Heat-treatable coloured glazing unit for solar applications

Abstract

A heat-treatable coloured glazing unit and a method for its production, where the glazing unit (1) includes at least a transparent or translucent glass substrate (11) and a selectively reflective coating (12) being at least partially applied to a first surface (111) of said substrate and consisting of a full-dielectric non-periodic thin-film interference filter comprising: a base layer (121); a reinforcing layer (122); a spectrally controlling system (123), itself comprising at least a plurality of consecutive high-refractive index layers (1231), a variable refractive index layer (1232) and an additional layer either consisting of a high- or a medium- refractive index layer (1233); and a capping layer (124).

Description

DescriptionTitle of Invention: Heat-treatable coloured glazing unit for solar applicationsTechnical Field

[0001] The invention relates to a heat-treatable coloured glazing unit particularly suitable for the aesthetic design of solar energy systems, such as, but not limited to BIPV (building integrated photovoltaic) and BIST (building integrated solar thermal) facades.Background Art

[0002] To respond to the growing importance of the building integrated photovoltaic (BIPV) sector, a whole range of photovoltaic (PV) solar energy conversion devices customisable in terms of dimensions, shapes, cells arrangement, opacity, and functionalities has emerged this last decade. New solutions make PV devices applicable to almost the entire building envelope (roofs, cladding, curtain walls, skylights, and other fagade elements such as balustrades).

[0003] On the aesthetic side, tendency is towards the camouflage of the active parts of the PV devices (near black-purple-indigo PV cells, metallic interconnectors, etc.). Colours, structures, set of textures, patterns, surface finishes are all design options that drastically increase the acceptance of PV devices as integrated elements of the building envelope1.

[0004] The building integrated solar thermal (BIST) sector is also concerned by this desire for aesthetic improvement and much research activities aiming at the aesthetic design and integration improvement of thermal solar collectors, have been carried out since the 2000s2.

[0005] The colouration of a solar energy conversion device can, amongst other options, be obtained by using coloured glazing unit, either as the front cover or as an interlayer located between the front cover and the active part (i.e., PV cell or thermal absorber) of such a device.

[0006] Colouration is generally obtained by applying to the glazing unit a coating that include absorbing pigments (e.g., ceramic or inks). The method allows an easy and almost infinite choice of colours as well as a high personalisation degree but since the colour is created by the absorption of a part of incoming solar radiation, resulting products are characterised by high efficiency losses as compared to conventional solar devices, thus still limiting their implementation in building projects.

[0007] Colouration can alternatively be obtained by applying a selectively reflective coating on the glazing unit. The method, by creating colour by reflection rather than by absorption, allows the minimisation of efficiency losses to acceptable levels.

[0008] For example, document W03004079278A1 discloses a glazing unit including a selectively reflective coating, consisting of a thin-film interference filter constructed as a periodic and symmetric alternation of high- (H) and low- (L) refractive index layers, for the aesthetic design of solar thermal collectors.

[0009] However, although allowing a great improvement of the overall appearance of solar thermal collectors, the method has been avoided due to strong colour angular variations which are generally not desired in the building sector.

[0010] Document EP3586071 B1 discloses a glazing unit comprising a photonic structure that limits the problem of the angular colour dependency while maintaining efficiency losses to acceptable levels.

[0011] The photonic structure consists of a periodic and symmetric full-dielectric interference filter (i.e., Bragg or similar filter) and a structured surface of a substrate on which the coating is applied, the structured surface compensating the lack of angular colour stability of the interference filter.

[0012] The document is silent regarding the quantification of the colour angular stability, but figures that can be found in a related articles3’4show that photonic structures lead to saturated colours characterized angular variations that are still relatively important.

[0013] Documents EP2897795B9 and EP2898534A1 discloses glazing units including selectively reflective coatings that further limits the problem of the angular colour dependency.

[0014] The selectively reflective coating consists here of a full-dielectric interference filter constructed as a periodic, but asymmetric alternation of H and L layers, where the coating asymmetry leads to higher colour angular stability as compared to precited documents.

[0015] However, periodic filters, even asymmetrically constructed, are lacking in terms of achievable colours. A wide palette of colours can only be produced by using various pairs of H / L materials in parallel (i.e., producing some colours from one pair of H / L materials and producing some other colours from another pair of H / L materials), which implies frequent changes of the industrial coater’s configuration, especially when considering PVD (physical vapour deposition) processes, and thus leads to frequent downtime.

[0016] Moreover, selectively reflective coatings disclosed in the precited documents include thick layers, and especially thick H layers imposing very limited deposition speeds and thus leading to high production costs.

[0017] Furthermore, the deposition of thick H layers, leads to stress accumulation within the multilayered interference filter, the latter being responsible for cracking, delamination and bowing of thin substrates during heat treatments.

[0018] Since the use of tempered front covers on building integrated solar energy conversion devices is a safety requirement that is mandatory in most specifications and building codes, the lack of heat-treatability of the glazing units disclosed in the aforementioned documents imposes “cut, temper, then coat” procedures that are not compatible with effective and cost-efficient industrial production.

[0019] Building integrated solar devices are generally characterized by shapes and dimensions which are unique to a specific building project. The lack of thermal treatability of such interference filters therefore also prohibits the constitution of stocks of coloured glass which burdens the production management.

[0020] Finally, since the coating of non-flat substrates by in-line coating processes is not permitted, the lack of heat-treatability and therefore heat-bendability of the glazing units depicted in precited documents precludes their use on curved or shaped building's envelope areas.

[0021] Starting from this prior art, the object of the present invention is to provide a glazing unit of improved properties.

[0022] The object is achieved according to the invention by a glazing unit according to claim 1 , a method for producing this glazing unit according to claim 12, a photovoltaic module that includes at least one glazing unit according to claim 13 and a solar thermal collector that includes at least one glazing unit according to claim 14. Advantageous developments of the invention can be found in the subclaims.Summary of Invention

[0023] Glazing units comprising selectively reflective coatings are of particular interest for the aesthetic design of solar energy systems such as solar facades, since they can procure a coloured appearance to such systems while maintaining their solar energy conversion rates at acceptable levels. It is however important that the colour angular instability which generally characterizes this type of products, and which is not desired in the building sector is limited.

[0024] Developments conducted in the past years made it possible to achieve this objective, but resulting selectively reflective coatings, consisting of full-dielectric periodic thin-film interference filters are incompatible with effective and cost-efficient industrial production, especially when in-line PVD (Physical Vapour Deposition or sputtering) processes are considered (cf. low deposition speed, frequent downtime due to modifications of the coater’s configuration and lack of heat-treatability imposing just- in-time production).

[0025] The present invention offers a solution to the problem mentioned hereinabove by providing a glazing unit, comprising a selectively reflective coating consisting of a full-dielectric non-periodic thin- film interference filter, that is heat-treatable and producible in a large variety of substantially angularly stable colours with a unique coater’s configuration, thus allowing a simplification of the production management and opening up new perspectives of application in the building sector (e.g., curved or shaped building’s envelope areas), but also in other sectors such as VIPV (vehicle integrated photovoltaics) with, for example, electric car curved photovoltaic roof tops.Brief Description of Drawings

[0026] Fig. 1 A shows the typical layout of a glazing unit 1 intended to be assembled to a solar thermal conversion device where, the spectrally selectively reflective coating 12, lying on a first surface 1 1 1 of a glass substrate 1 1 , characterized by nsuB comprised between 1 .4 and 1 .6 at the wavelength of 550 nm, is in direct contact with air 2, characterized by HEMA=1 , and where the second surface of the substrate 1 12 is in direct or indirect contact with an incident medium consisting of air, characterized by niNc = 1 .

[0027] Fig. 1 B shows the typical layout of a glazing unit 1 intended to be assembled to a photovoltaic conversion device where, the spectrally selectively reflective coating 12, lying on a first surface 1 1 1 of a glass substrate 1 1 , characterized by nsuB comprised between 1 .4 and 1 .6 at the wavelength of 550 nm, is in direct contact with an encapsulation layer 3, characterized by HEMP comprised between 1 .3 and 1 .7 at the wavelength of 550 nm, and where the second surface of the substrate 1 12 is in direct or indirect contact with an incident medium consisting of air, characterized by niNc = 1 .

[0028] Fig. 2 shows the detailed layout of a heat-temperable glazing unit 1 of the present invention in its minimal configuration, where a selectively reflective coating 12 being at least partially applied to a first surface 1 1 1 of a glass substrate 1 1 comprises a base layer 121 ; a reinforcing layer 122; a spectrally controlling system 123, itself consisting of a plurality of consecutive high-refractive index layers 1231 , a variable refractive index layer 1232 and an additional layer consisting of a high- or medium- refractive index layer 1233; and a capping layer 124.

[0029] Fig. 3 shows a possible assembly of a glazing unit of the invention with a photovoltaic conversion device. Here, a glazing unit 1 A is assembled as the front cover of a PV device 4A, including at least one PV cell 41 A by the help of an encapsulation layer 3A, with the selectively reflective coating 12A applied on the surface 1 1 1 A of a glass substrate 1 1 A which is opposite to incident solar radiation 5.

[0030] Fig. 4 shows another possible assembly of a glazing unit of the invention with a photovoltaic conversion device. Here, a glazing unit 1 B is assembled as an interlayer located between the conventional front cover 6 and the active parts i.e., at least one PV cell 41 B of the PV device 4B by the help of two encapsulation layers 3B and 3C, the selectively reflective coating 12B being located on the surface 1 1 1 B of the glass substrate 1 1 B which is opposite to incident solar radiation 5.

[0031] Fig. 5 shows a possible assembly of a glazing unit of the invention with a solar thermal conversion device. Here, a glazing unit 1 C used as the front cover of a ST device 7A, is directly mounted, in front of a thermal absorber 71 A, into or onto the frame 8A of such a device, with the selectively reflective coating 12C being located on the surface 1 1 1 C of the glass substrate 1 1 C which is opposite to incident solar radiation 5.

[0032] Fig. 6 shows another possible assembly of a glazing unit of the invention with a solar thermal conversion device. Here, a glazing unit 1 D is integrated to a multi-layered glazed structure additionally including a transparent or translucent substrate 9 and an encapsulation layer 3D before its mountinginto / onto the frame 8B of a ST device 7B, with the selectively reflective coating 12D being located on the side 1 1 1 D of the glass substrate 1 1 D which is opposite to the incident solar radiation 5.Description of Embodiments

[0033] The present invention discloses a heat-treatable coloured glazing unit according to claim 1 , that is particularly suitable for the aesthetic design of solar systems such as, but not limited to BIPV (building integrated photovoltaics) and BIST (building integrated solar thermal) facades.

[0034] The glazing unit of the invention 1 comprises or consists of a transparent or translucent glass substrate 1 1 , and a selectively reflective coating 12, being at least partially applied, on a first surface 1 1 1 of said substrate.

[0035] The substrate consists of a material preferably chosen amongst borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, or soda-lime glass characterized by a thickness preferably comprised between 1 mm and 19 mm.

[0036] The second surface of the substrate 1 12 is possibly structured, textured or both structured and textured.

[0037] The second surface of the substrate can further comprise an additional coating whose purpose can either be functional (e.g., heat-treatable anti-reflective coating) or decorative (e.g., a ceramic frit pattern or logo).

[0038] The selectively reflective coating consists of a thin-film interference filter preferably deposited by plasma processes, more preferably by PVD (physical vapour deposition), CVD (chemical vapour deposition) or combination of both processes, most preferably by in-line PVD processes.

[0039] The selectively reflective coating is designed by numerical simulation with the help of commercial thin-film design software packages well known to those skilled in the art, such as OptiLayer5or TFCalc6, which by an iterative approach optimize (or “refine”) various coating characteristics (e.g., sequence of layers, refractive index, thickness) to reach the desired and initially defined optical coating characteristics (e.g., reflectance / transmittance at a given wavelength or in a specific range of wavelengths, colour coordinates at a specific incidence angle or within a specific range of incidence angles).

[0040] Depending on application, the selectively reflective coating is either in direct contact with air 2 (e.g., ST device), or with an encapsulation layer 3, preferably consisting of crosslinking or thermoplastic polymers such as EVA, PVB, POE, TPO, TPU, or silicone (e.g., PV device). The optimisation of the interference filter is therefore conducted for an incident medium air characterized by niNc = 1 , a substrate characterized by a refractive index nsuB typically comprised between 1 .4 and 1 .6 at the wavelength of 550 nm, and either for an exit medium air (EMA) characterized by HEMA = 1 , or for an exit medium polymer (EMP) characterized by HEMP typically comprised between 1 .3 and 1 .7 at the wavelength of 550 nm, accordingly to the layouts respectively depicted in Figures 1 A and 1 B.

[0041] In the context of the present invention, it is desirable to provide a glazing unit declinable in a large variety of substantially angularly stable colours which are of particular interest for building facades, especially relatively light and relatively desaturated colours, such as light greys and beiges that match the conventional building construction materials (e.g., concrete, stone).

[0042] A first object of this invention is therefore to provide a selectively reflective coating which is spectrally tuneable to provide a glazing unit characterized, either for an EMA or an EMP, depending on application, by:

[0043] a glass-side reflective L‘o- value (simulated or measured) preferably higher than 40,

[0044] a glass-side reflective a‘o- value (simulated or measured) preferably comprised between about -25 and +25, most preferably comprised between about -15 and +15,

[0045] a glass-side reflective b‘o- value (simulated or measured) preferably comprised between about -25 and +25, most preferably comprised between about -20 and +20,

[0046] C ab value preferably lower than 35, most preferably lower than 25,

[0047] AE‘ o°->55 value preferably lower than 9 and most preferably lower than 6,

[0048] Where:

[0049] L*o° indicates lightness and a‘o- and b‘o- are chromaticity coordinates in the CIE 1976 L*a*b* colour space (also referred as to CIELAB) at a normal incidence angle (i.e., at 0°), under CIE-D65 illuminant,

[0050] C ab refers to the colour saturation at normal incidence defined by C*ab = (a*o°2+ b*o°2)1 / 2

[0051] AE1o°->55° represents the variation of the glass-side reflective colour of the glazing unit between an incidence / observation angle of 0° and an angle of 55°, defined by AE*o°->55° = ((L*55° - L*o°)2+ (a*55° - a*o°)2+ (b‘55- - b*o°)2)1 / 2, where (L*o°, a*o°, b‘o-) and (L*55°, a*55°, b‘55-) are respectively the colour coordinates in the CIELAB colour space at 0° and 55°, under CIE-D65 illuminant.

[0052] Another object of this invention is to provide a glazing unit able to effectively mask the technical parts (e.g., PV cells, solar absorber) of the solar conversion device to which it is assembled. It is therefore a question here of providing, either for EMA or EMP, depending on application, a glazing unit characterized by a visible reflectance Rvis (i.e., the spectral reflectance, simulated under WHITE illuminant or measured, in the 380 to 780 nm wavelength range) preferably higher than 14 %, most preferably higher than 16 %.

[0053] It is also desirable that the solar transmittance Tsoi(i.e., the spectral transmittance, simulated under WHITE illuminant or measured, in the 300 to 2500 nm wavelength range) of the glazing unit, for EMA or EMP, depending on application, remains higher than about 75 % to maintain the efficiency of the solar energy conversion device assembled with such a glazing unit to an acceptable level. Thisminimal Tsoivalue is however non-binding, since most architects and end-customers are ready to go below this value provided that the solar facade has the desired aesthetics.

[0054] Another object of this invention is to limit downtime by providing a palette of colours that are all producible with a unique coater configuration, the coater preferably consisting of an industrial in-line PVD coater.

[0055] Another object of this invention is to weight down production management by providing a selectively reflective coating that is constructed in such a way that the glazing unit is heat treatable. By heat treatable, it must be understood a glazing unit which after a heat treatment (HT) i.e., thermal tempering, heat bending or thermal heat strengthening process at a temperature of at least about 580 degrees C for a period of several minutes, is:

[0056] free from visible defects such as burns, cracks, scratches, oxidation / corrosion spots, roller pluck and haze, under an artificial sky according to the EN 1096-1 , and

[0057] characterized by limited straightness deviations and presents a normal fragmentation pattern as per EN 12150-1 / -2 or other equivalent international standards, and

[0058] characterized by a colour difference AE*AN->HT as compared to the glazing unit before HT preferably lower than 9, most preferably lower than 6, AE*AN->HT being defined by AE*AN->HT = ((L*HT - L*AN)2+ (a*HT - a*AN)2+ (b*m - b*AN)2)1 / 2, where (L*AN, a*AN, b*AN) and (L*HT, a*m, b*m) are respectively the glass-side colour coordinates in the CIELAB colour space of the glazing unit before and after HT, measured at a normal incidence for EMA, under CIE-D65 illuminant.

[0059] The value of AE*AN->HT is not in itself binding since there is no question in the context of this application of mixing HT glazing units with non-HT glazing units on a fagade project, but a low value, on the one hand confirms the good thermal stability of the coating and, on the other hand, helps to build up a portfolio.

[0060] In general, all objects and / or needs listed hereinabove are fulfilled by providing a glazing unit 1 , as represented in Fig. 2, comprising a transparent or translucent glass substrate 1 1 characterized by a thickness tsuB preferably comprised between 3 mm and 6 mm, and a refractive index nsuB comprised between 1 .4 and 1 .6 at the wavelength of 550 nm and a selectively reflective coating 12 being at least partially deposited on a first surface 1 1 1 of said substrate, consisting of a full-dielectric non-periodic multi-layered thin-film interference filter, that comprises:

[0061] A base layer 121 in direct contact with the substrate, aimed at ensuring good adhesion levels between the coating and the substrate and at improving the thermal and chemical stability of the overall coating stack,

[0062] A reinforcing layer 122 aimed at filling and sealing any possible crack or pinhole of the base layer on which it is lying, thus further enhancing the thermal stability of the coating,

[0063] A spectrally controlling system 123, configurable to provide a large variety of substantially angularly stable colours with a single coater configuration,

[0064] A capping layer 124 aimed at protecting the full coating stack against environmental influences and avoiding the presence of visible defects such as scratches.

[0065] Where:

[0066] The base layer 121 consists of a medium refractive index layer preferably comprising nitrogen rich silicon oxynitride SiOxNy (i.e., 0 < x / (x+y) < 0.5), being possibly additionally doped by Al, characterized by a refractive index comprised between 1 .75 and 2.1 at the wavelength of 550 nm and deposited to a thickness preferably comprised between about 20 and 120 nm, most preferably between about 20 and 60 nm,

[0067] The reinforcing layer 122 consists of a low refractive index layer preferably comprising oxygen rich silicon oxynitride SiOxNy (i.e., 0.5 < x / (x+y) < 1), being possibly additionally doped by Al, characterized by a low refractive index comprised between 1 .4 and 1 .75 at the wavelength of 550 nm and deposited to a thickness preferably comprised between about 5 and 50 nm, most preferably between 10 nm and 30 nm,

[0068] The spectrally controlling system 123 consists of a non-periodic arrangement of dielectric layers, comprising at least:

[0069] A plurality of consecutive high refractive index layers 1231 (i.e., a minimum of two consecutive high refractive index layers) consisting of NbOx, TaOx, TiOx, ZrOx, or mixtures of these, possibly additionally containing dopants such as Ce, Co, Cu, Cr, Fe, Mn, or Mo, characterised by a refractive index comprised between about 2.1 and 2.6 at the wavelength of 550 nm, deposited to a thickness preferably comprised between about 5 nm and 60 nm, most preferably comprised between 5 and 30 nm, where two contiguous layers are characterized by two different refractive indices.

[0070] A variable refractive index layer 1232 preferably consisting of SiOxNy with 0 < x / (x+y) < 1 , possibly additionally containing Al as dopant, characterised by a refractive index tuneable between about 1 .4 and 2.1 at the wavelength of 550 nm and deposited to a thickness preferably comprised between about 10 nm and 120 nm, most preferably comprised between about 10 nm and 90 nm,

[0071] One additional layer 1233 either consisting of a high refractive index layer comprising a material chosen amongst NbOx, TaOx, TiOx, or ZrOx, or mixtures of these, possibly additionally containing dopants such as Ce, Co, Cu, Cr, Fe, Mn, or Mo, characterised by a refractive index comprised between about 2.1 and 2.6 at the wavelength of 550 nm and deposited to a preferred thickness comprised between about 5 nm and 60 nm, most preferably comprised between 5 and 30 nm, or of a medium refractive index layer consisting of SiOxNy (i.e., 0 < x / (x+y) < 0.5), being possiblyadditionally doped by Al, characterized by a medium refractive index comprised between 1 .75 and 2.1 at the wavelength of 550 nm and deposited to a thickness preferably comprised between about 10 nm and 120 nm, most preferably comprised between about 10 nm and 90 nm.

[0072] The capping layer 124 consists of a low-refractive index layer comprising SiOx, AIOx or mixture of these, characterized by a refractive index comprised between 1 .4 and 1 .75 at the wavelength of 550 nm and deposited to a thickness preferably comprised between about 20 nm and 120 nm, most preferably comprised between about 20 nm and 60 nm.

[0073] The spectrally controlling system is depicted hereinabove in its minimal configuration. It can of course include more than two consecutive high-refractive index layers and further comprise additional low-, medium-, high-, and / or variable- refractive index layers between the additional layer 1233 of the spectrally controlling system 123 and the capping layer 124, without departing from the scope of the present invention.

[0074] In the same way, the addition of any structure, texture, or combination of both, on the first surface 1 1 1 of the substrate 1 1 does not change the scope of the invention as defined in the appended claims.

[0075] In a preferred embodiment, the selectively reflective coating that fulfils all objects and / or needs listed hereinabove is a non-periodic arrangement of type M1L1H1H2H3VH4H5M2L2, wherein:

[0076] Mi denotes a first medium refractive index layer comprising Al doped SisN4, characterized by HMI = 2.06 + / - 0.04 at 550 nm and 20 nm < tMi 60 nm,

[0077] Li denotes a first low refractive index layer comprising Al doped SiC>2, characterized by nu = 1 .48 + / - 0.04 at 550 nm and 10 nm < tn < 30 nm,

[0078] Hi denotes a first high refractive index layer comprising TiC>2, characterised by nm =2.45 + / - 0.04 at 550 nm and 5 nm < tm 30 nm,

[0079] H2 denotes a second high refractive index layer comprising Nb2Os, characterised by nH2 = 2.36 + / - 0.04 at 550 nm and 5 nm < tH2 30 nm,

[0080] H3 denotes a third high refractive index layer comprising TiC>2, characterised by nH3 =2.45 + / - 0.04 at 550 nm and 5 nm < tH3 30 nm,

[0081] V denotes a variable refractive index layer comprising Al doped SiOxNy, characterised by 1 .4 < nv 2.1 at 550 nm and 10 nm < tv 90 nm,

[0082] H4 denotes a fourth high refractive index layer comprising TiC>2, characterised by nm =2.45 + / - 0.04 at 550 nm and 5 nm < tm^ 30 nm,

[0083] Hs denotes a fifth high refractive index layer comprising Nb20s, characterised by nns = 2.36 + / - 0.04 at 550 nm and 5 nm < tns^ 30 nm,

[0084] M2 denotes a second medium refractive index layer comprising Al doped SisN4, characterised by nM2 = 2.06 + / - 0.04 at 550 nm and 10 nm < tM2 90 nm,

[0085] L2 denotes a second low refractive index layer comprising Al doped SiC>2, characterized by ni_2 = 1 .48 + / - 0.04 at 550 nm and 20 < ti_2^ 60 nm,

[0086] and wherein H3, H4, Hs and M2 are optional layers.

[0087] It has been found that the aperiodicity of the selectively reflective coating, beyond allowing the introduction of buffer, reinforcing and capping layers that considerably improves the chemical and thermal stability as well as the visual quality of the overall coating stack, provides an excellent control over the colour angular stability, while the introduction of the V layer facilitates the fine tuning of the colour over a wide range of lightness values.Examples

[0088] Examples of coating stacks leading to heat-treatable glazing units of highly angularly stable relatively light desaturated colours are given in Table 1 (see Ex. A to Ex. F).

[0089] Thicknesses of the different layers constituting the coating stack are given in manometers.

[0090] Since V layer is characterized by a tuneable refractive index, nvvalues at the wavelength of 550 nm are also given for each example in Table 1 .

[0091] Values at 550 nm of the respective refractive indices of the other constituting layers of the coating stack are as follows: HMI = nM2 = 2.06; nu = ni_2 = 1 .48; nw = nH3 = nH4 = 2.45 and nH2 = HHS = 2.36.

[0092] Characteristics of glazing units consisting of these coating stacks deposited on the surface opposite to incident solar radiation of extra-clear float glass substrate, characterized by tsuB = 4 mm and nsuB = 1 .51 at 550 nm, are given in Table 2.

[0093] L*, a*, and b* are the glass side colour coordinates, Cab* is the colour saturation and AE*o°->55° is the colour angular variation of these glazing units, under CIE-D65 illuminant.

[0094] Rvis and Tsoiare respectively the visible reflectance and the solar transmittance under WHITE illuminant.

[0095] Perceived colour corresponds to the glass-side reflective colour at normal incidence of a glazing unit after heat-treatment and assembly to a solar conversion device.

[0096] Characteristics of Ex. A are given for EMA (e.g., ST device) whereas characteristics of Ex. B to F are given for EMP (e.g., PV device).

[0097] It should be noted that all examples of glazing units provided in this application are producible with a unique PVD coater’s configuration, provided that the latter is configured to produce designs of the type M1L1H1H2H3VH4H5M2L2.

[0098] Table 1

[0099] Table 2Industrial Applicability

[0100] The selectively reflective coating of the invention is optimized with the help of a commercial thin - film optical simulation software, as follows:

[0101] Step 1 : defining the coating environment i.e., defining the nature and the thickness of the substrate, the side of the substrate on which the coating is intended to be applied, an incident medium and an exit medium.

[0102] Step 2: defining analysis parameters such as the reference wavelength, the illuminant, the range of incidence angle of light radiation, and the spectral range to be considered.

[0103] Step 3: defining, based on experience, a first set of characteristics for the coating stack, i.e., attributing to each layer of the M1L1H1H2H3VH4H5M2L2 coating stack a material (or a mixture of materials) being either defined by a fixed refractive index value or by a variable refractive index value aimed at being optimized within specific ranges of values, and an initial thickness that can be constrained in a certain range of values or not.

[0104] Step 4: defining a set of desired coating specifications including the colour coordinates to be reached at a specific incidence angle, or within a specific range of incidence angles, and / or the optical characteristics to be reached i.e., reflectance and / or transmittance values to be reached at a specific wavelength or within a specific range of wavelengths.

[0105] Step 5: running optimization mode of the simulation software, which, by an iterative approach adapt the coating characteristics (e.g., thickness and / or refractive index of each layer) defined in step 3 to get as close as possible to the desired specifications defined in step 4.

[0106] Depending on the simulation results, the initial set of coating characteristics defined in step 3 and / or the set of desired coating specifications defined in step 4 can be adapted, and step 5 reconducted. This iterative process is conducted as many times as needed. When simulation results are satisfying, the optimized multi-layered stack is translated to a coating recipe.

[0107] Coating recipe is transferred to an industrial coating machine preferably consisting of an in-line PVD coater equipped by successive magnetron compartments in which sputtering targets are installed according to a specific sequence that allows the deposition, one after the other (i.e., one on top of the other) of the constituting layers of the coating recipe to be produced.

[0108] Magnetron compartments dedicated to the production of L, M and V layers are preferably equipped by metallic targets that are reactively sputtered in Ar / 02, Ar / N2, or Ar / N2 / C>2 gas mixtures, whereas the production of H layers is preferably conducted from oxidic targets that are reactively sputtered in Ar / 02 gas mixtures.

[0109] Within the framework of the present invention the sequence of sputtering targets is preferably settled once for all to avoid downtime related to changes in the configuration of the coater. It is therefore preferable to install the sequence of targets allowing the production of the most complex coating recipe and to turn off certain compartments to produce the simplest recipes. In the context of the present invention, the coater is preferably settled to produce coatings of type M1L1H1H2H3VH4H5M2L2, depicted hereinabove, with H3, H4, Hs and M2 being optional layers.

[0110] After the PVD coater has been configured (i.e., equipped by sputtering targets according to a specific preferred sequence), the deposition process takes place as follows:[01 1 1 ] Step 1 : a large glass substrate (e.g., a glass of 3.21 m width by 6 m long) is cleaned by wet processes and dried before entering the low-pressure area where the coating deposition is conducted. The glass substrate can eventually be additionally cleaned and / or textured by plasma etching at the entrance of the low-pressure area.

[0112] Step 2: the power applied on each necessary magnetron, the reactive gas mixtures compositions / gas flow rates, as well as the travel speed of the substrate through the coater are optimized to produce the selected coating recipe.

[0113] Optionally, masks that partially hide the surface of the substrate during the deposition process can be used to create a pattern, a logo, or a drawing.

[0114] Once coated, substrates are cut to the size and shape of the solar conversion device to which they are intended to be assembled.

[0115] After cutting, coated substrates are grinded to smooth the edges and remove any burrs produced during cutting, then washed, heat-treated (i.e., tempered or sometimes only hardened, depending on local building codes and eventually bended) through the process of heating and cooling its surface rapidly according to procedures usually followed in the glass industry.

[0116] After heat-treatment, small colour differences can be observed between the targeted and the measured colour coordinates at normal incidence, especially because the coating stacks of the invention include nitride or oxynitride layers that can partially oxidize during the heating process. If this difference is considered too large by the end-consumer, the coating stack is reworked by numerical simulation i.e., thicknesses of the constitutive layers of the coating stack are slightly adapted, to compensate this colour deviation, before final acceptance of the corresponding coating recipe.

[0117] Once ready, the glazing unit of the invention can be integrated to various types of solar conversion devices including PV and ST devices in different ways.

[0118] In a first example of application, a glazing unit 1 A is assembled as the front cover of a PV device 4A, including at least one PV cell 41 A by the help of an encapsulation layer 3A, with the selectively reflective coating 12A applied on the surface 1 1 1 A of the glass substrate 1 1 A which is opposite to incident solar radiation 5 as depicted in Fig. 3.

[0119] In another example of application, a glazing unit 1 B is assembled as an interlayer located between the conventional front cover 6 and the active parts i.e., at least one PV cell 41 B of the PV device 4B by the help of two encapsulation layers 3B and 3C, the selectively reflective coating 12B being located on the glass substrate 1 1 B side which is opposite 1 1 1 B to incident solar radiation 5 as depicted in Fig. 4.

[0120] In both previous examples of application, PV cells can either be based on crystalline silicon, CIS / CIGS thin film or any other type of PV technology adapted to generate electrical power from incident light.

[0121] For aesthetic purposes, PV conversion devices located behind coated substrates should preferably be of homogenous dark appearance (i.e. , full black crystalline PV module) and can therefore additionally include an array of fine stripes of black polymer or black tape, aimed at masking the interconnections and metallic contacts, being located between the PV cells and the encapsulation layer aimed at assembling the coloured glazing unit with such a device.

[0122] PV module with which the glazing unit is assembled can be of any size and shape and can either be curved or not.

[0123] It is obvious that several glazing units, either characterized by the same reflective colour or by different reflective colours can also be combined within the same PV module assembly.

[0124] It also goes without to say that, when the glazing unit of the invention is used as an interlayer, the glazing unit can be assembled with the PV device in both ways i.e., with the selectively reflective coating facing the incoming solar radiation or not, without departing from the scope of the invention as defined in the appended claims.

[0125] In another example of application, a glazing unit 1 C used as the front cover of a ST device 7A, is directly mounted, in front of a thermal absorber 71 A, into or onto the frame 8A of such a device, with the selectively reflective coating 12C being located on the surface 111 C of the glass substrate 1 1 C which is opposite to incident solar radiation 5, as depicted in Fig. 5.

[0126] In another example of application, a glazing unit 1 D is integrated to a multi-layered glazed structure additionally including a transparent or translucent substrate 9 and an encapsulation layer 3D before its mounting into / onto the frame 8B of a ST device 7B, with the selectively reflective coating 12D being located on the side 1 1 1 D of the glass substrate 1 1 D which is opposite to the incident solar radiation 5, as depicted in Fig. 6.

[0127] This second possible way of assembling ST device presents several advantages:

[0128] Possibility to combine PV and ST devices on the same building fagade without noticeable colour differences between the two kinds of solar conversion devices,

[0129] Improved mechanical resistance,

[0130] Absence of water condensation and subsequent formation of droplets on the selectively reflective coating that are responsible for local colour changes,

[0131] Possible application of an antireflective coating on the inner side of the multi-layered glazed structure, thus improving the solar conversion efficiency of the ST device.

[0132] It should also be noted that the multi-layered glazed structure comprising the glazing unit 1 D, can be installed / mounted into / onto of the frame of a ST device on the reverse way as compared to Fig.6, without departing from the scope of the present invention.

[0133] The examples of application given hereinabove are not restrictive. The glazing unit of the invention can of course be applied to:

[0134] other types of solar conversion devices intended for building projects (e.g., building integrated hybrid photovoltaic-thermal (PVT) devices or any other device aimed at converting the solar radiation into energy),

[0135] other elements such as dummy elements (i.e., inactive elements having the same appearance as a PV or ST device intended for poorly oriented or shaded surfaces), or

[0136] solar conversion devices intended for other applications such as street furniture (bus shelters, station platforms, bicycle parking lots) or VI PV (vehicle integrated photovoltaics) applications.

[0137] It also goes without saying that the addition of any substrate, any coating or combination of both, whose purpose can either be decorative or functional, at any level of any assembly described hereinabove, except between 1 1 A and 12A, respectively between 1 1 B and 12B, 1 1 C and 12C, or 1 1 D and 12D, does not change the scope of the invention as defined in the appended claims.Reference Signs List

[0138] 1 ; 1 A; 1 B; 1 C; 1 D Glazing unit

[0139] 1 1 ; 1 1A; 11 B; 1 1 C: 1 1 D Glass substrate

[0140] 1 1 1 : 111A; 1 1 1 B; 111 C; 1 1 1 D First surface of the glass substrate

[0141] 1 12 Second surface of the glass substrate

[0142] 12; 12A; 12B; 12C; 12D Selectively reflective coating

[0143] 121 Base layer

[0144] 122 Reinforcing layer

[0145] 123 Spectrally controlling system

[0146] 1231 Plurality of consecutive high-refractive index layers

[0147] 1232 Variable refractive index layer

[0148] 1233 High- or medium- refractive index layer

[0149] 124 Capping layer

[0150] 2 Air

[0151] 3; 3A; 3B; 3C; 3D Encapsulation layer

[0152] 4A; 4B PV solar energy conversion device

[0153] 41 A; 41 B Technical parts of a PV device (PV cell)

[0154] 5 Incident solar radiation

[0155] 6 Conventional front cover of a PV device

[0156] 7A; 7B ST solar energy conversion device

[0157] 71 A; 71 B Technical parts of a ST device (thermal collector)

[0158] 8A; 8B Frame of a ST device

[0159] 9 Transparent or translucent substrateCitation List

[0160] Citation List follows:Patent Literature

[0161] W03004079278A1

[0162] EP3586071 B1

[0163] EP2897795B9

[0164] EP2898534A1Non-Patent Literature

[0165] 1G. Eder and al., International Energy Agency, Photovoltaic Power Systems Programme, Coloured BIPV, Market, Research and Development, Report IEA-PVPS T15-07:2019

[0166] 2Maurer and al., Progress in building-integrated solar thermal systems, Solar Energy, Volume 154, 15 September 2017, Pages 158-186

[0167] 3B. Blasi and al., Morpho butterfly inspired coloured BIPV modules, 33rdEuropean PV Solar Energy Conference and Exhibition, 25-29 September 2017, Amsterdam, The Netherlands

[0168] 4C. Kutter and al., Decorated building-integrated photovoltaic modules: power loss, color appearance and cost analysis, 35thEuropean PV Solar Energy Conference and Exhibition, 24-28 September 2018, Brussels, Belgium

[0169] 5https: / / optilayer.com /

[0170] 6http: / / www.sspectra.com /

Claims

Claims

1. Heat-treatable glazing unit 1 for the aesthetic design of solar energy systems comprising at least a transparent or translucent glass substrate 1 1 and a selectively reflective coating 12 being at least partially deposited on a first surface 1 1 1 of said substrate, where the selectively reflective coating consists of a full-dielectric non-periodic multi-layered thin-film interference filter constructed as the superposition of a base layer 121 , a reinforcing layer 122, a spectrally controlling system 123 and a capping layer 124.

2. Glazing unit according to claim 1 where the base layer 121 consists of a medium refractive index layer comprising nitrogen rich SiOxNy where 0 < x / (x+y) < 0.5, being possibly additionally doped by Al, characterized by a medium refractive index comprised between 1.75 and 2.1 at the wavelength of 550 nm and deposited to a thickness comprised between 20 nm and 60 nm.

3. Glazing unit according to any of the previous claims where the reinforcing layer 122 consists of a low refractive index layer comprising oxygen rich SiOxNy where 0.5 < x / (x+y) < 1 , being possibly additionally doped by Al, characterized by a low refractive index comprised between 1.4 and 1.75 at the wavelength of 550 nm, and deposited to a thickness comprised between 5 nm and 50 nm.

4. Glazing unit according to any of the previous claims where the spectrally controlling system 123 consists of a non-periodic arrangement of dielectric layers, comprising at least:- a plurality of consecutive high refractive index layers 1231 consisting of materials chosen amongst HfOx, NbOx, TaOx, TiOx, ZrOx, or mixtures of these, possibly additionally containing dopants such as Ce, Co, Cu, Cr, Fe, Mn, or Mo, characterized by a high refractive index comprised between 2.1 and 2.6 at the wavelength of 550 nm, each individual layer being deposited to a thickness comprised between 5 nm and 60 nm, and where two contiguous layers are characterized by two different refractive indices,- a variable refractive index layer 1232 consisting of SiOxNy where 0 < x / (x+y) < 1 possibly additionally containing Al as dopant, characterized by a refractive index tuneable between 1 .4 and 2.1 at the wavelength of 550 nm, and deposited to a thickness comprised between 10 nm and 120 nm,

5. Glazing unit according to any of the previous claims where the spectrally controlling system 123 comprises further comprises one additional layer 1233 either consisting of:- a high refractive index layer consisting of HfOx, NbOx, TaOx, TiOx, ZrOx, or mixtures of these, possibly additionally containing dopants such as Ce, Co, Cu, Cr, Fe, Mn, or Mo characterized by a high refractive index comprised between 2.1 and 2.6 at the wavelength of 550 nm, deposited to a thickness comprised between 5 nm and 60 nm, or- a medium refractive index layer comprising nitrogen rich SiOxNy where 0 < x / (x+y) < 0.5, being possibly additionally doped by Al, characterized by a medium refractive index comprised between 1.75 and 2.1 at the wavelength of 550 nm and deposited to a thickness comprised between 20 nm and 120 nm.

6. Glazing unit according to any of the previous claims where the spectrally controlling system 123 further include additional low-, medium-, high- and / or variable- refractive index layers located between the additional layer 1233 of the spectrally selective 123 and the capping layer 124.

7. Glazing unit according to any of the previous claims where the capping layer 124 consists of a low-refractive index layer comprising SiOx, AIOx or mixture of these characterized by a low refractive index comprised between 1 .4 and 1 .75 at the wavelength of 550 nm and deposited to a thickness comprised between 20 nm and 120 nm.

8. Glazing unit according to any of the previous claims where the selectively reflective coating 12 is a full-dielectric non-periodic multi-layered stack of type M1L1H1H2H3VH4H5M2L2, where Ln, Mn, Hn, and V respectively denote low-, medium-,high- and variable- refractive index layers, and where H3, H4, Hs and M2 are optional layers.

9. Glazing unit according to any of the previous claims where the glass substrate 11 consists of a material chosen amongst borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, or soda-lime glass.

10. Glazing unit according to any of the previous claims where the first surface 111 and / or the second surface 112 of the glass substrate 11 is structured, textured, or both structured and textured.

11. Glazing unit according to any of the previous claims where the second surface 112 of the glass substrate 11 further comprises an additional coating whose purpose is either functional (e.g., anti-reflective coating) or decorative (e.g., ceramic frit pattern or logo).

12. A method for producing a glazing unit 1 comprising at least a transparent or translucent glass substrate 11 and a selectively reflective coating 12 characterized by the following steps:(1 ) Designing a selectively reflective coating 12 by numerical simulation,(2) Providing a transparent or translucent glass substrate 11 ,(3) Cleaning the substrate,(4) Applying the selectively reflective coating to a first surface 111 of the substrate by in-line PVD (Physical Vapour Deposition or sputtering) processes,(5) Cutting and grinding the glazing unit 1 ,(6) Washing the glazing unit 1 ,(7) Heat-treating the glazing unit 1 (i.e., tempering or only hardening, depending on local legislation, and eventually bending the coated glass).

13. Photovoltaic module comprising at least a glazing unit 1 A according to any of claims 1 to 1 1 , a PV solar energy conversion device 4A, comprising at least one PV cell 41 A and an encapsulant layer 3A.

14. Solar thermal collector comprising at least a glazing unit 1 C according to any of claims 1 to 1 1 , a ST solar energy conversion device 7A, comprising at least a solar absorber 71 A and a frame 8A.

15. Non-active (or “dummy”) element comprising at least a glazing unit according to any of claims 1 to 1 1 .

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