Transparent substrate for a laminated glazing unit for a head-up display and laminated glazing unit

Abstract

The invention relates to a transparent substrate for a laminated glazing unit (10) for a head-up display, provided with a reflective coating (18) configured to reflect p-polarised light (28), wherein the reflective coating (18) comprises a reflective module that comprises, from the transparent substrate, a first nitride-based dielectric layer, an oxide-based layer having a refractive index with a minimum between 800 and 1600 nm and an extinction coefficient that increases with the wavelength of the light, a second nitride-based dielectric layer, and a low-refractive-index layer, and wherein the refractive index of the low-refractive-index layer is lower than 1.9 at 550 nm. The invention also relates to a laminated glazing unit (10) for a head-up display comprising the transparent substrate provided with a reflective coating (18).

Description

DESCRIPTION TITLE: TRANSPARENT SUBSTRATE FOR LAMINATED GLAZING FOR HEAD-UP DISPLAYS AND LAMINATED GLAZING technical field

[0001] This presentation concerns a transparent substrate for laminated glazing for head-up displays and laminated glazing including the substrate. Previous technique

[0002] Modern vehicles are now equipped with display systems or devices called "head-up display", also known as HUD according to the English acronym for Head-Up Display.

[0003] These systems or devices include a projector, usually located near the vehicle's dashboard, configured to project an image onto a specific area of ​​the vehicle's windshield. The projected image appears to the driver as a virtual image behind the windshield, displaying information such as vehicle speed, navigation instructions, or warnings directly within their field of vision. The driver no longer needs to take their eyes off the road to view this information and can remain alert to events occurring outside the vehicle. HUD systems or devices thus contribute to improved road safety.

[0004] Most HUD devices rely on the emission of electromagnetic radiation polarized with an s-polarization and an angle of incidence of approximately 65° relative to the normal to the windshield. This angle is close to Brewster's angle for a glass-air interface, which is approximately 56.5° for soda-lime glass. The projected image is then reflected by the two main outer surfaces of the windshield. In addition to the main image, a secondary image also appears, more or less offset and partially overlapping the main image. This secondary image is called a "ghost image," "double image," or simply "ghost image."

[0005] To mitigate this unwanted ghosting effect, it is common practice to position the main surfaces of the windshield at different angles. The insertion of a laminated interlayer of varying thickness creates a superposition of the ghost image and the main image. This type of glazing is generally known as "wedge glazing" or "wedge windshield".

[0006] As an example, EP 0 420 228 describes a windscreen comprising a laminated interlayer whose thickness gradually decreases between a first and a second windscreen side so that the two sheets of glass in adhesive contact with said interlayer have two different angles of inclination with respect to the projector.

[0007] However, this type of glazing is expensive to manufacture, limited to certain viewing angles of the projected image, and does not prevent the formation of a ghost image when the glazing includes a functional coating.

[0008] It is common alternative practice to use HUD devices whose implementation relies on the emission of electromagnetic radiation polarized according to a p-type polarization and on a windshield comprising a functional coating adapted to the formation of a new reflective interface within said windshield for this type of radiation.

[0009] When p-polarized electromagnetic radiation is emitted towards the windshield at an angle of incidence close to Brewster's angle, it is weakly reflected by the glass-air interfaces. Reflection occurs only at the reflective interface formed by the functional coating. Various types of functional coatings can be used.

[0010] WO 2005 / 017600 describes a polarizing optical film comprising a plurality of individual layers having different optical refractive indices. The film is intended to be laminated into laminated glass to form a head-up display windshield comprising an area that predominantly reflects visible light polarized according to p-polarization. The film can also reflect infrared radiation to reduce greenhouse gas emissions in a vehicle.

[0011] DE 102014220189 describes laminated glazing comprising a metallic layer based on silver or aluminium and with a thickness between 5 nm and 9 nm. The metallic layer allows the reflection of visible light polarized according to a p polarization. Description of the invention

[0012] The present presentation aims to remedy at least some of these drawbacks.

[0013] To this end, the present exposition relates to a transparent substrate for laminated glazing for head-up display equipped with a reflective coating configured to reflect p-polarized light, the reflective coating comprising a reflective module comprising, from the transparent substrate, a first nitride-based dielectric layer, an oxide-based layer having a refractive index having a minimum between 800 and 1600 nm and an extinction coefficient increasing with the wavelength of the light, a second nitride-based dielectric layer and a low refractive index layer, the refractive index of the low refractive index layer being less than 1.9 at 550 nm.

[0014] The reflective coating makes it possible to obtain a reflected image of polarized light p of satisfactory quality and superior to known reflective coatings.

[0015] Indeed, since the coating is a reflective coating, at least 15%, or even 18%, of an incident light ray will be reflected even though the incident angle of the light ray is close to the Brewster angle.

[0016] When a transparent substrate with a reflective coating is used in laminated glass, the light ray diffracted through the transparent substrate with the reflective coating passes through the laminated glass. Since the angle of the diffracted light ray is close to Brewster's angle, a small proportion of the diffracted ray is reflected back towards the transparent substrate with the reflective coating. The formation of a so-called "ghost image" due to the reflection of the diffracted ray at the interface between the outer glass pane and the atmosphere is therefore significantly reduced.

[0017] Furthermore, the refractive index of the oxide-based layer passes through a minimum and the extinction coefficient increases with the wavelength of the light.

[0018] By modifying the deposition conditions of the oxide-based layer, it is possible to modify the characteristics of the reflective coating.

[0019] It is understood that the refractive index of the oxide-based layer passes through a minimum, and the value of the refractive index increases with the wavelength of light after passing through the minimum value.

[0020] The presence of the first nitride-based dielectric layer and the second nitride-based dielectric layer sandwiching the oxide-based layer helps to limit, or even prevent, the oxidation of the oxide-based layer and thus to preserve the properties of the oxide-based layer by avoiding the oxidation of the oxide-based layer.

[0021] By “light transmission”, TL, we mean the light transmission, denoted TL, as defined and measured and / or calculated in the ISO 13837:2021 standard.

[0022] By “solar factor”, TTS, it is understood the solar factor as defined according to the ISO 13837:2021 standard. It is equal to the sum of the direct solar transmittance, TE, and the secondary heat flux, qi.

[0023] By “direct solar transmittance”, TE, we mean the direct solar transmittance as defined and calculated according to ISO 13837:2021.

[0024] By "solar selectivity", SE, we mean the ratio between light transmission, TL, and direct solar transmittance, TE.

[0025] By "selectivity", s, we mean the ratio of light transmission, TL, to the solar factor TTS.

[0026] By “light reflection” R, we mean light reflection as defined and measured and / or calculated in ISO 13837:2021.

[0027] By transparent substrate, we mean that the substrate is preferably colorless, non-opaque and non-translucent in order to minimize the absorption of light and thus maintain maximum light transmission in the visible electromagnetic spectrum.

[0028] In some embodiments, the refractive index of the oxide-based layer has a difference between the minimum and a value at 400 nm greater than or equal to 0.8, in particular greater than or equal to 1.0.

[0029] In some embodiments, the extinction coefficient is less than 0.2, or even 0.1 at 500 nm and less than 2.0, or even less than 1.5 at 1200 nm.

[0030] In some embodiments, the extinction coefficient is greater than or equal to 0.5 at 1600 nm.

[0031] In some embodiments, the extinction coefficient has a difference between 400 nm and 1200 nm greater than or equal to 0.5.

[0032] Selectivity can thus be favorably increased.

[0033] In some embodiments, the reflective coating comprises at least two reflective modules.

[0034] In some embodiments, the oxide is a substoichiometric tungsten oxide, preferably of chemical formula WOx, x being between 2.55 and 2.98.

[0035] The presence of sub-stoichiometric tungsten oxide allows us to obtain a light transmission to solar factor ratio, i.e. a selectivity of satisfactory quality and superior to known reflective coatings.

[0036] In some embodiments, the physical thickness of the oxide-based layer is greater than or equal to 10 nm and less than or equal to 120 nm, preferably greater than or equal to 20 nm and less than or equal to 100 nm, preferably greater than or equal to 30 nm and less than or equal to 80 nm.

[0037] In some embodiments, the oxide is a doped tungsten oxide of formula MyWi-yOs, M representing at least one dopant element selected from the chemical elements of group 1 according to the IUPAC nomenclature and being between 0.01 and 0.4, preferably between 0.01 and 0.2, even more preferably between 0.01 and 0.1.

[0038] According to the IUPAC nomenclature, group 1 of the chemical elements includes hydrogen and the alkali elements, namely lithium, sodium, potassium, rubidium, cesium and francium.

[0039] The presence of doped tungsten oxide makes it possible to obtain a light transmission ratio to solar factor, i.e. a selectivity of satisfactory quality and superior to known reflective coatings.

[0040] In some embodiments, the doped tungsten oxide has the formula Cs y Wi- y 03, being between 0.01 and 0.4, preferably between 0.01 and 0.2, even more preferably between 0.01 and 0.1.

[0041] In some embodiments, a physical thickness of the oxide-based layer is greater than or equal to 5 nm and less than or equal to 80 nm, preferably greater than or equal to 5 nm and less than or equal to 60 nm.

[0042] In some embodiments, the first and / or second nitride-based dielectric layer is a silicon nitride-based dielectric layer and has a physical thickness greater than or equal to 5 nm.

[0043] In some embodiments, the first dielectric layer of the first nitride reflective module is a silicon nitride-based dielectric layer and has a physical thickness greater than or equal to 30 nm.

[0044] In some embodiments, the low refractive index layer is silica-based.

[0045] In some embodiments, the low refractive index layer is silica-based, comprising alumina.

[0046] In some embodiments, the low refractive index layer has a physical thickness greater than or equal to 40 nm and less than or equal to 150 nm, preferably greater than or equal to 60 nm and less than or equal to 130 nm.

[0047] In some embodiments, the substrate is a sheet of mineral glass or glass-ceramic.

[0048] By way of non-limiting examples, the glass may be a soda-lime silico-glass, borosilicate, aluminosilicate or alumino-borosilicate type glass.

[0049] In some embodiments, the substrate is a mineral glass that is colored throughout.

[0050] Coloration can generally be achieved by adding coloring oxides to the chemical composition of glass. Examples of coloring oxides include iron(II) oxide, copper oxide, chromium oxide, nickel oxide, gold oxide, manganese oxide, cobalt oxide, uranium oxide, neodymium oxide, and erbium oxide. Mixtures of oxides such as copper and tin oxide, or ionic complexes such as iron-sulfur or cadmium-sulfur complexes, can also be used.

[0051] In some embodiments, the reflective coating includes a protective coating for the reflective coating disposed opposite the substrate.

[0052] The protective coating may include several layers of protection.

[0053] This presentation also concerns laminated glass for head-up displays, comprising: - an outer sheet of glass; - an internal sheet of glass; - an intermediate adhesive lamination layer disposed between the outer glass sheet and the inner glass sheet; and the inner glass sheet being a transparent substrate provided with a reflective coating as defined above, an inner face of the inner glass sheet being provided with the reflective coating, the inner face being opposite the intermediate adhesive lamination layer.

[0054] Because the inner surface of the inner glass sheet is coated with a reflective material, the light ray diffracted at the interface between the reflective material and the inner glass sheet is less intense than the intensity of the diffracted light ray without the reflective material. The formation of a so-called "ghost image" due to reflection at the interface between the outer glass sheet and the atmosphere is reduced. The reduction in the intensity of the reflected light ray is also minimized because the angle of the diffracted light ray is close to Brewster's angle, which reduces the reflection of the diffracted light ray at the interface between the outer glass sheet and the atmosphere.

[0055] In some embodiments, the laminated glazing is devoid of a functional layer, for example a metallic solar control functional layer.

[0056] Laminated glazing has a light transmission greater than or equal to 71% and is color neutral in reflection and transmission.

[0057] In some embodiments, the selectivity of the laminated glazing is greater than or equal to 1.05, in particular greater than or equal to 1.10.

[0058] In some embodiments, the ratio of the light reflection of the reflective coating to the light reflection of an external face of the external glass sheet is greater than or equal to 26, or even greater than or equal to 27.

[0059] The higher the ratio, the better the quality of the head-up display will be, meaning that the "ghost" image will be of very low intensity compared to the image reflected by the reflective coating.

[0060] In some embodiments, the outer glass sheet and / or the inner glass sheet has a thickness of between 0.4 and 1.1 mm, in particular between 0.4 and 0.7 mm.

[0061] In some embodiments, the intermediate adhesive layer of lamination comprises one or more layers of thermoplastic material.

[0062] Examples of thermoplastic materials include polyurethane, polycarbonate, polyvinyl butyral (PVB), polymethyl methacrylate (PMMA), ethylene vinyl acetate (EA), or an ionomer resin.

[0063] In some embodiments, the adhesive intermediate layer of lamination has acoustic properties.

[0064] In some embodiments, the intermediate adhesive layer of lamination is UV-resistant. Brief description of the drawings

[0065] Other features and advantages of the object of this presentation will emerge from the following description of embodiments, given by way of non-limiting examples, with reference to the attached figures.

[0066] [Fig. 1] Figure 1 is a schematic view of laminated glazing according to one embodiment.

[0067] [Fig. 2] Figure 2 is a schematic cross-sectional view of a substrate equipped with a reflective coating according to one embodiment.

[0068] [Fig. 3] Figure 3 is a schematic cross-sectional view of a substrate with a prior art reflective coating.

[0069] [Fig. 4] Figure 4 is a graph representing the refractive index (unitless) as a function of the wavelength of light (in nm).

[0070] [Fig. 5] Figure 5 is a graph representing the extinction coefficient (unitless) as a function of the wavelength of light (in nm).

[0071] Across all figures, common elements are identified by identical numerical references. Detailed description

[0072] In what follows, the elements common to the different embodiments are identified by the same numerical references.

[0073] Figure 1 is a schematic cross-sectional view of laminated glazing according to one embodiment.

[0074] In the embodiment of Figure 1, the laminated glass 10 is laminated glass for head-up displays. The laminated glass 10 comprises an outer glass sheet 12 and an inner glass sheet 14. The laminated glass 10 includes an adhesive intermediate layer of lamination 16 disposed between the outer glass sheet 12 and the inner glass sheet 14. The outer glass sheet 12 has an outer face 20 and an inner face 22, and the inner glass sheet 14 has an outer face 24 and an inner face 26.

[0075] The outer face 20 of the outer glass sheet 12 is opposite the intermediate adhesive layer of lamination 16, i.e. the inner face 22 of the outer glass sheet 12 is closer to the intermediate layer of lamination 16 than the outer face 20 of the outer glass sheet 12.

[0076] The inner face 26 of the inner glass sheet 14 is opposite the intermediate adhesive layer of lamination 16, i.e. the outer face 24 of the inner glass sheet 14 is closer to the intermediate layer of lamination 16 than the inner face 26 of the inner glass sheet 14.

[0077] In this document, the terms "internal" and "external" are used in relation to laminated glass when it is installed on a motor vehicle, for example. The term "external" refers to an element closer to the exterior of the vehicle, and the term "internal" refers to an element closer to the interior of the vehicle.

[0078] In the embodiment of Figure 1, the inner face 26 of the inner glass sheet 14 is provided with a reflective coating 18.

[0079] In the embodiment of Figure 1, the laminated glazing is devoid of a functional layer, for example a metallic solar control functional layer.

[0080] As illustrated in Figure 1, an incident light ray 28 of p-polarized light is reflected by the reflective coating 18 to form a reflected light ray 30. The incident light ray 28 is oriented at approximately 65° with respect to the bisector 34 of the angle formed between the incident light ray 28 and the reflected light ray 30.

[0081] In the embodiment of Figure 1, the outer glass sheet 12, the inner glass sheet 14, and the intermediate adhesive lamination layer 16 have similar or even equal refractive indices. Therefore, the diffracted light ray 56 is only slightly modified when passing through the interfaces between the inner glass sheet 14, the intermediate adhesive lamination layer 16, and the outer glass sheet 12. When the diffracted light ray 56 reaches the interface between the outer glass sheet 12 and the external atmosphere, the diffracted light ray is reflected by the outer face 20 of the outer glass sheet 12 towards the inner glass sheet 14. The reflected light ray 58 from the outer face 20 of the outer glass sheet 12 is only slightly modified when passing through the interfaces between the outer glass sheet 12, the intermediate adhesive lamination layer 16, and the inner glass sheet 14.At the interface between the reflective coating 18 and the interior atmosphere, the reflected light ray 58 is diffracted and forms a secondary light ray 32. The intensity of the secondary light ray 32 creates, for an observer located on the inner face 26 of the inner glass sheet 14, i.e., inside the vehicle, a low-intensity secondary image, also called a ghost image, which is superimposed on the image created by the light ray reflected 30 by the reflective coating 18. The "ghost" images potentially created at the interfaces with the intermediate adhesive layer of lamination 16 are negligible compared to the light ray reflected 30 by the reflective coating 18 and the secondary light ray 32.

[0082] Figure 2 is a schematic cross-sectional view of a transparent substrate 40 fitted with reflective coating 18.

[0083] In the embodiment of Figure 2, the transparent substrate 40 is a sheet of glass, in particular the internal glass sheet 14 of the embodiment of Figure 1.

[0084] In the embodiment of Figure 2, the reflective coating 18 comprises two reflective modules, a first reflective module 36 and a second reflective module 38. Each reflective module 36, 38 comprises, starting from the transparent substrate 40, a first nitride-based dielectric layer 42A, 42B, an oxide-based layer 44A, 44B, having a refractive index with a minimum between 800 and 1600 nm and an extinction coefficient increasing with the wavelength of light, a second nitride-based dielectric layer 46A, 46B, and a layer with a refractive index of low refraction 48A, 48B, the refractive index of the low refractive index layer being less than 1.9 at 550 nm.

[0085] Figure 3 is a schematic cross-sectional view of a substrate with a prior art reflective coating 50 (Comparative Example). The prior art reflective coating 50 comprises two reflective modules, each reflective module comprising, from the transparent substrate 40, a high refractive index layer 52A, 52B and a low refractive index layer 54A, 54B, for example, silica containing alumina. The refractive index of the low refractive index layer 54A, 54B is less than 1.9 at 550 nm, and the refractive index of the high refractive index layer 52A, 52B is greater than 2.1 at 550 nm.

[0086] As an example, the deposition of a reflective coating comprising thin layers on a glass substrate is achieved by successively depositing each thin layer by passing the glass substrate through a succession of deposition cells adapted to deposit a given thin layer.

[0087] Deposition cells can use deposition methods such as magnetic field assisted sputtering (also called magnetron sputtering), ion beam assisted deposition (IBAD), evaporation, chemical vapor deposition (CVD), plasma-assisted chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), etc.

[0088] Magnetic field assisted spray deposition processes are particularly used.

[0089] The tungsten oxide target may in particular contain one or more dopant elements in the proportions as described for the doped tungsten oxide layer.

[0090] The tungsten oxide-based layer can be deposited by sputtering using the aforementioned target under a deposition atmosphere composed of 20 to 100% argon and 0 to 80% dioxygen, preferably 30 to 90% argon and 10 to 70% dioxygen.

[0091] The tungsten oxide-based layer can be deposited under a pressure of between 1 and 20 mTorr, preferably from 3 to 15 mTorr.

[0092] Preferably, the deposition can be carried out cold, i.e. at a temperature below 100°C, in particular between 20°C and 60°C, for the substrate.

[0093] The deposition can also be carried out hot, in particular at a temperature between 100°C and 400°C.

[0094] The transparent substrate 40 with reflective coating 18 can undergo annealing heat treatment. The annealing temperature can range from 450°C to 800°C, particularly from 550°C to 750°C, or even from 600°C to 700°C. The annealing time can range from 5 to 30 minutes, particularly from 5 to 20 minutes, or even from 5 to 10 minutes.

[0095] In the examples below, thin films are deposited by magnetic field assisted sputtering.

[0096] For example 1, example 2 and the comparative example, the outer glass sheet 12 is a soda-lime silico-glass with a thickness of 1.6 mm, the intermediate adhesive lamination layer 16 is a PVB with a thickness of 0.76 mm and the inner glass sheet 14 is a soda-lime silico-glass with a thickness of 2.1 mm.

[0097] The outer glass sheet 12 can undergo annealing heat treatment. The annealing temperature can range from 450°C to 800°C, particularly from 550°C to 750°C, or even from 600°C to 700°C. The annealing time can range from 5 to 30 minutes, particularly from 5 to 20 minutes, or even from 5 to 10 minutes.

[0098] Example 1

[0099] The first dielectric layer, based on 42A, 42B nitride, and the second dielectric layer, based on 46A, 46B nitride, are aluminum-doped silicon nitride. The target used is a Si:Al target comprising 92 wt% silicon and 8 wt% aluminum. The layer is deposited at a pressure between 3.2 x 10⁻¹¹ kJ / cm². -3 and 6.10 -3 mbar in an atmosphere of argon and nitrogen with an Ar / (Ar+N2) ratio of 55 (in flight%).

[0100] The oxide-based layer 44A, 44B, is made of substoichiometric tungsten oxide WOx. The target used is a tungsten target. The layer is deposited at a pressure of 12 mTorr in an atmosphere containing 60% dioxygen by volume.

[0101] The low refractive index layer 48A, 48B, is made of silica containing alumina. The target used is a Si:Al target comprising 92 wt% silicon and 8 wt% aluminum. The layer is deposited at a pressure of 4.10 -3 mbar in an atmosphere of argon and dioxygen with an Ar / (Ar+Û2) ratio of 36 (in flight%).

[0102] After deposition of the first reflective module 36 and the second reflective module, the transparent substrate 40 with the reflective coating 18 is annealed at 650°C for 10 min. The sub-stoichiometric tungsten oxide WOx has a value of x of approximately 2.9.

[0103] Example 2

[0104] The first dielectric layer, based on 42A, 42B nitride, and the second dielectric layer, based on 46A, 46B nitride, are aluminum-doped silicon nitride. The target used is a Si:Al target comprising 92 wt% silicon and 8 wt% aluminum. The layer is deposited at a pressure between 3.2 x 10⁻¹⁰⁸⁶. 3 and 6.10' 3 mbar in an atmosphere of argon and nitrogen with an Ar / (Ar+N2) ratio of 55 (in flight%).

[0105] The oxide-based layer 44A, 44B is made of cesium-doped tungsten oxide. The target used is a Cs / W / O ceramic target with a Cs / W ratio between 0.3 and 0.4. The layer is deposited at a pressure of 4 mTorr in an atmosphere containing 20% ​​oxygen by volume.

[0106] The low refractive index layer 48A, 48B, is made of silica containing alumina. The target used is a Si:Al target comprising 92 wt% silicon and 8 wt% aluminum. The layer is deposited at a pressure of 4.10 -3 mbar in an atmosphere of argon and dioxygen with an Ar / (Ar+Û2) ratio of 36 (in flight%).

[0107] After deposition of the first reflective module 36 and the second reflective module, the transparent substrate 40 with the reflective coating 18 is annealed at 650°C for 10 min. Cesium-doped tungsten oxide Cs y Wi- y 03 has a y value of approximately 0.05-0.06.

[0108] Comparative example

[0109] The high refractive index layer 52A, 52B, for example in substoichiometric titanium oxide TiOw, is deposited using a titanium oxide target at a pressure of 2.10-3 mbar in an argon atmosphere and nitrogen with an Ar / (Ar+N2) ratio of 95 (by volume%). The titanium oxide obtained is stoichiometric or close to it (x equal to 2 or almost).

[0110] The low refractive index layer 54A, 54B, for example, is made of silica containing alumina. The target used is a Si:Al target comprising 92% by weight silicon and 8% by weight aluminum. The layer is deposited at a pressure of 4.10' 3 mbar in an atmosphere of argon and dioxygen with an Ar / (Ar+Û2) ratio of 36 (in flight%).

[0111] After deposition of the high refractive index and low refractive index layers, the transparent substrate 40 provided with the coating is annealed at 650°C for 10 min.

[0112] Table 1 gives the physical thicknesses of each layer, the thicknesses being expressed in nm, for example 1, example 2 and the comparative example as well as the values ​​of the selectivity and the ratio R30 / R32 65°.

[0113] R30 / R3265° represents the ratio between the light reflection of the reflected light ray 30 by the reflective coating 18 and the secondary light ray 32 measured with an angle of the incident light ray 28 of 65° with respect to the normal, i.e. the bisector 34, to the laminated glazing 10.

[0114] [Table 1]

[0115] Figure 4 is a graph representing the refractive index (unitless) as a function of the wavelength of light (in nm). Curve 60 represents the evolution of the refractive index of sub-stoichiometric tungsten oxide as a function of the wavelength of light, curve 62 the evolution of the refractive index of cesium-doped tungsten oxide as a function of the wavelength of light, and curve 64 represents the evolution of the refractive index of stoichiometric tungsten oxide as a function of the wavelength of light. Curve 64 for stoichiometric tungsten oxide is provided for illustrative and comparative purposes. We observe that unlike curve 60 of sub-stoichiometric tungsten oxide and curve 62 of cesium-doped tungsten oxide, curve 64 of stoichiometric tungsten oxide does not pass through a minimum and varies little as a function of the wavelength of light.

[0116] Figure 5 is a graph representing the extinction coefficient (unitless) as a function of the wavelength of light (in nm). Curve 66 represents the evolution of the extinction coefficient of sub-stoichiometric tungsten oxide as a function of the wavelength of light, curve 68 the evolution of the extinction coefficient of cesium-doped tungsten oxide as a function of the wavelength of light, and curve 70 represents the evolution of the extinction coefficient of stoichiometric tungsten oxide as a function of the wavelength of light. Curve 70 for stoichiometric tungsten oxide is given for illustrative and comparative purposes. We observe that, unlike curve 66 of sub-stoichiometric tungsten oxide and curve 68 of cesium-doped tungsten oxide, curve 70 of stoichiometric tungsten oxide is not increasing but constant at 0.

[0117] The transparent substrate 40 and the laminated glass 10 are particularly suitable for automotive glazing applications. They can also be adapted for certain building glazing applications, notably as laminated glass.

[0118] Although the present exposition has been described with reference to a specific implementation example, it is clear that various modifications and changes can be made to these examples without departing from the scope The general nature of the invention as defined by the claims. Furthermore, individual features of the various embodiments mentioned may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

DEMANDS

1. Transparent substrate (40) for laminated glazing (10) for head-up display having a reflective coating (18) configured to reflect p-polarized light (28), the reflective coating (18) comprising a reflective module (36, 38) comprising, from the transparent substrate (40), a first nitride-based dielectric layer (42A, 42B), an oxide-based layer (44A, 44B) having a refractive index having a minimum between 800 and 1600 nm and an extinction coefficient increasing with the wavelength of the light, a second nitride-based dielectric layer (46A, 46B) and a low refractive index layer (48A, 48B), the refractive index of the low refractive index layer (48A, 48B) being less than 1.9 at 550 nm.

2. Transparent substrate (40) according to claim 1, the reflective coating (18) comprises at least two reflective modules (36, 38).

3. Transparent substrate (40) according to claim 1 or 2, wherein the oxide is a substoichiometric tungsten oxide, preferably of chemical formula WOx, x being between 2.55 and 2.

98.

4. Transparent substrate (40) according to claim 3, wherein a physical thickness of the oxide-based layer (44A, 44B) is greater than or equal to 10 nm and less than or equal to 120 nm, preferably greater than or equal to 20 nm and less than or equal to 100 nm, preferably greater than or equal to 30 nm and less than or equal to 80 nm.

5. Transparent substrate (40) according to claim 1 or 2, wherein the oxide is a doped tungsten oxide of formula MyWi-yOs, M representing at least one dopant element selected from the chemical elements of group 1 according to the IUPAC nomenclature and being between 0.01 and 0.4, preferably between 0.01 and 0.2, even more preferably between 0.01 and 0.

1.

6. Transparent substrate (40) according to claim 5, wherein the doped tungsten oxide has the formula Cs y Wi- y 03, being between 0.01 and 0.4, preferably between 0.01 and 0.2, even more preferably between 0.01 and 0.

1.

7. Transparent substrate (40) according to claim 5 or 6, wherein a physical thickness of the oxide-based layer (44A, 44B) is greater than or equal to 5 nm and less than or equal to 80 nm, preferably greater than or equal to 5 nm and less than or equal to 60 nm.

8. Transparent substrate (40) according to any one of claims 1 to 7, wherein the first and / or second nitride-based dielectric layer (42A, 42B, 46A, 46B) is a silicon nitride-based dielectric layer and has a physical thickness greater than or equal to 5 nm.

9. Transparent substrate (40) according to claim 8 in combination with claim 2, wherein the first dielectric layer (42A) of the first nitride-reflecting module (36) is a silicon nitride-based dielectric layer and has a physical thickness greater than or equal to 30 nm.

10. Transparent substrate (40) according to any one of claims 1 to 9, wherein the low refractive index layer (48A, 48B) is silica-based.

11. Transparent substrate (40) according to claim 10, wherein the low refractive index layer (48A, 48B) is silica-based comprising alumina.

12. Transparent substrate (40) according to claim 11, wherein the low refractive index layer (48A, 48B) has a physical thickness greater than or equal to 40 nm and less than or equal to 150 nm, preferably greater than or equal to 60 nm and less than or equal to 130 nm.

13. Laminated glass (10) for head-up display comprising: - an outer sheet of glass (12); - an internal sheet of glass (14); - an intermediate adhesive lamination layer (16) disposed between the outer glass sheet (12) and the inner glass sheet (14); and the inner glass sheet (14) being a transparent substrate (40) provided with a reflective coating (18) according to any one of claims 1 to 12, an inner face (26) of the inner glass sheet (14) being provided with the reflective coating (18), the inner face (26) being opposite the intermediate adhesive lamination layer (16).

14. Laminated glazing (10) according to claim 13, the laminated glazing (10) being devoid of a metallic solar control functional layer.

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