Classifications

• • A—HUMAN NECESSITIES
  • A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
  • A47G—HOUSEHOLD OR TABLE EQUIPMENT
  • A47G1/00—Mirrors; Picture frames or the like, e.g. provided with heating, lighting or ventilating means
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
  • G02B5/10—Mirrors with curved faces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R1/00—Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/3602—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer
  • C03C17/3657—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having optical properties
  • C03C17/3663—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal the metal being present as a layer the multilayer coating having optical properties specially adapted for use as mirrors
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/36—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal
  • C03C17/38—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating being a metal at least one coating being a coating of an organic material
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C17/00—Surface treatment of glass, not in the form of fibres or filaments, by coating
  • C03C17/34—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions
  • C03C17/42—Surface treatment of glass, not in the form of fibres or filaments, by coating with at least two coatings having different compositions at least one coating of an organic material and at least one non-metal coating
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S23/74—Arrangements for concentrating solar-rays for solar heat collectors with reflectors with trough-shaped or cylindro-parabolic reflective surfaces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S23/82—Arrangements for concentrating solar-rays for solar heat collectors with reflectors characterised by the material or the construction of the reflector
• • 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
  • G02B1/14—Protective coatings, e.g. hard coatings
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers

Definitions

• the invention relates to a mirror comprising a protective coating on the back to protect the reflective metal layer against corrosion.
• This mirror is particularly adapted to the external environment and can in particular act as a solar mirror.
• the mirrors generally comprise a glass substrate on which has been deposited a reflective layer of metal, usually silver.
• Reflective metal such as silver tends to oxidize in ambient air and should be protected to increase its life.
• a tin treatment is generally performed just after silvering to improve the corrosion resistance of the silver.
• Protective layers are then made as a layer of another metal, often based on copper, and / or one or more layers of paint.
• a layer of copper applied to the silver improves the resistance to corrosion in the face of silver ("full face" means in the middle as the center of gravity and not the edge).
• full face means in the middle as the center of gravity and not the edge.
• the mirror manufacturing processes require the successive deposition of several materials on the back of the mirror, which increases the complexity and the cost of manufacturing.
• today marketed mirrors have the following structure:
• Paints usually used to form protective layers contain high levels of lead, usually between 1 and 12% of lead, which is no longer acceptable given the toxicity of lead. It is therefore also desirable to use reduced lead paint.
• the presence of lead in the paints is also intended for mirrors comprising a layer of copper as this limits copper edge corrosion.
• the invention pale with the aforementioned problems. It has now been found that a coating combining two types of particular paints provides very effective protection, so much so that it does not make the usual copper layer indispensable, even for outdoor use.
• a paint contains at least one polymer resin and solvent.
• the invention firstly relates to a mirror comprising a glass sheet and a layer of silver applied to the glass and provided on its back with a protective coating comprising a layer of alkyd-type dried and cross-linked paint and a layer of dried and crosslinked polyurethane-type paint, the alkyd layer being located between the silver layer and the polyurethane layer.
• the coating according to the invention comprises a layer of alkyd type paint and a polyurethane (PU) type paint layer.
• the alkyd layer is applied to the mirror before the PU layer.
• the alkyd layer can be applied directly to the reflective metal layer (usually silver).
• the PU layer can be applied directly to the alkyd layer.
• the alkyd layer may have a thickness of 10 nm to 60 nm and preferably 25 nm to 40 nm.
• the PU layer may have a thickness ranging from 10 nm to 60 nm and preferably from 25 nm to 40 nm.
• the coating according to the invention may consist of the combination of an alkyd layer and a PU layer (without any other paint layer) applied directly to the reflective layer starting with the alkyd layer.
• the paint layers can be applied by spray techniques (Spray) or curtain.
• curtain technique a continuous stream of liquid paint is poured over the entire width of the back of the moving mirror.
• the paints are applied while being itself at ambient temperature (generally between 15 and 40 ° C.), the substrate to be coated possibly having been preheated, in particular between 40 and 60 ° C.
• the fluidity of these paints makes it possible, in particular by the technique of the curtain, to cover at least the edge of the silver layer and even almost the entire slice of the mirror (silver + glass).
• their viscosity is generally between 25 and 110 seconds and preferably between 30 and 100 seconds as measured in the Ford Cup No. 4 (ASTM D1200). Note that it is the desired viscosity regardless of the application temperature. It is therefore not necessary to give the viscosity value by binding it to a temperature.
• the paints of the coating according to the invention are applied to the mirror with its final shape (already cut and / or curved), the paints are advantageously applied to the edges of the mirror, at least on the edges of the silver layer.
• the curtain technique generally makes it possible to obtain such a covering of the slices on the entire perimeter of the mirror. We can play on the speed of movement of the mirror in the paint curtain to improve the recovery of the slice, knowing that a slowdown improves this recovery.
• the invention also relates to a mirror whose silver layer is coated on the entire perimeter of its edge by the protective coating according to the invention.
• the liquid paint as used (before drying) contains 0.1 to 50% and preferably 5 to 40% and even 10 to 35% by weight of polymer resin (of the alkyd or polyurethane type as the case may be).
• the paints contain solvent (which may be xylene) to thin them, which solvent is then removed by drying.
• the alkyd type paint contains at least 20% by weight and even 30% by weight of solvent (which is measured by determining the dry extract by heating at 140 ° C.) for example).
• PU type paint contains at least 20% by weight and even 30% by weight and even at least 35% by weight of solvent (which is measured by determining the dry extract by heating at 140 °).
• These layers are generally dried and crosslinked at a temperature between 120 and 250 and preferably between 150 and 210 0 C and so they have more tack. Each layer can be dried and cured in less than 10 minutes without residual tack.
• the PU paint contains an anti-UV type additive which may especially be titanium oxide or ZnO or benzophenone or benzotriazole or triazine advantageously combined with an antioxidant, for example of the HALS type.
• an anti-UV type additive which may especially be titanium oxide or ZnO or benzophenone or benzotriazole or triazine advantageously combined with an antioxidant, for example of the HALS type.
• the dried and crosslinked PU paint contains 0.1 to 0.5% by weight of antioxidant.
• the mirror prior to application of the coating according to the invention are not described in detail here, since the techniques known to those skilled in the art are used.
• the mirror Before application of the coating according to the invention, the mirror may be manufactured without copper, in particular by the following succession of steps:
• a fine underlayer one to a few molecular layers
• a priming agent which is generally of the silane type, in particular aminosilane.
• the mirror with a copper layer, in particular by the following method: - brightening of the glass surface,
• the coating according to the invention is then applied to this structure.
• the protective coating according to the invention thus comprises, as essential elements, a layer of alkyd-type dried and crosslinked paint and a layer of dried, cross-linked polyurethane paint, the alkyd layer being located between the silver layer and the polyurethane layer. .
• at least one other layer (called “additional layer") on the mirror between the silver layer and the protective coating according to the invention, but this is not necessary.
• this additional layer may be a layer of dried and crosslinked paint of the acrylic type.
• the alkyd paint layer after crosslinking may therefore be the first layer containing a crosslinked polymer applied after the silver layer.
• the solvent alkyd paint layer is applied directly to the silver layer, if appropriate after passivation of the silver and application of a primer, especially a silane.
• the polyurethane layer may be the outer layer, that is to say the last layer on the back of the mirror.
• the alkyd paint layer and the PU paint layer are dried and crosslinked, for example thermally (heating between 120 and 250 ° C.), generally in ambient air.
• the different layers of the mirror are applied to the same side of a glass sheet, usually a mineral glass (silica-based).
• a glass sheet usually a mineral glass (silica-based).
• the glass sheet has been cut, usually in quadrilateral, from a float glass ribbon or from another sheet of glass. bigger glass. If the final mirror must be curved, the glass sheet is curved before application of the silvering.
• the glass sheet has a thickness generally ranging from 2 to 6 mm.
• the glass is preferably extra-clear, that is to say having an energy transmission greater than 85% and even greater than 89% for a glass thickness of 3.2 mm (see in particular ISO9050 air mass 1.5). . This does not mean that the glass necessarily has a thickness of 3.2 mm, it means that the energy transmission is measured with this thickness.
• the glass marketed by Saint-Gobain Glass France under the Diamant brand is particularly suitable.
• the silver layer can have a thickness ranging from 500 to 1600 mg / m 2 .
• this layer is preferably thicker than 850 mg / m 2 , in particular with a thickness of between 900 and 1600 mg / m 2 , generally between 950 and 1300 mg / m 2 .
• a layer of silver of conventional thickness such as 750-800 mg / m 2 , which is good enough for domestic applications (bathroom mirrors, for example) does not reflect any light in the spectrum of sunlight, especially in the field of ultra-violet.
• the UV partially pass through the thin silver layers, which is not a disadvantage in domestic applications since these unreflected UV are not in the visible range.
• the good reflection of these UV is desirable because it is a significant amount of light energy that one gains to collect.
• the UV reaching the protective organic layers tend to accelerate the aging of the latter and from this point of view also, it is advantageous that the reflective layer stops UV as best as possible.
• the mirror according to the invention is intended to act as a solar mirror, it may be curved or planar. If it is flat, the mirror is usually an element forming part of a set of mirror elements arranged so as to constitute a Fresnel mirror or Heliostat type. This set converges the sunlight to a heat collector.
• this manifold consists of a tube traversed by a coolant (water, molten salts, synthetic oils, or steam). This fluid is heated by solar energy and it is made to return this energy in the form of electricity by any suitable method such as the so-called "Rankine Cycle".
• the various mirror elements are generally smaller than 3 m 2 .
• the smaller these flat mirrors the easier it will be to arrange them to converge the light rays towards the collector.
• These flat mirrors are generally cut after application of the different layers on their backs so that the edge of the silver layer is not coated. In this case, a good resistance to edge corrosion is particularly sought after.
• the different mirror elements can have a surface ranging from 1 m 2 to 25 m 2 .
• the mirror converts the light itself to the collector. Indeed, it seeks to give the mirror a parabolic profile in at least one direction (a single direction or two directions orthogonal to each other), the light rays being returned to the focus of said parabola, a collector of light energy being placed to this home. If the mirror is hot-bent in one direction, the skilled person is fluent in a form parabolic. Two of the edges of the mirror are linear.
• the collector is a linear pipe to which the mirrors return radiation, said collector being placed at the point of convergence of said radiation (the focus in the case of a parabola).
• the mirror In a plane perpendicular to the collector, the mirror is curved. In a plane parallel to the collector, the mirror is not curved.
• the final curved mirror (as installed in solar mirror fields) may consist of a single plate or comprise several juxtaposed plates each forming a parabola segment.
• the parabola in the plane perpendicular to the collector may consist of 2 or 4 juxtaposed plates.
• the plates have a shape that approaches the parabolic shape without necessarily completely corresponding to it, the essential being that the maximum of light rays reaches the collector at home.
• the different juxtaposed plates have different shapes.
• curved mirrors can be dimensioned by cutting before bending the glass, the bending being then made, then the different layers (silvering and protective layers) being applied in its back, the convex side.
• the edge of the mirror is also covered with the different protective layers so that the resistance to edge corrosion is less crucial than in case of cutting after application of the protective layers.
• a curved mirror (hot), especially for solar mirror application may have a surface ranging from 0.1 to 10 m 2 .
• the invention also relates to the method of manufacturing a mirror comprising
• the glass sheet Prior to the deposition of the silver layer, the glass sheet may undergo a hot bending, the silver layer and the paint layers being applied to the convex side of the glass sheet.
• the invention also relates to the device comprising a heat collector and a solar mirror comprising the mirror according to the invention.
• the mirror according to the invention is advantageously used outdoors to deflect solar light to a heat collector. This use is particularly advantageous in sunny regions, particularly in the field of terrestrial latitudes between 45 ° North and 45 ° South.
• FIG. 1 illustrates the influence of the thickness of a silver layer on UV transmission. This shows that above 800 mg / m 2 of silver, the UV transmission drops below 10% and the more this thickness is increased, the less UV passes through the silver layer. This low UV transmission is good for the integrity of the paint layer directly applied to the silver since it is known that UV degrade polymers and therefore paints.
• FIG. 2 illustrates the influence of the thickness of a silver layer on the energy reflectivity of a mirror according to the invention. We see that we gain significantly in reflection above 800 mg / m 2 .
• FIG. 3 illustrates the UV resistance over time of different mirrors made in the context of the examples.
• FIG. 4 illustrates the resistance to an atmosphere charged with SO 2 (in the context of a test according to the EN 1096-2 standard, of different mirrors made in the context of the examples (1 a and 2).
• Figure 5 illustrates the structure of the mirror according to the invention seen in section and at an edge.
• the thickness of the layers is not to scale.
• the glass 51 is first coated with the silver layer 52, then with the layer of alkyd dried and crosslinked paint 53, then with the layer of dried and crosslinked paint of the polyurethane type 54. It can be seen that these two paints sank on the slice and covered the slice with the silver layer 55 and part of the slice of the glass sheet 56. This overlap is substantially identical over the entire perimeter of the mirror.
• Figure 6 illustrates the process of applying paints to the back of an already curved mirror.
• a paint curtain 62 flows on the back (convex side) of the mirror 61.
• the mirror is scrolling in the direction of the arrow 65 under the curtain of paint which is fixed.
• the edge 63 of the mirror first attacks the curtain.
• the edge of this edge 63 is generally more coated than the edge of edge 64.
• the other two (unnumbered) edges of the mirror are linear and parallel.
• the mirror rests with these linear edges on the conveying rollers whose axis is perpendicular to the direction of movement of the mirror.
• These edges are usually properly covered by the paints, at least as far as the silver layer is concerned.
• the mirror was subjected to the CASS test according to the ISO 9227 standard and the distance of silver corroded from the edge was measured. It was measured according to whether the edges were covered by the different layers (including Ag and Cu) and whether the edges were not covered by the different layers.
• the distance between the plane and the highest point being about 60 mm.
• a silver layer is made on the convex side by one of the methods already mentioned above without a copper layer.
• the primer was silane A1100 from Silquest.
• an alkyd-type paint layer is applied.
• This paint was prepared from a reference paint 21775 marketed by FENZI to which xylene was added until a viscosity of 50 seconds at 20 ° C. was obtained at the Ford No. 4 cut.
• This formulation was applied to the convex side of the glass sheet at room temperature (the mirror was thus preheated to 50 ° C. and the paint was curtained at room temperature) by the so-called curtain technique. Dry in an oven at 90 ° C for one minute and 15 seconds. The convex side is then always applied and on the dried alkyd layer a layer of polyurethane paint.
• This polyurethane paint was prepared from a SK2410 brand paint marketed by the company VALSPAR to which xylene was added until a viscosity of 50 seconds at 20 ° C. was obtained at the No. 4 Ford cut. .
• This formulation was applied at room temperature by the so-called curtain technique. It is dried in an oven at 170 ° C. for 3 minutes.
• the "Thickness” column gives the thicknesses of each of the layers in mg / m 2 for the Ag and Cu layers and in ⁇ m for the others.
• the column “initial energy reflection” gives the reflection just after the manufacture of the mirror and therefore before any test (CASS or submission at 4000 h of UV). Examples 2 to 6
• Example 6 The procedure is as for Example 1 except that a different protective coating is applied (but according to similar techniques) the nature and thickness of which are specified in the table.
• a copper layer is applied from an aqueous solution of copper sulfate.
• Examples 2, 4, 5 and 6 are comparative and do not illustrate the invention.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Optics & Photonics (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Thermal Sciences (AREA)
• Combustion & Propulsion (AREA)
• General Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Optical Elements Other Than Lenses (AREA)
• Surface Treatment Of Glass (AREA)
• Mirrors, Picture Frames, Photograph Stands, And Related Fastening Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2008
  • 2008-09-22 FR FR0856355A patent/FR2936240B1/fr not_active Expired - Fee Related
• 2009
  • 2009-09-22 MX MX2011002900A patent/MX2011002900A/es not_active Application Discontinuation
  • 2009-09-22 BR BRPI0919315A patent/BRPI0919315A2/pt not_active IP Right Cessation
  • 2009-09-22 EP EP09748419A patent/EP2330951A1/de not_active Withdrawn
  • 2009-09-22 US US13/119,728 patent/US20110226234A1/en not_active Abandoned
  • 2009-09-22 WO PCT/FR2009/051778 patent/WO2010031981A1/fr active Application Filing
  • 2009-09-22 CN CN2009801368751A patent/CN102159119A/zh active Pending
  • 2009-09-22 KR KR1020117005235A patent/KR20110068991A/ko not_active Application Discontinuation

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