Process for obtaining glazing

Abstract

The invention relates to a method for obtaining glazing comprising depositing, in a first zone (Z1) of a first face of a glass sheet, a masking layer (5) soluble in a solvent, the surface of said glass sheet not being coated by the masking layer in a second zone (Z2), then depositing a stack of thin films in the first zone (Z1) and in at least a part of the second zone (Z2), and then removing the masking layer (5) by washing with said solvent, wherein the masking layer (5) is a discontinuous layer forming a pattern consisting of a two-dimensional network of lines (6i, 7i), each having a width (e) between 0.2 and 2.0 mm. Fig. 3

Description

Title of the invention: Method for obtaining glazing

[0001] The invention relates to the field of glazing, in particular glazing for motor vehicles.

[0002] In order to ensure the thermal insulation of vehicles, it is known to coat one face of at least one glass sheet of said glazing with a stack of thin layers, in particular comprising one or more metal layers, in particular silver. Alternatively, the stack may comprise at least one layer of transparent conductive oxide (TCO). Such stacks have the property of reflecting infrared radiation, thus limiting heat transfers between the exterior of the vehicle and the passenger compartment, which leads to reducing the consumption dedicated to heating and air conditioning of the vehicle.

[0003] Silver is, however, sensitive to corrosion, and it is known, to avoid its damage, to remove part of the stack at the periphery of the glass sheet, a process sometimes called "demarcation". The stack can also be removed in certain areas in order to allow good transmission of electromagnetic waves through certain parts of the glazing, and thus ensure the proper functioning of the sensors and communication or navigation instruments present on board. This creates communication windows without the stack.

[0004] To do this, mechanical processes, for example abrasion, can be used, but which can lead to scratching or even weakening the glass. These mechanical processes are used in particular when the stack has been previously deposited on large glass sheets (for example approximately 6*3 m2), which will subsequently have to be cut to obtain the glass sheets having the final dimensions for incorporation into the glazing. Laser ablation processes are also known, but their cost is high and tedious adjustment of the laser is necessary to avoid damaging the surface of the glass.

[0005] It is also possible to use masks deposited on the areas in which the stack is not to be deposited, the masks then being removed after deposition of the stack. This method is possible when the size of the final glazing and the positioning of the edges of this glazing are known at the time of deposition of the stack of thin layers. This is for example the case when the stack is deposited on primitives having dimensions greater than the final dimensions of the glass sheet at the time of its integration into the glazing. Such masks are for example metal parts, or even water-soluble masking layers, subsequently removed by washing, and which during their removal also make it possible to remove the overlying stack.

[0006] This latter method is not without drawbacks, however. It has been found that complete removal of the masking layer can require lengthy washing and expensive washing machines.

[0007] The invention aims to overcome these drawbacks by proposing a more efficient and more economical method.

[0008] To this end, the invention relates to a method for obtaining a glazing comprising the deposition, in a first zone of a first face of a glass sheet, of a masking layer soluble in a solvent, the surface of said glass sheet not being coated with the masking layer in a second zone, then the deposition of a stack of thin layers, in the first zone and in at least part of the second zone, then the removal of the masking layer by washing using said solvent, in which the masking layer is a discontinuous layer forming a pattern consisting of a two-dimensional network of lines each having a width of between 0.2 and 2.0 mm.

[0009] The invention also relates to a glazing obtained according to this method, comprising a glass sheet of which a first face is coated with a stack of thin layers which is discontinuous over a first zone and continuous over at least part of a second zone, in which, in the first zone, the parts not coated with the stack of thin layers form a pattern consisting of a two-dimensional network of lines each having a width of between 0.2 and 2.0 mm.

[0010] The inventors were able to demonstrate that the use of a discontinuous masking layer forming a particular pattern rather than a continuous masking layer made it possible to facilitate and in particular accelerate the subsequent removal of this layer. It is thus possible to use less efficient and therefore less expensive washing machines. Other advantages will also appear in the rest of the text.

[0011] The pattern formed by the masking layer consists of a two-dimensional network of lines, which will also be called a "grid" in this text. Without wishing to be bound by any scientific theory, it seems that the presence of these lines multiplies the possible entry points for the solvent and increases the ratio between the surface area accessible to the solvent and the total volume of masking layer to be removed. Washing is thus more efficient and faster.

[0012] The solvent is preferably water, the masking layer then being water-soluble. Alternatively, the solvent may be an organic solvent, for example an alcohol.

[0013] The two-dimensional network of lines creates in negative a network of areas separated from each other and devoid of masking layer. After removal of the masking layer, these areas remain coated with the stack of thin layers. A two-dimensional network of lines devoid of stacking is formed in negative. It turns out However, the successive lines, due to their continuous nature, block the passage of moisture from the edges of the glazing, thus preventing corrosion. The two-dimensional nature of the lines prevents this passage in both directions of the glazing. The use of a grid (i.e. both the use of lines and the two-dimensional nature of the pattern) thus ensures that it is not possible to cross the first zone without encountering a line without stacking. Corrosion by the edges is thus stopped.

[0014] The first zone preferably comprises a zone intended to be located on the periphery of the glazing, in order to protect the edges of the glazing, through which corrosion can begin and spread.

[0015] The presence of still coated areas of the stack provides additional advantages when the stack is deposited on a layer of enamel.

[0016] It is known to deposit a layer of enamel, in particular in an area, called the enameled area, intended to be located on the periphery of the final glazing. The enamel, generally opaque and black, makes it possible to conceal and protect the glazing mounting joints in the bodywork bay, and where appropriate the connections of the various sensors used.

[0017] An enamel is a mineral layer formed by printing a fluid enamel composition, comprising a glass frit, pigments and an organic medium (resin and solvent). After firing the enamel, during which the organic medium is removed and the glass frit melts and adheres to the glass sheet, an enamel layer is formed consisting of pigment particles in a vitreous or glass-crystalline binder.

[0018] When the glass sheet is curved, which is generally the case for automotive glazing, the enamel is likely to stick to the bending tools or to another glass sheet (in the case of laminated glazing and when the two glass sheets intended to be laminated are curved together). Enamels are known which are likely not to stick, generally due to the formation of refractory crystals during firing, by devitrification of the glass frit. Such so-called "antistick" enamels are however difficult to reconcile with a configuration in which the stack of thin layers is deposited on the enamel. The presence of such crystals in fact increases the roughness of the enamel, which contributes to reducing the quality of the overlying stack.

[0019] In such a case, it turned out that the presence of areas still coated with the stack on the enamel made it possible to avoid the aforementioned sticking, and therefore to use enamels that do not have "anti-stick" properties. In addition, the presence of areas still coated with the stack on the enamel makes it possible to reduce optical distortions in the boundary area between the enamel and the stack. It seems that this is due to a reduction in the difference in emissivity between the areas coated with the enamel, which absorbs infrared radiation, and the areas coated with the stack, which reflects the infrared radiation, a reduction which in turn leads to a reduction in the temperature gradients experienced during bending.

[0020] Thus, and preferably, the method is such that before the deposition of the masking layer, the first face of the glass sheet is coated with a layer of enamel in an enameled zone, and at least a portion of the first zone is located in said enameled zone. The glazing therefore preferably comprises a layer of enamel in an enameled zone, the stack of thin layers being deposited on said layer of enamel, and at least a portion of the first zone being located in said enameled zone. The first zone may be entirely located in the enameled zone.

[0021] Preferably, the enamelled zone is a zone intended to be located on the periphery of the final glazing. This zone preferably forms in the final glazing a strip located on the periphery of the glazing, in particular a peripheral strip extending from the edges of the glazing over a length ranging in particular from 3 to 25 cm. This distance may vary depending on the positioning. In this case, the first zone preferably comprises a zone intended to be located on the periphery of the glazing, therefore on the periphery of the enamelled zone, preferably in the form of a peripheral strip extending from the edges of the glazing over a length ranging in particular from 0.4 to 5 cm, or even from 0.6 to 4 cm.

[0022] The lines preferably have a width of between 0.3 and 1.0 mm, in particular between 0.4 and 0.8 mm. It is difficult to deposit lines of very small width using printing techniques such as digital printing or screen printing. Very small widths may also prove insufficient to prevent the passage of moisture.

[0023] The lines can have any possible shape. In particular, they can be straight lines. The lines can intersect at any possible angle, for example, a 90° angle. In the case of straight lines intersecting at right angles, the grid is a grid, and the areas still coated with the stack in the final glazing are rectangular or even square. The shape and size of these areas is determined by the distance between the lines.

[0024] The distance between the lines is preferably between 1 and 10 mm, in particular between 2 and 5 mm. The distance between the lines as well as the width of the lines make it possible to adjust the coverage rate of the first zone by the masking layer, in other words the percentage of the surface of the first zone occupied by the total surface of the lines.

[0025] The total area of ​​the lines preferably occupies from 10 to 50% of the area of ​​the first zone. This coverage rate is preferably between 15 and 40%, in particular between 20 and 35%. The area of ​​the first zone is determined by taking into account the smallest area surrounding the entire masking layer. The first zone may itself be composed of several elementary zones, when The masking layer is applied in several non-contiguous areas. Too high a coverage rate can lead to enamel sticking. A low rate can reduce corrosion resistance. The first area preferably occupies 1 to 10% of the surface of the glass sheet.

[0026] The glass sheet is typically a soda-lime-silica glass, but other glasses, for example borosilicates or aluminosilicates, may also be used. The glass sheet is preferably obtained by floatation, that is to say by a process consisting of pouring molten glass onto a bath of molten tin. The glass sheet may be clear glass or tinted glass, for example green, blue, gray or bronze. To achieve this, the chemical composition of the first glass sheet advantageously comprises iron oxide, in a weight content ranging from 0.5 to 2%. It may also comprise other coloring agents, such as cobalt oxide, chromium oxide, nickel oxide, erbium oxide, or selenium. The glass sheet preferably has a thickness in the range 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.

[0027] As indicated above, the method may comprise, before the deposition of the masking layer, the deposition of a layer of enamel. This deposition is preferably carried out by screen printing or by digital printing, in particular by ink jet. In the case of screen printing, a screen printing screen is placed on the glass sheet, which comprises meshes, some of which are closed, then the enamel composition is deposited on the screen, then a doctor blade is applied in order to force the enamel composition to pass through the screen in the areas where the meshes of the screen are not closed, so as to form a layer of wet enamel.

[0028] The enamel composition preferably comprises at least one glass frit, pigments and an organic medium. The organic medium preferably comprises a resin and a solvent. The pigments preferably comprise one or more oxides chosen from chromium, copper, iron, manganese, cobalt and nickel oxides. These may be, for example, copper and / or iron chromates. The glass frit is preferably a bismuth borosilicate and / or a zinc (boro)silicate. The composition of the frit is preferably adapted to obtain a layer of enamel with little roughness, by reducing the softening temperature of the frit and by reducing the risk of devitrification. A suitable enamel composition is for example described in application WO2022 / 225391.

[0029] The wet enamel layer is then preferably dried, in particular using infrared or ultraviolet radiation.

[0030] The enamel layer then preferably undergoes a pre-baking treatment, before the masking layer is deposited. Such treatment is preferably carried out at temperatures ranging from 300 to 600°C, particularly from 400 to 550°C.

[0031] The enamelled area preferably occupies from 2 to 25%, in particular from 3 to 20%, or even from 5 to 15% of the surface of the glass sheet or of the final glazing.

[0032] Preferably, the enamel layer is in direct contact with the glass sheet and the masking layer is in direct contact with the enamel layer.

[0033] The enamel layer preferably has a roughness Ra of at most 2.0 pm, in particular between 0.1 and 1.0 pm, or even between 0.1 and 0.7 pm. The roughness Rz is preferably at most 5 pm.

[0034] Washing is preferably carried out before depositing the masking layer.

[0035] The masking layer is preferably deposited by digital printing, particularly by inkjet or screen printing. These techniques allow a fluid composition to be applied according to a predetermined pattern. Digital printing is preferred.

[0036] Inkjet printing is preferably carried out using a print head whose movement (in particular the position and speed) is controlled by computer or using a series of fixed print heads opposite which the glass moves at a controlled speed. To do this, the or each print head comprises nozzles through which drops of ink are projected locally onto the glass sheet. This technique is sometimes called "drop on demand" (DOD). Advantageously, the glass frit and the pigments have a volume particle size distribution such that the D90 is at most 2 μm. The D90 is for example determined by laser particle size analysis. The viscosity of the ink is preferably between 1 and 50 mPa.s.

[0037] The fluid composition preferably comprises an organic medium, including in particular a solvent and a resin. It further preferably comprises a glass frit.

[0038] The deposition of the masking layer is preferably followed by drying, carried out before the deposition of the stack of thin layers. The drying can in particular be carried out using infrared or ultraviolet radiation. In the latter case, the fluid composition preferably comprises a photocrosslinkable resin.

[0039] The masking layer preferably has a thickness ranging from 10 to 60 μm, in particular from 15 to 50 μm, or even from 25 to 45 μm.

[0040] The stack of thin layers is preferably deposited by cathode sputtering, in particular assisted by a magnetic field (so-called "magnetron" process). 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 a very complex stack of layers on the same line by successively moving the glass sheet under different targets, generally in a single device.

[0041] The stack of thin layers is preferably deposited over the entire surface of the glass sheet. The stack of thin layers is preferably in direct contact either with the glass sheet in the second zone or with the masking layer in the first zone (the stack also being in direct contact with the glass sheet in the parts of the first zone not coated with the pattern).

[0042] The stack of thin layers preferably comprises at least one functional layer reflecting infrared radiation, in particular chosen from metallic layers (in particular silver, or even niobium or gold) and layers of an electrically conductive transparent oxide (TCO). The TCO is in particular chosen from indium and tin oxide, doped tin oxides (for example with fluorine or antimony) and doped zinc oxides (for example with aluminum or gallium). Thin layers are understood to mean layers whose thickness is normally at most 5 μm, in particular at most 1 μm.

[0043] According to a preferred embodiment, the stack of thin layers comprises at least one silver layer, in particular one, two or three, or even four silver layers. 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.

[0044] According to another preferred embodiment, the stack of thin layers comprises at least one layer of indium and tin oxide. Its physical thickness is preferably between 30 and 200 nm, in particular between 40 and 150 nm.

[0045] In order to protect the or each functional layer (whether metallic or based on transparent conductive oxide), 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. The stack may further comprise blocker layers, for example metallic or nitrided, protecting the functional layer against oxidation.

[0046] The washing step is preferably carried out by bringing the glass sheet into contact with a solvent in which the masking layer is soluble, preferably water. The washing can be carried out in an industrial washing machine, in particular one equipped with brushes.

[0047] The glass sheet can then undergo one or more cutting steps in order to bring it to the dimensions corresponding to those of the final glazing. This is the case when the steps of depositing the masking layer and the stacking of thin layers, and optionally that of the enamel layer, have been carried out on primitives. Alternatively, when these steps have been implemented on a glass sheet already having the desired dimensions, no cutting step is necessary after the deposition steps.

[0048] When the stack of thin layers is also intended to provide a heating function, current leads must be provided. These may in particular be strips of silver paste deposited by screen printing on the stack of thin layers, at two opposite edges of the glass sheet.

[0049] The method preferably comprises, after the removal of the masking layer, a step of bending the glass sheet. The glazing is therefore preferably curved glazing.

[0050] 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.

[0051] When the glass sheet is intended to be integrated into a laminated glazing, in which the glass sheet is adhesively bonded to another glass sheet, these two glass sheets are preferably curved together. In this case the glass sheets can be kept apart by placing an interlayer powder between them ensuring a space of a few tens of micrometers, typically 20 to 50 μm. The interlayer powder is for example based on calcium and / or magnesium carbonate, and is intended to reduce the risk of sticking between the glass sheets. During curving, the inner glass sheet (intended to be positioned inside the passenger compartment) is normally placed above the outer glass sheet.

[0052] As indicated previously, the method of the invention, thanks to the presence of zones where the stack remains above the enamel, makes it possible to avoid the enamel sticking either to the bending tools or to the other sheet of glass.

[0053] The glazing according to the invention may be laminated glazing, in which the glass sheet is adhesively bonded to another glass sheet by means of a lamination interlayer.

[0054] The lamination step can be carried out by autoclave treatment, for example at temperatures of 110 to 160°C and under a pressure of 10 to 15 bars. Prior to the autoclave treatment, the air trapped between the glass sheets and the lamination interlayer can be removed by calendering or by vacuum.

[0055] The lamination interlayer preferably comprises at least one sheet of polyvinyl acetal, in particular polyvinyl butyral (PVB). The lamination interlayer may be tinted or untinted in order, if necessary, to regulate the optical or thermal properties of the glazing. The lamination interlayer may advantageously have properties sound absorption in order to absorb sounds of airborne or solid-borne origin. It may in particular be made for this purpose of three polymeric sheets, including two so-called external PVB sheets framing an internal polymeric sheet, possibly in PVB, of lower hardness than that of the external sheets. The thickness of the lamination interlayer is generally in a range from 0.3 to 1.5 mm, in particular from 0.5 to 1 mm. The lamination interlayer may have a thinner 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 display (HUD) system.

[0056] The glazing according to the invention is preferably curved. It is preferably curved and laminated. In this case, the stack of thin layers is preferably on face 2 of the laminated glazing (therefore in contact with the lamination interlayer), the faces being conventionally numbered from the outside of the glazing. In other words, the first face of the glass sheet is on face 2 of the laminated glazing.

[0057] The glazing is preferably a motor vehicle roof or a motor vehicle windshield, or a motor vehicle rear window.

[0058] The following exemplary embodiments, as well as Figures 1 to 7 below, illustrate the invention in a non-limiting manner.

[0059] [Fig. 1] is a schematic representation of a glass sheet before deposition of the masking layer.

[0060] [Fig.2] is a schematic representation of a glass sheet after deposition of the masking layer and thin film stacking.

[0061] [Fig.3] is an enlarged view of a detail of [Fig.2].

[0062] [Fig.4] is a section of [Fig.3].

[0063] [Fig.5] is a schematic representation of a glazing obtained by the process of the invention.

[0064] [Fig.6] is an enlarged view of a detail of [Fig.5].

[0065] [Fig.7] is a section of [Fig.6].

[0066] In [Fig.l] a glass sheet 1 is shown in the form of a primitive, therefore having larger dimensions than the final glazing. In this figure, a single glazing will be obtained by cutting this primitive, but other embodiments are possible, in which a single primitive makes it possible to obtain several glazings.

[0067] On this glass sheet 1 has been deposited a layer of enamel 3 in an enameled zone having the shape of a strip intended to be located, after cutting, at the periphery of the final glazing. The layer of enamel is for example deposited by screen printing. In the present example the layer of enamel is opaque and black. Its clarity L* in reflection is preferably less than 5.

[0068] [Fig.2] represents the glass sheet 1 after deposition of the masking layer 5. The latter, deposited on the enamel and at the periphery of the enamel strip 3, at the level of what will be the edge of the glazing, is shown diagrammatically in the form of a grid. The entire area where the masking layer 5 is deposited corresponds to the first zone Z1. It is in this area that the stack of thin layers will be partially removed by eliminating the masking layer.

[0069] The masking layer 5 is shown enlarged in [Fig. 3]. In this figure the enamel layer 3 is shown with a hatched background. The masking layer 5, deposited on a first zone Zb is in this example in the form of a two-dimensional network of straight lines 6;, 7; and equally spaced intersecting at right angles so as to form separate and square-shaped zones. The lines 6;, 7; here all have the same width e. For example, the width e is 0.5 mm and the square zones have sides 3 mm long. The coverage rate, i.e. the share of the first zone occupied by the total surface of the lines is then 29%. The second zone Z2 is not covered by the masking layer 5. The stack of thin layers, deposited over the entirety of the first and second zones Zi and Z2, is not shown in this figure.

[0070] Other variants are of course possible: for example the lines may not be straight and / or not intersect at right angles and / or not be regularly spaced and / or not all have the same width.

[0071] A section of [Fig.3] is shown in [Fig.4]. In the first zone Zi, we see the lines 7; of width e of the masking layer 5 as well as the stack of thin layers 9 deposited in the first and second zones Zi and Z2. The stack is deposited both in contact with the enamel layer 3 (and outside the enameled zone in contact with the glass sheet 1, this part of the glazing not being shown here) and in contact with the lines 6;, 7;.

[0072] Figures 5 to 7 illustrate the final glazing, after removal by washing of the masking layer 5 and cutting of the glass sheet 1 to the final dimensions. The removal of the masking layer has the effect of removing the underlying stack of thin layers. In the first zone Zb at the periphery of the glazing, the stack of thin layers 9 is therefore discontinuous and comprises separate zones 12j, here of square shape. In this first zone Zi the parts not coated by the stack of thin layers 9 form a pattern consisting of a two-dimensional network of lines 10;, 11; each having a width e.

[0073] In an example according to the invention, the procedure was as shown in the figures. A layer of black enamel without anti-stick properties (Fenzi, 1L5350) was deposited on a sheet of float glass and a masking layer (Tecglass FC 1003) was deposited on a part of the enamel layer, at the edge of the glazing. The masking layer formed a grid-type pattern with lines 0.5 mm wide. spaced 3 mm apart. After washing in a washing machine, the masking layer could be completely removed. In a comparative example, however, in which the masking layer formed a continuous, patternless layer, the same washing was not able to completely remove the masking layer and the overlying stack. Bending tests also revealed the existence of bonding in the case of the comparative example, in the areas where the stack was removed, while no bonding was observed in the case of the example according to the invention.

Claims

Claims

1. A method for obtaining a glazing comprising the deposition, in a first zone (ZJ) of a first face of a glass sheet (1), of a masking layer (5) soluble in a solvent, the surface of said glass sheet (1) not being coated with the masking layer in a second zone (Z2), then the deposition of a stack of thin layers (9), in the first zone (Zi) and in at least a part of the second zone (Z2), then the removal of the masking layer (5) by washing using said solvent, in which the masking layer (5) is a discontinuous layer forming a pattern consisting of a two-dimensional network of lines (6;, 7;) each having a width (e) of between 0.2 and 2.0 mm.

2. Method according to claim 1, in which the first zone (ZJ) comprises a zone intended to be located at the periphery of the glazing.

3. Method according to one of the preceding claims, in which, before the deposition of the masking layer (5), the first face of the glass sheet (1) is coated with a layer of enamel (3) in an enameled zone, and at least a part of the first zone (ZJ is located in said enameled zone.

4. Method according to one of the preceding claims, in which the total area of ​​the lines (6;, 70 occupies 10 to 50% of the area of ​​the first zone (ZJ.

5. Method according to one of the preceding claims, in which the masking layer (5) has a thickness ranging from 10 to 60 pm.

6. Method according to one of the preceding claims, in which the masking layer (5) is deposited by digital printing or by screen printing.

7. Method according to one of the preceding claims, in which the stack of thin layers (9) is deposited by cathode sputtering.

8. Method according to one of the preceding claims, in which the stack of thin layers (9) comprises at least one functional layer reflecting infrared radiation, in particular chosen from metallic layers and layers of an electrically conductive transparent oxide.

9. Method according to one of the preceding claims, further comprising, after the removal of the masking layer (5), a step of bending of the glass sheet (1).

10. Glazing obtained according to the method of one of the preceding claims, comprising a glass sheet (1) of which a first face is coated with a stack of thin layers (9) which is discontinuous over a first zone (Zi) and continuous over at least part of a second zone (Z2), in which, in the first zone (Zi), the parts not coated with the stack of thin layers (9) form a pattern consisting of a two-dimensional network of lines (10;, 11;) each having a width (e) of between 0.2 and 2.0 mm.

11. Glazing according to the preceding claim, comprising an enamel layer (3) in an enameled zone, the stack of thin layers (9) being deposited on said enamel layer (3), and at least part of the first zone (Zi) being located in said enameled zone.