Motor vehicle roof comprising a glass sheet

Abstract

The invention relates to a roof (1) for a motor vehicle comprising a first glass sheet (2) having a light transmission coefficient of 2% to 30%, said first glass sheet having at least one face coated on only a portion thereof with at least one decorative transparent mineral coating (10, 12, 14).

Description

[0001] The present invention relates to the field of motor vehicle roofs comprising a glass sheet.

[0002] An increasing number of motor vehicles are equipped with glass-based roofs. These roofs can brighten the passenger compartment and give the vehicle an attractive design, especially when viewed from the outside. However, the roof's thermal performance must also be optimized to prevent overheating of the passenger compartment, which would require increased air conditioning costs in the summer and thus increase the vehicle's fuel consumption.

[0003] The object of the present invention is to propose a roof for a motor vehicle having an attractive decoration, in particular a decoration visible only from the inside of the vehicle or only from the outside.

[0004] To this end, the subject of the invention is a motor vehicle roof comprising a first glass sheet with a light transmission coefficient between 2 and 30%, said first glass sheet having at least one face coated only on part thereof with at least one decorative transparent mineral coating.

[0005] Another subject of the invention is a method for obtaining such a motor vehicle roof, comprising a step of depositing at least one transparent mineral coating forming a decoration on only part of the surface of a first glass sheet, said first glass sheet having a light transmission coefficient between 2 and 30%.

[0006] The presence of at least one transparent mineral coating forming a decoration on a very dark glass sheet makes it possible to impart unusual optical properties without compromising the light and thermal comfort of the vehicle occupants. More particularly, the decoration can be visible with good contrast, either by the occupants of the vehicle or by persons outside the vehicle, as the case may be.

[0007] The roof according to the invention is preferably curved to match the curvature of the vehicle. Thus, a distinction is made between an inner roof face intended to be located inside the vehicle (which is concave) and an outer roof face intended to be located outside the vehicle (which is convex).

[0008] According to a first embodiment, the roof is laminated, i.e. it also comprises an additional glass sheet adhesively connected to the first glass sheet by means of a thermoplastic laminating interlayer, in particular based on polyvinyl acetal. In this case, each glass sheet has an inner face facing the vehicle interior and an outer face facing the vehicle exterior.

[0009] In this embodiment, the first glass sheet is preferably intended for the interior of the vehicle. The side of the first glass sheet coated with the at least one transparent mineral coating is then preferably intended for the interior of the vehicle. This side is commonly referred to in the art as "side 4." Thus, the decoration is visible to passengers in the passenger compartment but not to those outside the vehicle.

[0010] Alternatively, the first glass sheet may be intended for the exterior of the vehicle. The face of the first glass sheet coated with the at least one transparent mineral coating is then preferably intended for the exterior of the vehicle, in other words, on "Face 1." In this case, the decoration is only visible from the exterior of the vehicle and is therefore not visible to passengers in the passenger compartment.

[0011] According to a second embodiment, the roof is monolithic, meaning it comprises only a single sheet of glass, in this case the first sheet. In this case, the first sheet of glass is typically made of tempered glass to meet regulatory safety requirements. Similar to what has been described for laminated roofs, the side coated with the transparent mineral coating can be either side 1 (intended for the exterior of the vehicle) or side 2 (intended for the interior), depending on whether the decoration must be visible from the outside or only from the inside.

[0012] The first glass sheet can be flat or curved. The first glass sheet is typically flat when the coating is deposited and is subsequently curved.

[0013] The glass of the first glass sheet is typically soda-lime-silica glass, but other glasses such as borosilicate or aluminosilicate glasses may also be used. The first glass sheet is preferably obtained by the float process, ie by pouring molten glass onto a bath of molten tin.

[0014] The first glass sheet is made of colored glass.

[0015] Choosing a light transmission factor of 2-30%, in particular 5-20%, ensures good contrast of the decoration and therefore good visibility of the decoration, but only on the side on which it is deposited.

[0016] To this end, the glass preferably contains the following coloring elements, the weight contents of which are defined as follows: Fe2O3 (total iron) 1.2-2.3%, particularly 1.5-2.2%, CoO 50-400 ppm, particularly 200-350 ppm, Se 0-35 ppm, particularly 10-30 ppm. The redox ratio is preferably between 0.1 and 0.4, particularly between 0.2 and 0.3. The redox ratio is the weight ratio of the ferrous iron content (expressed as FeO) to the total iron content (expressed as Fe2O3).

[0017] In this document, the light transmission coefficient is expressed by taking into account the illuminant D65 and the CIE-1931 standard observer. The light transmission coefficient of the glass sheet is of course measured without any coating.

[0018] The first glass sheet preferably has a thickness in the range of 0.7-19 mm, in particular 1-10 mm, in particular 2-6 mm, or even 2-4 mm.

[0019] The transverse dimensions of the first glass sheet (and, if necessary, the additional glass sheet) will be adjusted to the transverse dimensions of the laminated glazing in which it is intended to be integrated. The first glass sheet (and / or the additional glass sheet) preferably has a width of at least 1 m 2 surface area.

[0020] Depending on the desired decoration, the first glass sheet is preferably coated with a transparent mineral coating over 5-90%, in particular 10-80%, of the surface area of ​​the face of the glass sheet.

[0021] The first glass sheet or the additional glass sheet is preferably coated with an opaque layer, in particular made of enamel, usually black enamel, and arranged in particular on the periphery of the sheet, for example in the form of a peripheral band. The purpose of such a layer is generally to conceal and protect from UV radiation the polymer seal used to mount the roof in the window opening of the vehicle body.

[0022] The opaque layer is preferably deposited by screen printing.

[0023] In the case of a laminated roof, the opaque layer is preferably deposited on the additional glass sheet. For example, if the transparent mineral coating is deposited on face 4 of the laminated roof, the opaque layer is preferably deposited on face 2.

[0024] When the opaque layer and the transparent mineral coating are deposited on the first glass sheet, they can be deposited on the same side or on two opposite sides. The order in which the two coatings are deposited is not important, but when they are deposited on the same side, it is preferred to deposit the transparent mineral coating first and then the opaque layer, as described in more detail in the remainder of this document.

[0025] According to a preferred embodiment, a coating with low emissivity is placed between the first glass sheet and the transparent mineral coating. The normal emissivity of this coating measured at ambient temperature is preferably lower than 0.50, in particular lower than 0.30, even lower than 0.20 or lower than 0.10.

[0026] The refractive index and, if necessary, the color of the coating influence the final appearance of the roof.

[0027] The coating with low emissivity is preferably a stack of thin layers.

[0028] The thin-film stack is preferably in contact with the first glass sheet. It preferably covers all or at least 90% of the surface area of ​​the first glass sheet.

[0029] In this context, "in contact" means physical contact. The expression "based on" preferably refers to the fact that the layer in question contains at least 50% by weight, in particular 60% by weight, or even 70% by weight, or even 80% by weight or 90% by weight of the material in question. The layer may even consist essentially of or consist of this material. "Essentially consisting of" should be understood to mean that the layer may contain impurities that have no effect on its properties. The terms "oxide" or "nitride" do not necessarily mean that the oxide or nitride is stoichiometric. In fact, they can be substoichiometric, superstoichiometric, or stoichiometric.

[0030] The stack preferably comprises at least one nitride-based layer. The nitride is in particular a nitride of at least one element selected from the group consisting of aluminum, silicon, zirconium, and titanium. It may comprise nitrides of at least two or three of these elements, for example silicon zirconium nitride or silicon aluminum nitride. Preferably, the nitride-based layer is a silicon nitride-based layer, more particularly a layer consisting essentially of silicon nitride. When the silicon nitride layer is deposited by cathode sputtering, it typically contains aluminum, as it is common to dope the silicon target with aluminum to accelerate the deposition rate.

[0031] The nitride-based layer preferably has a physical thickness in the range of 2-100 nm, in particular 5-80 nm.

[0032] Nitride-based layers are frequently used in many thin-layer stacks, since they have advantageous barrier properties in the sense that they prevent oxidation of other layers present in the stack, in particular the functional layers to be described below.

[0033] The stack preferably comprises at least one functional layer, in particular an electrically conductive functional layer. The functional layer is preferably comprised between two thin dielectric layers, at least one of which is a nitride-based layer. Other possible dielectric layers are, for example, oxide layers or oxynitride layers.

[0034] The at least one electrically conductive functional layer is advantageously selected from:

[0035] - a metal layer, in particular made of silver or niobium, or even gold, and

[0036] - a transparent conductive oxide layer, in particular selected from indium tin oxide, doped tin oxide (for example doped with fluorine or antimony), doped zinc oxide (for example doped with aluminum or gallium).

[0037] These layers are particularly valued for their low emissivity, which provides excellent thermal insulation for glazing. In motor vehicle glazing, low-emissivity glazing allows a portion of solar radiation to be reflected outwards on hot days, thereby limiting heating of the vehicle's passenger compartment and, if necessary, reducing air conditioning costs. Conversely, in cold weather, these glazings allow heat to be retained within the passenger compartment, reducing the required heating energy. This is also true for glazing in buildings.

[0038] According to a preferred embodiment, the thin-film stack comprises at least one silver layer, in particular one, two, three or even four silver layers. The physical thickness of the silver layers or, if appropriate, the sum of the thicknesses of the silver layers is preferably 2-50 nm, in particular 3-40 nm.

[0039] According to another preferred embodiment, the thin-film stack comprises at least one indium tin oxide layer, the physical thickness of which is preferably between 30 and 200 nm, in particular between 40 and 150 nm.

[0040] In order to protect the or each conductive thin layer (whether metallic or based on a transparent conductive oxide) during the bending step, each of these layers is preferably surrounded by at least two dielectric layers. The dielectric layers are preferably based on an oxide, nitride and / or oxynitride of at least one element chosen from silicon, aluminum, titanium, zinc, zirconium and tin.

[0041] At least part of the thin-film stack can be deposited by various known techniques, such as chemical vapor deposition (CVD), or by sputtering, in particular magnetic field-assisted sputtering (magnetron method).

[0042] The stack of thin layers is preferably deposited by cathode sputtering, in particular magnetic field-assisted cathode sputtering. In this method, a plasma is generated under high vacuum near a target containing the chemical element to be deposited. By bombarding the target, the active species of the plasma tear off the elements, which are deposited on the glass sheet to form the desired thin layer. When the layer consists of a material produced by a chemical reaction between the elements torn off from the target and the gases contained in the plasma, the method is called a "reactive" method. The main advantage of this method is that it can deposit very complex layer stacks on the same production line by running the glass sheets continuously under different targets (usually in the same equipment).

[0043] The stack has conductive and infrared reflective properties for providing a heating function (defrosting, defogging) and / or a heat insulating function.

[0044] When the thin-film stack is intended to provide a heating function, an electric current supply must be provided. This can in particular be strips of silver paste deposited by screen printing on the thin-film stack at two opposite edges of the glass sheet.

[0045] Transparent mineral coatings allow for localized modification of the optical properties of the roof to create a decorative effect. The mineral coating preferably imparts a colored appearance; the coloration can result from interference phenomena or from the transmission color of the layer, for example due to the presence of a coloring substance. In the case of interference, the coloration is only visible at certain viewing angles, for example at large angles.

[0046] The decoration may be formed from a single transparent mineral coating. In some areas, the decoration may include multiple overlapping thicknesses of transparent mineral coatings of the same substance. Alternatively, the decoration may be formed from multiple transparent mineral coatings of different substances (optionally overlapping in some areas).

[0047] According to one embodiment, the first glass sheet has a face coated with at least two identical or different transparent mineral coatings forming a decoration, the at least two mineral coatings being superimposed in at least one region of the coated face. It has been observed that in the superimposed regions, the optical effects, in particular the colors, obtained differ from those obtained in the regions where a single mineral coating was deposited. Thus, by sequentially and optionally locally depositing two coatings, or even three, four, or more coatings, highly varied decorations can be achieved.

[0048] For example, the decoration may include a first region formed only of a first transparent mineral coating, a second region formed only of a second transparent mineral coating different from the first transparent mineral coating, and a third region formed by superimposing the first and second coatings.

[0049] When deposited on clear glass, the or each clear coating preferably has a light transmission coefficient of 40-95%, in particular 50-80%. Clear glass is a glass containing 0.05-0.1% total iron (expressed as Fe2O3) and having a light transmission coefficient of about 90%. Such glass is sold in particular under the references Planiclear, Planibel Clear or Optifloat Clear.

[0050] A transparent mineral coating may have anti-reflective properties (due to having a lower refractive index than that of glass). In this case, the decoration will generally be obtained by superimposing this coating with another transparent mineral coating.

[0051] This light transmission was chosen so as not to significantly reduce the brightness in the passenger compartment, but the trim remains clearly visible.

[0052] The physical thickness of the or each transparent mineral coating forming the decoration is preferably 20-250 nm, in particular 50-200 nm, or even 100-150 nm. This is the thickness in the final product, therefore after the optional curing or sintering step. In certain cases, particularly when the optical effect is achieved through interference effects, the choice of thickness allows the resulting color tone to be adjusted.

[0053] The or each transparent mineral coating is preferably based on an oxide.Such a coating has the advantage of not degrading the optional interposed low-E coating, in particular not unduly affecting its emissivity properties.

[0054] The oxide is preferably selected from titanium oxide, silicon oxide, zirconium oxide, tin oxide, zinc oxide, aluminum oxide, indium oxide and transition metal oxides. Transition metals are in particular copper, iron, cobalt, chromium and manganese.

[0055] The transparent mineral coating may have a colored appearance due to the presence of coloring substances, such as pigments or metal particles, such as gold particles.

[0056] The or each oxide-based transparent mineral coating is advantageously a sol-gel coating, ie a coating obtained by a sol-gel process.

[0057] The sol-gel method generally includes:

[0058] - forming a "sol", ie a solution containing at least one precursor of the oxide to be deposited,

[0059] - Apply this solution to the surface to be coated,

[0060] -Consolidation or densification of the coating by heat treatment.

[0061] The precursor comprises in particular a salt of the element whose oxide is to be deposited. It is in particular an organometallic compound or a nitrate, acetate, chloride, etc. Examples of organometallic compounds include alkoxides such as tetraorthosilicate (TEOS) in the case of silicon oxide layers or titanium tetraisopropoxide in the case of titanium oxide layers.

[0062] The sol may be partially aqueous. It preferably comprises an organic solvent, such as an alcohol, in particular selected from ethanol, isopropanol, butanol and glycols or glycol derivatives, and mixtures thereof. The sol may also comprise a viscosity modifier, such as a cellulose ether or a polyacrylate.

[0063] Preferably, the or each transparent mineral coating is based on an oxide and the deposition step comprises screen printing or digital printing of a precursor of this oxide, in particular a sol.

[0064] In the case of screen printing, a screen printing screen is placed on a first glass sheet, the screen comprising holes, some of which are blocked, and the composition, in particular the sol, is deposited on the screen, and a doctor blade is then applied to force the sol through the screen in the areas where the holes of the screen are not blocked, to form a wet sol-gel layer.

[0065] After deposition, the wet coating is preferably dried to remove the solvent, in particular at a temperature of 100 to 200°C.

[0066] When multiple transparent mineral coatings are deposited consecutively, a drying step is generally performed after each deposition.

[0067] In some cases, the transparent mineral coating (or all of these coatings) may subsequently be subjected to a pre-curing treatment, in particular at a temperature of 550-650° C. Such a treatment is particularly useful in the case of additional steps before bending (for example steps of assembly with additional glass sheets to produce a laminated roof, or steps of depositing an opaque layer), in particular on the side opposite to the side coated with the transparent mineral coating, where it is necessary to convey the film on the side coated with the transparent mineral coating.

[0068] For example, the method may comprise depositing a transparent mineral coating on a portion of the face of a first glass sheet, followed by drying and pre-curing, then conveying on this face, then depositing an opaque layer, in particular an enamel layer, on the other face, then bending, in the case of a monocoque roof, or, in the case of a laminated roof, a second pre-curing, assembly with an additional glass sheet, bending the two glass sheets together, and finally laminating.

[0069] After deposition of the transparent mineral coating, the first glass sheet and, if appropriate, the additional glass sheet are preferably bent.

[0070] When the transparent mineral coating is a sol-gel layer, bending may lead to densification and consolidation of the layer.

[0071] Bending can be done using gravity (the glass deforms under its own weight) or by pressing, at temperatures typically between 550 and 650°C.

[0072] According to a first embodiment, the two glass sheets (the first glass sheet and the additional glass sheet) are bent separately. According to a second embodiment, the first glass sheet and the additional glass sheet are bent together.

[0073] The lamination step can be carried out by treatment in an autoclave, for example at a temperature of 110 to 160° C. and a pressure of 10 to 15 bar. Prior to the autoclave treatment, the air trapped between the glass sheet and the laminating interlayer can be eliminated by calendering or applying negative pressure.

[0074] The additional glass sheet can be made of soda-lime-silica glass, or of borosilicate or aluminosilicate glass. It can be made of clear or colored glass. Its thickness is preferably between 0.5 and 4 mm, in particular between 1 and 3 mm.

[0075] The laminating interlayer preferably comprises at least one polyvinyl acetal sheet, in particular polyvinyl butyral (PVB) sheet. It advantageously consists of such a sheet. In particular, the laminating interlayer generally does not comprise an active layer based on liquid crystals.

[0076] If desired, the laminating interlayer may be tinted or non-tinted to adjust the optical or thermal properties of the glazing.

[0077] The laminated interlayer may advantageously have sound-absorbing properties in order to absorb sounds of airborne or solid origin. To this end, it may in particular be composed of three polymer sheets, including two "outer" PVB sheets surrounding an inner polymer sheet, optionally made of PVB having a lower hardness than that of the outer sheets.

[0078] The laminating interlayer may also have heat-insulating properties, in particular infrared radiation-reflecting properties. To this end, it may comprise a thin layer of coating with low emissivity, for example a coating comprising thin silver layers or a coating alternating dielectric layers with different refractive indices, deposited on an inner PET sheet surrounded by two outer PVB sheets.

[0079] The thickness of the laminating interlayer is typically in the range of 0.3-1.5 mm, in particular 0.5-1 mm. The laminating interlayer may be thinner at the edges of the window pane than in the center of the window pane to prevent double images when a head-up display system (referred to as "HUD") is used. Example

[0080] The following examples are combined Figure 1 The present invention is illustrated in a non-limiting manner.

[0081] [ Figure 1 ] shows an example of a vehicle roof 1 according to the invention.

[0082] The roof 1 is formed from a glass sheet 2 of dark grey soda-lime-silica glass with a thickness of 3.85 mm. The light transmittance of the glass sheet 2 is 10%. A low-emissivity coating (standard emissivity 0.30) comprising a thin layer of ITO is deposited on the glass sheet 2, which is not shown.

[0083] The decoration is then deposited by screen printing a sol-gel solution. First, strip 10 (Ferro TLU0050) is deposited, then strip 12 (also Ferro TLU0050), and finally an L-shaped strip 14 (Ferro TLU0055). The three strips are partially superimposed to form areas with different appearances.

[0084] Drying at 160° C. was performed after each deposition step.

[0085] The glass sheet 2 is subsequently bent and laminated together with the additional glass sheet so that the decoration is located on the face 4 of the laminated roof.

[0086] In area 20, where only coating 10 or 12 is applied, the appearance is silver. In area 24, where only coating 14 is applied, the appearance is gold. In area 22, where overlying coatings 10 and 12 are applied, the appearance is also gold. In area 26, where overlying coatings 12 and 14 are applied, the appearance is turquoise blue. Finally, in area 28, where overlying coatings 10, 12, and 14 are applied, the appearance is emerald green.

[0087] The emissivity of the low-E coating is not affected by the presence of the decoration, as it remains at 0.30 or 0.31 in the areas coated with the decoration.

[0088] However, in the comparative example in which the decoration was obtained by depositing enamel, the emissivity was severely decreased, having a value of about 0.8.

Claims

1. A roof (1) of a motor vehicle comprising a first glass sheet (2), wherein: A first glass sheet (2) is made of colored glass with a light transmission coefficient of 5% to 20%, the first glass sheet having at least one face coated on only a portion thereof with at least one transparent mineral coating (10, 12, 14) forming a decoration, and further comprising an additional glass sheet adhesively connected to the first glass sheet (2) via a thermoplastic laminating interlayer, wherein the first glass sheet is intended to be located on the inside of a vehicle, the face of the first glass sheet coated with the at least one decorative transparent mineral coating being intended to be located on the inside of the vehicle; or the first glass sheet is intended to be located on the outside of a vehicle, the face of the first glass sheet coated with the at least one decorative transparent mineral coating being intended to be located on the outside of the vehicle, wherein the first glass sheet is coated with a transparent mineral coating over 10-90% of the surface area of ​​the face of the glass sheet, The first glass contains the following coloring elements, and their weight contents are defined as follows: Fe2O 3， Total iron, 1.2-2.3%, CoO 50-400ppm, Se 0-35ppm, The redox degree is between 0.1 and 0.4, and the redox degree is the weight ratio of the ferrous content expressed as FeO to the total iron content expressed as Fe2O3.

2. The vehicle roof (1) according to claim 1, wherein The first glass sheet (2) is intended to be located on the inside of the vehicle.

3. The vehicle roof (1) according to any one of claims 1-2, wherein: The face of the first glass sheet (2) coated with the at least one decorative transparent mineral coating (10, 12, 14) is intended to be located on the inside of the vehicle.

4. The vehicle roof (1) according to any one of claims 1-2, wherein: When deposited on clear glass, the or each decorative transparent mineral coating has a light transmission coefficient of 40% to 95%.

5. The vehicle roof (1) according to any one of claims 1-2, wherein: The first glass sheet (2) or the additional glass sheet is coated with an opaque layer which is arranged on its periphery in the form of a peripheral strip.

6. The vehicle roof (1) according to any one of claims 1-2, wherein: A coating with low emissivity is sandwiched between the first glass sheet (2) and the transparent mineral coating (10, 12, 14) forming the decoration.

7. The vehicle roof (1) according to any one of claims 1-2, wherein: The first glass sheet (2) has a face coated with at least two identical or different decorative transparent mineral coatings (10, 12, 14), the at least two decorative transparent mineral coatings being superimposed in at least one region (22, 26, 28) of the coated face.

8. The vehicle roof (1) according to claim 4, wherein When deposited on clear glass, the or each decorative transparent mineral coating has a light transmission coefficient of 50% to 80%.

9. Vehicle roof (1) according to any one of claims 1-2, wherein the physical thickness of the or each transparent mineral coating (10, 12, 14) forming a decoration is 20-250 nm.

10. Vehicle roof (1) according to any one of claims 1-2, wherein the physical thickness of the or each transparent mineral coating (10, 12, 14) forming a decoration is 50-200 nm.

11. The vehicle roof (1) according to any one of claims 1-2, wherein: The or each transparent mineral coating (10, 12, 14) forming a decoration is based on oxides.

12. The vehicle roof (1) according to claim 11, wherein The or each decoration-forming transparent mineral coating (10, 12, 14) is a sol-gel coating.

13. The vehicle roof (1) according to claim 11, wherein The oxide is selected from titanium oxide, silicon oxide, zirconium oxide, tin oxide, zinc oxide, aluminum oxide, indium oxide and transition metal oxides.

14. The vehicle roof (1) according to claim 1, wherein The thermoplastic laminating interlayer is a thermoplastic laminating interlayer based on polyvinyl acetal.

15. The vehicle roof (1) according to claim 5, wherein The opaque layer is a black enamel opaque layer.

16. Method for obtaining a roof (1) for a motor vehicle according to any one of claims 1 to 15, comprising a step of depositing at least one transparent mineral coating (10, 12, 14) forming a decoration on only a portion of the face of a first glass sheet (2), said first glass sheet (2) having a light transmission coefficient of 5 to 20%.

17. Method according to claim 16, wherein the or each decoration-forming transparent mineral coating (10, 12, 14) is based on an oxide, the depositing step comprising screen printing or digital printing of a precursor of such an oxide.

18. Method according to claim 17, wherein the or each decoration-forming transparent mineral coating (10, 12, 14) is based on an oxide, the depositing step comprising screen printing or digital printing of a precursor sol of such an oxide.

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