METHOD FOR COATING A LAMINATED GLASS SHEET AND COATED LAMINATED GLASS SHEET

Description

FIELD OF INVENTION

[0001] The present invention relates to a method for manufacturing glass coated with a decorative layer and to such glass.

[0002] More specifically, the invention relates to a method of coating a laminated glass panel with a decorative layer being a reflective layer, as well as to the coated laminated glass panel thus obtained. TECHNOLOGICAL BACKGROUND

[0003] In the field of glass coated with a decorative layer, two types of decorative layers are particularly appreciated: light-reflecting layers so that the glass has the appearance of a mirror and "lacquer" type decorative layers, formed from a resin-rich paint and presenting a so-called taut appearance.

[0004] Thus, a mirror typically consists of a monolithic piece of glass, usually between 2 and 8 mm thick, coated with a layer of silver which gives it its reflective power. The thickness of the silver layer is typically on the order of a few tens of nanometers and its surface mass is generally at least 700 mg / m².

[0005] To improve the chemical and mechanical resistance of the silver layer, it can be covered with a protective varnish, most often several micrometers thick.

[0006] Lacquered glass typically consists of a monolithic glass, typically between 2 and 12 mm thick, covered with a layer of decorative paint of the "lacquer" type - most often several micrometers thick - which gives it the desired aesthetic appearance and has satisfactory chemical and mechanical resistance characteristics.

[0007] While these processes for coating monolithic glass are aesthetically satisfactory, they do not provide sufficient mechanical resistance properties for certain applications, particularly in the building sector.

[0008] The safety of coated monolithic glass obtained by conventional processes can be improved by means of an anti-shatter adhesive film placed on the back of the glass which holds the pieces of glass in case of breakage, the mechanical performance of such a structure remaining limited since the risk of breakage is not or is only slightly modified by the presence of the anti-shatter film.

[0009] In the glass industry, tempering is also known to improve the mechanical properties of glass. Tempered glass cannot be recut after tempering. Therefore, if one were to consider a decorative coating on tempered glass, one would be limited by the shape of the tempered glass piece before coating. This limitation is clearly significant for building applications such as closet doors, tables, and wall surfaces, which are often custom-made.

[0010] In the glass industry, laminating glass is still a common practice to improve its mechanical properties. Laminated glass is an assembly of glass sheets and interlayers of a plastic nature, typically in the form of a film, usually made of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA). The presence of the interlayer material increases mechanical resistance to breakage and prevents the formation of shards.

[0011] Various processes have been described which make it possible to obtain laminated glass mirrors or lacquered laminated glass, the decorative layer being sandwiched, or equivalently placed between two sheets of glass.

[0012] In particular, document GB224160 describes a process for obtaining a laminated glass mirror in which: a reflective coating is deposited on a first sheet of glass, then a second sheet of glass is glued onto the first sheet using an adhesive such as polyvinyl butyral (PVB) the reflective coating being sandwiched between the two sheets of glass.

[0013] Starting from such a process, it is not possible to simply reverse the order of the components to position the reflective coating on an external face of the final product. Indeed, on the one hand, the reflective coating (or any other decorative coating) thus positioned would then be mechanically damaged by the calendering or transport rollers used to assemble the two sheets, and on the other hand, the autoclaving phase on an industrial scale presents a risk of deterioration of the coatings of the layers of a given panel and of the glass panels gluing together.

[0014] Furthermore, the optical defects of the mirror formed by the GB224160 process are determined by those of the glass layer on which the reflective coating is deposited.

[0015] Similarly, WO2009 / 081077 describes lacquered laminated glass in which a layer of lacquer is sandwiched between two sheets of glass, the assembly then subjected to heat treatment under pressure to ensure the bond between the glass sheets. Such a process requires the use of a lacquer that withstands heat treatment under pressure, which limits the choice of colors. Furthermore, the adhesion of the PVB (polyvinyl butyral coating) can be affected, particularly with lacquers containing aqueous solvents. This presents a risk of future delamination of the product. It is known to apply reflective films to the outer surface of laminated glass to obtain a mirror effect. Luminis Film markets mirror-effect films under the name Miroir-200-x: https: / / en.luminis-films.com / _telechargement / luminis / categorie / ficheTechnique / MIROIR-200x_2.pdf?v=1.

[0016] The invention thus aims to propose a method of coating a laminated glass panel with a decorative layer allowing to obtain a laminated glass mirror having resistance to impact and / or perforation and an ability to retain fragments at least as good as those obtained by prior art processes and improved optical and decorative properties compared to prior art processes. SUMMARY OF THE INVENTION

[0017] Thus, the invention relates to a method for coating a laminated glass panel comprising: a laminated glass panel to be coated is provided, comprising at least two sheets of glass and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material forming after assembly an interlayer layer, the laminated glass panel to be coated having at least one upper face to be coated; a fluid decorative material is provided; a chemical hardener or a crosslinking catalyst is incorporated into the fluid decorative material in a ratio P_cata between the mass of chemical hardener or crosslinking catalyst and the mass of decorative material in the determined fluid state; at least one decorative coating layer is formed by applying the decorative material in the fluid state in which the chemical hardener or crosslinking catalyst is incorporated onto the upper face of the laminated glass panel to be coated;The decorative coating layer is dried by heating the laminated glass panel thus coated using a drying device with a set temperature greater than or equal to 100°C and less than 140°C. a process in which at least one decorative coating layer consists of a layer of reflective material so as to form a mirror and one or more layers of protective varnish, the thickness of the reflective material layer corresponding to a surface mass of silver exceeding the standard of 700 mg / m² 2 .

[0018] According to one embodiment, the process may include a step in which the heating time (t_chauff) of the laminated glass panel to the setpoint temperature (T_ext) and / or the ratio P_cata of the mass of chemical hardener or crosslinking catalyst and the mass of decorative material in the fluid state at the time of incorporation is determined as a function of said setpoint temperature (T_ext).

[0019] Thanks to these provisions, it is possible to manufacture on an industrial scale coated laminated glass panels without bubbling or yellowing of the interlayer material from already assembled laminated glass panels.

[0020] According to one embodiment of the process of coating a laminated glass panel, the polymer interlayer material can be chosen from polyvinyl butyral, ethylene-vinyl acetate, an ionoplast polymer, thermoplastic polyurethane and a casting resin.

[0021] These different polymer interlayer materials have different characteristics in terms of refractive index, mechanical resistance and hydrophobicity, which makes it possible to modulate the optical and / or mechanical and / or moisture resistance properties of the coated laminated glass panel according to its future use.

[0022] The coating process can also be used to manufacture mirror-type glass panels with a reduced carbon footprint over the product's lifespan. Indeed, laminated glass is approximately five times stronger and one hundred times more rigid than monolithic glass. Therefore, laminated glass mirrors can be expected to need replacing less frequently than mirrors made using earlier techniques. Depending on the coating process used for a laminated glass panel, at least one decorative coating layer consists of a reflective material and one or more protective varnish layers.

[0023] This feature makes it possible, in particular, to produce mirror-type laminated glass panels using the same generic process.

[0024] According to one embodiment of the process of coating a laminated glass panel, the ratio P_cata of the mass of chemical hardener or crosslinking catalyst and the mass of decorative material in the fluid state is greater than 0.1%.

[0025] Such a proportion of chemical hardener makes it possible in particular to limit the maximum surface temperature reached by the glass panel, so that the interlayer polymer material does not bubble or yellow and that the crosslinking of the decorative coating layer is satisfactory with a drying time at this maximum surface temperature limited and in particular acceptable in an industrial process.

[0026] According to one embodiment of the coating process for a laminated glass panel: if the setpoint temperature of the drying device (T_ext) is chosen in the range [100°C, 120°C], said heating time (t_chauff) in the drying device is greater than or equal to 7.5 minutes and said P_cata ratio is chosen in the range [0.1%; 5%], and if the setpoint temperature of the drying device (T_ext) is chosen in the range [120°C, 140°C], said heating time (t_chauff) in the drying device is less than or equal to 7.5 minutes and greater than or equal to 3 minutes and said P_cata ratio is chosen in the range [0.1%; 5%].

[0027] These parameter ranges make it possible to obtain a coated laminated glass panel without bubbling or yellowing of the polymer interlayer, with particularly satisfactory crosslinking of the decorative coating layer, and within production times perfectly compatible with industrial and automated use. Depending on the embodiment of the coating process for a laminated glass panel, the chemical hardener or crosslinking catalyst can be chosen from among acid catalysts and optionally from among hydrofluoric acid, phosphoric acid, and para-toluenesulfonic acid.

[0028] These chemical hardeners and crosslinking catalysts have, among other things, the advantage of allowing a lowering of the crosslinking temperature sufficient to avoid bubbling problems.

[0029] The invention also relates to a laminated glass panel comprising at least two sheets of glass and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material, the laminated glass panel having a first outer face (11a1) referred to as the upper face (11a1) and a second outer face (11b1) referred to as the lower face (11b1),the panel being characterized in that the upper face (11a1) of the laminated glass panel is coated with at least one decorative coating layer (13) formed at least in part from an organic fluid decorative material applied to the upper face (11a1) of the laminated glass panel after the at least two successive sheets of glass have been assembled using the polymer interlayer material and in which the at least one decorative coating layer consists of a layer of reflective material so as to form a mirror and one or more layers of protective varnish, the thickness of the reflective material layer corresponding to a surface mass of silver greater than the standard of 700 mg / m².

[0030] According to one embodiment, the polymer interlayer material does not exhibit any visible bubbling defects and the decorative coating layer withstands at least twenty back-and-forth movements in a swabbing test carried out by rubbing the surface of the decorative coating layer over a determined distance using a cloth soaked in a solvent for the decorative coating layer.

[0031] Such a glass panel can be obtained by the process according to the invention and, thanks to lamination, exhibits good mechanical resistance and splinter retention, as well as improved optical and / or decorative properties compared to coated glass panels of the prior art.

[0032] In one embodiment of the laminated glass panel, the decorative coating layer withstands at least two hundred swishes in the crimping test. Such resistance is suitable for the majority of applications of coated laminated glass panels, particularly in the building and furniture sectors.

[0033] According to one embodiment of the laminated glass panel, the polymer interlayer material is tinted.

[0034] It is therefore possible to obtain a tinted mirror whose tint is controlled by means of that of the polymer interlayer material, the coloring of which is easy to implement and can be done in a wide range of colors.

[0035] According to one embodiment of the laminated glass panel, heating means are incorporated in the polymer interlayer material or in at least one of the at least two glass sheets.

[0036] The invention also relates to the use of said laminated glass panel in the field of building or furniture. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Embodiments of the invention will be described below with reference to the drawings, briefly described below: [ Fig. 1 [ ] represents a side view of a laminated glass panel coated according to the invention. ] Fig. 2a ] is a photograph of a laminated glass panel coated with silvering and a protective varnish layer, the whole being heated to 170°C for 2 minutes, according to a prior art process, on which the bubbling of the polymer interlayer material can be observed. Fig. 2b ] is a photo of the laminated glass panel coated with the Fig. 2a , immediately after application of the protective varnish layer and just before the heating step according to the prior art process. Fig. 3] represents the temperature profile followed by the external surface of the decorative coating layer, monitored by means of six thermocouples distributed over this surface during the drying of the decorative coating layer according to a prior art process in the case of the coated laminated glass panel obtained at the Fig. 2a . [ Fig. 4 ] represents the temperature profiles followed by the external surface of the decorative coating layer, monitored by means of six thermocouples distributed over this surface during the drying of the decorative coating layer according to the six heating profiles tested to obtain the results in Table 1. Fig. 5 ] represents the theoretical evolution of the temperature T of the upper glass sheet of a coated laminated glass panel within the framework of a simplified thermal model.

[0038] In the drawings, identical references designate identical or similar objects. DETAILED DESCRIPTION

[0039] The invention relates to a method for coating a glass panel comprising: a laminated glass panel to be coated is provided, comprising at least two sheets of glass and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material forming after assembly an interlayer layer 12, the laminated glass panel to be coated having at least one upper face 11a1; a decorative material is provided in a fluid state; a chemical hardener or a crosslinking catalyst is incorporated into the decorative material in a fluid state in a ratio P_cata between the mass of chemical hardener or crosslinking catalyst and the mass of decorative material in a determined fluid state; at least one decorative coating layer 13 is formed by applying the decorative material in a fluid state in which the chemical hardener or crosslinking catalyst is incorporated onto the upper face 11a1 of the laminated glass panel to be coated;The decorative coating layer is dried by heating the laminated glass panel thus coated using a drying device with a setpoint temperature T_ext greater than or equal to 100°C and less than 140°C. The process in which at least one decorative coating layer consists of a layer of reflective material so as to form a mirror and one or more layers of protective varnish, the thickness of the reflective material layer corresponding to a surface mass of silver greater than the standard of 700 mg / m².

[0040] The heating time t_chauff of the laminated glass panel to this setpoint temperature T_ext and the ratio P_cata of the mass of chemical hardener or crosslinking catalyst and the mass of decorative material in the fluid state at the time of incorporation can be chosen according to the setpoint temperature T_ext.

[0041] The P_cata ratio is preferably expressed as a percentage of the mass of the decorative material in the fluid state.

[0042] The laminated glass panel to be coated therefore comprises at least two sheets of glass, of which an upper sheet of glass 11a and a lower sheet of glass 11b are defined. Any type of flat glass (or possibly curved by the bending processes known to those skilled in the art, when it comes to coating curved surfaces) can be used for each of the sheets of glass.

[0043] Each sheet of glass is by definition monolithic.

[0044] In one embodiment, one or more of the at least two sheets of glass are produced by the "float" process, which allows a flat and smooth sheet of glass to be obtained with very good precision, or by drawing or rolling processes.

[0045] In one embodiment, at least one or all of the glass sheets are tempered.

[0046] In one embodiment, the upper glass sheet 11a, one face of which will ultimately be coated with at least one layer of decorative coating 13 following the process according to the invention, is not made of tempered glass. Tempered glass can indeed exhibit micro-deformations that may alter the decorative qualities of the coating, particularly when this coating is obtained by a silvering process.

[0047] In the event that none of the glass sheets are tempered, the laminated glass panel has the advantage of being able to be recut to the desired dimensions and / or for downgrading of the edges if their characteristics are not satisfactory at the end of the process.

[0048] There are no limitations on the dimensions of the two or more sheets of glass, apart from those related to the manufacturing process of each of the sheets of glass and the assembly process.

[0049] Specifically, the thickness of a glass sheet can range from 2 to 12 mm (millimeters), or even more, depending on the end use of the coated laminated glass panel. For example, a thickness of 2 mm to 6 mm, or even 2 mm to 5 mm, 2 mm to 4 mm, or 2 mm to 3 mm, and in particular 2 mm, 3 mm, 4 mm, 5 mm, or 6 mm, for one or more of the at least two glass sheets, could be considered.

[0050] The two or more sheets of glass may have the same or different thicknesses and / or compositions.

[0051] The at least two glass sheets are superimposed one on top of the other in a stacking direction (Z'Z) and joined two-by-two using at least one polymer interlayer material, such that after assembly, at least one interlayer 12 is sandwiched (or equivalently sandwiched) between at least two successive glass sheets, as shown in the figure 1 .

[0052] Regardless of the number of overlapping glass sheets (two or more), the laminated glass panel to be coated therefore comprises at least: an upper glass sheet 11a whose external face to the assembly is intended to receive the coating and constitutes the so-called upper external face 11a1 of the laminated glass panel to be coated, and a lower glass sheet 11b constituted by the glass sheet furthest from the upper glass sheet 11a along the stacking direction (Z'Z) and whose external face to the assembly constitutes the so-called lower external face 11b1 of the laminated glass panel to be coated.

[0053] The polymer interlayer material may comprise one or more polymers.

[0054] Specifically, the polymer interlayer material can be polyvinyl butyral (PVB). PVB offers, among other advantages, the following: PVB has a refractive index close to that of the soda-lime-silicon glass commonly used for glazing, so the interlayer is invisible or virtually invisible. Furthermore, PVB effectively absorbs impacts and holds glass fragments together in the event of breakage.

[0055] It may also be ethylene-vinyl acetate (EVA). The hydrophobic properties of EVA are particularly interesting if the coated glass panel is intended to be installed in a humid environment or outdoors: the risk of delamination over time due to humidity is reduced by using EVA for the interlayer 12 of polymer material.

[0056] It is also possible to use a polymer interlayer material called "ionoplast", in particular of the SentryGlass ® type, which makes it possible to form laminated glasses that do not have bubble or yellowing defects even when exposed during their implementation to high temperatures, up to 80°C.

[0057] In another embodiment, the interlayer material can still be thermoplastic polyurethane (also called TPU or "Thermoplastic Polyurethane") or a casting resin (or equivalently "CIP" resin ("Cast In Place").

[0058] The interlayer material can be tinted before assembly, so as to give a particular colour to the laminated glass panel in association with the decorative coating once the panel is coated.

[0059] Once the laminated glass panel to be coated is supplied, a decorative material is provided in a fluid state.

[0060] The decorative material in fluid state can notably be in liquid state with a greater or lesser viscosity, this viscosity being adapted to allow the deposition of a layer of decorative material on the laminated glass panel, for example by means of a roller or a spray gun or even a curtain machine.

[0061] The decorative material is reflective after drying. It contains silver, which can be deposited, among other methods, by redox reaction, by contacting a solution of ammoniacal silver nitrate with a reducing agent solution.

[0062] The decorative material is therefore supplied in a fluid state, insofar as it includes one or more solvents.

[0063] In known processes of coating non-laminated glass with a decorative material in a fluid state, the fluid decorative material is deposited directly onto one face of the non-laminated glass so as to form a decorative coating layer, and this decorative coating layer is then dried.

[0064] In the case of a conventional silvering process, the protective varnish layer is applied over the reflective material layer, for example by means of a curtain varnisher, the varnish being dried by passing through an oven so that the temperature reached on the surface of the protective varnish layer is above 170°C for at least two minutes.

[0065] In summary, the varnishes classically used in the manufacture of mirrors are single-component paints which require sufficient thermal energy to crosslink and achieve the expected performance levels in terms of chemical (anti-corrosion) and mechanical (scratch) resistance, for which it is customary to keep the glass panel in an oven so that the temperature reached on the surface of the protective varnish layer is above 170°C for at least two minutes.

[0066] Regardless of the method used to deposit the decorative coating layer, it is observed that high-temperature heating drying is implemented in the coating processes of non-laminated glass classically used in the field of monolithic glass and is necessary to obtain the correct cross-linking of this decorative coating layer, and this in an acceptable time in an industrial manufacturing process.

[0067] Unfortunately, these processes cannot be directly transposed to laminated glass panels since the heating step causes the interlayer material to bubble.

[0068] There Fig. 2a is a photograph of a Stadip® type 44.2 laminated glass panel produced by Saint-Gobain, coated with a decorative silver layer and protective varnish after conventional heat treatment, i.e., heating in an infrared oven so that the surface temperature of the laminated glass panel reaches 170°C for two minutes. Fig. 2b corresponding to the same laminated glass panel just before heat treatment.

[0069] We observe on the Fig. 2athat the coating process according to the prior art causes bubbling of the interlayer material, including quite far from the edges, bubbling which is not present just before the heating stage as shown by the Fig. 2b .

[0070] It is not cost-effective to consider such processes followed by a step of cutting the edges and downgrading them.

[0071] Throughout the entire heating and drying stage that follows the application of the decorative coating in the case of the glass panel Fig. 2b The temperature profile of the external surface of the decorative coating layer was monitored using six thermocouples distributed across this surface. This profile is reproduced on the Fig. 3 .

[0072] We observe on the Fig. 3that all points on the external surface of the protective layer reach a temperature above 170°C for at least 30 seconds and a temperature above 140°C for at least 2 minutes and 30 seconds.

[0073] In addition to bubbling, heat treatment drying can, in some cases, cause the polymer interlayer material to yellow, which can be problematic in certain decorative coating applications according to the invention. Yellowing is particularly undesirable when the decorative coating is mirror-like, as it alters the color of the image reflected by the mirror.

[0074] It therefore appears essential to modify the drying processes of the decorative coating layer 13 of the prior art if one seeks to form a decorative coating layer 13 on an external face of a laminated glass panel.

[0075] Applying the decorative layer to an external face of the already formed laminated glass is a mandatory step in the process according to the invention, despite its difficulty in implementation because it offers several advantages.

[0076] Firstly, this allows the appearance of a previously manufactured laminated glass panel to be changed, possibly on another production line, and the decorative coating to be chosen afterward, possibly on a case-by-case basis.

[0077] Secondly, layering at least two sheets of glass beneath the decorative coating improves the optical quality of the coated laminated glass, particularly when creating a laminated glass mirror. Each sheet of glass exhibits flatness defects with a spacing on the order of a meter and optical defects with a spacing on the order of 1 to 10 cm, but these cannot all be perfectly aligned when the two glass sheets are joined. Therefore, the optical distortions of the coated laminated glass on its outer surface are less pronounced than if the coating had been sandwiched between the two glass sheets.

[0078] The inventors initially considered reducing the setpoint temperature T_ext of the drying device, and / or the maximum surface temperature reached on the laminated glass panel, and / or the duration for which this maximum surface temperature is reached (or the heating time t_chauff at the setpoint temperature, this heating time t_chauff being correlated to the maximum surface temperature reached and the duration for which it is reached, as shown in Example 2) in the case of a laminated and non-monolithic glass panel. A simple reduction of these parameters is not straightforward because it leads to insufficient cross-linking of the decorative coating layer 13, particularly—where applicable—of the protective varnish layer, so that the decorative coating layer will not be sufficiently resistant for subsequent handling or use.For example, problems with flaking of the decorative coating layer 13 are observed when handling a given coated laminated glass panel, and problems with the bonding of coated laminated glass panels together during possible passages through an autoclave, or even insufficient resistance to corrosion.

[0079] To overcome the technical problem of obtaining a suitably cross-linked decorative coating layer in a time acceptable for an industrial process (particularly for a continuous manufacturing process, in which the laminated glass panel to be coated is moved at a constant speed on a production line), typically on the order of a few minutes or a few tens of minutes, the inventors therefore considered using chemical hardeners or chemical catalysts.

[0080] In particular, consideration may be given to incorporating into the decorative material in the fluid state a total proportion of one or more crosslinking catalysts and / or chemical hardeners P_cata equal to or greater than 0.1%, or equal to or greater than 0.5% by mass, 1% by mass, 2% by mass of the decorative material in the fluid state, 2.5% by mass of the decorative material in the fluid state and optionally less than 10% by mass of the decorative material in the fluid state, or even less than 5% by mass of the decorative material in the fluid state.

[0081] The protective varnish can be chosen, without limitation, from: commercial anti-corrosion varnishes from suppliers such as FENZI (for example FENZI One coat LF 3 grey SG varnish, FENZI one coat WBLF 6 varnish), VALSPAR (for example references SK1420 or SK1440) or EUROCOATINGS (for example eurocoatings glasskin007 varnish).

[0082] Regarding the chemical hardener or crosslinking catalyst, it can be chosen according to the fluid decorative material.

[0083] In particular, an acid catalyst such as hydrofluoric acid, phosphoric acid, para-toluenesulfonic acid, or any other transesterification catalyst may be used.

[0084] The fluid decorative material, in which at least one chemical hardener and / or at least one crosslinking catalyst has been incorporated, is then deposited on the upper face 11a1 of the laminated glass panel to be coated so as to form at least one layer of decorative coating 13. The deposition of the fluid decorative material can be carried out by means of a device for depositing a fluid material such as a curtain varnisher, a roller or a gun.

[0085] The thickness of at least one layer of decorative coating may be greater than 10 micrometers.

[0086] Then the decorative coating layer is dried in order to obtain its cross-linking and at least partial evaporation of the solvents.

[0087] The proportion P_cata of chemical hardener or crosslinking catalyst must be chosen to allow the decorative coating to be applied in a fluid state, particularly during an industrial process. Specifically, this proportion can be chosen to allow the decorative coating to be applied using a device such as a curtain machine. In particular, it is not possible to increase the proportion of chemical hardener or crosslinking catalyst excessively, as too high a proportion leads to the product solidifying at too low a temperature and / or too quickly. In such a case, the decorative material does not remain in a fluid state long enough to allow its application to the upper surface 11a1 of the laminated glass panel to be coated.

[0088] Uncontrolled mass formation also leads to the obstruction of pipes or transport elements through which the decorative material must flow.

[0089] The time to set the catalyst was evaluated by observation with the naked eye in the case where the crosslinking catalyst is para-toluenesulfonic acid incorporated into the fluid decorative material is One Coat LF3 from the Fenzi brand in a proportion P_cata expressed as a percentage of the mass of the fluid decorative material.

[0090] The results are summarized in Table 3 below: [Table 3]

[0091] Table 3: Time to solidify as a function of the proportion P_cata of crosslinking catalyst P_cata (%) Time to mass formation (qualitative h) 0,1 > 24 0,5 > 24 1 > 24 2,5 > 24 5 > 24 10 9-24 25 2 50 0,5

[0092] It is observed that an excessive proportion of chemical hardener or crosslinking catalyst leaves little time for subsequent processing steps of the fluid decorative material, particularly for its application to the laminated glass panel to be coated.

[0093] It is therefore necessary to find a compromise between the proportion of chemical hardener or crosslinking catalyst, the drying temperature and the drying time.

[0094] A proportion P_cata of chemical hardener or crosslinking catalyst less than or equal to 10% by mass of the fluid decorative material, or even 5% by mass of the fluid decorative material, or even 2.5% by mass of the fluid decorative material may be suitable for the implementation of the process according to the invention.

[0095] These experiments further demonstrate that the implementation of chemical hardeners or chemical catalysts for the decorative coating layer of a laminated glass panel is not done without inventive activity: the inventors tested numerous temperature rise / fall profiles for heating the laminated glass panel covered with a decorative coating layer before achieving a satisfactory result.

[0096] Some of these profiles are reproduced on the Fig. 4 on an experimental campaign carried out on Stadip ® type laminated glass panels < 44.2 PVB dimensions 800mmx600mm silvered with a layer of thickness 700 mg / m 2 < on which a layer of One Coat LF3 varnish from the Fenzi brand was deposited in which 0.5% by mass of para-toluenesulfonic acid was incorporated, with a thickness equal to 50 micrometers.

[0097] The results of these experiments can be seen in Table 1 below, in which the effects of heating are shown for each test in terms of: bubbling of intercalated layer 12 (observed with the naked eye) yellowing of intercalated layer 12 (observed with the naked eye)

[0098] The cross-linking of a decorative coating layer can be assessed using a rub test (also known as a smear test or abrasion resistance test), which measures the number of passes required to damage the coating. More specifically, a rub test determines whether a coating is sufficiently cured or cross-linked by evaluating its resistance to dilution in the presence of a solvent. Generally, a rub test involves saturating a cloth with a specific solvent, which is a known diluent for the coating material being tested. The cloth can be fabric or non-woven material, made of natural or synthetic fibers. The rub test then consists of a number of passes, rubbing the soaked cloth back and forth over a predetermined distance on the surface of the coating being tested, for example, 20 cm (centimeters). The test can be repeated in several locations on the surface of the coating being tested.The test is performed manually, or using a machine.

[0099] An example of a wiping test on the laminated glass panel is as follows: using a cloth (or "pad") made of cellulose reinforced with polypropylene or polyester (TORK ® brand "heavy duty cleaning cloth" reference 530276) with dimensions of 200 mm * 100 mm, the cloth being saturated in a solvent and having a contact surface with the panel to be tested of 3 cm², back and forth movements are made on the surface of the panel over a distance of 5 cm at a speed of movement between 15 m / min, the pressure exerted on the coating being controlled by means of a weight of 1 kg and therefore equal to 32.7 kPa (kilopascals).

[0100] The solvent used to saturate the cloth is xylene, a solvent known for the decorative coating layer 13 made from an organic-phase fluid. Water can be used to saturate the cloth if the decorative coating layer was made from an aqueous-phase fluid.

[0101] The decorative coating layer 13 is said to be properly crosslinked if the decorative coating layer is not dissolved in the solvent saturating the cloth after a predetermined number N of back-and-forth movements. In particular, the predetermined number N of back-and-forth movements can be greater than or equal to 20, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 60, greater than or equal to 70, greater than or equal to 80, greater than or equal to 90, greater than or equal to 100, greater than or equal to 200, greater than or equal to 500. [Table 1] Essay Chain speed (m / min) Maximum surface temperature reached °C duration (in s) during which the surface temperature is above: bubbling Yellowing Number of round trips for the "rub test" 100°C 120°C 130°C 1 1.5 90 0 0 0 No No 20 2 1.5 102 25 0 0 No No 20 3 1.5 131 220 85 10 No No 30 4 1.0 120 304 0 0 No No 30 5 1.0 119 280 0 0 No No 50 6 0.7 130 472 218 0 No No > 200

[0102] Table 1 shows that the choice of temperature profile allows control of the cross-linking of the decorative coating layer. Profiles 1 to 6 all achieve resistance to the crimping test exceeding 20 cycles without yellowing or bubbling of the interlayer layer 12.

[0103] It is recalled that these results were obtained with a proportion P_cata equal to 0.5% of para-toluenesulfonic acid incorporated in the One Coat LF3 fluid material from the Fenzi brand.

[0104] By comparing the results obtained for the six profiles, we can see that the maximum surface temperature reached has an impact on crosslinking.

[0105] By comparing the results obtained for profile 4 with those obtained for profile 5, or the results obtained for profile 3 with those obtained for profile 6, we can still see that the speed and / or duration during which this maximum surface temperature is reached allows us to modulate the crosslinking of the decorative coating layer 13.

[0106] Of the six temperature profiles described here, profile 6 allows for a very satisfactory crosslinking of the decorative coating layer 13 with a resistance to the scrunching test of more than two hundred back-and-forth movements.

[0107] These experiments were carried out in parallel with the experiments in example 1 and example 2 described later.

[0108] These numerous experiments enabled the inventors to define the characteristics of the drying stage which, in combination with the addition of a chemical hardener or a crosslinking catalyst in the decorative material in the fluid state, makes it possible to obtain on an industrial basis a laminated glass coated with a layer of decorative coating exhibiting satisfactory chemical and / or mechanical resistance and improved optical and / or decorative properties compared to the prior art.

[0109] In particular, it has been shown that the heating time t_chauff during which the coated laminated glass panel is dried by the heating device after this heating device has reached its setpoint temperature T_ext, this setpoint temperature T_ext and the ratio P_cata of the mass of chemical hardener or crosslinking catalyst and the mass of decorative material expressed as a percentage are three parameters which cannot be chosen independently of each other.

[0110] In one particular embodiment, the P_cata ratio is chosen from the range [0.1%, 5%], more specifically from the range [0.5%, 2.5%], or even more specifically [0.75%, 1.25%]. In another particular embodiment, the P_cata ratio is equal to 1%. For each of the four preceding options for choosing the P_cata proportion, the setpoint temperature T_ext can be selected: in the range [120°C; 140°C], the heating time t_heating is then less than or equal to 7.5 minutes and optionally greater than 3 minutes, in the range [100°C; 120°C], the heating time t_heating is then greater than or equal to 7.5 minutes; in particular if the upper glass sheet 11a is clear glass and has a thickness between 2 mm and 6 mm, and if the decorative coating layer has a thickness before drying between 50 µm and 200µm.

[0111] At least one layer of decorative coating includes at least one layer of reflective material, so as to form a mirror.

[0112] At least one layer of reflective material can be deposited by all the processes commonly used in the field of silvering.

[0113] The thickness of the reflective material layer is adjusted to achieve a surface mass of silver exceeding the standard of 700 mg / m². As the reflective material is susceptible to oxidation and has low mechanical resistance, a protective varnish layer can be applied over the reflective material layer.

[0114] The invention also relates to a laminated glass panel comprising at least two sheets of glass and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material, the laminated glass panel having a first outer face (11a1) referred to as the upper face (11a1) and a second outer face (11b1) referred to as the lower face (11b1),the panel being characterized in that the upper face (11a1) of the laminated glass panel is coated with at least one decorative coating layer (13) formed at least in part from an organic fluid decorative material applied to the upper face (11a1) of the laminated glass panel after the at least two successive sheets of glass have been assembled using the polymer interlayer material and in which the at least one decorative coating layer consists of a layer of reflective material so as to form a mirror and one or more layers of protective varnish, the thickness of the reflective material layer corresponding to a surface mass of silver greater than the standard of 700 mg / m².

[0115] In one embodiment, the polymer interlayer material does not exhibit any visible bubbling defects and withstands at least twenty rubs, or even thirty, fifty, one hundred, or two hundred rubs. The adhesion of the decorative coating layer 13 can be quantified at a value of no more than 2 in the cross-cut test according to ISO 2409. More specifically, the cross-cut test involves

[0116] A cutting tool is applied to the surface of the decorative coating 13, applying uniform pressure to create initial parallel incisions. This operation is repeated, overlapping the initial incisions with subsequent incisions at 90° to form a grid. Adhesive tape is then applied to the grid. The incisions penetrate the decorative layer 13, preferably down to the substrate. The adhesive tape is then removed at an angle close to 180°. Adhesion is then assessed based on the amount of coating torn off by removing the tape. A value of 2 corresponds to flaking along the incised edges and / or at the grid interaction points, affecting slightly more than 15% of the total gridded area. This quantification, according to ISO 2409, corresponds to the expected quantification for a decorative layer on monolithic glass or on silvered monolithic glass.

[0117] Such a product can currently only be obtained using the process according to the invention, for the reasons previously explained.

[0118] In one embodiment of the coated laminated glass panel, the interlayer polymer material is tinted. Since the laminated glass panel is coated with a reflective material to form a mirror, this arrangement makes it possible to obtain a tinted mirror, for example bronze in color, without having to resort to the usual, cumbersome, and costly mirror tinting processes.

[0119] In one embodiment of the coated laminated glass panel, heating elements are incorporated either in the polymer interlayer material or in at least one of the two glass sheets. For example, heating microfilaments can be embedded in PVB, or one of the two glass sheets or the glass panel itself can be of the EGLAS® type from Saint-Gobain®. This arrangement makes it possible to obtain a heated coated glass panel, such as a heated mirror, with improved mechanical strength compared to prior art solutions.

[0120] The invention also relates to the use of a laminated glass panel: in the building sector, particularly for the production of decorative partition walls or floors that meet the required safety standards, or in the furniture sector for the production of furniture including decorative walls or wall elements that meet the required safety standards, for example custom-made furniture. EXAMPLES Example 1: Crosslinking test Operating procedure:

[0121] A 3mm thick monolithic glass panel coated with a layer of Fenzi ONE COAT LF3 GREY SG varnish (Trade reference: 23689 at the date of first priority) of 100 µm thickness is applied using a film puller, varnish in which the paratoluenesulfonic acid crosslinking catalyst has been previously incorporated in a proportion P_cata expressed as a percentage of the mass of varnish.

[0122] The laminated glass panel thus coated is placed in a hot air oven whose setpoint temperature is T_ext for a duration t_chauff at this setpoint temperature.

[0123] In the case of the experiments in Example 1, the time required to reach the set temperature after inserting the laminated glass panel into the oven is on the order of 2.5 minutes, so the time spent by the laminated glass panel in the hot air oven is on the order of t_chauff+2.5 minutes.

[0124] After cooling, the quality of the crosslinking of the varnish layer is assessed using the Persoz hardness test. Persoz hardness test:

[0125] The hardness test is carried out using a Persoz automatic hardness measuring pendulum, in accordance with ISO1522.

[0126] The Persoz pendulum system allows the number of oscillations of a stainless steel pendulum, with a mass of 500 g, resting on a material (in this case on the external face of the decorative coating layer) to be measured via two tungsten carbide balls with a diameter of 8 mm spaced 50 mm apart.

[0127] A sample of coated laminated glass panel is inserted into the Persoz pendulum and placed coated face up.

[0128] The pendulum is released at an angle of 12°, the number of oscillations N2 of the pendulum is counted until the amplitude of the oscillations reaches an angle of 4°.

[0129] The more cross-linked the paint, the harder the paint surface, and consequently, the greater the number of oscillations. Results :

[0130] The test results are summarized in Table 2 below: [Table 2]

[0131] Table 2: Number of oscillations measured in the Persoz pendulum test as a function of T_ext, P_cata and t_chauff T_ext(°C) t _ heating (minutes) N2 for P _ cata = 0.1% N2 for P _ cata = 0.5% N2 for P _ cata = 1% N2 for P _ cata = 2.5% 80 0 57 53 50 32 80 2,5 64 54 47 31 80 5 60 56 58 40 80 7,5 66 57 57 40 100 0 63 59 57 34 100 2,5 72 64 56 43 100 5 76 73 79 71 100 7,5 88 80 98 78 120 0 62 60 50 38 120 2,5 78 82 131 122 120 5 84 108 148 129 120 7,5 137 136 159 146 140 0 66 64 106 87 140 2,5 119 124 144 133 140 5 151 146 165 151 140 7,5 175 170 174 169 160 0 99 86 115 80 160 2,5 172 168 140 128 160 5 192 193 144 132 160 7,5 193 201 152 143

[0132] It is observed that, regardless of the proportion of catalyst P_cata tested between 0.1% and 2.5%, a heating time t_chauff less than or equal to 10 minutes (duration typically compatible with an industrialized process), at a setpoint temperature T_ext = 80°C does not allow for satisfactory crosslinking, i.e. in this case a number of oscillations greater than or equal to 150 with the Persoz test.

[0133] The same applies for a setpoint temperature T_ext = 100°C.

[0134] From T_ext = 120°C, we observe that it is possible to obtain satisfactory crosslinking provided that a heating time t_chauff and a proportion of catalyst P_cata are provided in relation to this setpoint temperature T_ext.

[0135] Specifically, the following combinations: T_ext= 120°C, t_chauff = 7.5 minutes and P_cata= 1%; T_ext= 140°C, t_chauff = 7.5 minutes and P_cata= 0.1%, 0.5%, 1% or 2.5%; T_ext= 140°C, t_chauff = 5 minutes and P_cata= 0.1%, 1% or 2.5%; T_ext= 160°C, t_chauff = 2.5 minutes and P_cata= 0.1% or 0.5%; T_ext= 160°C, t_chauff = 5 minutes and P_cata= 0.1% or 0.5%; T_ext = 160°C, t_chauff = 7.5 minutes and P_cata= 0.1%, 0.5% or 1%; allow us to obtain satisfactory crosslinking, i.e. for this series of experiments a number of oscillations N2 greater than or equal to 150 with the Persoz test. Conclusion :

[0136] The experiment in Example 1 shows that, counterintuitively, the quality of the crosslinking does not always vary in the same direction as the P_cata proportion. In particular, a P_cata proportion that is too high can be counterproductive.

[0137] The experience of example 1 also proves that obtaining correct crosslinking of the decorative coating layer 13 depends on the combination of three parameters: the heating temperature of the laminated glass panel after application of the decorative material in the fluid state in which a chemical hardener or crosslinking catalyst is incorporated, the proportion of chemical hardener or crosslinking catalyst, and the duration of this heating for the purpose of drying.

[0138] This example should be combined with the evaluation of bubbling of the polymer interlayer material forming the interlayer layer 12 and optionally the yellowing of this material. To avoid any bubbling, the pair (setpoint temperature T_ext, heating time at this setpoint temperature t_chauff) must be chosen appropriately, the heating time being correlated to the proportion P_cata. Example 2: Estimation of the parameters T_ext, t_chauff and P_cata

[0139] A simplified model is put in place to estimate the parameters of the drying stage of the decorative coating layer. Model assumptions:

[0140] We consider in a first approach that the system formed by the upper glass sheet 11a and the decorative coating layer 13 has, at time t, a homogeneous temperature T(t) and is placed in contact with a thermostat at the temperature T 0 (T 0 being equal to T_ext when the coated laminated glass panel is placed in a hot air oven having reached its setpoint temperature T_ext) then.

[0141] Between two instants t and t+dt, the temperature T satisfies the following differential equation: h S T − T 0 = ρ c V dT dt

[0142] Where V is the volume of the system, S is the surface area of ​​the system in contact with the thermostat, c is the heat capacity of the system, ρ is the density of the system and h is the heat transfer coefficient characterizing the heat transfers between the system and the thermostat.

[0143] The solution to this differential equation is written: T t − T 0 T i − T 0 = exp − h S ρ c V t with T i = T(t=0)

[0144] The temperature of the upper glass sheet 11a and the decorative coating layer therefore follows an exponential evolution with characteristic time τ, where: τ = ρ c V h S = ρ c e h where e = V / S is the thickness of the system along the stacking direction (Z'Z) of the coated laminated glass panel.

[0145] This evolution is represented as an example on the figure 5 with the following parameters: ρ = masse volumique du verre = 2530 kg / m 3 c = capacité thermique massique du verre = 800 J / kg / K h = 100 W / m 2 / K T i = T t = 0 = 20 ° C

[0146] With these parameters, the characteristic time τ of the temperature variations T is on the order of 80 seconds. Conclusion :

[0147] We observe with the assumptions of this simplistic model that in the case of heating to T_ext = 160°C, the temperature T of the upper coated glass sheet 11a quickly reaches T = 80°C and then T = 100°C, respectively after 45s and 68s respectively.

[0148] The temperature rise is rapid, with a steady-state limiting temperature higher than the bubbling temperature of the interlayer polymer material. Thus, under such heating conditions, the interlayer polymer material will begin to bubble after a relatively short heating time t_chauff, particularly at the edges of the laminate where heat exchange with the interlayer layer 12 is amplified, and will then bubble throughout the mass of this interlayer layer 12.

[0149] We also observe that the time required for the temperature T of the system to rise from T = 80°C to T = 100°C naturally increases with the decrease in T 0, which makes it possible to increase the heating time t_chauff to perfect the crosslinking of the varnish without causing the PVB to bubble.

[0150] A more complex purely theoretical modelling and / or experimental results can be used for the choice of T_ext, t_chauff and P_cata.

[0151] Specifically, if the Biot number of the system is such that the assumption of temperature homogeneity T is not experimentally verified, it can be agreed that, as a precaution, to prevent bubbling of the polymer interlayer material, heating should be stopped at the latest when the system temperature T is equal to the limiting temperature T_lim at which bubbling of the polymer interlayer material is observed, minus a safety margin M_sec. Furthermore, the decorative coating layer 13, however thin, acts as a thermal shield, delaying heat transfer.

[0152] The thermal effusivity of the glass constituting the upper glass sheet 11a can also impact the characteristic time of heat transfer to the polymer interlayer material.

[0153] For example, we can take into account all of these influencing factors by considering that the parameters of the drying stage must be chosen so that the temperature T_max reached by the system, and in particular by the external surface of the system, after a heating time t_chauff is equal to T_lim - M_sec.

[0154] Particularly in the case of the coated laminated glass panel used for example 1, where the polymer interlayer material is PVB, we can consider that the combination of heating times t_chauff and temperature T_ext = T_0 corresponding to the hatched area on the figure 5 between the curves T_0 = 100°C and T_0 = 140°C is suitable, provided that the proportion of chemical hardener or crosslinking catalyst is compatible with the corresponding heating times t_chauff. LIST OF REFERENCE SIGNS

[0155] 1: Coated laminated glass panel 11a: Top glass sheet 11a1: Top face of the laminated glass panel to be coated 11b: Bottom glass sheet 11b1: Bottom face of the laminated glass panel to be coated 12: Interlayer of polymer material 13: Decorative coating layer

Claims

1. A method of coating a laminated glass panel comprising: - a laminated glass panel to be coated is provided, comprising at least two sheets of glass (11a, 11b) and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material forming, after assembly, an interlayer (12), the laminated glass panel to be coated having at least one upper face (11a1) to be coated; - a fluid decorative material is provided; - a chemical hardener or a cross-linking catalyst is incorporated into the fluid decorative material in a ratio P_cata between the mass of the chemical hardener or cross-linking catalyst and the mass of the decorative material in the determined fluid state; - at least one decorative coating layer (13) is formed by applying the decorative material in the fluid state, in which the chemical hardener or the cross linking catalyst is incorporated, to the upper face (11a1) of the laminated glass panel to be coated; - the decorative coating layer is dried by heating the laminated glass panel thus coated by means of a drying system, the set point temperature (T_ext) of which is greater than or equal to 100°C and less than 140°C, method wherein the at least one decorative coating layer consists of a layer of reflective material in order to get a mirror and of one or more layers of protective varnish, the thickness of the layer of reflective material corresponding to a silver surface mass above the standard of 700 mg / m2.

2. A method of coating a laminated glass panel according to claim 1 wherein the polymer interlayer material is selected from polyvinyl butyral, ethylene vinyl acetate, an ionoplast polymer, thermoplastic polyurethane and a casting resin.

3. Process for coating a laminated glass panel according to one of the preceding claims, in which the at least one decorative coating layer consists either of a layer of reflective material and one or more layers of protective varnish or of one or more layers of lacquer and optionally of one or more layers of protective varnish.

4. Process for coating a laminated glass panel according to one of the preceding claims, in which the ratio P_cata of the mass of the chemical hardener or cross linking catalyst and the mass of the decorative material in the fluid state is greater than 0.1%.

5. Process for coating a laminated glass panel according to one of the preceding claims in which: - if the set temperature of the drying system (T_ext) is chosen in the range [100°C, 120°C], said heating time (t_chauff) by means of the drying system is greater than or equal to 7.5 minutes and said ratio P_cata is chosen in the range [0.1% ; 5%] , - and if the set point temperature of the drying system (T_ext) is chosen in the range [120°C, 140°C], said heating time (t_chauff) by means of the drying system is less than or equal to 7.5 minutes and greater than or equal to 3 minutes and said ratio P_cata is chosen in the range [0.1%; 5%].

6. Process for coating a laminated glass panel according to one of the preceding claims, in which the chemical hardener or the cross linking catalyst is chosen from acid catalysts and optionally from hydrofluoric acid, phosphoric acid and para toluenesulphonic acid.

7. Method according to any one of the preceding claims comprising a step in which the heating time (t_chauff) of the laminated glass panel at the set point temperature (T_ext) and / or the ratio P_cata of the mass of the chemical hardener or cross linking catalyst and of the mass of the decorative material in the fluid state during incorporation is determined depending on said set point temperature (T_ext).

8. Laminated glass panel comprising at least two sheets of glass and in which at least two successive sheets of glass are assembled by means of a polymer interlayer material, the laminated glass panel having a first outer face (11a1) referred to as the upper face (11a1) and a second outer face (11b1) referred to as the lower face (11b1), the panel being characterized in that the upper face (11a1) of the laminated glass panel is coated with at least one decorative coating layer (13) formed at least in part from an organic fluid decorative material applied to the upper face (11a1) of the laminated glass panel after the at least two successive sheets of glass have been assembled by means of the polymer interlayer material and wherein the at least one decorative coating layer consists of a layer of reflective material in order to get a mirror and of one or more layers of protective varnish, the thickness of the layer of reflective material corresponding to a silver surface mass above the standard of 700 mg / m2.

9. Laminated glass panel according to the preceding claim in which: the polymer interlayer material does not have any bubbling defects observable to the naked eye, and the decorative coating layer (13) withstands at least twenty passages of a rub test carried out by rubbing the surface of the decorative coating layer (13) over a determined distance using a cloth ) made of cellulose reinforced with polypropylene or polyester measuring 200 mm * 100 mm, the cloth being soaked in a solvent for the decorative coating layer (13) and having a contact surface area with the panel to be tested of 3 cm2, back and forth across the surface of the panel over a distance of 5 cm at a speed of movement of between 15 m / min, the pressure exerted on the coating being controlled by means of a weight of 1 kg.

10. Laminated glass panel according to claim 9, the decorative coating layer (13) of which withstands at least two hundred rub-test passes.

11. A laminated glass panel according to any one of claims 8 to 10 in which the polymer interlayer material is tinted.

12. A laminated glass panel according to any one of claims 8 to 11 in which heating resources are incorporated in the polymer interlayer material or in at least one of the at least two sheets of glass.

13. Use of a laminated glass panel according to any one of claims 8 to 12 in the building or furnishing sector.