Articles coated with low refractive index layers based on organosilsesquioxane compounds

Abstract

The invention relates to an article comprising a substrate having at least one main surface coated with a layer A having a refractive index of less than or equal to 1.55 wherein said layer A is obtained by depositing an activating substance generated from at least one silsesquioxane compound C in gaseous form, the compounds are substituted with R1, R2, R3, R4, R5, R6, R7 and R8 groups independently selected from the group consisting of alkyl, aryl, vinyl, acrylic, methacrylic, substituted alkyl, and-OSiRaRbRc wherein Ra, Rb and Rc independently represent H, alkyl, vinyl, aryl, hydroxyl or a hydrolysable group, with the proviso that Ra, Rb and Rc are not all selected from H or a hydrolysable group.

Description

[0001] The present invention generally relates to: articles having an organic layer based on a silicone compound, preferably optical articles, in particular ophthalmic lenses, which combine very good mechanical properties, heat resistance and a low refractive index; and a method for producing such articles.

[0002] It is known to coat mineral or organic optical articles such as ophthalmic lenses or screens with interference coatings, in particular antireflection coatings, these coatings generally being formed by a multilayer stack of dielectric mineral materials such as SiO, SiO 2 , Si 3 N 4 , TiO 2 , ZrO 2 , Al 2 O 3 , MgF 2 or Ta 2 O 5 formed.

[0003] In the case of ophthalmic lenses, the antireflection coating prevents the formation of parasitic reflections, which are harmful to the wearer and to the person with whom he / she interacts.

[0004] Reflective coatings produce the opposite effect, that is to say, they increase the reflection of light. For example, this type of coating is used to obtain a mirror effect in sunglasses lenses.

[0005] One of the problems encountered with any type of mineral interference coating (this type of coating is generally deposited by vacuum evaporation or by sputtering) is its high brittleness from a mechanical point of view, which is mainly due to its mineral nature. These coatings are more or less strained internally and may find it difficult to withstand deformation or substantial expansion, since the stresses to which they are subjected often lead to problems of adhesion and / or cracking propagating over all regions of the coating, generally rendering it unusable, and this problem gets worse as the thickness of the layer increases.

[0006] For example, during the edging and fitting of glasses by an optician, the glasses are subjected to mechanical deformations, which can produce cracks in the mineral interference coating, especially when the operation is not carried out carefully. Similarly, thermal stresses (heating of the frame) can produce cracks in the interference coating. Depending on the number and size of the cracks, the latter can impair the wearer's vision and prevent the glasses from being sold.

[0007] The application WO 2013 / 098531 in the name of the present applicant describes an article having improved thermomechanical properties, which article comprises a substrate having at least one main surface coated with a multilayer interference coating, said coating comprising a layer A having a refractive index less than or equal to 1.55 and not formed from an inorganic precursor compound, which layer A may constitute the outer layer of the interference coating and has been obtained by depositing an activated substance generated from at least one organosilicon precursor compound in gaseous form, such as octamethylcyclotetrasiloxane (OMCTS), under an ion beam.

[0008] The patent applications WO 2014 / 199103, WO 2017 / 021670 and WO 2020 / 161128 in the name of the present applicant describe multilayer interference coatings obtained by similar techniques, which multilayer interference coatings comprise at least one layer obtained from an organosilicon precursor such as 2,4,6,8 - tetramethylcyclotetrasiloxane (TMCTS), decamethyltetrasiloxane (DMTS) or 1,3,5 - tris(3,3,3 - trifluoropropyl)-1,3,5 - trimethylcyclotrisiloxane (FCTS).

[0009] These layers based on organosilicon compounds have interesting mechanical properties, but there is still a need to further improve the heat resistance, and in practice, their refractive index is too high, usually exceeding 1.50, typically 1.52, resulting in lower optical performance in antireflection coatings.

[0010] In fact, it is advantageous to use a material having a sufficiently low refractive index (n ≤ 1.50) in an antireflection coating, because the lower the refractive index, the better the optical performance. For example, SiO having a refractive index of 1.48 at 500 nm 2 has better antireflection performance, but has lower mechanical properties, especially lower elasticity.

[0011] Another existing low - refractive - index material, MgF 2 usually needs to be heated at a high temperature (such as 250 °C) to obtain good adhesion properties, which prevents its use on organic substrate materials. In addition, when deposited at a low temperature such as the low temperature required for polymer deposition, MgF 2 is sensitive to water.

[0012] Using hollow or porous materials is another solution to ensure a low refractive index, but they are usually very sensitive to water. As an alternative, materials deposited by glancing - angle deposition can be employed, but due to their porosity, their mechanical properties are insufficient.

[0013] Polyhedral silsesquioxane compounds are organic materials mainly used for surface functionalization (anti-liquid coatings in EP 3337859 or semiconductor / integrated circuit surfaces in EP1271634), combustion deposition (EP 2242730), or as a nano-dispersed phase blended in organic monomers for manufacturing coatings by liquid deposition (US 9939557).

[0014] The aim of the present invention is to propose an efficient means for satisfactorily reducing the intrinsic brittleness of mineral interference coatings. The present invention aims to obtain coatings, especially interference coatings, and in particular anti-reflection coatings, having layers with a low refractive index while maintaining high thermo-mechanical and durability properties. In particular, the present invention relates to articles having an improved critical temperature (i.e., good crack resistance when they are subjected to a temperature increase).

[0015] Another aim of the present invention is to provide a method for manufacturing interference coatings that is simple, easy to implement, and reproducible.

[0016] The inventors have found that modifying the properties of one or more inorganic layers of an interference coating (i.e., at least one low refractive index layer, typically a silica layer) allows the target aims to be achieved. According to the present invention, this low refractive index layer is a hybrid layer formed by depositing activating substances (obtained from silsesquioxane organic precursor materials in gaseous form) under an ion beam, preferably in the absence of inorganic precursors.

[0017] To meet the needs of the present invention and remedy the mentioned drawbacks of the prior art, the applicant provides an article comprising a substrate having at least one main surface coated with layer A - having a refractive index less than or equal to 1.55 - which layer A is obtained by depositing activating substances produced from at least one compound C having the following formula in gaseous form:

[0018]

[0019] where R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 、R 8 are independently selected from the group consisting of alkyl, aryl, vinyl, acrylic, methacrylic, substituted alkyl, and -OSiR a R b R c ,where R a 、R b and Rc independently represents H, an alkyl group, a vinyl group, an aryl group, a hydroxyl group or a hydrolyzable group, provided that R a , R b and R c are not all selected from H or hydrolyzable groups, and the deposition of the layer A is carried out by applying bombardment to the layer A with an ion beam while forming the layer A.

[0020] When considered in conjunction with the accompanying drawings, the foregoing and other objects, features and advantages of the present invention will become apparent to those skilled in the art by reading the following detailed description, in which Figure 1 the FTIR spectra of layers formed by evaporation of the silsesquioxane compounds of formula (IV) of the present invention under different ion-assisted conditions are shown. Detailed Description

[0021] In the present application, when an article has one or more coatings on its surface, the expression "depositing a layer or coating on the article" should be understood to mean depositing the layer or coating on the uncovered (exposed) surface of the outer coating of the article (i.e., the coating that is furthest from the substrate).

[0022] A coating "on" a substrate or that has been deposited "on" a substrate is defined as a coating that: (i) is positioned above the substrate, (ii) does not necessarily contact the substrate (although preferably it does), i.e., one or more intermediate coatings can be arranged between the substrate and the coating in question, and (iii) does not necessarily completely cover the substrate (although preferably it does). When "layer 1 is located under layer 2", it is understood that layer 2 is further from the substrate than layer 1.

[0023] Articles produced according to the present invention include a substrate, preferably a transparent substrate, which has a front major face and a back major face, and at least one and preferably both of said major faces include layer A.

[0024] The "back face" of the substrate (the back face is usually concave) should be understood to be the face that is closest to the wearer's eyes when the article is in use. Conversely, the "front face" of the substrate (the front face is usually convex) should be understood to be the face that is furthest from the wearer's eyes when the article is in use.

[0025] Although the articles according to the present invention can be any type of article, such as a screen, a glazing unit, a pair of protective glasses that can be used especially in a work environment, a mirror, or an article used in an electronic device (e.g., an OLED), it is preferably an optical article, more preferably an optical lens, and even more preferably an ophthalmic lens or a blank optical or ophthalmic lens of a pair of glasses such as a semi-finished optical lens, and especially an eyeglass lens. The lens can be a polarized or colored lens or a photochromic lens. Preferably, the ophthalmic lens according to the present invention has a high transmittance.

[0026] Layer A according to the invention can be formed on at least one major surface of a bare substrate (i.e., an uncoated substrate) or on at least one major surface of a substrate that has already been coated with one or more functional coatings.

[0027] The substrate of the article according to the invention is preferably an ophthalmic lens, which is made of, for example, a thermoplastic or thermosetting plastic. The substrate can be selected from the substrates mentioned in patent application WO 2008 / 062142 and can be, for example, a substrate obtained by (co)polymerization of diethylene glycol bis-allyl carbonate, a poly(thio)urethane substrate or a substrate made of (thermoplastic) bis-phenol-A polycarbonate (PC).

[0028] Before layer A is deposited on at least one major surface of a substrate (which is optionally coated with, for example, an anti-abrasion and / or anti-scratch coating), it is common to subject the surface of the optionally coated substrate to a physical or chemical activation treatment aimed at improving the adhesion of layer A. This pretreatment is usually carried out under vacuum. It can be a bombardment with high-energy and / or reactive species (such as an ion beam (ion pre-cleaning or IPC) or an electron beam), a corona discharge treatment, a glow discharge treatment, a UV treatment or a treatment in a low-pressure vacuum plasma (usually an oxygen or argon plasma, while other gases like nitrogen can be present). It can also be a question of an acidic or basic surface treatment and / or a treatment with a solvent (water or one or more organic solvents). Several of these treatments can be combined. By virtue of these cleaning treatments, the cleanliness and reactivity of the substrate surface are optimized.

[0029] The term "high-energy species" (and / or "reactive species") should be understood in particular to mean ionic species having an energy in the range of 1 to 300 eV, preferably 1 to 150 eV, still better 10 to 150 eV and even still better 40 to 150 eV. High-energy species can be chemical species such as ions, radicals, or species such as photons or electrons.

[0030] A preferred pretreatment of the substrate surface is an ion bombardment treatment carried out by an ion gun, the ions being particles formed from gas atoms from which one or more electrons have been stripped. At an acceleration voltage typically in the range of 50 to 200 V, a current density typically included between 10 and 100 μA / cm 2 at the activated surface, and typically at a residual pressure in the vacuum chamber in the possible range of 8×10 -5 mbar to 2×10 -4 mbar, argon is preferably used as the ionized gas (Ar + ions), although oxygen or a mixture of oxygen and argon can also be used.

[0031] The article according to the present invention comprises layer A, which preferably forms a layer of a single-layer interference coating or a multi-layer interference coating (preferably its outer layer, i.e., the layer of the interference coating that is farthest from the substrate in the stacking order), preferably a multi-layer interference coating. The interference coating is preferably formed on a wear-resistant and / or scratch-resistant coating, preferably those coatings based on the hydrolysis products of epoxy silanes containing at least two and preferably at least three hydrolyzable groups bonded to silicon atoms. The hydrolyzable groups are preferably alkoxysilyl groups.

[0032] The interference coating can be any interference coating conventionally used in the field of optical devices, especially ophthalmic optical devices, provided that it comprises layer A (preferably in an external position) formed by activating substances generated by depositing at least one organic compound C in gaseous form under an ion beam. The interference coating can be, without limitation, an antireflection coating, a reflective (mirror) coating, an infrared filter or an ultraviolet filter, or an antireflection coating in the visible light range but filtering ultraviolet light and / or blue light and / or infrared light. The interference coating is preferably an antireflection coating.

[0033] Layer A according to the present invention can be used in an interference coating to replace a conventional low refractive index material (such as silica), for example, to obtain an interference coating with better performance. Layer A can be located at different positions in the interference coating. In one embodiment, the interference coating is a single-layer interference coating composed of layer A. In another embodiment, the interference coating is a multi-layer interference coating, and its outermost (external) layer is preferably layer A according to the present invention, i.e., the layer of the interference coating that is farthest from the substrate in the stacking order. In another embodiment, layer A is a sub-layer of the interference coating.

[0034] In one embodiment, the interference coating comprises one layer A, preferably as the outermost layer. In another embodiment, the interference coating comprises at least two layer A that are the same or different in composition and / or thickness.

[0035] An antireflection coating is a coating deposited on the surface of an article, which improves the antireflection characteristics of the final article. The antireflection coating reduces the reflection of light at the article / air interface over a relatively wide portion of the visible spectrum.

[0036] As is well known, these interference (preferably antireflection) coatings conventionally contain a single layer or a multi-layer stack of dielectric materials. These are preferably multi-layer coatings, which comprise layers with a high refractive index (HI) and layers with a low refractive index (LI).

[0037] In the present patent application, when the refractive index of a layer of an interference coating is higher than 1.55, preferably higher than or equal to 1.6, more preferably higher than or equal to 1.8 and even more preferably higher than or equal to 2.0, it is referred to as a high refractive index layer. When the refractive index of a layer of an interference coating is lower than or equal to 1.55, preferably lower than or equal to 1.50 and more preferably lower than or equal to 1.45, it is referred to as a low refractive index layer. Unless otherwise specified, the refractive index mentioned in the present invention is expressed for a wavelength of 550 nm at 25 °C.

[0038] HI layers are conventional high refractive index layers well known in the art. They typically contain one or more metal oxides such as, without limitation, zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), tantalum pentoxide (Ta 2 O 5 ), neodymium oxide (Nd 2 O 5 ), hafnium oxide (HfO 2 ), praseodymium oxide (Pr 2 O 3 ), praseodymium titanate (PrTiO 3 ), La 2 O 3 , Nb 2 O 5 , Y 2 O 3 , 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.

[0039] LI layers are also well-known layers and can contain, without limitation, SiO 2 , MgF 2 , ZrF 4 , a small proportion of aluminum oxide (Al 2 O 3 ), AlF 3 and mixtures thereof, but preferably SiO 2 layers. Layers made of SiOF (fluorine-doped SiO 2 ) can also be used.

[0040] Typically, the HI layer has a physical thickness in the range of 10 nm to 120 nm, and the LI layer has a physical thickness in the range of 10 nm to 125 nm, preferably 10 nm to 125 nm.

[0041] The total thickness of the interference coating is preferably less than 1 µm, more preferably less than or equal to 800 nm and even more preferably less than or equal to 500 nm. The total thickness of the interference coating is typically greater than 100 nm and preferably greater than 150 nm.

[0042] Even more preferably, the interference coating (which is preferably an anti-reflection coating) comprises at least two low refractive index (LI) layers and at least two high refractive index (HI) layers. The total number of layers in the interference coating is preferably less than or equal to 8 and more preferably less than or equal to 6.

[0043] The HI and LI layers do not need to alternate in the interference coating, although they may in one embodiment of the invention. Two (or more) HI layers can be deposited on top of each other, just as two (or more) LI layers can be deposited on top of each other.

[0044] Preferably, all low refractive index layers of the interference coating according to the invention other than layer A are essentially inorganic (i.e., the other low refractive index layers of the interference coating preferably do not contain any organic compounds).

[0045] Preferably, all layers of the interference coating according to the invention other than layer A are essentially inorganic, or in other words, layer A is preferably the only organically natured layer in the interference coating according to the invention (the other layers of the interference coating preferably do not contain organic compounds).

[0046] According to one embodiment of the invention, the interference coating comprises a sublayer. In this case, the sublayer typically forms the first layer of the interference coating in the deposition sequence of the layers, i.e., the sublayer is the layer of the interference coating that contacts the underlying coating (which is typically an anti-wear and / or anti-scratch coating) or the layer of the interference coating that contacts the substrate when the interference coating is deposited directly on the substrate.

[0047] The expression "sublayer of the interference coating" should be understood to mean a relatively thick coating used for the purpose of improving the resistance of said coating to wear and / or scratching and / or promoting the adhesion of the coating to the substrate or the underlying coating. The sublayer according to the invention can be selected from the sublayers described in patent application WO 2010 / 109154. Preferably, the sublayer is 100 to 200 nm thick. The sublayer is preferably uniquely essentially inorganic and preferably made of silicon dioxide SiO 2 made.

[0048] In one embodiment, one or more so-called "impedance layers" (or adaptation layers, also referred to as layers reducing interference fringes) are inserted between the sub-layer and the underlying coating (or substrate), thereby forming an impedance coating that limits interference fringes caused by the refractive index difference between the sub-layer and the underlying coating or substrate. Embodiments in which the interference coating includes an impedance layer are fully described in WO 2018 / 192998.

[0049] The article of the present invention can be made antistatic by incorporating at least one conductive layer into the interference coating. The term "antistatic" should be understood to mean the property of not storing and / or accumulating perceptible static charges. An article is generally considered to have acceptable antistatic properties when it does not attract and does not retain dust and small particles after one of its surfaces has been rubbed with a suitable cloth.

[0050] The conductive layer can be located at different positions in the interference coating, provided that it does not interfere with the antireflection properties of the latter. If there is a sub-layer, the conductive layer can be deposited, for example, on this sub-layer of the interference coating. The conductive layer is preferably located between two dielectric layers of the interference coating and / or below the low refractive index layer of the interference coating.

[0051] The conductive layer must be thin enough not to reduce the transparency of the interference coating. Generally, depending on its nature, the thickness of the conductive layer ranges from 0.1 to 150 nm and preferably from 0.1 to 50 nm. A thickness less than 0.1 nm generally does not allow obtaining sufficient conductivity, while a thickness greater than 150 nm generally does not allow obtaining the required transparency and low absorption properties.

[0052] The conductive layer is preferably made of a conductive and highly transparent material. In this case, the thickness of the conductive layer preferably ranges from 0.1 to 30 nm, more preferably from 1 to 20 nm and even more preferably from 2 to 15 nm. The conductive layer preferably contains a metal oxide selected from indium oxide, tin oxide, zinc oxide and mixtures thereof. Indium tin oxide (tin-doped indium oxide, In 2 O 3 :Sn), indium oxide (In 2 O 3 ), and tin oxide SnO 2 are preferred. According to a best embodiment, the conductive and optically transparent layer is an indium tin oxide (ITO) layer.

[0053] Generally, the conductive layer contributes to the obtained antireflection properties and forms a high refractive index layer in the interference coating. This is the case for a layer made of a conductive and highly transparent material (such as an ITO layer).

[0054] The conductive layer can also be a very thin layer of noble metal (Ag, Au, Pt, etc.), typically with a thickness less than 1 nm and preferably a thickness less than 0.5 nm.

[0055] Each layer of the interference coating other than layer A (including the optional antistatic layer) is preferably deposited by vacuum deposition using one of the following techniques: i) evaporation, optionally ion-assisted evaporation, ii) ion beam sputtering, iii) cathode sputtering, or iv) plasma-enhanced chemical vapor deposition. These different techniques are described respectively in the following books: "Thin Film Processes" and "Thin Film Processes II", edited by Vossen and Kern, Academic Press, 1978 and 1991. Vacuum evaporation techniques are particularly recommended.

[0056] Preferably, the layers of the interference coating are deposited by vacuum evaporation.

[0057] Optionally, the deposition of one or more of these layers is carried out by supplying (supplementing) gas into the vacuum chamber during the deposition step of the layer, as disclosed in US2008 / 206470. Specifically, additional gases such as noble gases (e.g., argon, krypton, xenon, neon), gases such as oxygen, nitrogen, or a mixture of two or more of these gases are introduced into the vacuum deposition chamber while depositing the layer. The gas employed during this deposition step is not an ionized gas, and more preferably not an activated gas.

[0058] This gas supply enables the regulation of pressure and is different from ion bombardment treatments (such as ion assistance). It generally enables the limitation of stress in the interference coating and enhances the adhesion of the layers. When using this deposition method, which is referred to as deposition under gas pressure regulation, it is preferred to work in an oxygen atmosphere (so-called "passive oxygen"). The layers produced by using an additional gas supply during the deposition of the layer are structurally different from the layers deposited without an additional gas supply.

[0059] Layer A is a low refractive index layer as defined according to the present invention, since it has a refractive index of ≤ 1.55. In some embodiments of the present invention, the refractive index of layer A is preferably lower than or equal to any one of the following values: 1.50, 1.49, 1.48, 1.47.

[0060] Layer A is obtained by depositing an activated substance derived from at least one compound C in gaseous form. In addition, the deposition of layer A is carried out by applying bombardment to layer A with an ion beam while forming layer A (ion assistance, or "IAD"), and layer A is preferably not formed from an inorganic precursor compound.

[0061] Layer A contains silicon, oxygen, preferably carbon, and optionally nitrogen in its structure.

[0062] Preferably, the deposition is carried out in a vacuum chamber including an ion gun for guiding the substrate to be coated, and the ion gun emits a beam of positive ions generated in the plasma within the ion gun towards the substrate. Preferably, the ions generated from the ion gun are particles formed by gas atoms from which one or more electrons have been stripped, and the gas is a noble gas such as argon, oxygen, or a mixture of two or more of these gases.

[0063] In one embodiment, the deposition of layer A is carried out by applying bombardment with an ion beam containing oxygen ions. In another embodiment, the deposition of layer A is carried out by applying bombardment with an ion beam containing noble gas ions, preferably argon ions, with or without oxygen ions.

[0064] The precursor (compound C) sublimes from a solid state (usually a powder) to a gaseous state in the vacuum chamber and is activated under the action of the ion gun. The ion beam dissociates the precursor molecules in the gas phase and causes the fragments to react on the deposition surface to form a film.

[0065] Without wishing to be limited to any one theory, the inventors believe that the plasma of the ion gun accumulates in the region between the anode and the cathode but does not reach the substrate to be coated. It projects an ion beam accompanied by electrons to keep it quasi-neutral. The ion beam occupies a much larger volume than the initial plasma, and the activation / dissociation of the precursor compound C preferentially occurs in this region and on the surface of the deposited film.

[0066] This deposition technique using an ion gun and a gaseous precursor (sometimes called "ion beam deposition" or "ion-assisted deposition") is particularly described in patent US 5508368.

[0067] According to the present invention, the ion gun is preferably the only place where plasma is generated in the chamber.

[0068] If necessary, the ion beam can be neutralized before it leaves the ion gun. In this case, the bombardment is still considered to be ion bombardment because the ions are still sent to the surface independently of the electrons. Generally, ion bombardment causes atomic rearrangement in the layer being deposited and densification of the layer, thereby compressing it while forming the layer.

[0069] During the implementation of the method according to the present invention, the surface to be treated is preferably bombarded with ions, where the current density on the activated surface generally ranges between 20 and 1000 μA / cm 2 preferably between 30 and 500 μA / cm 2 more preferably between 30 and 200 μA / cm 2 and generally at a residual pressure in the vacuum chamber (which may range from 6×10 -5 mbar to 2×10 -4mbar and preferably 8×10 -5 mbar to 2×10 -4 mbar). An argon and / or oxygen ion beam is preferably used. When using a mixture of a noble gas and oxygen, the amount of oxygen preferably ranges from 0.1% to 40% by volume, more preferably from 0.1% to 5%, 10%, 20% or 30% by volume. It preferably ranges from 1% to 10% by volume. This ratio can be controlled by adjusting the gas flow rate in the ion gun. The argon gas flow rate preferably ranges from 5 to 30 sccm. The oxygen O 2 gas flow rate preferably ranges from 0 to 30 sccm and increases proportionally with the flow rate of the precursor compound of layer A.

[0070] The ions of the ion beam (preferably generated from the ion gun used during the deposition of layer A) preferably have an energy ranging from 75 to 150 eV, more preferably from 80 to 140 eV and even more preferably from 90 to 110 eV. The activated species formed are typically radicals or ions.

[0071] The technique of the present invention differs from deposition by plasma (e.g., PECVD) in that it involves bombarding the layer A being formed with an ion beam, which beam is preferably emitted by an ion gun. Compared with chemical vapor deposition processes, the technique of the present invention has several advantages, such as less contamination of the ion source and thus better reproducibility of the discharge parameters and lower material investment.

[0072] In addition to ion bombardment during deposition, plasma treatment of layer A can be carried out, optionally accompanied by deposition under an ion beam. Layer A is preferably deposited without plasma assistance at the substrate level.

[0073] When the precursor compound C does not contain (or does not contain sufficient) nitrogen atoms and it is desired for layer A to contain a certain proportion of nitrogen, layer A can be deposited in the presence of a nitrogen source.

[0074] In addition to layer A, other layers of the interference coating can be deposited under an ion beam. Evaporation of the precursor material of layer A carried out under vacuum can be achieved using a Joule effect heat source.

[0075] The precursor material of layer A includes at least one compound C, which at least one compound C contains silicon, carbon, oxygen, optionally at least one hydrogen atom and optionally at least one nitrogen atom in its structure. Compound C is an organosilicon compound and is considered to be essentially organic in the present application.

[0076] The concentration of each chemical element (Si, O, C, H, N, …) in layer A can be determined using Rutherford backscattering spectrometry (RBS) technique, elastic recoil detection analysis (ERDA) or X-ray photoelectron spectroscopy (XPS).

[0077] The atomic percentage of carbon atoms in layer A is preferably less than 40%, more preferably less than 35%. Its range is preferably from 3% to 40%, more preferably from 20% to 35%. The range of the atomic percentage of silicon atoms in layer A is preferably from 10% to 45% and more preferably from 20% to 40% or from 25% to 35%. The atomic percentage of oxygen atoms in layer A is preferably higher than 30%, more preferably higher than 35%. Its range is preferably from 30% to 60%, more preferably the range is from 35% to 50%.

[0078] The O / Si atomic ratio in layer A preferably ranges from 1 to 3, preferably from 1.25 to 2. The C / Si atomic ratio in layer A is preferably greater than or equal to 1, more preferably greater than or equal to 1.5, 2 or 3. The C / Si atomic ratio in layer A is preferably less than or equal to 6.

[0079] The precursor compound C of layer A has the following formula:

[0080]

[0081] where R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 、R 8 are independently selected from the group consisting of: alkyl, aryl, vinyl, acrylic, methacrylic, substituted alkyl, and -OSiR a R b R c where R a 、R b and R c independently represent H, alkyl, vinyl, aryl, hydroxyl or a hydrolysable group, provided that R a 、R b and R c are not all selected from H or hydrolysable groups.

[0082] Compound C is an organosilicon compound having a silsesquioxane core, which can be structurally represented by a cage structure having Si-O-Si linkages and tetrahedral Si vertices. The cage structure consists of 8 silicon atoms and 12 oxygen atoms.

[0083] The silsesquioxane is a member of polyhedral oligomeric silsesquioxane ("POSS"). Compound C has a unique hybrid structure because they are characterized by an inorganic silicate core surrounded by an organic exterior. Their chemical composition (RSiO 1.5 ) is intermediate between silica (SiO2 ) and between the chemical composition of siloxane (R 2 SiO).

[0084] As is well known, silsesquioxane can be synthesized by hydrolysis of organotrichlorosilane or by condensation of the corresponding silanetriol.

[0085] These materials are solid, which is an advantage over the liquid silicone compounds used in the prior art for forming hybrid coatings, because the evaporation of compound C of the present invention does not require an expensive injection pipeline adapted to the gasification of liquids.

[0086] Due to the combination of the optical properties of the inorganic film and the polymer-like mechanical behavior of the plastic substrate, layer A is named a hybrid.

[0087] Compound C contains silicon, oxygen, at least one carbon atom, and optionally at least one nitrogen atom in its structure. According to one embodiment, compound C does not contain any Si-N groups and preferably does not contain any nitrogen atoms. In one embodiment, compound C does not contain any fluoroalkyl groups.

[0088] The precursor compound C of layer A preferably contains at least one silicon atom with at least one alkyl group, that is, connected to the silicon atom through a carbon atom, preferably a C1-C4 alkyl group.

[0089] The O / Si atomic ratio in compound C preferably ranges from 1 to 3, preferably from 1.25 to 2. The C / Si atomic ratio in compound C is preferably higher than or equal to 1, more preferably higher than or equal to 1.5, 2 or 3. The C / Si atomic ratio in compound C is preferably lower than or equal to 6.

[0090] The different substituents R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 can be attached to the Si center. In one embodiment, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 groups are all the same. In another embodiment, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R7 The groups are all the same, while R 8 is different from these groups.

[0091] In one embodiment, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 groups are independently selected from -OSiR a R b R c groups, where R a , R b and R c independently represent H, alkyl, vinyl or aryl, preferably H or alkyl. In one embodiment, -OSiR a R b R c group is -OSiR a R b H group, where R a , R b are alkyl groups having 1 to 4 carbon atoms, preferably the same alkyl groups. An example of such a compound is octa(dimethylsilyloxy)silsesquioxane of formula (IV):

[0092]

[0093] In the present patent application, the term "alkyl" means a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted hydrocarbon-based group containing 1 to 25 carbon atoms, preferably 1 to 12 carbon atoms, especially including acyclic groups containing 1 to 8 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, butyl and n-hexyl, preferably cycloalkyl groups containing 3 to 7 carbon atoms, preferably cycloalkylmethyl groups containing 4 to 8 carbon atoms. The alkyl group is connected to the rest of the molecule via sp 3 hybridized carbon atoms. The preferred alkyl group is methyl.

[0094] As used herein, the term "substituted alkyl" includes an alkyl group as defined above that is connected via sp 3 carbon atoms and is substituted by one or more aryl groups and / or contains one or more heteroatoms such as N, S, halogen such as F, or O. Examples to be mentioned include arylalkyl groups such as trityl (-CPh 3 ), benzyl or 4-methoxybenzyl, alkoxyalkyl groups, especially dialkoxymethyl groups such as diethoxymethyl or dimethoxymethyl, methoxymethyl, the formula CH 2 CO 2 R 11group, wherein R 11 represents an optionally substituted alkyl or aryl group.

[0095] In one embodiment, the substituted alkyl is a fluoroalkyl group.

[0096] In the present application, the term "aryl" represents an aromatic monovalent carbocyclic group containing only one ring (e.g., phenyl) or several fused rings (e.g., naphthyl or terphenyl), which may optionally be substituted by one or more groups such as, but not limited to, alkyl (e.g., methyl), hydroxyalkyl, aminoalkyl, hydroxy, thiol, amino, halogen (fluorine, bromine, iodine or chlorine), nitro, alkylthio, alkoxy (e.g., methoxy), aryloxy, monoalkylamino, dialkylamino, acyl, carboxyl, alkoxycarbonyl, aryloxycarbonyl, hydroxy sulfonyl, alkoxy sulfonyl, aryloxy sulfonyl, alkyl sulfonyl, alkyl sulfinyl, cyano, trifluoromethyl, tetrazolyl, carbamoyl, alkylcarbamoyl or dialkylcarbamoyl. Alternatively, two adjacent positions of the aromatic ring may be substituted by methylenedioxy or ethylenedioxy.

[0097] Non-limiting examples of hydrolysable groups are: acyloxy groups having the formula -O-C(O)R 4 wherein R 4 is a preferably C6-C12 aryl group optionally substituted by one or more functional groups, or a straight-chain or branched-chain and preferably C1-C6 hydrocarbon group optionally substituted by one or more functional groups and possibly also containing one or more double bonds, such as phenyl, methyl or ethyl; aryloxy and alkoxy groups having the formula -O-R 5 wherein R 5 is a preferably C6-C12 aryl group optionally substituted by one or more functional groups, or a straight-chain or branched-chain and preferably C1-C6 hydrocarbon group optionally substituted by one or more functional groups and possibly also containing one or more double bonds, such as phenyl, methyl or ethyl; halogen is preferably F, Cl, Br or I; groups of the formula -NR 1 R 2 may denote an amino group NH 2 or alkylamino, arylamino, dialkylamino or diarylamino; R 1 and R 2 independently denote a hydrogen atom, a preferably C6-C12 aryl group optionally substituted by one or more functional groups, or a straight-chain or branched-chain and preferably C1-C6 hydrocarbon group optionally substituted by one or more functional groups and possibly also containing one or more double bonds, such as phenyl, methyl or ethyl; and groups of the formula -N(R 3 )-Si, which are attached to the silicon atom through their nitrogen atom and whose silicon atom naturally contains three other substituents, wherein R 3Specify a preferred C6-C12 aryl optionally substituted by one or more functional groups, or a straight-chain or branched-chain and preferably C1-C6 hydrocarbon group optionally substituted by one or more functional groups and possibly further containing one or more double bonds, such as phenyl, methyl or ethyl.

[0098] The preferred acyloxy group is acetoxy. The preferred aryloxy group is phenoxy. The preferred halogen is Cl. The preferred alkoxy groups are methoxy and ethoxy.

[0099] Groups containing Si-O-Si chains are not considered "hydrolyzable groups" in the context of the present invention.

[0100] Other suitable examples of compound C according to the present invention are those in which R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 、R 8 are independently selected from alkyl (such as octamethylsilsesquioxane of formula (I)), vinyl (such as octavinylsilsesquioxane of formula (II)), aryl (such as octa(aminophenyl)silsesquioxane of formula (III)):

[0101]

[0102] In one embodiment, the R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 and R 8 groups are independently selected from fluoroalkyl groups.

[0103] The fluoroalkyl group of compound C can be straight-chain or branched-chain. It preferably contains 1 to 25 carbon atoms, more preferably 1 to 10 or 1 to 5 and ideally 1 to 3 carbon atoms. In one embodiment, the group is a perfluoroalkyl group.

[0104] The fluoroalkyl group of compound C is preferably a group of formula (V):

[0105] -(C x' H y' F z' )-(L 1 ) p' -(C x H y F z ) m -(L 2 ) p"-R"(V)

[0106] wherein R" is a hydrogen or fluorine atom, an acyl group or a hydrocarbon group (which is straight-chain or branched-chain, may be substituted by one or more heteroatoms or functional groups, and may additionally contain one or more double bonds), L 1 and L 2 are straight-chain or branched-chain divalent groups (which may be the same or different), x' is an integer ranging from 1 to 10, preferably from 1 to 5, more preferably equal to 2, y' and z' are integers such that y'+z' = 2x', x is an integer ranging from 1 to 20, preferably from 1 to 15, more preferably from 2 to 8, y and z are integers such that y+z = 2x, m is equal to 0 or 1, preferably 0, p' is equal to 0 or 1, preferably 0, and p" is equal to 0 or 1, preferably 0. R''' may also represent an aliphatic or aromatic acyl group, especially an acetyl group or a trifluoroacetyl group.

[0107] The R" group is preferably a straight-chain or branched-chain fluoroalkyl group, more preferably a perfluoroalkyl group. It preferably contains 1 to 10 carbon atoms, more preferably 1 to 5 and ideally 1 to 3 carbon atoms and particularly represents a trifluoromethyl group.

[0108] The group of formula (C x H y F z ) is preferably a group of formula (CF 2 ), where x is as defined previously. The group of formula (C x ) is preferably a group of formula (CH x’ H y’ F z’ ), where x' is as defined previously. 2 ) x’ When the L

[0109] and L 1 and L 2 groups are present, they may be selected from the divalent groups L, L' and L" mentioned previously, and may also represent an oxyalkylene group (-O-alkylene-) or an alkyleneoxy group (-alkylene-O-), which is preferably a C 2 -C 4 group, more preferably a C 2 -C 3 group. -(L 2 ) p" -R" group is preferably a fluoroalkyl group or a perfluoroalkyl group, ideally a trifluoromethyl group.

[0110] In one embodiment, the fluoroalkyl group of compound C is a group of formula (V), where m = p' = p" = z' = 0 and R" = perfluoroalkyl.

[0111] Examples of the fluoroalkyl group of formula (V) are groups of the following formula:

[0112] F(CF 2 ) c -(CH 2 ) d -(CF 2 ) e -(CH 2 ) f - (II)

[0113] H(CH 2 ) g -(CF 2 ) h -(CH 2 ) i -(CF 2 ) j - (III)

[0114] wherein c, d, e, f, g, h, i and j each represent an integer ranging from 0 to 10, at least one of c, d, e and f is not 0, and at least one of g, h, i and j is not 0. Preferably, 2 ≤ c + d + e + f ≤ 12 and / or 2 ≤ g + h + i + j ≤ 12, and more preferably 3 ≤ c + d + e + f ≤ 8 and / or 3 ≤ g + h + i + j ≤ 8.

[0115] Examples of the group of formula (V) are (perfluoroalkyl)alkyl, such as 3,3,3-trifluoropropyl. An example of a suitable compound C according to this embodiment is octakis(3,3,3-trifluoropropyl)silsesquioxane of formula (VI):

[0116]

[0117] In one embodiment, at least one, preferably one, of the R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 groups is an alkyl group substituted with one or more amino groups, such as but not limited to N-(2-aminoethyl)-3-aminopropyl or 3-aminopropyl. An example of a suitable compound C according to this embodiment is heptakis(isobutyl)N-(2-aminoethyl)-3-aminopropylsilsesquioxane of formula (VII):

[0118]

[0119] In one embodiment, layer A is not formed from an organosilicon compound that does not contain any cage structure composed of oxygen and silicon atoms. In another embodiment, layer A is not formed from an organic compound that does not contain silicon. In a further embodiment, layer A is not formed from an organic compound that is not compound C according to the present invention.

[0120] Preferably, the precursor compound of layer A is introduced in gaseous form into the vacuum chamber in which the article according to the present invention is produced, while controlling its flow rate. In other words, it is preferably not vaporized in the vacuum chamber. The feed of the precursor compound of layer A is preferably located at a distance ranging from 30 to 50 cm from the outlet of the ion gun.

[0121] According to the present invention, layer A is preferably not formed from a pure inorganic (mineral) precursor compound, and in particular, it is preferably not formed from a precursor having the nature of a metal oxide. Thus, in this case, it is particularly different from the "hybrid" layer described in patent US6919134. Preferably, layer A does not contain a separate metal oxide phase, and more preferably does not contain any inorganic compound. In the present application, a metalloid oxide is considered to be a metal oxide.

[0122] Therefore, the method allowing the formation of the interference coating according to the present invention is much simpler than the method in which an organic compound and an inorganic compound are co-evaporated (such as the method described in patent US 6919134). In practice, the co-evaporation method is very difficult to implement and control due to reproducibility problems. Specifically, the respective amounts of the organic and inorganic compounds present in the deposited layer vary greatly from one operation to another.

[0123] Since layer A is formed by vacuum deposition, it does not contain any silane hydrolysis products and is thus different from a sol-gel coating obtained by liquid treatment.

[0124] Layer A preferably has a thickness ranging from 20 to 250 nm and more preferably 50 to 200 nm. When it forms the outer layer of the interference coating, layer A preferably has a thickness ranging from 60 to 100 nm.

[0125] The extinction coefficient (also known as the attenuation coefficient, denoted as k) of a particular substance measures the energy loss of electromagnetic radiation passing through the medium. This is the imaginary part of the complex refractive index. Preferably, the extinction coefficient k of layer A according to the present invention at 550 nm is less than or equal to 1.5x10 -2 、more preferably less than or equal to 10 -2 、even more preferably less than or equal to 10 -3 .

[0126] The mechanical properties of layer A can be evaluated by nanoindentation measurements. To this end, the elastic modulus E and the hardness H of the material forming layer A are measured by an instrument-controlled penetration test (indentation) according to the method described in detail in the experimental part. If necessary, reference will be made to the standard NF EN ISO 14577. The hardness H characterizes the ability of the material to withstand permanent indentation or deformation when the material is in contact with the indenter under a compressive load. The elastic modulus E (or Young's modulus, or storage modulus, or tensile elastic modulus) makes it possible to evaluate the ability of the material to deform under the action of the applied force.

[0127] Layer A according to the invention preferably exhibits a hardness H of ≥ 2.5 GPa, preferably ≥ 4 GPa, more preferably ≥ 5 GPa.

[0128] Layer A according to the invention preferably exhibits the following H / E ratio: higher than or equal to 0.10; 0.11; 0.12; 0.13; 0.14; 0.15 (the higher the better), where H and E are expressed in the same unit, typically MPa or GPa.

[0129] Without being bound by theory, it is considered that the H / E ratio represents fracture resistance (tolerance to crack propagation). The layers and articles according to the invention are durable because they exhibit good fracture resistance.

[0130] The elastic modulus E of the material forming layer A preferably varies from 15 to 80 GPa, more preferably from 20 to 50 GPa.

[0131] Process parameters such as the oxygen ion content in the ion beam and the discharge current can be used to adjust the chemical composition of layer A and thus its mechanical properties.

[0132] Without wishing to be bound by any theory, it is believed that the dissociation process of the ion source excitation of compound C is accompanied by a strong oxidation of the organic substances, thereby converting some of them into volatile substances that cannot participate in film growth. Therefore, when oxygen ions are present in the ion beam, the decrease in the organic content in layer A is more significant.

[0133] The critical temperature (as defined below) of the coated article according to the invention is preferably higher than or equal to 70 °C or 80 °C. In the present application, the critical temperature of the article or coating is defined as the temperature at which cracks appear in the stack present on the surface of the substrate, which results in the deterioration of the coating. This higher critical temperature is due to the presence of layer A on the surface of the article, as demonstrated in the experimental part.

[0134] Due to its good mechanical properties, layer A (which optionally forms part of an interference coating) can be applied in particular to a single face of a semi-finished lens, typically its front face, while the other face of the lens still needs to be machined and processed. The stack present on the front face of the lens will not be deteriorated by mechanical stresses caused by the processing to which the back face is subjected when the coating is deposited on it.

[0135] Preferably, the article coated with the interference coating according to the invention has an average reflection factor (denoted as R m ) in the visible light range (400 - 700 nm) that is lower than 2.5% / face of the article, preferably lower than 2% / face of the article, and even more preferably lower than 1% / face of the article. In one embodiment, the article comprises a substrate, the two main surfaces of which are coated with the interference coating according to the invention. The light reflection factor R v of the interference coating according to the invention is lower than 2.5% / face of the article, preferably lower than 2% / face of the article, more preferably lower than 1% / face of the article, even more preferably ≤ 0.75%, and still more preferably ≤ 0.5%.

[0136] In the present application, the "average reflection factor" R m (average spectral reflection over the entire visible spectrum between 400 and 700 nm) and the "light reflection factor" R v are defined as in standard ISO 13666:1998 and measured according to standard ISO 8980 - 4.

[0137] Taking into account the standard light source D65 and the observer (angle of incidence: 15°), the colorimetric coefficients C* and h of the optical article according to the invention are calculated between 380 nm and 780 nm in the international colorimetry CIE L*a*b*. The observer is the "standard observer" (10°) as defined in the international colorimetric system CIEL*a*b*.

[0138] In some aspects of the invention, the optical material has a chromaticity (C*) that is lower than or equal to 10 (for an angle of incidence of 15°), more preferably lower than or equal to 8, 5, 4, or 3. In the case of a lens, from the perspective of the wearer's comfort, it is preferred to obtain an article with a low residual color intensity (chromaticity).

[0139] In some applications, preferably, before depositing layer A or a multilayer coating comprising layer A, the main surface of the substrate is coated with one or more functional coatings. These functional coatings conventionally used in optical devices can be, but are not limited to, a primer layer for improving the impact resistance and / or adhesion of subsequent layers in the final product, an anti-wear and / or anti-scratch coating, a polarization coating, a photochromic coating or a colored coating, and can in particular be a primer layer coated with an anti-wear and / or anti-scratch layer. The latter two coatings are described in more detail in patent applications WO 2008 / 015364 and WO 2010 / 109154.

[0140] The article according to the invention may also include a coating formed on the interference coating that can change the surface properties of the interference coating, such as a hydrophobic coating and / or an oleophobic coating (anti-fouling top coating) or an anti-fog coating. These coatings are preferably deposited on the outer layer of the interference coating. They are generally less than or equal to 10 nm thick, preferably 1 to 10 nm thick and more preferably 1 to 5 nm thick. They are described respectively in patent applications WO 2009 / 047426 and WO 2011 / 080472.

[0141] Typically, the article according to the invention comprises a substrate sequentially coated with an adhesion and / or impact-resistant primer layer, an anti-wear and / or anti-scratch coating, an antistatic interference coating optionally according to the invention and comprising layer A usually as the outer layer, and a hydrophobic and / or oleophobic coating.

[0142] The invention also relates to a method for manufacturing an article as defined above, which method at least comprises the following steps:

[0143] - Providing an article comprising a substrate having at least one main surface,

[0144] - Depositing on the main surface of the substrate layer A having a refractive index less than or equal to 1.55, the deposition of layer A being carried out by applying an ion beam bombardment to layer A while forming layer A, the ion beam preferably comprising oxygen ions,

[0145] - Recovering an article comprising a substrate having a main surface coated with said layer A, said layer A being obtained by depositing an activated substance produced by at least one compound C in gaseous form having the following formula:

[0146]

[0147] - Recovering an article comprising a substrate having a main surface coated with said layer A, wherein said layer A is obtained by depositing an activated substance produced by at least one compound C in gaseous form, wherein R 1 、R 2 、R 3 、R4 , R 5 , R 6 , R 7 , R 8 has the meaning indicated above.

[0148] Said layer A is preferably deposited by vacuum evaporation of at least one compound C, typically by ion-assisted thermal evaporation.

[0149] The present invention is illustrated in a non-limiting manner by the following examples. Unless otherwise indicated, the refractive index is given for a wavelength of 550 nm and T = 20 °C - 25 °C.

[0150] Examples

[0151] 1. General procedure

[0152] The articles used in the examples have a substrate with a thickness of 2.0 mm (Example 8) or a B270 glass slide (Examples 1 - 7). In Example 8, the lens substrate is coated, in this order from the core of the substrate to the outside, with an impact-resistant primer coating of a polyurethane material based on that disclosed in the experimental part of WO 2010 / 109154, W234 TM and, deposited thereon, a wear- and scratch-resistant coating (hard coating) (having a refractive index of 1.48) disclosed in Example 3 of EP 0614957, said hard coating being coated with a multilayer antireflection coating comprising layer A according to the present invention.

[0153] For Examples 1 - 7, the vacuum deposition chamber is a Boxer Pro (Leybold Optics) machine equipped with an electron beam source (HPE-6) (which can be used for the evaporation of precursor materials), a thermal evaporator, an end Hall ion source (ion gun) eH-1000 (from Kaufman & Robinson Inc.) for use in the preparatory stage of preparing the surface of the substrate by argon ion bombardment (IPC) and in the ion-assisted deposition (IAD) of layer A or other layers, and a vapor flowmeter (MKS1150C) from MKS.

[0154] For Example 8, a BAK vacuum coater from Physimeca equipped with a Mark II+ ion gun from Veeco is used.

[0155] To vaporize the precursor compound C, a thermal evaporation technique is used. The compound C (840 ± 40 mg) in powder form is loaded into a small round copper container covered with a custom-made copper mesh, which is used to reduce the loss of the compound, prevent material spillage, and homogenize its flow towards the substrate. The loaded container is placed on an evaporation boat, and the precursor vapor exits from a tube inside the machine at a distance of about 30 cm from the ion gun. The evaporation is carried out in an argon atmosphere at a pressure of 0.24 mTorr. An argon gas flow and optionally an oxygen gas flow are introduced into the ion gun. The total gas flow is kept constant at 20 sccm.

[0156] Layer A according to the invention is formed by vacuum evaporation under ion bombardment without heating the substrate of a compound of formula (IV) obtained from Hybrid Plastics Inc. [C 16 H 56 O 20 Si 16 , CAS n° 125756 - 69 - 6, white powder, Mw = 1017.99 g / mol]. The comparative layer is formed without ion bombardment of the precursor compound C (Comparative Example 1: ion gun not activated, argon atmosphere).

[0157] Comparative Example 2 differs from Example 2 in that layer A is replaced by a silica layer evaporated under an electron beam without ion assistance.

[0158] The method for producing an optical article according to the invention (Example 8) includes introducing the substrate into a vacuum deposition chamber; the step of preheating the tube and the vapor flowmeter (about 20 min); the primary pumping step; and then the secondary pumping step for 400 seconds and allowing to obtain a secondary vacuum (about 2 × 10 -5 mbar, pressure read from a Bayard - Alpert gauge); the step of activating the surface of the substrate with an argon ion beam (IPC: 1 minute, 100 V, 1 A, stop the ion gun at the end of this step); and then sequentially evaporating the required number of layers, and finally the venting step. Layer A is deposited with ion assistance (ion gun: 2 A, 140 V, 10% oxygen).

[0159] Comparative Example 3 differs from the stack according to Example 8 of the invention in that layer A is replaced by a silica layer of the same thickness evaporated under an electron beam without ion assistance.

[0160] The thickness of the deposited layer is controlled in real time using a quartz crystal microbalance. The deposition rate is typically 11 - 17 nm / min. Once the desired thickness is obtained, the supply of the precursor compound is stopped and then the ion gun is turned off. Unless otherwise specified, the thicknesses mentioned are physical thicknesses.

[0161] 2. Characterization

[0162] The critical temperature of the article can be measured within 24 hours after its preparation in the manner indicated for the measurement of the critical temperature in Application WO 2008 / 001011, except that the relative humidity is > 90% instead of 50%, typically 100%. The critical temperature can also be measured in an ambient atmosphere at 50% relative humidity.

[0163] The measurement of the refractive index n and the extinction coefficient k (as defined in Application WO 2005 / 059603) is carried out by ellipsometry at a wavelength of 550 nm in the manner disclosed in WO 2015 / 166144.

[0164] A triboindenter TI 950 system (Hysitron Inc.) equipped with a Berkovich tip is used to determine the mechanical properties of the coating (i.e., the elastic modulus E, the hardness H, and the elastic recovery rate R of the material constituting the layer) by depth-sensing indentation techniques. Such nanoindentation measurements are detailed in WO 2015 / 166144. From these measurements, the indentation cycle is analyzed using the Oliver and Pharr method, which is disclosed in "Improved technique for determining hardness and elastic modulus using load displacement sensing indentation experiments", Journal of Materials Research, Vol. 7, pp. 1564 - 1583, 1992. Subsequently, the (E) and (H) characteristics of the film are extracted using the ISO 14577-4 standard.

[0165] The elastic recovery rate R corresponds to the portion of the total feedback energy returned after an indentation test. The higher the elastic recovery rate, the less permanent deformation remains after the test. It is evaluated by dividing the reversible work (W e ) of the indentation by the total work (W 总计 ) of the indentation. In this study, for all samples, R was determined using indentations made with a maximum applied load of 1000 μN in order to obtain a contact depth greater than the circular portion of the tip while having a penetration depth small enough to minimize substrate effects:

[0166]

[0167] The surface roughness was determined by optical microscopy. Information on the chemical composition was obtained by FTIR.

[0168] The chemical composition and structure of the deposited layers were studied by Fourier transform infrared spectroscopy (FTIR). Double-polished IR-transparent Si wafers were used as substrates. The normal-incidence infrared transmission spectra were measured with an infrared ellipsometer (IR-VASE) instrument from J.A. Woollam in the range of 400 - 4000 cm -1 with a resolution of 8 cm -1 .

[0169] 3. Results

[0170] The following table indicates the deposition conditions of layer A and the comparative layers according to the invention, as well as the results of the tests to which the articles were subjected.

[0171]

[0172] %R: Elastic recovery rate at 1 mN. n: Refractive index at 550 nm.

[0173] I: Anodic current. k: Extinction coefficient at 550 nm.

[0174] O 2 Flow rate (%) represents the molar concentration of O in the gas mixture. 2

[0175] * No ion bombardment was carried out during the deposition of the layer. ** SiO 2 layer was used instead of layer A.

[0176]

[0177] I = 2 A, 10% O 2 .

[0178] The layer obtained from compound C exhibits a low refractive index (n ≤ 1.55). Compared with an article having a layer consisting only of silica (Comparative Example 2), the article according to the invention exhibits a low average light reflection factor Rv in the visible range, while maintaining a relatively low extinction coefficient at 550 nm, as well as a good H / E ratio and elastic recovery rate. An H / E ratio of about 0.15 indicates very good mechanical strength.

[0179] It can be observed that when the precursor compound C is deposited by evaporation without ion assistance, the resulting layer has a rather rough and non-uniform surface structure (Comparative Example 1). Its mechanical properties are reduced.

[0180] It can also be observed that the use of oxygen ions during ion beam assisted deposition allows reducing the refractive index and extinction coefficient of the resulting layer A (Example 2 vs. Example 5).

[0181] An increase in the discharge current at a constant oxygen percentage in the ion beam results in a reduction of the extinction coefficient of the layer and an increase in the refractive index (Examples 4 - 6).

[0182] A comparison of Examples 2 and 5 shows that when layer A is deposited by bombarding with an ion beam containing oxygen ions, the resulting layer A has a lower refractive index and less absorption (reduced k) compared to the layer deposited by bombarding with an ion beam without oxygen ions (only argon). The roughness of the resulting layer A is also reduced, and its surface is more uniform.

[0183] The chemical composition of the deposited layer is studied by FTIR. As Figure 1 (bottom graph) shows, the absorption bands in the spectrum of layer A of Comparative Example 1 evaporated without ion assistance are very narrow, representing a very regular structure. The strongest absorption bands are attributed to CH 3 (2966 cm -1 ), Si-CH 3 (1257 cm -1 ), Si-H (2144 cm -1 ), Si-O-Si (1095 cm -1 ), H-Si-O (903 cm -1 ), and Si-C (771 cm -1 ).

[0184] The Si-O-Si peak at 1095 cm -1 represents a cage structure, indicating that the compound C molecules maintain their chemical composition after evaporation.

[0185] As Figure 1 (middle graph and top graph) shows, the FTIR spectra of layer A using the ion source discharge current show that the ion beam results in a reduction and broadening of all the original peaks.

[0186] In the spectrum of the sample deposited under the ion beam, a new absorption band can be noticed at 1050 cm -1 next to the peak corresponding to the Si-O-Si bonds of the cage structure. This peak is assigned to Si-O-Si bonds, which are components of the network structure. It can be observed that a further increase in the discharge current changes the ratio between these two peaks, such that the Si-O-Si network bonds dominate in the spectrum. This process is accompanied by CH 3 , Si-CH 3Partial loss of the Si-H peaks. The above results indicate that during deposition, the interaction of the ion source discharge with compound C causes significant chemical transformations, including dissociation of the terminal organic groups of the molecule and the inorganic cage (which is replaced by the Si-O-Si network), to an extent depending on the process conditions.

[0187] In Figure 1 The influence of oxygen on the chemical composition of the layer can be seen on the top graph. Adding only a small amount of 5% oxygen flow to the working gas mixture of the ion beam depleted the signal from the bonds with the organic elements (Example 3). The Si-O-Si network band overlapped with the cage absorption band and was no longer distinguishable. Further increase of the oxygen percentage exacerbated the decrease of the signal from the organic bonds and made the Si-O-Si network band narrower.

[0188] It was observed that the critical temperature of the article of Example 8 was higher than that of Comparative Example 3 (+10 °C), showing that replacing the silica layer with layer A according to the invention allows improving the heat resistance of the optical article.

[0189] Thus, the present invention provides new materials for manufacturing optical layers, which combine a low refractive index and interesting mechanical and durability properties.

Claims

1. An article comprising a substrate having at least one major surface coated with a layer A - having a refractive index less than or equal to 1.55 - wherein said layer A is obtained by depositing an activated substance generated from at least one compound C having the following formula in gaseous form: wherein R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 、R 8 are independently selected from the group consisting of: alkyl, aryl, vinyl, acrylic, methacrylic, alkyl substituted with one or more heteroatoms, and -OSiR a R b R c , wherein R a 、R b and R c independently represent H, alkyl, vinyl, aryl, hydroxyl or a hydrolysable group, provided that R a 、R b and R c are not all selected from H or hydrolysable groups, and the deposition of the layer A is carried out by applying bombardment to the layer A with an ion beam while forming the layer A.

2. The article according to any one of the preceding claims, wherein, the deposition of said layer A is carried out by applying bombardment with an ion beam containing oxygen ions.

3. The article according to any one of the preceding claims, wherein, The said R 1 、R 2 、R 3 、R 4 、R 5 、R 6 、R 7 and R 8 groups are independently selected from -OSiR a R b R c groups, wherein R a 、R b and R c independently represent H, alkyl, vinyl or aryl.

4. The article according to any one of the preceding claims, wherein, compound C contains at least one silicon atom bearing at least one alkyl group.

5. The article according to any one of the preceding claims, wherein, layer A has a refractive index less than or equal to 1.5, preferably less than or equal to 1.

48.

6. The article according to any one of the preceding claims, wherein, the atomic percentage of carbon atoms in layer A ranges from 20% to 35%.

7. The article according to any one of the preceding claims, wherein, the C / Si atomic ratio in layer A is greater than or equal to 1.

8. The article according to any one of the preceding claims, wherein, layer A is not formed from a pure inorganic precursor compound.

9. The article according to any one of the preceding claims, wherein, layer A has a thickness ranging from 20 to 250 nm and preferably 50 to 200 nm.

10. The article according to any one of the preceding claims, wherein, the article is an optical lens, preferably an ophthalmic lens.

11. The article according to any one of the preceding claims, wherein, layer A is a layer of a multilayer interference coating.

12. The article according to claim 11, wherein, the interference coating is an antireflection coating.

13. A method for manufacturing an article according to any one of the preceding claims, the method at least comprises the following steps: - providing an article comprising a substrate having at least one major surface, - depositing on the major surface of said substrate a layer A having a refractive index less than or equal to 1.55, the deposition of said layer A being carried out by applying bombardment to layer A with an ion beam while layer A is being formed, - recovering an article comprising a substrate having a major surface coated with said layer A, wherein said layer A is obtained by depositing an activated substance generated from at least one compound C having the following formula in gaseous form: wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 have the meanings indicated in claim 1.

14. The method according to claim 13, wherein, layer A is deposited by vacuum evaporation of at least one compound C.

15. The method according to claim 13 or 14, wherein, the ion beam contains oxygen ions.

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