FR3118626A1 - Automotive roof comprising a sheet of glass - Google Patents

Abstract

The invention relates to a motor vehicle roof (1) comprising a first glass sheet (2) whose light transmission factor is between 2 and 30%, said first glass sheet having at least one coated face, on a only of this, of at least one transparent mineral coating forming a decoration (10, 12, 14). Fig 1

Description

Automotive roof comprising a sheet of glass

The invention relates to the field of roofs for motor vehicles comprising a sheet of glass.

An increasing number of motor vehicles are fitted with glass-based roofs. These roofs make it possible to increase the brightness of the passenger compartment and give the vehicle an attractive design, especially seen from the outside. The thermal properties of the roof must also be optimized so as to avoid overheating of the passenger compartment, which would require an increase in air conditioning costs and therefore the consumption of the vehicle in summer.

The object of the invention is to propose automobile roofs having an attractive decoration, in particular a decoration visible only from inside the vehicle or only from the outside.

To this end, the subject of the invention is a motor vehicle roof comprising a first sheet of glass whose light transmission factor is between 2 and 30%, said first sheet of glass having at least one coated face, on a only of this one, of at least one transparent mineral coating forming a decoration.

Another object of the invention is a process for obtaining such a motor vehicle roof, comprising a step of depositing on only part of one face a first sheet of glass, the light transmission factor of which is comprised between 2 and 30%, of at least one transparent mineral coating forming a decoration.

The presence of at least one transparent mineral coating forming a decoration on a very dark sheet of glass makes it possible to confer original optical properties, without however harming the light and thermal comfort of the occupants of the vehicle. More particularly, a decoration may be visible, with good contrast, depending on the case, by the occupants of the vehicle or by persons outside the vehicle.

The roof according to the invention is preferably curved, so as to match the curvature of the vehicle. We then distinguish the interior face of the roof, intended to be located on the interior side of the vehicle, which is the concave face, and the exterior face of the roof, intended to be located on the exterior side of the vehicle, which is the convex face.

According to a first embodiment, the roof is laminated, that is to say it further comprises an additional glass sheet adhesively bonded to the first glass sheet by means of a thermoplastic lamination insert, in particular at polyvinylacetal base. In this case, each sheet of glass has an internal face, facing the interior of the vehicle, and an external face, facing the exterior of the vehicle.

In this embodiment, the first sheet of glass is preferably intended to be located on the interior side of the vehicle. The face of the first sheet of glass coated with said at least one transparent mineral coating is then preferably intended to be located on the interior side of the vehicle. This face is conventionally called "face 4" in the art. In this way, the decor is visible to the occupants of the passenger compartment, but not by people outside the vehicle.

Alternatively, the first sheet of glass may be intended to be located on the exterior side of the vehicle. The face of the first sheet of glass coated with said at least one transparent mineral coating is then preferably intended to be located on the exterior side of the vehicle, in other words on “face 1”. In this case, the decoration is only visible from outside the vehicle, therefore not by the occupants of the passenger compartment.

According to a second embodiment, the roof is monolithic, that is to say it only comprises a single sheet of glass, in this case the first sheet of glass. In this case, the first sheet of glass is normally made of tempered glass in order to meet regulatory requirements in terms of safety. Similar to what has been described in the case of a laminated roof, the face covered by the transparent mineral coating can be face 1 (intended to be located outside the vehicle) or face 2 (intended to located inside the vehicle), depending on whether the decor should be visible only from the outside or only from the inside.

The first sheet of glass can be flat or curved. The first sheet of glass is generally flat when the coating is deposited and is then curved.

The glass of the first glass sheet is typically a silico-soda-lime glass, but other glasses, for example borosilicates or aluminosilicates can also be used. The first sheet of glass is preferably obtained by floating, that is to say by a process consisting in pouring molten glass onto a bath of molten tin.

The first sheet of glass is tinted glass.

The choice of a light transmission factor between 2 and 30%, in particular between 5 and 20%, ensures good contrast, and therefore good visibility of the decoration, but only on the side where it is placed.

To do this, the glass preferably comprises the following coloring elements, in the weight contents defined below: Fe ₂ O ₃ (total iron) from 1.2 to 2.3%, in particular from 1.5 to 2.2 %, CoO from 50 to 400 ppm, in particular from 200 to 350 ppm, Se from 0 to 35 ppm, in particular from 10 to 30 ppm. The redox is preferably between 0.1 and 0.4, in particular between 0.2 and 0.3. Redox means the weight ratio between the ferrous iron content (expressed as FeO) and the total iron content (expressed as Fe ₂ O ₃ ).

In this text, the light transmission factors are expressed taking into account the D65 illuminant and the CIE-1931 reference observer. The light transmittance of the glass sheet is obviously measured in the absence of any coating.

The first sheet of glass preferably has a thickness comprised in a range ranging from 0.7 to 19 mm, in particular from 1 to 10 mm, particularly from 2 to 6 mm, or even from 2 to 4 mm.

The lateral dimensions of the first sheet of glass (and if necessary of the additional sheet of glass) are to be adapted according to those of the laminated glazing into which it is intended to be integrated. The first sheet of glass (and/or the additional sheet of glass) preferably has an area of at least 1 m².

The first glass sheet is preferably coated with a transparent mineral coating on 5 to 90% of the surface of the face of the glass sheet, in particular on 10 to 80%, depending on the desired decoration.

The first sheet of glass, or the additional sheet of glass, is preferably coated with an opaque layer, in particular in enamel, typically in black enamel, in particular placed at its periphery, for example in the form of a peripheral band. Such a layer generally has the purpose of concealing and protecting against ultraviolet radiation the polymer seals used for mounting the roof in the body bay.

This opaque layer is preferably deposited by screen printing.

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

When the opaque layer and the transparent mineral coating are deposited on the first sheet of glass, they can be on the same side or on two opposite sides. The order of deposition of the two coatings is irrelevant, but when they are deposited on the same face, it is preferable to first deposit the transparent mineral coating then the opaque layer, as explained in more detail in the following text.

According to a preferred embodiment, a low-emissivity coating is interposed between the first sheet of glass and the transparent mineral coating. The normal emissivity of this coating, measured at room temperature, is preferably less than 0.50, in particular 0.30 and even 0.20 or even 0.10.

The refractive index of this coating and, where appropriate, its color can influence the final appearance of the roof.

The low-emissivity coating is preferably a stack of thin layers.

The stack of thin layers is preferably in contact with the first sheet of glass. It preferably covers all, or at least 90% of the surface of the first sheet of glass.

By “contact”, we mean in this text a physical contact. The expression “based on” preferably means the fact that the layer in question comprises at least 50% by weight of the material considered, in particular 60%, even 70% and even 80% or 90%. The layer can even essentially consist or consist of this material. By “essentially consist”, it should be understood that the layer can comprise impurities without influencing its properties. The terms "oxide" or "nitride" do not necessarily mean that the oxides or nitrides are stoichiometric. They can indeed be under-stoichiometric, over-stoichiometric or stoichiometric.

The stack preferably comprises at least one layer based on a nitride. The nitride is in particular a nitride of at least one element chosen from aluminum, silicon, zirconium, titanium. It may comprise a nitride of at least two or three of these elements, for example a silicon and zirconium nitride, or a silicon and aluminum nitride. Preferably, the layer based on a nitride is a layer based on silicon nitride, more particularly a layer consisting essentially of a silicon nitride. When the silicon nitride layer is deposited by sputtering, it generally contains aluminum, because it is customary to dope silicon targets with aluminum in order to accelerate the deposition rates.

The layer based on a nitride preferably has a physical thickness comprised in a range ranging from 2 to 100 nm, in particular from 5 to 80 nm.

Nitride-based layers are commonly used in a number of stacks of thin layers because they have advantageous blocking properties, in the sense that they prevent the oxidation of other layers present in the stack, in particular functional layers. which will be described below.

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 layers of oxides or oxynitrides.

At least one electrically conductive functional layer is advantageously chosen from:
- the metallic layers, in particular silver or niobium, or even gold, and
- the layers of a transparent conductive oxide, chosen in particular from indium and tin oxide, doped tin oxides (for example with fluorine or antimony), doped zinc oxides (for example aluminum or gallium).

These layers are particularly appreciated for their low emissivity, which gives the glazing excellent thermal insulation properties. In the glazing fitted to motor vehicles, low-emissivity glazing makes it possible in hot weather to reflect part of the solar radiation outwards, and therefore to limit the heating of the passenger compartment of said vehicles, and if necessary to reduce the air conditioning expenses. Conversely, in cold weather, these glazings allow the heat to be retained within the passenger compartment, and therefore reduce the energy cost of heating. It is the same in the case of the glazing equipping the buildings.

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

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

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

At least part of the stack of thin layers can be deposited by various known techniques, for example by chemical vapor deposition (CVD), or by cathode sputtering, in particular assisted by a magnetic field (magnetron process).

The stack of thin layers is preferably deposited by sputtering, in particular assisted by magnetic field. In this process, a plasma is created under a high vacuum in the vicinity of a target comprising the chemical elements to be deposited. The active species of the plasma, by bombarding the target, tear off said elements, which are deposited on the glass sheet, forming the desired thin layer. This process is called "reactive" when the layer is made of a material resulting from a chemical reaction between the elements torn from the target and the gas contained in the plasma. The major advantage of this process lies in the possibility of depositing on the same line a very complex stack of layers by successively scrolling the glass sheet under different targets, generally in a single device.

The aforementioned stacks have electricity conduction and infrared reflection properties that are useful for providing a heating function (defrosting, demisting) and/or a thermal insulation function.

When the stack of thin layers is intended to provide a heating function, current leads must be provided. It may in particular be strips of silver paste deposited by screen printing on the stack of thin layers, at the level of two opposite edges of the glass sheet.

The transparent mineral coating makes it possible to locally modify the optical properties of the roof in order to create a decor. The mineral coating preferably gives a colored appearance, the coloring possibly coming from interference phenomena or from a color in transmission of the layer, due for example to the presence of coloring species. In the case of interference, the coloration may only be seen at certain viewing angles, for example at wide angles.

The decor can be formed from a single transparent mineral coating. In some areas, the decoration may include several superimposed layers of a transparent mineral coating of the same nature. Alternatively, the decor can be formed from a plurality of transparent mineral coatings of different natures, possibly superimposed in certain areas.

According to one embodiment, the first sheet of glass has a face coated with at least two transparent mineral coatings forming a decoration, which are identical or different, said at least two mineral coatings being superimposed in at least one zone of said coated face. It was observed that in the superposition zones, the optical effect obtained, in particular the color, was different from that obtained in the zones where a single mineral coating is deposited. It is thus possible, by depositing successively and possibly locally, two coatings, or even three, four or more, to obtain very varied decorations.

For example, the decoration may comprise a first zone formed solely of a first transparent mineral coating, a second zone formed solely of a second transparent mineral coating, different from the first, and a third zone formed by the superposition of the first coating and the second coating.

The light transmission factor of the or each transparent coating, when it is deposited on clear glass, is preferably between 40 and 95%, in particular between 50 and 80%. A clear glass is a glass comprising 0.05 to 0.1% total iron (expressed in the form Fe ₂ O ₃ ), whose light transmission factor is approximately 90%. Such a glass is notably marketed under the references Planiclear, Planibel Clear or even Optifloat clear.

The transparent mineral coating can have anti-reflective properties, by having a lower refractive index than glass. In this case, the decoration will generally be obtained by superimposing this coating with another transparent mineral coating.

The choice of such a transmission makes it possible not to significantly reduce the brightness inside the passenger compartment, the decor remaining however clearly visible.

The physical thickness of the or each transparent mineral coating forming a decoration is preferably between 20 and 250 nm, in particular between 50 and 200 nm, or even between 100 and 150 nm. This is the thickness in the final product, i.e. after a possible baking or sintering step. In some cases, especially when the optical effects are obtained thanks to interference effects, the choice of the thickness makes it possible to adjust the shade obtained.

The or each transparent mineral coating is preferably oxide-based. Such coatings have the advantage of not degrading any interposed low-emissivity coating and in particular of not affecting its emissivity properties too much.

The oxide is preferably chosen from the group formed by titanium oxides, silicon oxides, zirconium oxides, tin oxides, zinc oxides, aluminum oxides, indium oxides and transition metal oxides. The transition metals are in particular copper, iron, cobalt, chromium and manganese.

The transparent mineral coating may have a colored appearance due to the presence of coloring species, such as pigments or metallic particles, for example gold.

The or each transparent oxide-based mineral coating is advantageously a sol-gel coating, that is to say a coating obtained by a sol-gel process.

A sol-gel process typically includes:
- the formation of a "sol", that is to say a solution containing at least one precursor of the oxide to be deposited,
- the application of this solution on the surface to be coated,
- the consolidation or densification of the coating by means of a heat treatment.

The precursor notably comprises salts of the element whose oxide is to be deposited. These include organometallic compounds or even nitrates, acetates, chlorides, etc. Examples of organometallic compounds include alkoxides, for example tetraorthosilicate (TEOS) in the case of a layer of silicon oxide or titanium tetraisopropoxide in the case of a layer of titanium oxide.

The soil may be partially watery. It preferably comprises an organic solvent, for example an alcohol, chosen in particular from ethanol, isopropanol, butanol and glycols or derivatives of glycols, and mixtures thereof. The sol may additionally contain viscosity-regulating agents, such as cellulose ethers or polyacrylates.

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

In the case of screen printing, a screen printing screen is placed on the first sheet of glass, which comprises meshes, some of which are closed off, then the composition, in particular the ground, is deposited on the screen, then a doctor blade is applied in order to to force the soil to cross the screen in the zones where the meshes of the screen are not closed, so as to form a moist soil-gel layer.

After deposition, the wet coating is preferably dried in order to eliminate the solvent, in particular at a temperature ranging from 100 to 200°C.

When several transparent mineral coatings are successively deposited, a drying step is normally carried out after each deposit.

In some cases, the transparent mineral coating (or all of these coatings) can then undergo a pre-baking treatment, in particular at a temperature ranging from 550 to 650°C. This treatment is particularly useful in the case of additional steps before bending, for example an assembly step with an additional sheet of glass for the manufacture of a laminated roof, or even a step of depositing a opaque layer, in particular on the face opposite the face coated with the transparent mineral coating, requiring conveying on the latter face.

For example, the method can comprise the deposition of a transparent mineral coating on a part of one face of the first sheet of glass, then a drying and a pre-baking, then a conveying on this face, then the deposition of an opaque layer, in particular of enamel, on the other side, then, in the case of a monolithic roof, a bending, or, in the case of a laminated roof, a second pre-baking, assembly with an additional sheet of glass, the bending of the two sheets of glass together, and finally the lamination.

After the deposition of the transparent mineral coating, the first sheet of glass, and if necessary the additional sheet of glass, is preferably bent.

When the transparent mineral coating is a sol-gel layer, the bending can lead to the densification and consolidation of this layer.

The bending can in particular be carried out by gravity (the glass deforming under its own weight) or by pressing, at temperatures typically ranging from 550 to 650°C.

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

The lamination step can be carried out by treatment in an autoclave, for example at temperatures of 110 to 160° C. and under a pressure ranging from 10 to 15 bars. Prior to the autoclave treatment, the air trapped between the glass sheets and the lamination insert can be eliminated by calendering or by depression.

The additional glass sheet can be made of silico-soda-lime glass, or even of borosilicate or aluminosilicate glass. It can be clear or tinted glass. Its thickness is preferably between 0.5 and 4 mm, in particular between 1 and 3 mm.

The lamination interlayer preferably comprises at least one sheet of polyvinylacetal, in particular of polyvinylbutyral (PVB). It advantageously consists of such sheets. In particular, the lamination interlayer does not normally comprise an active layer based on liquid crystals.

The lamination insert can be tinted or untinted in order to regulate the optical or thermal properties of the glazing if necessary.

The lamination insert can advantageously have sound absorption properties in order to absorb sounds of aerial or solid-borne origin. It may in particular consist for this purpose of three polymeric sheets, including two so-called outer PVB sheets framing an inner polymeric sheet, optionally made of PVB, of lower hardness than that of the outer sheets.

The lamination insert can also have thermal insulation properties, in particular for reflecting infrared radiation. It may for this purpose comprise a coating of thin layers with low emissivity, for example a coating comprising a thin layer of silver or an alternating coating of dielectric layers of different refractive indices, deposited on an internal PET sheet flanked by two external PVB sheets.

The thickness of the lamination insert is generally within a range ranging from 0.3 to 1.5 mm, in particular from 0.5 to 1 mm. The lamination insert may have a lower thickness on one edge of the glazing than in the center of the glazing in order to avoid the formation of a double image when using a head-up vision system, known as HUD ( head-up display).

Examples

The following examples illustrate the invention in a non-limiting manner, in connection with the .

represents an example of a roof 1 according to the invention.

The roof 1 is made of a sheet of glass 2 of a silico-sodolime glass of dark gray tint, with a thickness of 3.85 mm. The light transmission factor of the glass sheet 2 is 10%. On this glass sheet 2 was deposited a low-emissivity coating (normal emissivity of 0.30), not shown, comprising a thin layer of ITO.

The decoration was then deposited by serigraphy of sol-gel solutions. Strip 10 (Ferro TLU0050) was first deposited, then strip 12 (also Ferro TLU0050) and finally strip 14, L-shaped (Ferro TLU0055). The three bands overlap in places to create areas of different appearance.

Drying at 160° C. was carried out after each deposition step.

The sheet of glass 2 was then curved with an additional sheet of glass and laminated so that the decoration is opposite 4 of the laminated roof.

In areas 20, coated only with coating 10 or 12, the appearance was silver. In area 24, coated only with coating 14, the appearance was golden. In area 22, coated with the overlap of coatings 10 and 12, the appearance was also golden. In area 26, coated with the overlap of coatings 12 and 14, the appearance was turquoise blue. Finally, in area 28, coated with the overlay of coatings 10, 12 and 14, the appearance was emerald green.

The emissivity of the low-emissivity coating was not impacted by the presence of the decoration, since it remains at 0.30 or 0.31 in the areas covered with the decoration.

In a comparative example where the decoration was obtained by deposition of enamel, the emissivity was on the other hand greatly degraded, with values around 0.8.

Claims (12)

Motor vehicle roof (1) comprising a first sheet of glass (2) whose light transmission factor is between 2 and 30%, said first sheet of glass having at least one face coated, on only part of the latter , at least one transparent mineral coating forming a decoration (10, 12, 14). Roof (1) according to claim 1, further comprising an additional glass sheet adhesively bonded to the first glass sheet (2) by means of a thermoplastic lamination interlayer, in particular based on polyvinylacetal. Roof (1) according to the preceding claim, in which the first sheet of glass (2) is intended to be located on the interior side of the vehicle. Roof (1) according to one of the preceding claims, in which the face of the first sheet of glass (2) coated with the said at least one transparent mineral coating (10, 12, 14) is intended to be located on the interior side of the vehicle . Roof (1) according to one of the preceding claims, in which a low-emissivity coating is interposed between the first sheet of glass (2) and the transparent mineral coating (10, 12, 14). Roof (1) according to one of the preceding claims, in which the first sheet of glass (2) has one face coated with at least two transparent mineral coatings (10, 12, 14) forming a decoration, identical or different, said at least two mineral coatings being superposed in at least one zone (22, 26, 28) of said coated face. Roof (1) according to one of the preceding claims, in which the light transmission factor of the or each transparent coating, when it is deposited on clear glass, is between 40 and 95%, in particular between 50 and 80% . Roof (1) according to one of the preceding claims, in which the physical thickness of the or each transparent mineral coating (10, 12, 14) forming a decoration is between 20 and 250 nm, in particular between 50 and 200 nm. Roof (1) according to one of the preceding claims, in which the or each transparent mineral coating (10, 12, 14) is oxide-based, in particular is a sol-gel coating. Roof (1) according to the preceding claim, in which the oxide is chosen from the group formed by titanium oxides, silicon oxides, zirconium oxides, tin oxides, zinc oxides, oxides of aluminium, indium oxides and transition metal oxides. Method for obtaining a motor vehicle roof (1) according to one of the preceding claims, comprising a step of depositing on only part of one face a first sheet of glass (2) whose transmission factor luminous is between 2 and 30%, of at least one transparent mineral coating forming a decoration (10, 12, 14). Process according to the preceding claim, in which the or each transparent mineral coating (10, 12, 14) is oxide-based, the deposition step comprising screen printing or digital printing of a precursor of this oxide, in particular of a ground.