WO2025098949A1

WO2025098949A1 - Vehicle head-up display

Info

Publication number: WO2025098949A1
Application number: PCT/EP2024/081102
Authority: WO
Inventors: Xavier Laloyaux; Laurent VANDIEVOET; Thomas LAMBRICHT; Adrien NELIS
Original assignee: AGC Glass Europe SA
Current assignee: AGC Glass Europe SA
Priority date: 2023-11-10
Filing date: 2024-11-05
Publication date: 2025-05-15
Anticipated expiration: 2026-05-10

Abstract

The present invention relates to a head-up display system (1) for a vehicle (100), comprising (i) an image source (13) configured to project an image (15)onto a combiner (10), said image source (13) being positioned in a dashboard (11) of the vehicle, (ii) a combiner (10) integrated to the dashboard (11) for reflecting the said projected image toward an observer for observation According to the present invention, the said combiner (10) comprises at least one chemically tempered glass sheet (20) having an inner face (22) and an outer face (22).

Description

Vehicle head-up display

FIELD OF THE INVENTION

[1] The present invention relates in general to head-up displays (HUD) system for producing images and presenting the images for observation of the type used in motor vehicles, and more specifically to head-up displays (HUD) system having a glass part integrated to a dashboard providing increased driver visual comfort. The present invention additionally provides a head-up display system that does not depend on the design of the vehicle and/or the inclination of the windshield installed in the vehicle.

BACKGROUND OF THE INVENTION

[2] In general, there are two types of head-up displays in motor vehicles. One type utilizes the windshield as the surface onto which a projection system projects a virtual image, which is visible to the driver, wherein the projection system comprises an image-generating unit (known in the art as a projector) and an image-forming mirror (also known as a beam splitter) which can be spherical, aspherical, or freely formed. This type of HUD is costly. Such head-up displays are described in CN104267498B.

[3] The other type uses a combiner which is separated from the windshield, such as example, a transparent plate made of glass or plastic or a suitably designed prism. A combiner of this type is typically situated above the instrument panel, also called dashboard, close to the windshield, as viewed by the driver, and often can be retracted into or folded down parallel with a top surface of the instrument panel. The combiner reflects the image generated by the projector in the direction of the driver. Such head- up display systems are described in US7978414 and US20170059872.

[4] The image projected onto and reflected off of the combiner reaches the driver's eyes as a spatially-delimited light beam, which is commonly referred to as a “light bundle” in the art. The light bundle spans and defines a so-called eyebox, within which the driver's eyes must be located in order for the information displayed by the head- up display to be visible to the driver. The vertical position of the eyebox must be adapted to the sitting height of the specific driver. For this purpose, the driver has the option of adjusting the height position of the eyebox until it is optimally visible, wherein the eyes of the driver are located well within the eyebox. In order to ensure that the driver has a certain freedom of motion, within which the image remains visible, the eyebox must have a certain minimum size having a height of, typically, 50 mm. A suitable installation space for the head-up display is necessary for this purpose, in particular a certain height of the projector or of the combiner or of an image-forming mirror. Further, depending on the model of the vehicle (dashboard with limited space and/or degree of windshield slope... ), a head-up display system with p-polarized light rays directed by the image source may not be installed in the dashboard limiting the options for design of vehicle.

[5] Although HUDs are useful in a variety of applications, there are several problems with conventional HUDs, among which mainly compatibility with standard sunglasses, generally p-polarized sunglasses, high cost, narrow viewing angles, mechanical constraints, and low contrast of images are of particular concern. Moreover, conventional combiners are either undesirably thick or heavy for most applications, or are thin and undesirably highly curved. The thick combiners often contain a pair of cooperative lens elements, at least one of which includes an embedded spherical surface coated with a spectrally reflecting thin film. The external surfaces of these thick combiners are flat so as to provide an undistorted view of the background scene. Thin combiners, on the other hand, typically employ a pair of spherical external surfaces, one of which carries the spectrally reflecting thin film. Thin combiners thus typically do not provide the necessary undistorted view of the background scene, especially when the combiner is thick enough to be adequately durable.

[6] Thus, it is desirable to provide a head-up (HUD) display system for vehicle for producing images and presenting the images for observation that may solve at least one of the foregoing-described problems. More particularly, it is desirable to provide a head-up display system for producing images to be viewed by an observer wearing sun glasses and more particularly p-polarized sun glasses.

[7] The problem addressed by the invention is to provide a head-up system that is more easily implemented since the system allows more flexibility for its installation in the vehicle. Thus, it is easier to manage the position angle of its installation and/or to reduce the installation space of the HUD system.

SUMMARY OF THE INVENTION

[8] It is an object of the present invention to provide a head up display system for a vehicle, comprising a combiner comprising at least one chemically tempered glass sheet having an inner face and an outer face integrated to the dashboard providing an efficient combiner useful for the majority of vehicles independently of its shape and/or the degree of windshield slope. The combiner (also called in the rest of description, glass dashboard part) is positioned so as to reflect the image projected from a lighting projecting source, the projecting source being integrated to the dashboard too. The combiner has an inner surface and an outer surface, the image being reflected by the inner and/or outer surface towards the driver.

[9] Thus, the present invention discloses a head-up display system comprising: a. an image source configured to project an image onto a combiner, said image source being positioned in the dashboard of the vehicle, b. a combiner integrated to the dashboard for reflecting the said projected image toward an observer for observation.

[10] According to the present invention, the combiner comprises at least one chemically tempered glass sheet having an inner face and an outer face. To avoid any doubt, the term “tempered” may be also be understood as “strengthened”, both terms may be used in the text.

[11] Thus, thanks to the present invention, the combiner may be thin with improved optical properties and mechanical resistance. Also, by using a thin glass combiner allows to decrease the distance between the well-known ghost image and the primary image. Thus, the ghost is not visible by the user. The HUD-system is then improved.

[12] The present invention further concerns a head-up display system comprising a combiner comprising at least one chemically tempered glass sheet having an inner face and an outer face, the said glass sheet being provided with a p-polarized light reflective coating on its inner face or its outer face. More preferably, the p-polarized light reflective coating provided on its inner face. Thus, a lighting source projecting p- polarized light rays may be used to project an image towards the combiner in order to be reflected by it and to be viewed by the driver/observer. The p-polarized light reflective coating may be provided partly or totally over the surface of the inner or the outer face of the at least chemically tempered glass sheet.

[13] Thus, the inventors have found surprisingly that a combiner comprising at least one chemically tempered glass sheet and provided with a p-polarized light reflective coating provided on its inner or outer face has an increased durability in comparison with existing combiner. The lifetime of the HUD system is increased. Furthermore, thanks to the invention, the combiner may be coated before it is bended or curved. The p-polarized light reflective coating preferably resists to bending process (temperature... ). Thus, a curved glass combiner without wrinkles can be obtained.

[14] The present invention further concerns the use of a chemically tempered glass as a combiner to reflect image projected from a light source projecting at least 50% p- polarized light towards the combiner. This allows for the use of less stringent polarizers and for flexibility of the projected light, depending on situational conditions, such as the amount of natural light available, the weather or other external conditions. The advantage of having at least 50% p-polarized light, is that the system is compatible with standard sunglasses (generally p-polarized sunglasses). In other instances, the light source may provide for 100 % p-polarized light. For the avoidance of doubt, the combiner according to the present invention is not the windshield itself. However, the combiner may be in the vicinity of the windshield.

[15] According to the present invention, the combiner is not attached to the windshield and is separated from it. Thus, a combiner according to the invention, preferably close to the field of view of the driver or occupant compatible with sunglasses, and particularly with p-polarized sunglasses, with a maximum flexibility for its implementation in a car (volume and position) is proposed. Furthermore, with the HUD system according to the present invention, the projected image may be seen all the time and under any conditions (weather...).

[16] For avoidance of doubt, terms as “combiner” or “dashboard glass part” may be used indifferently to define the combiner according to the present invention. Also, terms as “image source” or “light source” may be used indifferently to define the the image source according to the present invention

[17] The present invention also provides a method for producing a combiner for an HUD system for a vehicle as described above.

[18] The method comprises the following steps: a. Providing at least one glass sheet chemically tempered having an inner face and outer face, b. Providing a p-polarized light reflective coating or a p-polarized light reflective film onto at least a part of the inner face of the at least one glass sheet, c. Assembling the glass sheet provided with step b) to a dashboard support.

BRIEF DESCRIPTION OF THE DRAWINGS

[19] FIG. 1 is a schematic cross-sectional view of a portion of a vehicle having a head-up display system according to one embodiment of the present invention.

[20] FIG. 2 is a schematic cross-sectional view of a portion of a vehicle having a head-up display system according to another embodiment of the present invention.

[21] FIG. 3a and FIG.3b is a schematic cross-sectional view of a combiner according to one embodiment of the present invention.

[22] FIG. 4 is a schematic top view of a combiner according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[23] Referring to FIG. 1 and 2, the present invention is directed to a head-up display system 1 for use in a vehicle 100. By vehicle, it is meant a passenger vehicle, truck, train, airplane, watercraft or the like. The windshield 200 of a conventional vehicle 100 is typically produced from glass represented here with the purpose to better represent the location of the head-up system 1 in the vehicle.

[24] The HUD system 1 comprises an image source 13 configured to project an image 15 onto a combiner 10, said image source 13 being positioned in the dashboard 11 of the vehicle.

[25] According to the invention, the combiner 10 is integrated to the dashboard for reflecting the said projected image 15 toward an observer 300 for observation, the combiner 10 having at least one glass sheet 20 having an inner face and an outer face.

[26] According to an embodiment of the present invention, the combiner 10 is placed with an angle of 25° to 65° to the head-up display light source 13.

[27] According to the present invention, the head-up display image source 13 can be placed above (light/image is projected down to the combiner) as shown in FIG.1 or below the combiner 10 (light/image is projected up to the combiner) as shown in FIG.2. The light source 13 is placed in order to project an image onto the combiner 10 (as represented by small arrows in FIGS). The combiner 10 is at least partially facing the the image source 13 to project the information on the driver I observer’s eye 300.

[28] In FIG.1 , the light/image source 13 is integrated into the bottom part of the dashboard 11 and the combiner 10 according to the present invention is placed above the light source at a position above the image source 13 in the upper part 11 of the dashboard. The combiner 10 is placed at an angle to allow the observer to see the image projected on it. Thus, the combiner 10 may be placed at the same position in the dashboard where most of the instruments and switches are. Such instruments are for example monitor vehicle speed, engine speed, and engine temperature.

[29] Thus, in FIG.2, the combiner 10 is integrated into the bottom part of the dashboard 11 and the light/image source 13 is placed above the combiner 10 at a position in the upper part of the dashboard. The combiner 10 is placed at an angle to allow the observer 300 to see the image projected on it. The image source 13 may be placed at the same position in the dashboard where most of the instruments and switches are. The requirements of its position regarding the combiner 10 are accordingly adjusted. Such instruments are for example monitor vehicle speed, engine speed, and engine temperature.

[30] Throughout the present text, when a numerical range is indicated, the limits of the range are considered to be included in the range. In addition, all the integral and subdomain values in the numerical range are expressly included as if explicitly written.

[31] The combiner 10 (glass dashboard part) according to the invention comprises at least one sheet made of glass whose matrix composition is not particularly limited and may thus belongs to different glass categories. The glass may be a soda-lime- silicate glass, an alumino-silicate glass, an alkali-free glass, a boro-silicate glass, etc. Preferably, the glass dashboard part 10 of the invention is made of a soda-lime glass or an alumino-silicate glass.

[32] The composition of the glass is not crucial for the purpose of the present invention, provided said glass sheet is appropriate to be chemically tempered and for transportation applications. The glass may be clear glass, extra-clear glass or colored glass, comprising one or more component (s)/colorant(s) in an appropriate amount as a function of the effect desired. Colored glass include grey, green or blue float glass. In some circumstances, colored glass may be advantageous to provide for appropriate and desired color of the final glazing, within the limitations of applicable legislation.

[33] The glass may be flat or totally or partially curved to correctly fit with the particular design of the vehicle or the potentially glass support, as the shape requires for the application.

[34] According to an embodiment of the invention, the glass dashboard 10part has a composition comprising, in a content expressed in percentages of the total weight of the glass, indicated in Table 1 below.

[35] Table 1

[36] Such a soda-lime-type base glass composition has the advantages to be inexpensive even if it is less mechanically resistant as such. Ideally, according to this last embodiment, the glass composition does not comprise B2O3 (meaning that it is not intentionally added, but could be present as undesired impurities in very low amounts). The use of glass with high alumina content provided with a p-polarized projector can help to reduce the amount of reflection and glare, resulting in sharper and more accurate images. Additionally, the higher refractive index of the glass can improve the overall brightness and contrast of the projected image.

[37] Furthermore, soda-lime glass with high alumina content has a low birefringence compared to other glass materials, meaning it does not split light into different polarizations as much. This reduces distortion and aberration, resulting in more accurate and consistent images. The low birefringence is due to the uniform distribution of the alumina in the glass matrix, which results in a more isotropic material, i.e. , a material with uniform properties in all directions. This isotropic property of the glass reduces the difference in the refractive indices for different polarizations, which, in turn, reduces the birefringence.

[38] In an alternative more preferred manner, the at least one glass sheet of the combiner 10 has a composition comprising, in a content expressed in percentages of the total weight of the glass: SiO2 55 - 70%; AI2O3 6 - 18%; B2O3 0 - 4%; CaO 0 - 10%; MgO 0 - 10%; Na2O 5 20%; K2O 0 - 10% BaO 0 - 5%.

[39] Such an alumino-silicate-type base glass composition has the advantages to be more mechanically resistant. Ideally, according to this last embodiment, the glass composition does not comprise B2O3 (meaning that it is not intentionally added, but could be present as undesired impurities in very low amounts).

[40] According to an advantageous embodiment of the invention, combinable with previous embodiments on base glass composition, the at least one glass sheet of the combiner 10 has a composition comprising a total iron (expressed in terms of Fe2Os) content ranging from 0.002 to 0.06 weight%. A total iron (expressed in the form of Fe2Os) content of less than or equal to 0.06 weight% makes it possible to obtain a glass dashboard part with almost no visible coloration and allowing a high degree of flexibility in aesthetic designs. The minimum value makes it possible not to be excessively damaging to the cost of the glass as such, low iron values often require expensive, very pure, starting materials and also purification of these. Preferably, the composition comprises a total iron (expressed in the form of Fe2Os) content ranging from 0.002 to 0.04 weight%. More preferably, the composition comprises a total iron (expressed in the form of Fe2Os) content ranging from 0.002 to 0.02 weight%. In the most preferred embodiment, the composition comprises a total iron (expressed in the form of Fe2Os) content ranging from 0.002 to 0.015 weight%.

[41] The at least one glass sheet 20 of the combiner 10 (glass dashboard part ) according to the invention may have a thickness of from 0.1 to 10 mm and preferably from 0.1 to 6 mm when the combiner is made of a laminated glass. Advantageously, the at least one glass sheet 20 of the combiner 10 is made a glass with a thickness from 0.5 to 3 mm. More advantageously, in particular if the dashboard shape requires bending, the thickness of the combiner (glass dashboard part) is of from 0.5 to 2.1 mm in order to have a thin combiner. [42] In a preferred embodiment, the thickness of at least one glass sheet 20 of the combiner 10 is lower than 2.1 mm and more preferably lower than 1.6 mm. Thus, the weight of the HUD system 1 is reduced. Furthermore, the thin glass part may have more complex shape as being curved and may be more easily fitted to the shape of the dashboard. However, thicker glass may be used.

[43] In a preferred embodiment, the combiner further comprises a second glass sheet and an interlayer laminating the first glass sheet and the second glass sheet. The interlayer is usually made of polyvinyl butyral (PVB), polyurethane (PU) or ethylene-vinyl acetate (EVA). Thus, the combiner 10 is a laminated combiner. The first and the second glass sheets may have the same or different composition, size, thickness... The glass combiner may be also laminated with a plastic sheet such as PVC or a polycarbonate sheet.

[44] In an embodiment of the present invention, the combiner may be curved, the curvature may being obtained by cold bending in case of thin at least one glass sheet 20 or by hot bending for thicker at least one glass sheet 20. Technics of glass cold and hot bending are well known for the skill man in the art. Thus, complex shape can be obtained.

[45] According to an embodiment, the combiner 10 of the invention comprises at least one float glass sheet. The term “float glass sheet” is understood to mean a glass sheet formed by the float process, which consists in pouring the molten glass onto a bath of molten tin, under reducing conditions. A float glass sheet comprises, in a known way, a “tin face”, that is to say a face enriched in tin in the body of the glass close to the surface of the sheet. The term “enrichment in tin” is understood to mean an increase in the concentration of tin with respect to the composition of the glass at the core, which may or may not be substantially zero (devoid of tin). Therefore, a float glass sheet can be easily distinguished from sheets obtained by other glassmaking processes, in particular by the tin oxide content which may be measured, for example, by electronic microprobe to a depth of ~ 10 pm.

[46] According to another preferred embodiment, the combiner 10 of the invention comprises at least one glass sheet formed by a slot draw process or by a fusion process, in particular the overflow downdraw fusion process. These processes, in particular the fusion process produces glass sheets whose surfaces may reach superior flatness and smoothness necessary in some applications, but they are also more expensive than the float process for large scale glass production.

[47] According to the present invention, the combiner 10 comprises at least one chemically tempered (or strengthened) glass sheet. The glass sheet is tempered by ion exchange, or “chemical” tempering. The process of chemical tempering comprises a step where the original glass is immerged into a molten alkali salt at a temperature below the glass transition. Processes to chemically strengthen/temper glass are well known to the skilled man in the art.

[48] Typically, chemical tempering/strengthening is performed by exchanging Na+ ions by K+ ions at the surface of the glass sheet by dipping the glass sheet in a molten salt bath at a temperature below the glass transition temperature. Advantageously, the bath consist of high purity KNO3 and the treatment is performed at temperature between 350°C and 470°C, for 1 to 24hours. Chemical tempering/strengthening is preferably applied for glass sheet of thickness below 3mm, more preferably below 2mm and even more preferably below 1 mm, or even better below 0.7mm.

[49] According to one embodiment of the present invention, the head-up display system 1 for a vehicle comprises a combiner 10 comprising at least one glass sheet having an outer 21 and an inner face 22, the inner 22 or the outer 21 face being provided with a p-polarized light reflective coating 23.

[50] FIG.3a and FIG.3b show a combiner according to one embodiment of the present invention. According to one embodiment of the present invention, the inner face 22 of the combiner is provided with a p-polarized light reflective coating 23. In the scope of the present invention, a p-polarized light reflective coating is intended to describe a coating or stack of thin layers which is capable of reflecting incident p- polarized light, at any angle of incidence. For avoidance of doubt, the inner face of the combiner is the face facing the interior of the vehicle which also the face facing the observer (also called front surface). The coating as applied to the glass acts as a semimirror. The coating is configured to reflect the p-polarized light. FIG. 3a shows a combiner comprising one glass sheet 20 with an inner face 22 and an outer face 21 . In case of a laminated combiner as shown as an example in FIG. 3b, the combiner 10 comprises a first glass sheet 20 having an inner P4 and an outer face (P3) and a second glass sheet 24 comprising also an inner (P1 ) and an outer face (P2). In that case, it used the nomenclature commonly used in automotive glazing to characterized the outer face and the inner face of the laminated glazing. The two glass sheets are generally bound together thanks to an interlayer film or any suitable material. Thus, the most outer face of the laminated combiner is called P1 (corresponding by analogy to the outer face 21 of the first glass sheet 20 of FIG.3a), then the face of the first glass sheet facing the interlayer film (or any suitable material to fix the two glass sheets) is called P2, P3 being the face of the second glass sheet 24 facing the interlayer film (or any suitable material to fix the two glass sheets) and finally P4 being the face of the laminated combiner facing the interior of the vehicle (corresponding by analogy to inner face 22 of the first glass sheet 20 of FIG.3a). It is understood that the combiner may be a laminated combiner with at least one first glass sheet laminated with any suitable material as for example another glass sheet, a plastic material as PVC, poly carbonate... suitable for the application of HUD-up system.

[51] This p-polarized light reflective coating 23 is advantageously applied over the inner face of combiner 10 namely face 22 as represented in FIG. 3a when the combiner comprises one glass sheet or on the inner face of the laminated combiner namely P4 as represented in FIG. 3b to increase the amount of reflection of incident p-polarized light. By improving the reflection of p-polarized light, the present coating may allow for the use of light projector projecting at least 50% p-polarized light and still achieve a sharp and well-defined image. Such projectors are readily available at accessible cost. The projector may also project 100% p-polarized light, if the use so requires.

[52] In the scope of the invention, the p-polarized reflective coating 23 may typically comprise at least one sequence of layers of high refractive index layers/low refractive index layers, or high/low sequence. The high/low sequence may occur more than once, that is, the sequence may be repeated at least 2 times, up to 3 or 4 times.

[53] In the scope of the present invention, the p-polarized reflective coatings may preferably be a magnetron sputtered p-polarized reflective coating, having the advantage of being easily processed, easily adaptable to the selected function, and cost efficient.

[54] In the scope of the present invention, the thickness of the coatings and thin layers are geometrical thicknesses expressed in nm, unless indicated otherwise.

[55] In the scope of the present invention, the terms “below”, “underneath”, “under” indicate the relative position of a layer vis a vis a next layer, within the layer sequence starting from the substrate. In the scope of the present invention, the terms “above”, “upper”, “on top” , “on” indicate the relative position of a layer vis a vis a next layer, within the layer sequence starting from the substrate. [56] In the scope of the present invention, a high refractive index is typically > 1.8, alternatively > 1 .9, alternatively > 2.0, alternatively > 2.1 , at a wavelength of 550 nm.

[57] The high refractive index layers may be selected from oxides of Zn, Sn, Ti, Nb, Zr, Ni, In, Al, Ce, W, Mo, Sb, Bi and mixtures thereof; nitrides or oxynitrides of Si, Al, Zr, B, Y, Ce, La; and mixtures thereof.

[58] In the scope of the present invention, a low refractive index is typically < 1.7, alternatively < 1 .6, at a wavelength of 550 nm.

[59] The low refractive index layers may be selected from silicon oxide, silicon oxycarbide, aluminum oxide, mixed silicon aluminum oxide, mixed silicon zirconium oxide (with n < 1.7), aluminum doped zinc oxide, magnesium fluoride, or mixtures thereof.

[60] The refractive index at a wavelength of 550 nm of the high refractive index materials is typically higher than the refractive index of the low refractive index materials. The refractive indices of the high and low refractive index materials may differ by a value of at least 0.1 , preferably by a value of at least 0.2, more preferably by a value of at least 0.25.

[61] According to one embodiment of the present invention, a first suitable p- polarized reflective coating 23 is provided on the glass surface ( inner or outer face) of the combiner and comprises, in sequence starting from the glass surface,

- at least one high refractive index layer having a thickness of from 50 to 100 nm, and

- at least one low refractive index layer having a thickness of from 70 to 160 nm, wherein the least one high refractive index layer comprises at least one of

- an oxide of Zr, Nb, Sn;

- a mixed oxide of Ti, Zr, Nb, Si, Sb, Sn, Zn, In;

- a nitride of Si, Zr;

- a mixed nitride of Si, Zr (with n > 1.7).

[62] A layer in the present first suitable p-polarized reflective coating 23 may comprise more than one sub-layer.

[63] Such a first suitable p-polarized reflective coating is already efficient having p- polarized light reflection > 15 %, with a low complexity of design, and is resistant to thermal treatment.

[64] A second particularly suitable p-polarized reflective 23 coating comprises, in sequence starting from the substrate surface, optionally a first layer, composed of one or more high refractive index sublayers, the first coating having a thickness of from 1 to 100 nm, and a second layer, composed of one or more low refractive index sub-layers, the second layer having a thickness of from 1 to 220 nm, and a third layer, composed of one or more high refractive index sub-layers, the third layer having a thickness of from 40 to 150 nm, and a fourth layer, composed of one or more low refractive index sub-layers, the fourth layer having a thickness of from 40 to 200 nm, and further comprising at least one first layer of absorbent material, said at least one first layer of absorbent material having a thickness of from 0.2 to 15 nm, and said absorbent material having an average refractive index n above 1 and an average extinction coefficient k above 0.1 , with the averages n and k calculated over the values at the wavelengths of 450 nm, 550 nm and 650 nm.

[65] This second particularly suitable p-polarized light reflecting coating optionally comprises a first layer, composed of one or more sub-layers of high refractive index materials and a second layer, composed of one or more sub-layers of low refractive index material. This optional pair of layers provide improved reflection of p-polarized light, but at a higher production cost.

[66] The first layer, when present, is composed of one or more sub-layers of high refractive index material, independently selected from the materials described above. When present, the first layer may have a thickness of from 1 to 100 nm, alternatively of from 2 to 80 nm, alternatively of from 4 to 65 nm, alternatively of from 4 to 15 nm.

[67] The second layer, when present, is composed of one or more sub-layers of low refractive index material, independently selected from the materials described above. When present, the second layer may have a thickness of from 1 to 220 nm, alternatively of from 2 to 210 nm, alternatively of from 4 to 200 nm, alternatively of from 100 to 200 nm.

[68] The third layer is composed of one or more sub-layers of high refractive index material, independently selected from the materials described above. The third layer may have a thickness of from 40 to 150 nm, alternatively of from 45 to 135 nm, alternatively of from 50 to 125 nm.

[69] The fourth layer is composed of one or more sub-layers of low refractive index material, independently selected from the materials described above. The fourth layer may have a thickness of from 400 to 200 nm, alternatively of from 45 to 160 nm, alternatively of from 50 to 150 nm.

[70] Each of the optional first, optional second, third or fourth layer may thus independently consist of one single layer, or may comprise two or more sub-layers.

[71] The high refractive index materials of the second particularly suitable p- polarized reflective coating may be selected from

- an oxide of Zr, Nb, Sn, Zn or Ti;

- a mixed oxide of two or more of Ti, Zr, Nb, Si, Sb, Sn, Zn, In;

- a nitride of Si, Zr, Al, B;

- a mixed nitride of two or more of Si, Zr, Al, B.

[72] The high refractive index materials of the second particularly suitable p- polarized reflective coating may preferably be selected from mixed titanium zirconium oxide, mixed titanium silicon oxide, mixed niobium zirconium oxide, mixed silicon zirconium nitride, aluminum doped silicon nitride, zirconium oxide, mixed indium tin oxide, mixed zinc rich aluminum oxide, mixed antimony tin oxide, mixed titanium zinc oxide, mixed zinc tin oxide.

[73] In some occurrences, an undercoat may be present in contact with the surface of the combiner surface (outer face 21 or inner face 22). Such an undercoat is distinct from any of the first or second or third or fourth layer of the second particularly suitable primary p-polarized reflective coating. Such an undercoat does not provide any optical impact to the p-polarized light reflective coating, but may function as a diffusion barrier from the substrate or as a seed layer to the subsequent layers. In preferred embodiments, the undercoat may present particularly in absence of the first and second layers.

[74] By ' 'absorbent material" is meant a material which absorbs a part of the visible radiation.

[75] The absorbent material may be characterized by an average refractive index n above 1 and an average extinction coefficient k above 0.1 , with the averages n and k calculated over the values of n and k at 3 wavelengths, namely 450 nm, 550 nm and 650 nm.

[76] The average n is thus calculated using the values of refractive index of the material at the 3 wavelengths of 450 nm, 550 nm and 650 nm. The average k is calculated using the values of extinction coefficient of the material at the 3 wavelengths of 450 nm, 550 nm and 650 nm.

[77] The skilled person in the art is familiar with the n and k optical parameters. Thin film optical simulation software such as Thin Film Center or CODE, have their own databases but also provide a reliable tool for person skilled in the art to fit n and k optical models of thin films deposited with known physical thickness and a characterized substrate.

[78] The at least one first layer of absorbent material may be selected from NiCr, W, Nb, Zr, Ta, Pd, Si, Ti, or alloys based on Ni and/or Cr and/or W or alloys based on Cr and Zr, or on W and Zr or Cr, or on W and Ta, optionally including an additional element selected from Ti, Nb, Ta, Ni and Sn; or from TiN, CrN, WN, NbN, TaN, ZrN, NiCrN, or NiCrWN, or a mixture of these nitrides.

[79] The nitrides may also be partially oxidized provided absorption is maintained with k above 0.1 over the range between 450 nm and 650 nm.

[80] The absorbent material layer may be provided with at least one barrier layer above and/or below said absorbent layer. Such a barrier layer may have a geometric thickness comprised between 5 and 50 nm. Examples of such barrier layers include silicon nitride or aluminum doped zinc oxide or titanium oxide or mixed titanium zirconium oxide.

[81] That is, in some instances, the at least one first layer of absorbent material may comprise a layer of NiCr or NiCrW provided with at least one barrier (below or above) of silicon nitride, or be flanked by (below and above) a first dielectric coating formed essentially of silicon nitride and a second dielectric coating formed essentially of silicon nitride, each independently having a geometric thickness comprised between 5 and 50 nm; or the at least one first layer of absorbent material may comprise a layer of Pd (palladium) flanked by a first dielectric coating formed essentially of aluminum doped zinc oxide and a second dielectric coating formed essentially of aluminum doped zinc oxide, each independently having a geometric thickness comprised between 5 and 50 nm. Such a layer of absorbent material allows for optimal reflection of p-polarized light with optimal light absorption.

[82] The at least one first layer of absorbent material may preferably be selected from NiCr, W, Nb, Pd, Si, Ti, or alloys based on Ni and/or Cr and/or W; or from TiN, CrN, WN, NbN, TaN, ZrN, NiCrN, or NiCrWN, or a mixture of these nitrides.

[83] The at least one first layer of absorbent material may more preferably be selected from NiCr, W, Pd, Si, Ti, or alloys based on Ni and/or Cr and/or W; or from TiN, CrN, WN, NiCrN, or NiCrWN, or a mixture of these nitrides.

[84] For the sake of information, the average refractive index n and average extinction coefficient k, for various absorbent materials and for silver are presented in Table 1. This average is calculated over 3 values of wavelength, namely at 450, 550 and 650 nm. An average refractive index n < 1 is indicative of a material which does not suit as absorbent material. Silver, gold, copper, aluminum having an average n < 1 , are thus not suitable.

TABLE 1

[85] Although not mandatory, heat resistance of the absorbent material may be useful, that is, it preferably remains essentially unchanged upon a heat treatment above a temperature of 400°C.

[86] The absorbent material does not comprise silver. A material such as silver does not provide the necessary enhancement of the reflection of the p-polarized light due to its low refractive index n below 1 , and does not allow for the positioning of the p- polarized reflective coating on a surface of the glazing pane facing the interior of the compartment (surface P4 in case of laminated combiner or P2 in case of simple glass combiner).

[87] The at least one first layer of absorbent material may have a thickness of from 0.2 to 15 nm, alternatively of from 0.5 to 15 nm, alternatively of from 2 to 12 nm.

[88] The at least one first layer of absorbent material may be

- either inserted between at least two adjacent coatings of the said first, second, third or fourth layer, or

- inserted within at least one of the said first, second, third or fourth layer.

[89] Such a second suitable p-polarized reflective coating is very efficient having p- polarized light reflection > 20%, is resistant to thermal treatment and may be tuned for efficiency without sacrificing on light transmittance. [90] The particulars of this second suitable primary p-polarized reflective coating in the scope of the present invention, is that it does not mandatorily need to have a light transmittance > 70%, when used in a laminated combiner of 2 clear glass sheets 2.1 mm with a clear interlayer of 0.76 mm, since it is not intended to be transparent to the view. The advantage of such a second suitable primary p-polarized coating is that the reflectance of p-polarized light may reach up to at least 20% p-polarized light reflection when positioned on a display area having TL < 30%, while color neutrality need not be optimized.

[91] In the scope of the present invention, the p-polarized reflective coating 23 itself may have any light transmittance, that is, a light transmittance less than 90%, less than 70%, alternatively less than 65%, alternatively less than 60%, and greater than 30%, alternatively greater than 40%, when measured on a sheet of monolithic clear float glass of 2.1 mm.

[92] The p-polarized light reflective coating is considered a nonconductive coating, that is, its sheet resistance may be > 100 Ohm/square.

[93] The p-polarized light reflective coating 23 is sufficiently durable and resistant to scratches to be present in outer or inner face of the combiner, facing the exterior or the interior of the vehicle’s habitable. In a preferred embodiment, the p-polarized light reflective coating is provided on the inner face of the combiner in order to be closer to the projector.

[94] The p-polarized light reflective coating may be optimized in order to maximize the ratio of the p-polarized light reflection and total reflection (internal) at a certain angle of incidence (Rp-pol/Rin), measured at a wavelength of 550 nm +/- 100 nm.

[95] That is, at said angle of incidence at a visible wavelength, the p-polarized light reflection is maximized and the interior reflection is minimized.

[96] The angle of installation of the combiner may thus be selected such that the ratio Rp-pol/Rin is maximized. This has the advantage that, although the p-polarized light reflection is maximized - at that particular angle of incidence, the driver or vehicle occupant is not disturbed by the dashboard reflection (in the visible range).

[97] Thus, an image (light) source 13 projecting p-polarized light may be used to project an image 15 toward the combiner according to the present invention.

[98] The inventors have found that advantageously use of a combiner 10 comprising at least one chemically tempered glass 20 provided with a p-polarized light reflective coating 23 provided on its inner 22 face (or P4 in case of the laminated combiner) allows to increase durability of the combiner and consequently the lifetime of the whole HUD system. Furthermore, the combiner offers a bigger surface of reflection. The combiner 10 is also produced according to an easiest method.

[99] According to one embodiment of the present invention, a combiner 10 is provided with a p-polarized light reflective film 23. The film is provided preferably on the inner face of the combiner facing towards the vehicle interior, where it provides for optimal reflection of p-polarized light. The p-polarized light reflective film 23 is selected for example from films comprising at least one transparent liquid crystal layer; films comprising at least one cholesteric liquid crystal layers; films comprising a plurality of alternating polymeric interference layers, and the like.

[100] For example, a reflective film comprising liquid crystal layers can be bonded to the surface of the glazing pane as a functional foil. In this case, corresponding liquid crystal layers are applied as a stack of functional layers, for example, to carrier foils made of cellulose triacetate (TAC), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA) or other conventional polymeric materials. High precision coating processes for the manufacture of such functional liquid crystal films are available and known in the art and the functional films are commercially available. Advantageously, the foils can be applied to the surface of a combiner pane facing the interior, which surface is intended to serve as a projection surface.

[101] Commercial examples of such reflective films are available from 3M under the tradename 3M® WCF, or the reflective films available from Toray under the tradename PICASUS®VT, or the reflective films available from Fujifilm under the tradename Wavista®.

[102] According to one embodiment of the present invention, the combiner 10 comprises further a dashboard structure support configured to be fixed to the dashboard.

[103] The dashboard support structure may comprise at least a first part 32 that may include means to fix/attached the combiner to the dashboard.

[104] The dashboard support 30 may comprise a first part 32 that may be a carrier plate or frame supporting the glass sheet of the combiner supporting at least a part of the surface of the at least one chemically tempered glass sheet of the combiner 10. Thus, depending on the thickness of the glass sheet 20, the glass sheet 20 may be cold bended by fixing it to the frame or the back plate. The combiner may be then more accurately fitted to the dashboard. [105] According to one embodiment of the present invention, the carrier 32 may have the requested shape to fit with the requested final shape of the combiner.

[106] According to one embodiment of the present invention, the at least first part of dashboard support 30 is a frame to limit the deformation of the glass 20 allowing at the same time to absorb the energy in case of static and dynamic loading/shock thanks to the appropriate construction.

[107] According to another embodiment of the present invention, the at least first part of dashboard support 30 is a carrier plate extended over at least a part of the surface of the glass sheet of the combiner 10 to limit the deformation of the glass allowing at the same time to absorb the energy in case of static and dynamic loading/shock thanks to the appropriate construction. The back carrier 32 may be a safety backing improving the safety of the glass and prevent fragment to spread in the vehicle in case of breakage.

[108] The frame and/or the carrier 32 may be made out of thermoplastics material, or steel, or composite material, or a combination of those, in order to brings to the module glass with frame/carrier a sufficient rigidity to reduce the glass deformation and reduce the risk of glass breakage.

[109] The first part 32 of the dashboard support is preferably made of plastic. The current invention is taking the advantage that the plastics can be easily adapted and formed by different processes, and can also be fixed to the glass. Therefore all the fixing elements can be included inside the plastic frame that will be fixed to the glass, which will be used as user interface and providing a much better finishing aspects to the user.

[110] Preferably, the at least first part 32 of the dashboard support (frame or back plate) is for example made of a material chosen among thermoplastics such as for example Polybutylene terephthalate (PBT), Polycarbonate-Acrylonitrile Butadiene Styrene (PC-ABS), Polyamide (PA6), Polyamide copolymer (PA66), Polyoxymethylene (POM), Polypropylene (PP) with or without fillers to bring additional properties, such as glass fibers for mechanical reinforcement. Thermoplastic elastomers (TPE) or thermosets material such as Polyurethane (PUR), Epoxies (EP) having a hardness of higher than 90 Shore A may also be used.

[111] According to an embodiment of the present invention, the first part 32 of the dashboard support 30 may be fixed to the combiner in an injection mold. The first part of the dashboard support is then provided in the injection mold in a flat or substantially flat shape and bent in the requested shape into the injection mold. Thus, the mold may be used not only to bend the glass panel but also to bend the first part of the dashboard support and to inject the injection material to fix the at least one glass sheet of the combiner to the first part of the dashboard support.

[112] According to an embodiment of the present invention, the carrier that may be made of a rigid material may be provided with fixing means 33. Fixing means are preferably provided with the carrier plate or frame. Fixing means are provided to fix/attached the combiner to the dashboard 11 .

[113] The dashboard support may comprise a second part extending or not over all the surface of the at least one chemically tempered glass sheet 20 of the combiner 10. The second part 31 of the dashboard support is preferably provided between the at least one glass sheet 20 of the combiner and the first part of the dashboard support structure. The second part 31 of the dashboard support is preferably a material injected between the at least one glass sheet and the first part of the dashboard support structure. According to one embodiment of the present invention, the second part of the dashboard structure is made of a soft material 31 injected between the first part 32 (carrier plate or a frame) and the at least one glass sheet of the combiner. The soft material has preferably a hardness of less than 90 Shore A. The at least one glass sheet of the combiner is then fixed to the carrier plate via the sot material. The soft material may be injected according to known techniques of glass encapsulation.

[114] According to an embodiment the present invention, the soft material having a hardness of less than 90 Shore A is a thermoplastic polymer such as polypropylene, thermoplastic elastomers (TPE) such as olefinic thermoplastic elastomers (TPO), polyurethane, polyamide or soft polyvinyl chloride, Silicone or similar materials or any material suitable for reactive injection molding. The soft material is made of an appropriate material to withstand the thermal expansion difference of the different materials of the carrier plate and the glass. Thus the use of a viscoelastic material as mentioned, such as preferably a glue (Pll, Silicon, MS Polymer) or a thermoplastics elastomers with an appropriate shear strain are used.

[115] According to one embodiment of the present invention, the soft material is injected over all the surface of the at least one glass sheet of the combiner and/or the carrier, between the glass panel and the carrier, to lead to a full surface adhesion of the glass combiner to the first part.

[116] By injecting the soft material over all the surface of the at least one glass sheet and/or the first part (carrier or frame), the stresses applied on the soft material which is used to bond the glass to the carrier are reduced and the glass combiner is well bonded over all its surface to the first part of the dashboard support. Thus, deformation of the glass panel is avoided. Therefore, the bent glass panel is fixed to the curved carrier after bending to retain the curvature of the glass panel

[117] . The glass sheet may be then cold bended. Cold bend the glass to form the combiner has the advantage that the p-polarized light reflective coating may be applied on the glass before it is bent. Thus, the coating is provided uniformly over the surface of the face of the combiner to be coated.

[118] The at least first part of the dashboard structure support may be made of plastic. The current invention is taking the advantage that the plastics can be easily adapted and formed by different processes, and can also be fixed to the glass. Therefore all the fixing elements can be included inside the plastic frame that will be fixed to the glass, which will be used as user interface and providing a much better finishing aspects to the user.

[119] According to one embodiment of the present invention, fixing means may be provided on the at least first or second parts of the dashboard support structure. The fixing means may allow to fix the combiner to the dashboard by screwing, clipping, heat stacking or any suitable way to fix the combiner to the dashboard.

[120] Thus, according to one embodiment of the present invention, the dashboard support may comprise a first part and a second part that can be made of different material.

[121] A combiner according to one embodiment of the present invention is shown is FIG. 4.

[122] The FIG. 4 shows a combiner 10 provided with a dashboard support 30. The dashboard support structure 30 comprises as a first part 32 made of a rigid material as for example made of a Polybutylene terephthalate (PBT), Polycarbonate- Acrylonitrile Butadiene Styrene (PC-ABS), Polyamide (PA6), Polyamide copolymer (PA66), Polyoxymethylene (POM), Polypropylene (PP). The first part in the form od a carrier plate 32 is provided over all the surface of the chemically tempered glass sheet of the combiner 10. The carrier plate 32 is fixed to the at least glass sheet in a mold to encapsule glass.

[123] The carrier plate 32 is fixed to the at least glass sheet with a second part 31 .

[124] The first part 32 of the dashboard support structure 30 may comprise fixing means 33 configured to fix the combiner to the dashboard. The fixing means may be made with the same material of the first part material and may be extended parts from the first part of the dashboard support structure.

[125] A second part 31 of the dashboard support 30 provided over the surface of the at least one glass sheet 20 of the combiner 10 and the inner face 22 of the first part 32 of dashboard support by injecting a soft material chosen for example amongst polypropylene, expanded polypropylene, polyvinyl chloride, or acrylonitrile I styrene acrylate between the at least one glass sheet 20 of the combiner and the first part 32. Thus, the first part 32 is fixed to the at least one glass sheet thanks to the second part 31.

[126] According to one embodiment of the present invention, the combiner may be fixed to the dashboard by screwing, clipping, heat stacking or any suitable way to fix the combiner to the dashboard. Techniques of encapsulation of glass are well known by skilled man in the art.

[127] According to one embodiment of the present invention, the combiner is at least partly directly laminated to the dashboard. The lamination may be performed by applying adhesive material on part of the glass part, for example around at least part of the edge of the glass part, or by applying adhesive material to the entire contact area between the at least one glass sheet and the dashboard structure. The adhesive material is then provided over at least a part of the outer face of the at least one glass sheet.

[128] According to the present invention, the combiner 10 (or glass dashboard part) is placed into the dashboard in a manner that the image received from a light source is reflected toward an observer in order to be viewed.

[129] According to one embodiment of the present invention, the combiner can be retracted into or folded down parallel with a top surface of the dashboard.

[130] In a preferred embodiment, the image source for projecting an image onto a combiner is a light source projecting at least 50% p-polarized light towards the combiner light at an angle of incidence of 5 to 65° and wherein the light projected by the light source is incident on and reflected from said combiner.

[131] Thus, the combiner may be located in a limited part in the dashboard or extended over from the driver’s A-pillar to the passenger’s A-pillar of the vehicle. Thus, one or more images may be projected onto the combiner provided on the dashboard.

[132] According to one embodiment of the present invention, the HUD system may comprises one or multiple combiners.

[133] According to the present invention, the combiner may size as classical combiner used nowadays in vehicle meaning they are at least sized to receive a visible and clear image form the light source. The dimensions of the combiner are the same than the one already used in vehicle, however according to the present invention they can be wider than classical combiner since they can extend from driver’s A-pillar to the passenger’s A-pillar.

[134] According to one preferred embodiment of the present invention, the combiner has a light transmittance < 30%, the interference of the air/outer pane interface is reduced, and as such, the image is sharp and ghosting effect if reduced or eliminated. When the display area is an area having a light transmittance < 1 %, the interference of the air/outer pane interface is eliminated, and as such, the image is sharper and free of ghost.

[135] The light transmittance of less than 30% of the display area may be achieved by different opacifying means, selectively arranged in said display area. The selected opacifying means are intended to either shade and/or opacify, such that TL is < 30% or less, as discussed above.

[136] The opacifying means of the display area may be at least one selected from

- a dark print;

- a dark insert;

- a dark patch;

- or combinations thereof.

[137] When a dark print is used as opacifying means, the dark print may be selected from enamel, paint, and/or ink. The dark print may be applied on the outer face 21 of the combiner or in case of laminated combiner on what is commonly called P1 , P2, P3 of the laminated combiner.

[138] Among dark prints, enamel is preferably used to opacify the projection area, when deposited on either one of inner or outer face of the combiner. In case the combiner is made of laminated glass sheets (known as outer and inner glass sheets), the enamel may be provided on the outer and/or inner face of the outer glass sheet of laminated combiner or the inner face of the inner glass sheet of the laminated combiner. Typical enamel compositions typically comprise a glass frit, pigments and other additives in a medium. Additives include adhesion promoters, crystalline seed materials, reducing agents, conductive metals (e.g. silver particles), rheological modifiers, flow aids, adhesion promoters, stabilizers, etc.

[139] The main advantage of an enamel opacifying means is that total opacity may be achieved, that is TL may be < 5%, preferably < 1 %, most preferably equal to 0%.

[140] Thus, high image quality without ghost can be obtained since the double image coming from the outer face of the combiner can be avoided.

[141] In a preferred embodiment of the present invention, the combiner 10 is provided with a p-polarized light reflective coating on the inner face of the combiner and an opacifying mean on the outer face of the combiner.

[142] According to an embodiment of the present invention, an anti-reflective coating can be applied on the outer face of the combiner in order to reduce the ghost image. The anti-reflective coating is based on refractive index gradient or texture coating like porous anti-reflective coating.

[143] The present invention also provides a method for producing a combiner for an HUD system for a vehicle as described above.

[144] The method comprises the following steps: a. Providing at least one glass sheet chemically tempered having an inner face and outer face; b. Providing a p-polarized light reflective coating or a p-polarized light reflective film onto at least a part of the inner face of the at least one glass sheet; c. Assembling the glass sheet provided with step b) to a dashboard support structure.

[145] The method for producing a combiner for an HUD system for a vehicle comprises a further step of bending the glass sheet.

[146] As described above, the dashboard support structure may comprise at least a first part that may include means to fix/attached the combiner to the dashboard.

[147] The present invention covers also the use of a combiner comprising at least one chemically tempered glass sheet in a vehicle to reflect an image projected from a light source projecting at least 50% p-polarized light towards the combiner.

[148] The present invention covers also a head-up display system as described above.

[149] While the preferred embodiments of the present invention are described above, obvious modifications and alterations of the present invention may be made without departing from the spirit and scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereto.

Claims

1 . A head-up display system for a vehicle, comprising: a. an image source (13) configured to project an image onto a combiner (10), said image source (13) being positioned in a dashboard (11 ) of the vehicle b. a combiner (10) integrated to the dashboard (11 ) for reflecting the said projected image (15) toward an observer (300) for observation, wherein said combiner (10) comprises at least one chemically tempered glass sheet (20) having an inner face (22) and an outer face (21 ).

2. A head-up display system for a vehicle (1 ) of claim 1 wherein the combiner (10) comprises further a p-polarized light reflective coating (23) provided on the inner face (22) or the outer face (21 ) of the said at least one chemically tempered glass sheet (20).

3. A head-up display system for a vehicle (1 ) of claim 2 wherein the p-polarized light reflective coating (23) comprises at least one sequence of layers of high refractive index layers/low refractive index layers.

4. A head-up display system for a vehicle of claim 1 wherein the at least one glass sheet of the combiner is made a glass with a thickness between 0.5 to 2.1 mm.

5. A head-up display system for a vehicle of claim 1 wherein the combiner is placed on an upper part or a bottom part of the dashboard, as viewed by the driver.

6. A head up display system for a vehicle (1 ) of claim 1 wherein the combiner (10) comprises further a dashboard support (30) configured to be fixed to the dashboard (11 ).

7. A head-up display for a vehicle (1 ) of claim 6 wherein the dashboard support (30) comprises at least first part (32) and a second part (31 ).

8. A head-up display for a vehicle (1) of claim 7 wherein the dashboard support

(30) comprises at least first part (32) made of a rigid material and a second part

(31 ) made of a soft material.

9. A head up display system for a vehicle (1) of claim 1 wherein the combiner is at least partly laminated to the dashboard’s support structure.

10. A head up display system (1 ) for a vehicle (1 ) of claim 1 wherein the combiner has a light transmittance < 30%.

11. A head up display system for a vehicle (1 ) of claim 1 wherein the combiner comprises further preferably on it outer face (21 ) provided with by at least one opacifying means.

12. A head up display system for a vehicle of claim 1 wherein the image source (13) for projecting an image onto a combiner is a light source projecting at least 50% p-polarized light towards the combiner light at an angle of incidence of 25 to 65° and wherein the light projected by the light source is incident on and reflected from said combiner 10).

13. A method for producing a combiner for an head up display system for a vehicle of claims 1 to 12 comprising at least the following steps: a. Providing at least one glass sheet chemically tempered (20) having an inner face (22) and outer face (21 ); b. Providing a p-polarized light reflective coating (23) or a p-polarized light reflective film (23) onto at least a part of the inner face (22) of the at least one glass sheet (23); c. Assembling the glass sheet provided with step b) to a dashboard support structure.

14. Use of a combiner (10) in a vehicle (100) wherein the combiner comprise at least one chemically tempered glass to reflect an image projected from a light source projecting at least 50% p-polarized light towards the combiner.

15. Vehicle comprising a head up display according to anyone of claim 1 to 14.