Classifications

• • 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
  • C03C17/22—Surface treatment of glass, not in the form of fibres or filaments, by coating with other inorganic material
  • C03C17/23—Oxides
  • C03C17/25—Oxides by deposition from the liquid phase
• • 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
  • C03C17/22—Surface treatment of glass, not in the form of fibres or filaments, by coating with other inorganic material
  • C03C17/23—Oxides
• • 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
  • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
  • C03C10/0018—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents
  • C03C10/0027—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and monovalent metal oxide as main constituents containing SiO2, Al2O3, Li2O as main constituents
• • 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
  • C03C17/001—General methods for coating; Devices therefor
  • C03C17/002—General methods for coating; Devices therefor for flat glass, e.g. float glass
• • 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
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
• • 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
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
• • 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
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
  • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
• • 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
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
  • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
  • C03C3/093—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium containing zinc or zirconium
• • 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
  • C03C2201/00—Glass compositions
  • C03C2201/06—Doped silica-based glasses
  • C03C2201/30—Doped silica-based glasses containing metals
  • C03C2201/54—Doped silica-based glasses containing metals containing beryllium, magnesium or alkaline earth metals
• • 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
  • C03C2204/00—Glasses, glazes or enamels with special properties
  • C03C2204/04—Opaque glass, glaze or enamel
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
  • C03C2217/212—TiO2
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
  • C03C2217/214—Al2O3
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
  • C03C2217/218—V2O5, Nb2O5, Ta2O5
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
  • C03C2217/22—ZrO2
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/20—Materials for coating a single layer on glass
  • C03C2217/21—Oxides
  • C03C2217/23—Mixtures
• • 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
  • C03C2217/00—Coatings on glass
  • C03C2217/70—Properties of coatings
  • C03C2217/76—Hydrophobic and oleophobic coatings
• • 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
  • C03C2218/00—Methods for coating glass
  • C03C2218/10—Deposition methods
  • C03C2218/11—Deposition methods from solutions or suspensions
  • C03C2218/112—Deposition methods from solutions or suspensions by spraying

Definitions

• the present invention relates to a glass or glass-ceramic plate. More specifically, it concerns a glass or glass-ceramic plate intended to serve as a furniture surface and/or a cooking surface as well as an article comprising such a glass or glass-ceramic plate.
• Ceramic hobs are traditionally used as cooking plates. They also find applications in fields requiring heat resistance, for example to form fireplace inserts. Recently, their use has been extended to other areas of daily life: glass-ceramic hobs can thus be used as furniture surfaces, in particular to form worktops, central islands, consoles, etc. the surface they occupy in these new applications being greater than in the past. Glass plates can, for certain applications, be an alternative to glass-ceramic plates, in particular for covering furniture but also, under certain conditions, for cooking plates. Depending on their use, the glass or glass-ceramic plates may be provided with keys, tactile zones, buttons or other controls, their surface being in all cases (even in the case of a simple furniture surface) subjected to multiple contacts.
• the existing textures or coatings are generally not suitable for systematically remedying the problems of fingerprints.
• the most frequently used coatings are above all coatings chosen to resist high temperatures, such as enamels, used locally to form decorative patterns or signaling heating zones, for example, or paints used more flat as opacifiers.
• these traditional coatings generally do not prevent fingerprints related to the handling and use of the coated substrates.
• Enamels can also locally reduce the mechanical resistance of glass-ceramic plates and flake off.
• paints are not suitable for all heating methods for hotplates due to their lower resistance, in particular thermal resistance. It is also known to use other coatings based in particular on thin metal layers deposited solidly over a large part of the surface of the substrate, but such layers sometimes contribute, on the contrary, to the problems of fingerprints.
• the present invention proposes an improved glass or glass-ceramic plate making it possible to limit the visibility of fingerprints on its surface, in particular a glass or glass-ceramic plate intended to be used with one or more heating elements such as a cooking areas, or intended to be used as furniture surfaces.
• the plate according to the invention has anti-fingerprint properties, without harming the other properties sought for its use, in particular their ease of maintenance and cleaning, its mechanical resistance, in particular resistance to scratches and abrasion, and where appropriate its thermal resistance.
• the present invention relates to a plate comprising a glass or glass-ceramic substrate coated with a coating based on metal oxide, in particular aluminum oxide or mixed aluminum oxide, characterized in that said coating has a coverage rate of 25% to 90% and the plate, that is to say the coated substrate, has a roughness RSm less than or equal to 300 ⁇ m, preferably less than or equal to 250 ⁇ m.
• the substrate is preferably a glass-ceramic substrate, in particular a lithium aluminosilicate glass-ceramic substrate.
• the chemical composition of the glass-ceramic substrate typically comprises (or essentially consists of) the following constituents within the limits defined below, expressed in percentages by weight and the sum of which is between 97 and 100%: SiO 2 52 - 75 % AI2O3 18 - 27 % Li 2 O 2.5 - 5.5 % K 2 O 0 - 3 % Na 2 O 0 - 3 % ZnO 0 - 3.5 % MgO 0 - 3 % CaO 0 - 2.5 % BaO 0 - 3, 5% SrO 0 - 2% TiO2 1.2 - 5.5%
• the substrate can also be a glass substrate whose composition is of the lithium aluminosilicate, borosilicate or alumino-borosilicate type.
• the chemical composition of lithium aluminosilicate glass typically comprises (or essentially consists of) the following constituents, varying within the weight limits defined below:
• the chemical composition of borosilicate glass typically comprises (or essentially consists of) the following constituents, varying within the weight limits defined below:
• the chemical composition of alumino-borosilicate type glass typically comprises (or essentially consists of) the following constituents, varying within the weight limits defined below and the sum of which is between 97 and 100%: SiO 2 45-68%, AI2O3 8-20% B2O3 4-18% RO 5-30% R2O at most 10%.
• RO refers to the alkaline earth oxides MgO, CaO, SrO and BaO
• R2O refers to the alkaline oxides, in particular Na2O and K2O.
• the expression “consists essentially of” within the meaning of the present invention means the oxides mentioned constitute at least 95%, even 97% or even 99% by weight of the composition.
• the refining agents are typically chosen from arsenic, antimony, tin, cerium oxides, halogens, metal sulphides, in particular zinc sulphide.
• the content by weight of refining agents is normally at most 1%, preferably between 0.1 and 0.6%.
• the plate is generally colored in the mass.
• the composition thus generally comprises colorants chosen in particular from vanadium oxide, iron oxide, cobalt oxide, cerium oxide, selenium oxide, chromium oxide, even nickel oxide, copper oxide and manganese oxide.
• this is preferably a glass-ceramic colored with vanadium oxide. It may comprise from 0.01 to 0.5% by weight of vanadium oxide optionally in combination with other dyes such as iron oxide, cobalt oxide or manganese oxide.
• the glass or glass-ceramic substrate typically has a light transmission of less than 65%, or even less than 40%, or less than 20%, or even less than 10%. It is preferably less than 5%, in particular in the case of a glass-ceramic substrate, in particular colored with vanadium oxide.
• Light transmission is measured according to EN 410:2011, under illuminant D65, taking into account both direct and diffuse transmission. It can be measured using a spectrometer equipped with an integrating sphere.
• the substrate is preferably a dark substrate, i.e. it has a lightness L*, as defined in the CIE L*a*b* system, of less than 50, preferably less than 40, more preferably less than 30.
• the substrate is in the form of a plate typically having a thickness of 2 to 15 mm, in particular 3 to 10 mm, for example 4, 5, 6, 7 or 8 mm.
• the dimensions (length and width) of the plate depend on the application for which it is intended: it generally has dimensions of 20 to 120 cm, in particular for applications in cooking devices, but can also have larger dimensions. , for example a width of up to 120 cm, or even 180 cm, and a length greater than 200 cm, for worktop applications.
• the substrate preferably has a coefficient of linear thermal expansion of at most 50.10 -7 K 1 . In the case of a glass substrate, it typically has a coefficient of linear thermal expansion of 25 to 45.10'7 K 1 .
• the absolute value of the expansion coefficient is typically less than 25.10' 7 K 1 , or even less than 15.10' 7 K 1 , or even less than 5.10' 7 K 1 .
• the coefficient of linear thermal expansion is measured according to the ISO 7991: 1987 standard between 20 and 300°C.
• the coating is preferably based on aluminum oxide, titanium oxide, niobium oxide, zirconium oxide or a mixed oxide of these, in particular mixed aluminum oxide, more preferably based on aluminum oxide or mixed aluminum oxide.
• the term "based on” means that the coating generally comprises at least 50% by weight of the oxide in question, preferably at least 60% and even 70% or 80%, or even 90%, 95% or 99% by weight of this element. In some cases, the coating may consist of this oxide, barring impurities.
• the mixed aluminum oxide is preferably chosen from binary or ternary aluminum oxides, in particular from mixed aluminum and titanium oxides, mixed aluminum and zirconium oxides and mixed aluminum oxides, titanium and silicon, preferably from mixed aluminum and titanium oxides and mixed aluminum, titanium and silicon oxides.
• the coating preferably comprises at least 30% by weight, preferably at least 40% to 80%, of alumina relative to the total weight of the oxides.
• a coating based on mixed oxide of aluminum and titanium makes it possible to maintain a relatively low clarity and a relatively high gloss, particularly appreciated for applications such as a cooktop.
• the coating according to the invention is typically obtained by spraying a material based on metal oxide, in particular aluminum oxide or mixed aluminum oxide, in powder form.
• deposition methods consist of the projection at very high speed of powder particles, preferably in fusion.
• the particles arriving on a surface to be coated are crushed in the form of drops (splat s).
• the coating according to the invention is generally a discontinuous deposit.
• the coating typically takes the form of a surface distribution of solid drops of a material based on metal oxide, in particular aluminum oxide or mixed aluminum oxide, randomly distributed over the surface of the plaque.
• This type of coating is typically obtained by thermal spraying, in particular by plasma spraying, by oxy-gas flame spraying or by high-speed thermal spraying, preferably by plasma spraying.
• Fig.l representing an SEM image of a coating according to the invention, on the scale of a few hundred microns (for example 500 um), certain areas are covered with drops, which may overlap or be superimposed, while other areas are not covered.
• the recovery rate is greater than or equal to 25%, preferably greater than or equal to 35% and less than or equal to 90%, preferably less than or equal to 80%.
• the recovery rate is more preferably from 30 to 70%, or even from 40 to 60%. In certain embodiments, it may be less than or equal to 50%, in particular from 35 to 50%, or greater than or equal to 50%, in particular from 60 to 90%.
• the term "coverage rate" within the meaning of the present invention the ratio, expressed as a percentage, of the surface of the plate actually covered by the surface dispersion of drops of material based on aluminum oxide or oxide aluminum mixture on the total surface theoretically covered by the coating (the surface of the plate on which the coating was deposited).
• the recovery rate is measured by image analysis taken with an optical microscope, followed by image processing by thresholding and binarization.
• the coverage rate corresponds to the ratio of the pixels corresponding to the coating (generally the white pixels) on the totality of the pixels.
• the recovery rate is typically measured on coating areas from 0.9 mm 2 (typically 1.1 mm x 0.8 mm) to 3.7 mm 2 (typically
• the average diameter of the drops is preferably 10 to 200 ⁇ m, more preferably 20 to 160 ⁇ m.
• the average diameter of the drops is measured by image analysis from optical microscopy.
• the plate according to the invention has a roughness RSm less than or equal to 300 ⁇ m, preferably from 50 to 250 ⁇ m.
• the Ra/Rsm ratio is preferably greater than or equal to 0.0030, and typically less than or equal to 0.1000, and more preferably from 0.0030 to 0.0500, or even from 0.0035 to 0.0100. It generally has a roughness Ra of less than or equal to 2.5 ⁇ m, preferably less than or equal to 2.0 ⁇ m, or even less than or equal to 1.5 ⁇ m, and typically greater than or equal to 0.3 ⁇ m.
• Rdq roughness is preferably 3.0 to 25.0°.
• the coated plate preferably has a roughness of Rz greater than or equal to 3.0 ⁇ m, or even greater than or equal to 3.5 ⁇ m and typically less than or equal to 20 ⁇ m, preferably less than or equal to 15 ⁇ m.
• the roughness Rt is typically greater than or equal to 5 ⁇ m and preferably less than or equal to 15 ⁇ m or less than or equal to 9 ⁇ m.
• Roughnesses RSm, Ra, Rdq, Rz and Rt are defined conventionally according to ISO 4287:1997. It goes without saying that the roughness parameters characteristic of the present invention are measured on the surface coated with the coating according to the invention.
• RSm represents the average width of the elements of the roughness profile corresponding to the average value of the widths of the elements of the profile inside a base length.
• Ra represents the mean deviation of the roughness profile corresponding to the arithmetic mean of the absolute values of the deviations between the successive peaks and troughs within a base length.
• Rdq represents the rms slope of the roughness profile corresponding to the rms value of the local slopes within a base length.
• rz represents the maximum height of the roughness profile corresponding to the sum of the greatest of the heights of the protrusion of the roughness profile and the greatest of the depths of the valley of the roughness profile within a base length.
• Rt represents the total height of the roughness profile corresponding to the sum of the greatest of the protrusion heights of the roughness profile and the greatest of the depths of the valley of the roughness profile within the evaluation length.
• Roughnesses RSm, Ra, Rdq and Rz are measured over a base length of 0.8 mm and roughness Rt over an evaluation length of 4 mm using a contact roughness meter such as the SJ-401 roughness meter from the Mitutoyo company.
• the coating has a coverage rate of 30 to 70%, preferably 40 to 60%, and the plate has a roughness RSm less than or equal to 250 ⁇ m, a roughness Ra of less than 1.5 ⁇ m and an Ra/RSm ratio of 0.003 to 0.01. It has in fact been observed that these embodiments, in addition to the reduction in the visibility of fingerprints, provide improved mechanical properties to the glass or glass-ceramic plate (improved scratch resistance and/or reduced visibility of scratches) and do not generate no excessive blur, thus ensuring good visibility of the displays placed below the plate.
• Another object of the present invention relates to a process for the manufacture of a glass or glass-ceramic plate as described previously comprising the deposition of a coating based on metal oxide by thermal spraying on the surface of a substrate in glass or glass-ceramic, characterized in that the surface of the substrate is at a temperature greater than 300°C during the deposition of the coating.
• thermal spraying Coating methods by so-called thermal spraying are well known to those skilled in the art. It may in particular be plasma spraying, oxy-gas flame spraying or high-speed thermal spraying (or HVOF: High Velocity Oxy-Fuel). THE particles of the powder to be sprayed are brought to temperatures above the melting point of the powder. The deposited drops adhere to the substrate mainly due to the diffusion of atoms at the substrate/drops interface or mechanically due to the plastic deformation of the particles, and to a lesser extent by Van der Waals forces.
• the coating according to the invention is preferably obtained by plasma spraying.
• the projection parameters such as the electrical power, the total flow of plasma gases, the composition of the plasma gases, the flow of powder, the linear speed of the torch and the number of passes are set in a manner well known to those skilled in the art. profession, depending on the type of torch and the characteristics of the powder used, to generate a flow of correctly melted particles at an adequate speed so as to obtain spreads of unburst, adherent and slightly cracked drops and obtain a coating according to the invention.
• the electrical power can be from 30 to 65 kW, the total flow of gas from 40 to 80 L/min, the flow of powder from 0.5 to 15 g/min, the linear speed of movement of the torch from 1000 to 5000 mm/s, the step of advance is from 3 to 15 mm and the number of passes from 1 to 10.
• the powder flow rate, the linear speed of movement of the torch, the step of advance (distance separating 2 lines of movement of the torch) as well as the number of passes make it possible in particular to modulate the coverage rate and the roughness of the coating according to the invention.
• the powder used in the process according to the invention is generally identical in nature to the desired coating, that is to say a powder of metal oxide, in particular a powder of aluminum oxide or mixed oxide of aluminum, preferably chosen from binary or ternary aluminum oxides, in particular from mixed aluminum and titanium oxides and mixed aluminum, titanium and silicon oxides.
• the powder typically has a particle size such that the diameter Dio is between 3 and 20 ⁇ m, and such that the diameter D90 is between 20 and 75 ⁇ m.
• the Dio diameters, respectively D90 are understood so that 10%, respectively 90%, by number of the particles of the powder have a diameter less than the Dio value, respectively D90. They are determined by laser diffraction.
• the powder is preferably a powder with dense grains, that is to say having a porosity of less than 1%. It is preferably powder resulting from a fusion process (melted - ground) in order to improve the adhesion of the coating.
• a heat treatment can also be carried out after the deposition of the coating according to the invention to improve its adhesion.
• the plate according to the invention can, if necessary, be coated with other functional coatings (anti-overflow layer, opacifying layer, etc.) and/or decorative, in particular localized, such as usual patterns based on enamels.
• the plate may have a localized coating of decorative enamel, generally on the same face as the coating according to the invention, and generally above the latter, (to form par patterns or logos or to delimit/indicate certain areas, in particular heating), and/or or an opacifying layer on all or part of the face of the plate opposite to the coating according to the invention (to hide, for example, internal elements arranged under the plate).
• the plate according to the invention can be used for various applications such as worktops, cooking devices, for example cooking plates, in particular induction, fireplace inserts, fireproof glazing or even as a decorative element.
• the present invention also relates to an article, in particular a worktop, a cooking device, a fireplace insert, fireproof glazing or a decorative element, comprising a glass or vitroceramic plate as described above. or obtained by the process described above. It is preferably a cooking device.
• the plate according to the invention is such that, in the configuration of use, the coating according to the intention is placed on the surface of the plate facing the user.
• the article according to the invention may also comprise internal elements comprising a heating means, a display device and/or a control device.
• the display device may be a light source, in particular light-emitting diodes or an LCD screen, possibly associated with optical filters or optical guides.
• the heating means can be chosen from radiant or halogen heating means, atmospheric gas burners, and induction heating means.
• the control device can be an electronic control panel with sensitive keys.
• the article can also be provided with (or associated with) additional functional element(s) such as a frame, stiffener(s), connector(s), cable(s), element(s) ) command, etc.
• the present invention is illustrated by the following non-limiting examples. Dark glass-ceramic plates of the KeraBlack+ type marketed by the Eurokera company were coated by plasma spraying with various coatings based on aluminum oxide and mixed aluminum oxides. The deposits of the coatings are carried out on substrates heated to between 400 and 720° C. using an HP 8 torch marketed by the company Saint-Gobain Coating Solutions.
• the projection parameters for Sample II are as follows:
• Samples C1 to C3 and 12 to 15 are obtained identically to sample II with the difference of certain projection parameters, in particular the powder flow rate, the linear speed of the torch and the number of passes.
• the aluminum oxide powders used are dense grain powders (melted-ground) with the following characteristics:
• the coverage rate of the different coatings obtained was measured by image analysis taken under an optical microscope (Leica DMC 2900), followed by image processing at using ImageJ software.
• the processing consists in using the thresholding function (Threshold) of the software, by adjusting the levels of gray then by binarizing the image so that the drops appear in white pixels and the uncovered surface appears in black.
• Fig.2 shows an image of a sample taken under an optical microscope
• Fig.3 shows the corresponding image after image processing allowing calculation of the coverage rate.
• Samples II through 15 show significantly improved anti-fingerprint properties over Samples C1 through C3 which are no better than the uncoated reference glass-ceramic.

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