Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/11—Anti-reflection coatings
  • G02B1/113—Anti-reflection coatings using inorganic layer materials only
  • G02B1/115—Multilayers

Definitions

• the present invention relates to a transparent organic substrate coated with a multilayer anti-reflective coating having an increased resistance to temperature.
• the present invention relates to a transparent organic substrate coated with a multilayer anti-reflective coating.
• an ophthalmic lens In the field of ophthalmic optics, it is conventional to coat an ophthalmic lens with various coatings in order to confer on this lens various mechanical and / or optical properties.
• coatings such as anti-shock, anti-abrasion, anti-reflective coatings are successively formed on an ophthalmic lens.
• an anti-reflective coating is a coating deposited on the surface of a lens and intended to reduce the reflection of light on the surface of the lens.
• the anti-reflective coatings according to the invention preferably have a pj [(per side) value less than or equal to 2.5%, preferably less than or equal to 2% and better still less than or equal to 1.5%. In an optimal embodiment, the anti-reflective coating has a pjyj value (per side) of between 0.7 and 0.8.
• Anti-reflective coatings are well known and conventionally consist of a monolayer or multilayer stack of dielectric materials such as SiO, Si0 2 , Si 3 N 4 , Ti0 2 , Zr0 2 , Al 2 O 3 , MgF 2 or Ta 2 0 5 , or mixtures thereof.
• the anti-reflective coatings are preferably multilayer coatings alternately comprising layers of high refractive index and layers of low refractive index.
• the layers of the anti-reflective coatings are applied by vacuum deposition, according to one of the following techniques: by evaporation, optionally assisted by ion beam, by ion beam spraying, by cathode sputtering, or by chemical vapor deposition assisted by plasma.
• a particularly recommended technique is the vacuum deposition technique.
• conventional anti-reflective coatings have good temperature resistance up to temperatures of the order of 70 ° C. When the temperature exceeds this value, cracks can appear on the surface of the substrate, which translates into degradation of the anti-reflective coating.
• At least one layer of the antireflection stack comprises a praseodymium titanate, preferably of formula PrTi0 3.
• said layer comprising a praseodymium titanate comprises at least 50% by mass of praseodymium titanate, better 70 % by mass and better still 85% by mass.
• Said layer can therefore comprise, in addition to praseodymium titanate, one or more materials conventionally used for the manufacture of an antireflection layer, for example one or more materials chosen from the dielectric materials described previously in this description.
• said layer comprises 100% by mass of praseodymium titanate.
• PrTi0 3 is used as a high index material.
• the material is deposited on the substrate starting from a non-stoichiometric compound (available from Merck under the name of substance H2) which is deposited by deposition in the presence of oxygen. The compound is then in the oxidized form and forms a transparent film which corresponds to the formula PrTi0 3 .
• the refractive index of PrTi0 3 is 2,00095 at 635 nm (reference wavelength).
• the multilayer anti-reflective coating consists of an alternating stack of layers comprising a praseodymium titanate and layers of a material with a lower refractive index.
• the multilayer anti-reflective coating has an outer layer, the furthest from the substrate, which does not comprise MgF 2 .
• the lower refractive index material has a refractive index n of 1.50 or less at 635 nm.
• the material with a lower refractive index does not comprise MgF 2 .
• the material with a lower action ref index is a silicon oxide.
• the material with a lower refractive index is silicon dioxide.
• Si02, whose refractive index is 1.4786 at 635 nm has been found to be particularly suitable.
• the total number of layers of the anti-reflective coating is less than or equal to 6.
• the total physical thickness of the anti-reflective coating is less than 1 micrometer, better less than or equal to 500 nm and better still less than or equal to 250 nm.
• a preferred embodiment is an antireflection stack with four layers, deposited in this order, from the surface of the substrate: PrTi0 3 10 to 40 mm thick, preferably 15-35 mm; SiO 10 to 100 mm thick, preferably 10 to 50 mm; PrTi0 3 40 to 150 mm thick, preferably 50 to 150 mm; SiO 2 40 to 150 mm thick, preferably 50 to 150 mm.
• a particularly preferred embodiment is stacking with four layers deposited in this order, from the surface of the substrate: PrTi0 3 (15 to 25 mm) / Si0 2 (15 to 25 mm) / PrTiO 3 (70 to 100 mm) / Si0 2 (70 to 100 mm).
• the thicknesses mentioned above, and generally in this patent application, are physical thicknesses.
• the layers of the antireflection stack according to the invention can be deposited by any conventional method known in the state of the art such as evaporation, sputtering.
• the layers of the antireflection stack are deposited by evaporation.
• a treatment with energetic activated species before the deposition of one or more layers of the antireflection stack, in particular a cleaning by ion bombardment or by a plasma, which makes it possible to increase the adhesion of the layers.
• This treatment can be carried out on the substrate itself, coated or not, for example with an anti-abrasion layer, or on a layer of the antireflection before the deposition of the subsequent layer of the antireflection.
• the surface preparation step is carried out using an ion gun (Commonwealth of the Mark II type for example).
• the step preferably consists of bombardment of the surface to be treated with Argon ions (Ar + ), with a density of between 10 and 100 / ⁇ A / cm 2 on the activated surface and under a residual pressure in the enclosure to vacuum can vary from 8x10 "s mbar to 2x10 " 4 mbar.
• Argon ions Ar +
• no stage of treatment with energetic activated species is carried out concomitantly with the deposition of the anti-reflection layers. More precisely, it is preferred to deposit the layers of the antireflection stack without ionic assistance, that is to say that none of the layers is deposited under ionic assistance.
• the anti-reflective coating according to the invention has no polarizing effect, that is to say that the transmitted light is not polarized.
• a hydrophobic and / or oleophobic coating is deposited on the substrate in order to protect the anti-reflective coating from dirt.
• This coating is deposited on the outer layer, furthest from the substrate, of the anti-reflective coating. It is obtained by depositing a fluorosilane, preferably comprising at least two hydrolyzable groups per molecule.
• the precursor fluorosilanes are preferably polyfluoroethers and better still poly (perfluoroethers).
• This hydrophobic and / or oleophobic coating preferably has a thickness less than or equal to 10 nm, preferably from 1 to 5 nm.
• organic glass substrates suitable for the opthalmic lenses according to the invention mention may be made of polycarbonate substrates and those obtained by polymerization of alkyl methacrylates, in particular C 4 -C 4 alkyl methacrylates, such as methyl (meth) acrylate. and poly (meth) acrylate, polyethoxylated aromatic (meth) acrylates such as polyethoxylated bisphenolate dimethacrylates, allyl derivatives such as allyl carbonates of aliphatic or aromatic polyols, linear or branched, thio- (meth) acrylics, substrates made of polythiourethane, polycarbonate (PC) and polyepisulfide.
• alkyl methacrylates in particular C 4 -C 4 alkyl methacrylates, such as methyl (meth) acrylate. and poly (meth) acrylate, polyethoxylated aromatic (meth) acrylates such as polyethoxylated bisphenolate dimethacrylates
• substrates obtained by polymerization of polyol allyl carbonates among which there may be mentioned ethylene glycol bis allyl carbonate, diethylene glycol bis 2-methyl carbonate, diethylene glycol bis (allyl carbonate), ethylene glycol bis (2-chloro allyl carbonate), triethylene glycol bis (allyl carbonate), 1,3-propanediol bis (allyl carbonate), propylene glycol bis (2-ethyl allyl carbonate), 1,3-butylene diol bis (allyl carbonate), 1,4-butenediol bis (2-bromo allyl carbonate), dipropylene glycol bis (allyl carbonate), trimethylene glycol bis (2-ethyl allyl carbonate), pentamethylene glycol bis (allyl carbonate), isopropylene bis phenol -A bis (allyl carbonate).
• ethylene glycol bis allyl carbonate diethylene glycol bis 2-methyl carbonate
• diethylene glycol bis (allyl carbonate) ethylene glycol bis (2-
• substrates obtained by polymerization of diethylene glycol bis allyl carbonate, sold under the trade name CR 39 ® by PPG Industrie (ORMA lens ® ESSILOR).
• substrates also recommended, mention may be made of the substrates obtained by polymerization of thio (meth) acrylic monomers, such as those described in French patent application FR-A-2 734 827.
• the substrates can be obtained by polymerization mixtures of the above monomers.
• the organic substrates preferred in the context of the invention are those having a thermal expansion coefficient of 50 x 10 "6 ° C " 1 to 180 x 10 "6 " C “1 , and preferably 100 x 10 " 6 ° C to 180 x 10 "6 ° C.
• the anti-reflective coating can be deposited directly on the substrate, but it is preferably deposited on an abrasion-resistant coating previously deposited on the substrate.
• the abrasion-resistant coating can be any layer conventionally used as an abrasion-resistant coating in the field ophthalmic lenses.
• the abrasion-resistant coating is preferably produced from at least one alkoxysilane such as an epoxysilane, preferably trifunctional, and / or a hydrolyzate thereof, obtained for example by hydrolysis with a hydrochloric acid solution HC1 After the hydrolysis step, the duration of which is generally between 2 h and 24 h, preferably between 2 h and 6 h, catalysts are added, optionally A surfactant compound is preferably also added in order to promote the optical quality of the deposit.
• the preferred epoxyalkoxysilanes comprise an epoxy group and three alkoxy groups, the latter being directly linked to the silicon atom.
• a preferred epoxyalkoxysilane can be an alkoxysilane carrying a ⁇ - (3,4-epoxycyclohexyl) group, such as ⁇ - (3,4-epoxycyclohexyl) ethyltrimethoxysilane.
• the particularly preferred epoxyalkoxysilanes correspond to formula (I): (I) in which: R 1 is an alkyl group of 1 to 6 carbon atoms, preferably a methyl or ethyl group, R 2 is a methyl group or a hydrogen atom, a is an integer from 1 to 6, b represents 0 , 1 or 2.
• epoxysilanes examples are ⁇ -glycidoxypropyl-triethoxysilane or ⁇ -glycidoxypropyltrimethoxysilane.
• ⁇ -gly cidoxypropyltrimethoxysilane is used.
• epoxysilanes it is also possible to use epoxydialkoxysilanes such as ⁇ -glycidoxypropylmethyldimethoxysilane, ⁇ -glycidoxypropylmethyldiethoxysilane and - ⁇ -glycidoxyethoxypropylmethyldimethoxysilane.
• the epoxydialkoxysilanes are preferably used at lower contents than the epoxytrialkoxysilanes mentioned above.
• Other preferred alkoxysilanes correspond to the following formula:
• R and R are chosen from substituted or unsubstituted alkyl, methacryloxyalkyl, alkenyl and aryl groups (examples of substituted alkyl groups are halogenated alkyls, in particular chlorinated or fluorinated);
• Z is an alkoxy, alkoxyalkoxy or acyloxy group;
• c and d represent 0, 1 or 2, respectively; and
• c + d represents 0, 1 or 2.
• This formula includes the following compounds: (1) tetraalkoxysilanes, such as methylsilicate, ethylsilicate, n-propylsilicate, isopropylsilicate, n-butylsilicate, sec-butylsilicate, and t-butylsilicate, and / or (2) trialkoxysilanes, trialkoxyalkoxylsilanes or triacyloxysilanes, such as methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriméthoxyéthoxysilane, vinyltriacetoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, ⁇ -chloropropyl-trimethoxysilane, ⁇ - trifluoropropyl, methacryloxypropyltrimethoxysilane, and / or (3)
• an alkoxysilane (s) hydrolyzate When an alkoxysilane (s) hydrolyzate is used, it is prepared in a manner known per se. The techniques set out in EP 614957 and US 4,211,823 can be used.
• the silane hydrolyzate is prepared by adding water or a solution of hydrochloric acid or sulfuric acid to the silane (s). It is also possible to carry out hydrolysis without adding solvents and by simply using alcohol or the carboxylic acid formed during the reaction between water and the alkoxysilane (s). We can also substitute these solvents by other solvents, such as alcohols, ketones, alkyl chlorides, and aromatic solvents. Hydrolysis with an aqueous solution of hydrochloric acid is preferred.
• abrasion-resistant coating compositions can be deposited on the faces of the optical article by dipping or centrifugation, then cured, preferably thermally.
• the thickness of the abrasion-resistant coating generally varies from 2 to 10 microns, preferably from 3 to 5 microns.
• a layer of adhesion or impact-resistant primer can be deposited on the substrate. Any anti-shock primer layer conventionally used for articles made of transparent polymeric material, such as ophthalmic lenses, can be used as anti-shock primer layer.
• compositions based on thermoplastic polyurethanes such as those described in Japanese patents 63-141001 and 63-87223, compositions of poly (meth) acrylic primers, such as those described in US Pat. No. 5,015,523, compositions based on thermosetting polyurethanes, such as those described in patent EP- 0404111 and compositions based on poly (meth) acrylic latexes and polyurethane latexes, such as those described in patent documents US Pat. No. 5,316,791, EP-0680492.
• the preferred primer compositions are polyurethane-based compositions and latex-based compositions, in particular polyurethane latexes.
• Poly (meth) acrylic latexes are latexes of copolymers mainly constituted by a (meth) acrylate, such as for example ethyl or butyl (meth) acrylate, or methoxy or ethoxyethyl, with a generally minor proportion of at least one other comonomer, such as for example styrene.
• the preferred poly (meth) acrylic latexes are the latexes of acrylate-styrene copolymers.
• Such latexes of acrylate-styrene copolymers are commercially available from Zeneca RESI ⁇ S under the name Neocryl ®.
• Polyurethane latexes are also known and commercially available.
• polyurethane latexes containing polyester units By way of example, mention may be made of polyurethane latexes containing polyester units. Such latexes are also marketed by the company ZENECA RESINS under the name NEOREZ ® and by the company BAXENDEN CHEMICAL under the name WITCOBOND ® . Mixtures of these latexes, in particular polyurethane latex and poly (meth) acrylic latex, can also be used in the primer compositions.
• primer compositions can be deposited on the surfaces of the substrate by soaking or centrifugation and then preferably dried at a temperature of at least 70 ° C and possibly up to 100 ° C, preferably of the order of 90 ° C , for a period of 2 minutes to 2 hours, generally of the order of 15 minutes, to form primer layers having thicknesses, after baking, preferably from 0.2 to 2.5 ⁇ m, and better still from 0.5 at 1.5 ⁇ m.
• the invention also relates to an ophthalmic lens, characterized in that it comprises an anti-reflective treated substrate as defined in the present description.
• Example: a four-layer anti-reflective coating is prepared comprising the following stack deposited in this order from the surface of the substrate: PrTi0 3 (28-30nm) / SiO 2 (18-20 nm) / PrTi0 3 (73 nm) / SiO 2 ( 80nm).
• the thicknesses mentioned are physical thicknesses.
• the substrate is an ORMA® ophthalmic lens, diameter 65 mm, power -2.00 diopters and thickness 1.2 mm, coated with an abrasion-resistant coating based on a gamma glycidoxypropyltrimethoxysilane hydrolyzate as described in l Example 3 of patent EP614957.
• the abrasion-resistant coating is obtained by depositing and curing a composition comprising by weight, 224 parts of GLYMO, 80.5 parts of 0.1 N HCl, 120 parts of dimethyldiethdxysilane, 718 parts of colloidal silica at 30% in the methanol, 15 parts of aluminum acetylacetonate and 44 parts of ethylcellosolve.
• the composition also comprises 0.1% relative to the total weight of the FLUORAD FC 430 surfactant composition from 3M.
• the substrate is introduced into a vacuum deposition chamber, for example a BAK760.
• a layer of PrTi0 3 of a thickness indicated above is deposited, at a starting pressure of 2.5 ⁇ 10 ⁇ 5 mbar under 100 volts of voltage at the anode and 1 A of ion current in the following conditions: Evaporation rate: 3 nm / s, Oxygen pressure: 5.10 "s mbar to 8. 10 " 5 mbar, Evaporation source: electron gun.
• the thickness of the deposited layer is monitored by means of a quartz balance and the evaporation is stopped when the thickness indicated above is reached.
• a layer of SiO 2 with a thickness indicated above is deposited, under the same conditions.
• a total of 4 layers are thus deposited alternately, as indicated above.
• the anti-reflective coating has a pj ⁇ j of 0.8.
• the substrate carrying an anti-reflective coating obtained according to Example 1 is placed in an oven heated to a temperature of 60 ° C for one hour.
• the set temperature of the oven is increased by 5 ° C and the test is repeated.
• the critical temperature is then defined as being that at which the substrate exhibits cracks.
• the critical temperature obtained in the case of the coated substrate of the example is

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