of a second material with a refractive index greater than 1.55 and which are located between two said adjacent low-index layers in said stacking, the second material being predominantly or exclusively composed of a mineral oxide chosen from ZrO2 and Ta2O5, and the lens is characterized in that the coating has a thickness less than or equal to 600 nm and a Bayer ISTM abrasion resistance value greater than 10.

[0010] According to the present invention, the average light reflectance factor Rv in the visible range is as defined in ISO 13666:1998 and measured according to ISO 8980-4 (at an angle of incidence less than 17°, typically 15°). It is known to be the weighted average of the spectral reflectance over the entire visible spectrum between 380 nm and 780 nm. Advantageously, this average factor Rv can be equal to or greater than 8%, or even 15%.

[0011] Also according to the present invention, said Bayer ISTM value of abrasion resistance which further characterizes said multilayer inorganic coating is measured according to ISTM 02-002 standard with an abrasive material Alundum ®< ZF-12, and advantageously this Bayer ISTM value of said coating according to the invention can be equal to or greater than 12, even more advantageously to 14, or even to 15.

[0012] In this description, unless otherwise specified: The indication of a range of values ​​"from X to Y" or between "X and Y" in the present invention is understood to include the values ​​X and Y; the expression "deposit a layer or coating" means that the layer or coating is deposited on the exposed surface of the lens, i.e., on the surface furthest from the substrate, it being specified that "deposited on" means "over all or part of the exposed surface" (i.e., deposited above and not necessarily in contact with that surface); the back (i.e., inner) face of the substrate means the face (generally concave) that, when using the ophthalmic lens, is closest to the wearer's eye, and conversely, the front face of the substrate means the face (generally convex) furthest from that eye; and all thicknesses disclosed in this description are physical thicknesses (i.e.(not optical thicknesses), it being recalled that the physical thickness of a layer is by definition equal to the quotient of its optical thickness by the refractive index of that layer (unless otherwise indicated, the refractive indices referred to in this description are expressed at 25°C for a wavelength of 550 nm).

[0013] It should be noted that a coating according to the invention, compared to the aforementioned inorganic reflective coatings of the prior art, has, on the one hand, a reduced thickness and therefore a reduced sensitivity to mechanical stresses (e.g., improved resistance to cracking) and, on the other hand, significantly improved resistance to scratches.

[0014] It should also be noted that this coating includes at least two said low index layers not consecutive in the stacking (i.e. one of which does not directly cover the other) which are connected to each other by said at least one high index layer.

[0015] It should also be noted that the very high BAYER values ​​obtained demonstrate that this coating of the invention is capable of minimizing the appearance of scratches on the front surface. In other words, this coating almost single-handedly prevents scratches, unlike the multilayer inorganic anti-reflective coatings presented in the aforementioned document JP-A-2005-292204. Indeed, these BAYER values ​​were not predictable in view of the visual results obtained in JP-A-2005-292204 by the "steel wool" test, due to the very different abrasion conditions used for this "steel wool" test and for the Bayer test defined by the ISTM 02-002 standard with the abrasive material Alundum ®< ZF-12 (for example, one can refer to document WO 2015 / 0033182 A1 on behalf of the Applicant for measurements carried out according to the "steel wool" test and according to a BAYER ISTM test).

[0016] Advantageously, said coating may be devoid of any said low index layer of thickness greater than or equal to 225 nm, and / or of any said high index layer of thickness greater than or equal to 105 nm.

[0017] It should be noted that this thickness of less than 225 nm for each low index layer and / or this thickness of less than 105 nm for the one or each high index layer differ from the examples of coatings tested in the aforementioned document JP-A-2005-292204.

[0018] Also advantageously, said inorganic coating: includes at least one said low index layer of thickness between 100 nm and 200 nm and / or at least one said high index layer of thickness less than or equal to 50 nm, and is devoid of any metallic layer of thickness greater than 5 nm.

[0019] It should be noted that this document JP-A-2005-292204 taught, on the contrary, in many of its tested coatings, to use a metallic layer made of chromium and having a thickness greater than 5 nm.

[0020] It should also be noted that said inorganic coating according to the invention may include one or more thin metallic layer(s) of thickness less than or equal to 5 nm, used in particular as an adhesion promoter.

[0021] According to the invention, said coating surmounts at least one organic anti-abrasion layer covering said substrate.

[0022] Preferably, said at least two low-index layers form at least 65% and even more preferably at least 75% of the thickness of said coating.

[0023] According to another feature of the invention, the one of said at least two low index layers that is closest to said substrate, or proximal low index layer, may have an exposed surface that is covered by said high index layer and that is free from the product of a reaction between said first material and ion bombardment.

[0024] It should be noted that this exposed (i.e., external) surface of the aforementioned low-index proximal layer is thus advantageously not subjected to prior ion bombardment before the deposition of the high-index layer covering it. "Ion bombardment" is understood to mean, in a known manner, bombardment by ions (e.g., argon ions) with an energy greater than or equal to 30 eV, preferably 40 eV, it being specified that it has been verified that this ion bombardment chemically modifies the activated surface of the low-index proximal layer.

[0025] Indeed, the Applicant unexpectedly discovered that ion bombardment (usually used to activate a low-index SiO₂ sub-layer before depositing a high-index layer, for example, a ZrO₂ layer, of a multi-layer anti-reflective or reflective coating as described in document WO 2008 / 107325 A1) significantly reduces the abrasion resistance gain of BAYER ISTM, compared to depositing the same high-index layer on the low-index layer without ion bombardment. In other words, not activating the exposed surface of said proximal low-index layer further increases the coating's abrasion resistance.

[0026] It should also be noted that this absence of activation of the said low-index proximal layer makes it possible to maintain good productivity, because cycle times are not lengthened by the use of such ion bombardment.

[0027] Advantageously, said low index proximal layer, the exposed surface of which is free from the product of a reaction between said first material and said ion bombardment, can be the innermost layer of said stack and can have a thickness between 100 nm and 200 nm.

[0028] According to another advantageous feature of the invention which is coupled to this absence of ion bombardment of said low index proximal layer, this low index proximal layer (preferably forming the innermost layer of the stack) can be obtained from the deposition of a precursor of said first material evaporated in a vacuum chamber with a gas introduced into said chamber which is chosen from argon, krypton, neon, oxygen and a mixture of at least two of these gases and which is preferably oxygen.

[0029] It should be noted that this introduction of this gas into the evaporation chamber during deposition has the effect of modifying the porosity of the low index layer thus deposited and, combined with the aforementioned absence of ion bombardment, makes it possible to further improve the abrasion resistance of the coating.

[0030] According to a first embodiment of the invention, said coating has three layers comprising successively, moving away from said substrate: a said low-index inner layer, preferably with a thickness between 120 nm and 170 nm, a said high-index intermediate layer, preferably with a thickness between 10 nm and 40 nm, and a said low-index outer layer, preferably with a thickness between 20 nm and 40 nm, said coating having: * a thickness less than 300 nm and preferably between 150 nm and 250 nm, * a thickness of the low index layers at least equal to 83% and preferably at least equal to 90% of the thickness of said coating, and * an average light reflectance factor Rv in the visible range greater than 8%.

[0031] It should be noted that this thickness of the low index layers, at least equal to 83% and preferably at least equal to 90% of the thickness of said coating, is equivalent to a ratio of thickness of low index layers / high index layer greater than 5 and preferably greater than or equal to 10.

[0032] According to a second embodiment of the invention, said coating comprises four to six layers comprising successively, moving away from said substrate: a said high-index inner layer, preferably with a thickness between 80 nm and 120 nm, a first said low-index intermediate layer, preferably with a thickness between 40 nm and 80 nm, a first said high-index intermediate layer, preferably with a thickness between 40 nm and 80 nm, optionally a second said low-index intermediate layer, preferably with a thickness between 80 nm and 120 nm, optionally a second said high-index intermediate layer, preferably with a thickness between 20 nm and 50 nm, and a said low-index outer layer, preferably with a thickness between 200 nm and 240 nm, said coating having: * a thickness between 400 nm and 580 nm, * a thickness of the low index layers at least equal to 60% of the thickness of said coating, and * an average light reflectance factor Rv in the visible range greater than 30%, preferably equal to or greater than 35%.

[0033] It should be noted that this thickness of the low index layers, at least equal to 60% of the thickness of said coating, is equivalent to a ratio of thickness of low index layers / high index layers greater than 1.55.

[0034] According to the invention: said first material is predominantly (according to a mass fraction preferably greater than or equal to 80%) or exclusively made up of SiO2, preferably of SiO2 for the innermost layer of said stack and of SiO2 or of a mixture of SiO2 +Al2O3 for at least one other said low index layer (in particular of silica doped with alumina, the latter contributing to increasing the thermal resistance of the coating), and said second material is predominantly (according to a mass fraction preferably greater than or equal to 80%) or exclusively made up of a mineral oxide of at least one metal preferably chosen from ZrO2 and Ta2O5.

[0035] Optionally, each low-index layer may also contain a high-index ingredient, provided that the overall refractive index of the resulting layer is less than 1.55.

[0036] When a low-index coating comprising a mixture of SiO₂ and Al₂O₃ is used, it preferably contains 1 to 10%, and even more preferably 1 to 5% by mass of Al₂O₃ relative to the total mass of SiO₂ + Al₂O₃ in that coating. For example, SiO₂ doped with 4% or less of Al₂O₃ by mass or with 8% Al₂O₃ may be used. Commercially available SiO₂ / Al₂O₃ mixtures may be used, such as LIMA®< marketed by Umicore Materials AG (refractive index n = 1.48–1.50 at 550 nm), or the L5®< substance marketed by Merck KGaA (refractive index n = 1.48 at 500 nm).

[0037] Preferably, the outermost layer (i.e. distal to the substrate) of said multilayer inorganic coating is silica-based, preferably comprising at least 80% by mass of silica as indicated above and even more preferably being made of silica.

[0038] As for the high index layer or each layer, it may also contain silica or other low refractive index materials, provided that the overall refractive index of the resulting layer is greater than 1.55.

[0039] It should be noted that the choice of the number of layers for said multilayer inorganic coating can be guided by the desired reflection characteristics for this coating, for example the desired reflection value and the chromaticity combined with the hue angle of the reflection.

[0040] A manufacturing process according to the invention of an ophthalmic lens as defined above comprises deposition in a vacuum chamber of said at least two low index layers and said at least one high index layer, without subjecting to ion bombardment the exposed surface of that of said at least two low index layers which is closest to said substrate, or proximal low index layer, before deposition of said high index layer covering it.

[0041] It should be noted that this process of the invention is easy to implement and has little impact on the manufacturing cycle time of the lenses, which is particularly relevant in the context of mass production in order to limit costs and energy consumption, in particular.

[0042] Advantageously and in accordance with said first embodiment of the invention, the inner layer for said stacking can be said low index proximal layer which is directly covered by said adjacent high index layer without being subjected to said ion bombardment beforehand.

[0043] In this case, we can submit: said low index layer for said stacking by introducing into said enclosure a gas chosen from argon, krypton, neon, oxygen and a mixture of at least two of these gases, preferably oxygen, said at least one high index layer with or without introduction of said gas into said enclosure, and at least one other said low index layer without introducing said gas into said enclosure.

[0044] In general, the multilayer inorganic coating of the ophthalmic lens according to the invention can be deposited on any substrate, and preferably on organic glass substrates, for example a thermoplastic or thermosetting plastic material.

[0045] Suitable thermoplastic materials for substrates include (meth)acrylic (co)polymers, especially poly(methyl methacrylate) (PMMA), thio(meth)acrylic (co)polymers, polyvinyl butyral (PVB), polycarbonates (PC, including homopolycarbonates, copolycarbonates and sequenced copolycarbonates), polyesters such as poly(ethylene terephthalate) (PET) or poly(butylene terephthalate) (PBT), polycarbonate / polyester copolymers, cyclo-olefin copolymers such as ethylene / norbornene or ethylene / cyclopentadiene copolymers and their combinations, and ethylene / vinyl acetate thermoplastic copolymers.

[0046] Suitable thermosetting materials for substrates include polyurethanes (PU), poly(thiourethanes), allylcarbonate (co)polymers of polyols, polyepisulfides, and polyepoxides.

[0047] Other thermosetting materials suitable for substrates are acrylic (co)polymers with a refractive index between 1.5 and 1.65, typically close to 1.6. These acrylic (co)polymers are obtained by polymerizing mixtures of (meth)acrylate monomers and optionally aromatic allylic and / or vinyl monomers. The (meth)acrylate monomers (i.e., acrylate or a methacrylate) can be monofunctional or multifunctional, typically bearing 2 to 6 (meth)acrylate groups. These monomers can be aliphatic, cyclic, aromatic, polyalkoxylated, derived from compounds such as bisphenol, and / or bear other functional groups such as epoxy, thioepoxy, hydroxyl, thiol, sulfide, carbonate, urethane, and / or isocyanate.

[0048] The substrates can be obtained by polymerization of mixtures of the above monomers, or can also include mixtures of these polymers and (co)polymers.

[0049] The substrates particularly recommended are those obtained by (co)polymerization of bis-allyl carbonate of diethylene glycol, sold, for example, under the trade name CR-39 ®< by the company PPG Industries (ORMA ®< ESSILOR lenses), or thermoplastic substrates of the polycarbonate type.

[0050] In certain applications, it is preferable for the main front surface of the substrate to be coated with one or more functional coatings prior to the deposition of the multilayer inorganic coating. These functional coatings, commonly used in optics, can include, but are not limited to, a shock-resistant primer, an abrasion-resistant and / or scratch-resistant coating, a polarizing coating, a photochromic coating, or a colored coating. Generally, this main front surface of the substrate is thus coated with a shock-resistant primer, an abrasion-resistant and / or scratch-resistant coating, or a shock-resistant primer coated with an abrasion-resistant and / or scratch-resistant coating.

[0051] The multilayer inorganic coating according to the invention is preferably deposited on an abrasion-resistant and / or scratch-resistant coating, which may be any coating conventionally used as an abrasion-resistant and / or scratch-resistant coating in the field of ophthalmic lenses. These abrasion-resistant and / or scratch-resistant coatings are preferably hard coatings based on poly(meth)acrylates or silanes, generally comprising one or more mineral fillers intended to increase the hardness and / or refractive index of the coating once cured, and they are preferably prepared from compositions comprising at least one alkoxysilane and / or a hydrolysate thereof, obtained, for example, by hydrolysis with a hydrochloric acid solution and optionally condensation and / or curing catalysts.Examples include coatings based on epoxysilane hydrolysates such as those described in documents FR 2702486 (EP 0614957), US 4,211,823 and US 5,015,523.

[0052] A preferred composition for an abrasion-resistant and / or scratch-resistant coating is that disclosed in document FR 2702486 on behalf of the Applicant. It comprises a hydrolysate of epoxy triacoxysilane and dialkyl dialcoxysilane, colloidal silica, and a catalytic amount of an aluminum-based curing catalyst such as aluminum acetylacetonate, the remainder consisting essentially of solvents conventionally used for formulating such compositions. Preferably, the hydrolysate used is a hydrolysate of γ-glycidoxypropyltrimethoxysilane (GLYMO) and dimethyldiethoxysilane (DMDES).

[0053] The abrasion-resistant and / or scratch-resistant coating composition can be deposited onto the main surface of the substrate by dipping or centrifugation. It is then cured by the appropriate method (preferably thermal or UV). The thickness of the abrasion-resistant and / or scratch-resistant coating generally varies from 2 µm to 10 µm, preferably from 3 µm to 5 µm.

[0054] Prior to applying the abrasion-resistant and / or scratch-resistant coating, a primer (also called an adhesion layer) can be applied to the substrate to improve impact resistance and / or the adhesion of subsequent layers in the final product. This primer can be any type of impact-resistant primer commonly used for transparent polymer materials, such as ophthalmic lenses.

[0055] Preferred primer compositions include thermoplastic polyurethane compositions, such as those described in JP 63-141001 and JP 63-87223; poly(meth)acrylic primer compositions, such as those described in US 5,015,523; thermosetting polyurethane compositions, such as those described in EP 0404111; and poly(meth)acrylic latex or polyurethane-type latex compositions, such as those described in US 5,316,791 and EP 0680492. Preferred primer compositions are polyurethane-based and latex-based compositions, particularly polyurethane latex compositions optionally containing polyester motifs.Commercial primer compositions suitable for the invention include Witcobond(R) 232, Witcobond(R) 234, Witcobond(R) 240, Witcobond(R) 242, Neorez(R) R-962, Neorez(R) R-972, Neorez(R) R-986 and Neorez(R) R-9603.

[0056] Mixtures of these latexes, in particular polyurethane latex and poly(meth)acrylic latex, can also be used in primary compositions.

[0057] These primer compositions can be deposited by dipping or centrifuging and then dried at a temperature of at least 70°C and up to 100°C, preferably around 90°C, for a period of 2 minutes to 2 hours, generally around 15 minutes, to form primer layers having thicknesses, after baking, of 0.2 µm to 2.5 µm, preferably 0.5 µm to 1.5 µm.

[0058] Before the multilayer inorganic coating is deposited onto the substrate, which may be coated with an abrasion-resistant layer, for example, the substrate surface can be subjected to a physical or chemical activation treatment to increase coating adhesion. This pretreatment is generally carried out under vacuum. It may involve bombardment with energetic species, such as an ion beam ("Ion Pre-Cleaning" or "IPC"), corona discharge treatment, effluvium treatment, UV treatment, or vacuum plasma treatment, typically with oxygen or argon plasma. It may also involve acidic or basic surface treatment and / or solvent treatment (water or organic solvent).

[0059] The various layers of the multilayer inorganic coating and any underlayer are preferably deposited by vacuum deposition using one of the following techniques: (i) evaporation, possibly assisted by ion beam, (ii) ion beam sputtering, (iii) sputtering, or (iv) plasma-assisted chemical vapor deposition.

[0060] These different techniques are described in the books "Thin Film Processes" and "Thin Film Processes II," Vossen & Kern, Ed., Academic Press, 1978 and 1991 respectively. One particularly recommended technique is vacuum evaporation.

[0061] Preferably and as indicated above, the deposition of each of the layers of said coating and of the possible undercoat is carried out by vacuum evaporation.

[0062] The ophthalmic lens of the invention can be made antistatic, that is, not to retain and / or develop an appreciable electrostatic charge, by incorporating at least one electrically conductive layer into said multilayer inorganic coating. This electrically conductive layer is preferably located between two layers of said inorganic coating, and / or is adjacent to a high-refractive-index layer of this coating. Preferably, this electrically conductive layer is located immediately beneath said low-refractive-index layer and ideally constitutes the penultimate layer of said coating, being located immediately beneath the outermost (low-index, e.g., silica-based) layer of said coating.

[0063] The electrically conductive layer must be sufficiently thin so as not to impair the transparency of the coating, and it is preferably made from an electrically conductive and highly transparent material. In this case, its thickness preferably ranges from 1 nm to 15 nm, or better yet, from 1 nm to 10 nm. This conductive layer preferably comprises a metal oxide, possibly doped, selected from indium, tin, zinc oxides and mixtures thereof. Tin-indium oxide (In₂O₃:Sn for tin-doped indium oxide), zinc-doped aluminum oxide (ZnO:Al), indium oxide (In₂O₃), and tin oxide (SnO₂) are preferred. Even more preferably, this optically transparent conductive layer is a tin-indium oxide layer (ITO) or a tin oxide layer.

[0064] An ophthalmic lens according to the invention may also include additional functionalities such as, but not limited to: coatings formed on the external (i.e. exposed) surface of said multilayer inorganic coating and capable of modifying its surface properties, such as an anti-fouling or anti-fog external coating (“top coat” in English); specific filtration functionalities such as UV, blue-violet (400 nm - 460 nm) or IR filtration, within a coating or directly integrated into the substrate; and / or a polarized function.

[0065] As examples of antifouling coatings that can typically be hydrophobic and / or oleophobic and generally have a thickness of 10 nm or less, preferably from 1 nm to 10 nm, and better still from 1 nm to 5 nm, fluorosilane or fluorosilazane coatings can be cited. These can be obtained by depositing a precursor fluorosilane or fluorosilazane, preferably comprising at least two hydrolyzable groups per molecule. The precursor fluorosilanes preferentially contain fluoropolyether groups and, even better, perfluoropolyether groups. These fluorosilanes are well known and are described, among others, in US documents 5,081,192, US 5,763,061, US 6,183,872, US 5,739,639, US 5,922,787, US 6,337,235, US 6,277,485 and EP 0933377. A preferred hydrophobic and / or oleophobic coating composition is marketed by Shin-Etsu Chemical under the name KP 801 M(R).Another preferred hydrophobic and / or oleophobic coating composition is marketed by Daikin Industries under the name OPTOOL DSX(R). It is a fluorinated resin containing perfluoropropylene groups.

[0066] Thus, an ophthalmic lens according to the invention can, for example, comprise a substrate successively coated on its main front face with a layer of shock-resistant primer, an anti-abrasion and / or anti-scratch layer, said multilayer inorganic coating according to the invention and an external hydrophobic and / or oleophobic coating.

[0067] As for the main rear face of the substrate, it can, for example, be successively coated with a layer of shock-resistant primer, an anti-abrasion and / or anti-scratch layer, an anti-reflective coating preferably with low reflection in the UV range and a hydrophobic and / or oleophobic coating.

[0068] Other features, advantages and details of the present invention will become apparent from the following description of several illustrative and non-limiting embodiments of the invention, the description being made with reference to the accompanying drawings, among which: There figure 1a is a schematic planar section view, in a plane transverse to the front and rear faces of the substrate, of a six-layer inorganic coating according to the prior art with high and low refractive indices, The figure 1b is a schematic planar sectional view in said transverse plane of a six-layer inorganic coating according to the invention with high and low refractive indices, The figure 2a is a schematic planar sectional view in said transverse plane of a prior art bilayer inorganic coating with high and low refractive indices, The figure 2b is a schematic planar section view in said transverse plane of a three-layer inorganic coating according to the invention with high and low refractive indices, The figure 3a is a schematic planar sectional view in said transverse plane of a high refractive index, single-layer inorganic coating according to the prior art, The figure 3b is a schematic planar sectional view in said transverse plane of another three-layer inorganic coating according to the invention with high and low refractive indices, and The figure 4 is a graph showing the BAYER ISTM abrasion resistance values ​​obtained for the coatings of the figures 1a, 1b, 2a, 2b, 3a, 3b . Exemples de réalisation

[0069] The ophthalmic lenses used in the following examples include a thermoplastic substrate made of polycarbonate (PC) of designation AIRWEAR (ESSILOR) with a diameter of 65 mm, a refractive index of 1.50, a power of -2.00 diopters and a thickness of 1.2 mm.

[0070] This substrate has been coated on its main front face with an abrasion-resistant coating of a composition defined in the following ranges and having a dry extract of approximately 30%: 3-6% tetraethoxysilane (TEOS) 1-3% HCl 0.1 N 10-20% γ-glycidoxypropyltrimethoxysilane (GLYMO) 1-30% glycidoxypropylmethyldiethoxysilane 30-40% of a 30% wt dispersion of colloidal silica in methanol 10-20% of a solvent Dowanol PM 1.5% aluminium acetylacetonate (Al(AcAc)) 0.1% surfactant Fluorad FC 430.

[0071] Next, the layer(s) of a reflective inorganic coating conforming or not to the invention were deposited by vacuum evaporation in an enclosure without heating of the substrate (evaporation source: electron gun), then this inorganic coating was covered with an external hydrophobic coating designated DSX ®< .

[0072] The deposition frame was a Satis 1200DLF machine equipped with a Temescal electron gun (8kV) for evaporating oxides.

[0073] The thickness of the layer or layers of each reflective inorganic coating was checked using a quartz microbalance, and spectral measurements were carried out on a Perkin-Elmer Lambda 850 variable incidence spectrophotometer with a URA (Universal Reflectance Accessory).

[0074] To prepare the ophthalmic lenses for testing, the following steps were successively implemented: a step of introducing the substrate coated on its front face with the anti-abrasion coating into a vacuum deposition chamber, a pumping step until a secondary vacuum is obtained, a step of activating the surface of the substrate by an argon ion beam, a stop of the ionic irradiation, the formation on the anti-abrasion coating of the layer(s) of the reflective inorganic coating by successive evaporations, then a ventilation step.

[0075] To test the reflective inorganic coating of each lens thus prepared, the following measurements were taken: its average light reflectance factor Rv in the visible range as defined in ISO 13666:1998 and measured according to ISO 8980-4 at an angle of incidence of 15°, and the Bayer ISTM value of abrasion resistance according to ISTM 02-002 with an abrasive material Alundum ®< ZF-12 (marketed by Saint-Gobain).

[0076] In summary, the Bayer ISTM abrasion test involves abrading the main front surface of each coated lens by exposing it to this abrasive material in a plate that oscillates back and forth for 600 cycles (150 cycles per minute for 4 minutes). The average haze levels are measured before and after abrasion by calculating the ratio of the haze measured on an uncoated reference ophthalmic lens to the haze measured on the coated lens.

[0077] Six ophthalmic lenses L1 to L6 were tested, each comprising substrate 1 (PC) provided on its main front surface with said anti-abrasion coating, which was surmounted by a reflective inorganic coating 2 (non-conforming or conforming to the invention) deposited by vacuum evaporation and the external coating 3 (in DSX®), among which: the L1 lens according to the prior art, schematically represented at the figure 1a comprised, as a reflective inorganic coating 2, a six-layer coating deposited by evaporation under oxygen-free vacuum within the enclosure, formed successively of an inner layer of Ti3O5 75 nm thick, a layer of SiO2 45 nm thick, a layer of Ti3O5 111 nm thick, a layer of SiO2 35 nm thick, a layer of Ti3O5 90 nm thick, and an outer layer of SiO2 230 nm thick, and L1 exhibited on its front face a reflected emerald-colored light; the lens L2 according to the invention schematically shown in the figure 1b comprised, as a reflective inorganic coating 2, a six-layer coating formed successively of an inner layer of ZrO₂ 104 nm thick, a layer of SiO₂ 59 nm thick, a layer of ZrO₂ 64 nm thick, a layer of SiO₂ 103 nm thick, a layer of ZrO₂ 30 nm thick, and an outer layer of SiO₂ 219 nm thick, these layers having been deposited by vacuum evaporation of ZrO₂ in the presence of oxygen in the chamber for the ZrO₂ layers and without oxygen in the chamber for the SiO₂ layers, and L2 exhibited on its front face a reflected light of emerald color analogous to that of lens L1; lens L3 according to the prior art, schematically represented in the figure 2a comprised, as a reflective inorganic coating 2, a bilayer coating consisting of an inner layer of CrO2 17 nm thick deposited by vacuum evaporation and an outer layer of SiO2 20 nm thick deposited by vacuum evaporation, without oxygen being introduced into the chamber for these two layers, and L3 exhibited a reflected silvery light on its front face; the lens L4 according to the invention schematically shown in the figure 2b comprised, as a reflective inorganic coating 2, a three-layer coating formed successively of an inner layer of SiO2 150 nm thick deposited by vacuum evaporation of SiO2 in the presence of oxygen in the chamber and not subjected to ion bombardment treatment after its deposition, a layer of ZrO2 17 nm thick deposited by vacuum evaporation of ZrO2 in the presence of oxygen in the chamber, and a layer of SiO2 34 nm thick deposited by vacuum evaporation without the introduction of oxygen into the chamber, and L4 exhibited on its front face a reflected light of a silvery color analogous to that of lens L3; lens L5 according to the prior art, schematically represented in the figure 3a comprised, as a reflective inorganic coating 2, a 45 nm thick CrO2 monolayer deposited by vacuum evaporation without the introduction of oxygen into the chamber, and L5 exhibited on its front face an intense silvery reflected light; and the lens L6 according to the invention schematically shown in the figure 3b included as a reflective inorganic coating 2 a three-layer coating formed successively of an inner layer of SiO2 150 nm thick deposited by vacuum evaporation of SiO2 in the presence of oxygen in the enclosure and not subjected to ion bombardment treatment after its deposition, a layer of ZrO2 34 nm thick deposited by vacuum evaporation of ZrO in the presence of oxygen in the enclosure, and a layer of SiO2 27 nm thick deposited by vacuum evaporation without introduction of oxygen into the enclosure, and L6 exhibited on its front face an intense silvery reflected light analogous to that of lens L5.

[0078] Table 1 below details the total thicknesses e T, the low index layer thickness ratios e BI / e T, and the average light reflectance factors Rv in the visible range obtained for the respective reflective inorganic coatings 2 of lenses L1 to L6. Tableau 1 : L1 L2 L3 L4 L5 L6 e T (nm) 586 579 37 201 45 211 e BI / e T (%) 53 66 54 92 0 84 Rv (%) - 35 - 8,5 - 15

[0079] The graph of the figure 4 illustrates the average Bayer ISTM abrasion resistance values ​​measured according to ISTM 02-002 with the abrasive material Alundum ®< ZF-12, for each of the lenses L1 to L6.

[0080] This figure 4 shows that the lenses L2, L4 and L6 according to the invention exhibit both: (i) a high average visible reflectance factor Rv (Rv greater than 8 for L4 and L6 and greater than 30 for L2), (ii) a reduced total thickness (less than 580 nm for L2 and even less than 220 nm for L4 and L6), and (iii) an average Bayer ISTM value greater than 10 (greater than 10.5 for L2 and even greater than 14 for L4 and substantially equal to 16 for L6).

[0081] These results also show that an e BI / e T ratio greater than 60% (i.e. a clearly major quantity of low index material such as silica in the stack) contributes to improving the hardness and abrasion resistance of the inorganic coating.

[0082] Furthermore, another comparative test was carried out demonstrating that ion bombardment by argon ions of the exposed surface of the low index inner layer (in SiO2) of L4, which chemically modifies this surface before the (unchanged) deposition of the ZrO2 and SiO2 layers, has the negative effect of decreasing by one Bayer ISTM point the gain in abrasion resistance of the thus modified coating of L4.

[0083] The synergistic effect according to the invention between the absence of treatment of the exposed surface of the low index inner layer (e.g. in SiO2) previously deposited in the presence of a gas (e.g. oxygen) introduced into the enclosure and the high index layer (e.g. in ZrO2) directly covering it, is thus established.

Claims

1. Ophthalmic lens (L2, L4, L6) forming a sunglass lens having a reflective front face, the lens comprising a substrate (1) having a front main face and a rear main face, said front main face being surmounted by a multilayer inorganic coating (2) that has an average luminous reflectance factor Rv in the visible equal to or higher than 4% and that consists of a stack comprising: - two or three low-refractive-index layers that each consist of a first material of refractive index lower than 1.55, the first material mostly or exclusively consisting of SiO2, and - one to three high-refractive-index layer(s) that consist(s) of a second material of refractive index higher than 1.55 and that is or are located between two said low-index layers that are adjacent in said stack, the second material mostly or exclusively consisting of a mineral oxide of a metal chosen from ZrO2 and Ta2O5, wherein said coating (2) has a thickness smaller than or equal to 600 nm and a Bayer ISTM abrasion-resistance value higher than 10, the Bayer ISTM value being measured according to standard ISTM 02-002 with an abrasive material Alundum® ZF-12, said coating being able to minimize the appearance of scratches on said reflective front face, wherein said coating (2) surmounts at least one abrasion-resistant organic layer covering said substrate (1) and is devoid of underlayer, and wherein said low-index layers form at least 65% of the thickness of said coating (2).

2. Ophthalmic lens (L2, L4, L6) according to Claim 1, wherein said average luminous reflectance factor Rv in the visible is equal to or higher than 8%.

3. Ophthalmic lens (L2, L4, L6) according to Claim 1 or 2, wherein said coating (2) is devoid of any said low-index layer of thickness larger than or equal to 225 nm, and / or any said high-index layer of thickness larger than or equal to 105 nm.

4. Ophthalmic lens (L2, L4, L6) according to one of Claims 1 to 3, wherein said coating (2) - comprises at least one said low-index layer of thickness comprised between 100 nm and 200 nm and / or at least one said high-index layer of thickness smaller than or equal to 50 nm, and - is devoid of any metal layer of thickness larger than 5 nm.

5. Ophthalmic lens (L2, L4, L6) according to one of the preceding claims, wherein said at least two low-index layers form at least 75% of the thickness of said coating (2).

6. Ophthalmic lens (L2, L4, L6) according to one of the preceding claims, wherein that of said at least two low-index layers which is the closest to said substrate (1), or the proximal low-index layer, has an exposed surface that is covered by a said high-index layer.

7. Ophthalmic lens (L4, L6) according to Claim 6, wherein said proximal low-index layer is the most internal layer of said stack and has a thickness comprised between 100 nm and 200 nm.

8. Ophthalmic lens (L4, L6) according to one of the preceding claims, wherein said coating (2) is made up of three layers comprising, in succession, starting from closest to said substrate (1): - an internal said low-index layer, - an intermediate said high-index layer, and - an external said low-index layer, said coating having: * a thickness smaller than 300 nm, * a thickness of the low-index layers at least equal to 83% of the thickness of said coating, and * an average luminous reflectance factor Rv in the visible higher than 8%.

9. Ophthalmic lens (L4, L6) according to Claim 8, wherein said coating (2) comprises, in succession, starting from closest to said substrate (1): - said internal low-index layer, of thickness comprised between 120 nm and 170 nm, - said intermediate high-index layer, of thickness comprised between 10 nm and 40 nm, and - said external low-index layer, of thickness comprised between 20 nm and 40 nm, said coating having: * a thickness comprised between 150 nm and 250 nm, and * a thickness of the low-index layers at least equal to 90% of the thickness of said coating.

10. Ophthalmic lens (L2, L4, L6) according to one of the preceding claims, wherein said first material consists of SiO2 for the most internal layer of said stack, and of SiO2 or of a mixture of SiO2+Al2O3 for at least one other said low-index layer.

11. Process for manufacturing an ophthalmic lens (L2, L4, L6) forming a sunglass lens according to one of the preceding claims, characterized in that the process comprises depositing, in a vacuum chamber, said at least two low-index layers and said at least one high-index layer, without subjecting to an ion bombardment the exposed surface of that of said at least two low-index layers which is the closest to said substrate (1), or the proximal low-index layer, before deposition of a said high-index layer that covers it.

12. Process according to Claim 11, wherein the layer that is internal to said stack is said proximal low-index layer, which is directly covered by said adjacent high-index layer without being subjected beforehand to said ion bombardment.

13. Process according to Claim 12, wherein the following are deposited: - said low-index layer that is internal to said stack while introducing into said chamber a gas chosen from argon, krypton, neon, oxygen and a mixture of at least two of these gases, preferably oxygen, - said at least one high-index layer with or without introduction of said gas into said chamber, and - at least one other said low-index layer without introducing said gas into said chamber.

14. Process according to one of Claims 11-13, wherein said coating (2) is deposited on at least one abrasion-resistant organic layer covering said substrate (1), without providing said coating (2) with an underlayer.