WO2021139995A1

WO2021139995A1 - Glass vehicle side window and partition window with active projection transparent screen

Info

Publication number: WO2021139995A1
Application number: PCT/EP2020/086795
Authority: WO
Inventors: Johannes Wolf; Michele CAPPUCCILLI
Original assignee: Saint-Gobain Glass France
Priority date: 2020-01-06
Filing date: 2020-12-17
Publication date: 2021-07-15
Also published as: CN113383306A

Abstract

The invention concerns a vehicle glazing and display system (1) comprising a vehicle compound glazing unit (10; 10'; 10'') comprising a layer or surface (12a; 12b; 14) switchable between active first state and a second state, which, in the first state, diffusely reflects incident light directed to the glazing unit from a first side of the vehicle compound glazing unit (10; 10'; 10'') to a second side of the vehicle compound glazing unit (10; 10'; 10'') and having a maximum gain in the range of 0.03 to 0.8, preferably between 0.3 and 0.6 and an intrinsic viewing angle α for a real image element generated within the glazing plane of more than 60°, in a first direction and of more than 30°, in a second direction, perpendicular to the first direction in a reflection geometry, and which in the second state is transparent, a projector (4) for projecting an image to the vehicle glazing unit to generate a real image in the plane of the glazing unit and wherein the vehicle compound glazing unit (10; 10'; 10'') is a side window or partition window (3) and a projector control unit for controlling the projector and the switching of the layer or surface.

Description

Glass vehicle side window and partition window with active projection transparent screen

Field of the Invention

The invention is in the field of displaying information on a glazing element of a vehicle. More specifically, the invention is in the automotive field, but it is not restricted to this field but can be implemented in buses, railway cars, boats, airplanes or other vehicles. More specifically, the invention is related to a vehicle glazing and display system, comprising a vehicle compound glazing unit and a projector for projecting an image to the glazing unit.

Background / Prior Art

In this technical field, there are many patents or patent applications which are, to a certain extent, background art to the present invention.

US 7 157 133 discloses the basic concept of diffuse reflection with embedded diffusing surface.

EP 2 185 966 discloses an element with a diffusing surface on which a reflective layer is deposited, the whole being in an envelope of the same refractive index as the diffusing element. The assembly is designated as a numerical aperture expander working in reflection, which seems functionally close to a diffuser and a transparent element in transmission. In this patent, the integration of such an element in a head-up display (HUD) projection system for generating virtual images is mentioned.

US 8 519 362 B2 to Saint-Gobain describes an HUD system assembled into a car. It is based on a laminated windshield where the HUD function comes from a layer of luminophore material. US 7 230 767 B2 describes a display system in a car glass pane using a light emitting material projecting the image to the driver. The image is a virtual image, focused meters away from the eyes of the driver and from the windshield.

A preparation process of an HUD system integrated into a laminated glass pane is described in the Saint-Gobain owned patent EP 2 883 693.

Regarding the general concept of transparent glazing units which have a certain degree of diffuse reflection, there are several patent publications of Saint-Gobain, e.g. EP 2 670 594, EP 2 856 256, EP 2 856 533, EP 2 872 328, EP 3 063 002, WO 2012 104 547, WO 2018 015 702, and FR 3 054 17. In these patent documents, it is, inter alia, disclosed that such diffusely reflective glazing can contain a rough internal surface and a coating provided thereon and that such glazing can be used for OLED display solutions or for projection-based display solutions.

EP 3 395 908 A1 discloses a transmission type screen as head-up-display for automotive applications, in which the screen is particle based.

In EP 3 151 062 A1 a video projection structure for integration into an automotive window is presented, wherein the window contains a reflection film applied on a surface having random irregularities.

JP 2016 9271 A discloses a video display system, which is equipped with detection means to detect a movement of the observer, wherein display system can be operated by the movement of the observer.

CN 203340200 U and CN 208156364 U disclose projection on a PLDC device.

DE 10 2004 051 607 A1 discloses a device and a method for displaying a digital image onto a geometrical and photometrical non-trivial surface. In particular, the document discloses to project an image with one or more projectors onto a non-planar surface. The projection method comprises in particular a calibration with a camera connected to a control system which is adapted to control the one or more projectors for adjusting the projection of the image for each displayed pixel of the image.

In US 2015 358574 A1 a display is used to simulate an environment. The display can be positioned behind a wall opening to provide a window effect. The display terminates its active image area outside of a region from which the display can be viewed to create a seemingly infinite simulated environment.

The glazing of WO 2014 096717 A1 comprises a variable light diffusion system having a layer based on active elements, that can switch between a transparent state and a translucent state, at least two substrates arranged either side of the variable light diffusion system, and at least one substrate comprising a set of discrete diffusing elements forming a pattern.

US 2019 025692 A1 discloses a transparent screen with an image projected from a projector. The transparent screen includes a display panel including a diffusion film which diffuses projection light from the projector, and a tinted film which is disposed to be remoter from the projector than the diffusion film is. The tinted film has a transmittance which is variable.

It is an object of the present invention, to provide a vehicle glazing and display system comprising a vehicle compound glazing unit, which is adapted for a broad range of applications in future mobility solutions. More specifically, it is an object to provide a system which makes it possible to display rich content to basically all persons which use a vehicle or at least to all those persons, which sit or stand close to a respective glazing unit. Furthermore, a solution is required which can be implemented, to a far extent, on the basis of available technologies and which is safe, reliable and cost-efficient.

These, and further, objects are solved by a vehicle glazing and display system according to claim 1. Preferred embodiments of the invention are subject of the respective dependent claims.

The vehicle glazing and display system according to the invention comprise a vehicle compound glazing unit comprising a layer or surface which diffusely reflects incident light directed to the glazing unit from the first side of the vehicle compound glazing unit and a projector for projecting an image to the vehicle glazing unit to generate a real image in the plane of the glazing unit, wherein the image is in particular visible from the second side. The vehicle compound glazing unit is used in a transmission geometry. The vehicle glazing unit is a window inside a vehicle (partition window) or a side or back window of the vehicle. The vehicle glazing and display system further comprises a projector control unit for switching the vehicle compound switching unit and switching the projector. The vehicle glazing with display system shows a maximum gain (also referred to as peak gain) in the range of 0.03 to 0.8, preferably between 0.3 and 0.6. The intrinsic viewing angle a for a real image element generated within the plane of glazing is larger than 40°, preferably larger than 60° and more preferably larger than 70° or more in a first direction and larger than 20°, preferably larger than 30° in a second direction, which is perpendicular to the first direction. When using these intrinsic viewing angles within practical application at standard environment conditions, a practical viewing angle of larger than 60°, preferably larger than 90° and more preferably larger than 120° or more in a first direction and larger than 30°, preferably larger than 45° in a second direction, which is perpendicular to the first direction, can be achieved. The practical viewing angle is dependent of both the luminous environment and the used projector. Nevertheless, the practical viewing angle is a commonly used feature for screen specification and can be determined for chosen environment conditions related to a particular use case. For standard environmental conditions and projector specification the following values could be used:

External illuminance 2200 Lux (outside the car); internal illuminance 100 Lux (inside the car); flux from projector 3500 Lumen; Projection surface: 16:9 screen with 9“ diagonal (20 cm width); the practical view angle can then be extracted from gain curve via a mathematical formula.

The practical viewing angle is studied on the basis of the contrast of the screen. The contrast of a screen is commonly defined as the luminance ratio between a white and a black picture, wherein a minimum ratio of 4.5: 1 (white picture to black picture) is considered as necessary for information reading. Based on this, the practical viewing angle can be derived as the observation angle Q within the position where at least the minimum contrast of 4.5: 1 is achieved.

The intrinsic viewing angle a of a projection screen is measured at the full width half maximum (FWHM) of the peak around the maximum value of the gain, independent of the value of the observation angle Q at the peak center. The Q =0° reference for the gain curve measurement corresponds to the specular reflection direction. Thus, the intrinsic viewing angle a is a property of the screen and not dependent on environmental luminance and projector specification. Thus, as the maximum of the gain curve often occurs at 9=0°, the instrinsic view angle can also be defined in this case as twice the observation angle Q at the position of the gain curve where the half maximum width of the gain curve is achieved.

The viewing angle (intrinsic and practical) shall be maximized as large viewing angles are necessary to ensure that all passengers of a vehicle can clearly see the projected content at the same time independent of the seat occupied by a person. However, with a given screen total reflectivity, a compromise between a high peak gain and a large viewing angle has to be found. The vehicle glazing according to the invention provides such a good compromise between peak gain and viewing angle.

In a preferred embodiment of the invention, the transparent screen of the vehicle glazing has a maximum gain between 0.03 and 0.8 and a practical viewing angle superior to 60° in one direction and larger than 30° in the other one. Typically, for the practical viewing angle values between 120° to 150° in horizontal plane and between 30 and 180° in vertical plane are derived. Within the intrinsic angle definition an intrinsic viewing angle superior to 40°, more preferably superior to 60°, even more preferably between 70° and 150°, in horizontal plane and between 20° and 180°, preferably between 30° and 180°, in vertical plane is derived. Vertical plane and horizontal plane are defined within the assembly situation of the vehicle glazing within the car body.

Thanks to the mentioned practical and intrinsic viewing angles, all the occupants in the vehicle can see the display when the projector is on, if the second side of the display is directed towards the occupants. If the vehicle glazing unit is a side window or back window, the display is directed to observers outside the vehicle. According to a further aspect of the invention, the displayed image is a real image. A real image differs from a virtual image concerning the plane of focus. For virtual images the plane of focus has a certain distance to the projection screen, e.g. one meter or up to several meters. In contrast to this for real images the plane of focus is near to the screen. Preferably, the plane of focus for a real image according to the invention has a maximum distance of 30 cm to the projection screen.

When the projector is off and the glazing is switched to the transparent state the glazing is optically similar to a traditional glazing, maintaining transparency with a slightly higher haze value. A typical haze value for such a glazing is between 1 % and 10 %, preferably between 4.5 % and 9.5 % measured according to the standard ASTM D 1003. The haze measures the fraction of transmitted light that is deviated from the straight path with an angle larger than 2.5°. High haze values correspond to a loss of contrast of the image projected on the screen. Within the given range of low haze values a good transparency of the screen is obtained. Switching of the active glazing changes the haze, while the light transmission of the glazing stays the same. Thus a homogeneous background is created, in order for the observer to concentrate on the projected image and create privacy to the rear.

According to a further preferred aspect, the reflective layer or surface within the glazing unit has a transmission of visible light of higher than 60 %, preferably of 70 % or more, for example 80 % or more in the transparent state. These transmission values (also referred to as global luminous transmission TL) quantify the ability of the reflective layer or surface to transmit light of wavelength between 400 nm to 800 nm, which is the range of the spectrum visible to human eye. For those measurements no distinction between diffused light and non-diffused light has to be made. Nevertheless, the technology according to the invention is also applicable to glazing in which a lower light transmission is desired. To measure the gain and determine suitable viewing angles of a transparent screen, one has to measure the luminance of the screen as a function of the observation angle with a projector illuminating the screen with a normal incidence (0°). The luminance of an ideal screen (Lambertian reference called Spectralon) is measured under the same conditions. An ideal screen is defined as a screen whose luminance does not depend on the projection or observation angle and whose reflectivity is 100%. The Lambertian reference screen is a surface perfectly obeying Lambert’s cosine law saying that the luminous intensity observed from an ideal diffusely reflecting surface is directly proportional to the cosine of the angle between the direction of the incident light and the surface normal. The human eye can only recognize the luminance, which is a measure of luminous intensity per unit area of light travelling in a given direction, and describes the amount of light that is reflected from a particular area. Thus, a Lambertian surface with ideal diffuse reflection is seen by the human eye as showing the same luminance and brightness independent of the observation angle from which it is viewed. Experimentally an ideal Lambertian diffuser is accessible by commercially available reference materials known as “Spectralon”, which is made of sintered polytetrafluoroethylene (PTFE). To retrieve the gain of the screen at each observation angle, the ratio between the screen luminance and the ideal screen luminance is calculated. The peak gain of the screen is the maximum gain value reachable for the screen. The maximum gain (also referred to as peak gain) is often measured at 0° but some specifically designed screen may have their maximum gain at other observation angle. It is to be noted that for a transparent screen, the value at 0° may not be measureable because of the hotspot (specular reflection of projector light on the external flat glazing surface) and is therefore extrapolated from gain at small angle.

Preferred intrinsic viewing angles are defined from the gain as being within the full width half maximum of the gain curve (see Figure 3). This definition is an intrinsic one. The gain denotes the luminance of the projection screen relative to the luminance of an ideal screen, which is a perfect Lambertian diffuser.

An alternative, more practical, definition of the viewing angle would be to define a practical viewing angle as the observation angle where the contrast is lower than 4.5:1 , but such definition depends on observation and illumination conditions and projector. Thus, the intrinsic definition of viewing angles, being within the full width half maximum of the gain curve, is preferred. The gain curve can be determined as already described and has for example the shape of a Gaussian curve. The inventors detected that not only observation angles inferior to the half of the intrinsic view angle (i.e. within the full width half maximum of the gain curve) are suitable for practical application of the transparent screens. Adequate observation results can be achieved under observation angles inferior to the half of a practical view angle in the range of 120° to 180° within horizontal plane, preferably 120° to 150° within horizontal plane, and 30° to 180° within vertical plane.

To achieve a sufficient contrast, the projector should have an output flux higher than 1000 Lumen, better higher than 3000, ideally between 2000 and 10Ό00. The best projector flux values have to be chosen depending on the environmental conditions.

The projection screen size can be big, depending by the projector brightness; position and screen gain and viewing angle. A typical image size, in operation of the system, is larger than 10” (25cm), usually between 10” (25 cm) and 60” (152cm), with preference between 30” (76 cm) and 50”(127cm). The image size is measured as diagonal size in the unit inch as it is common within the field of screen technology. With the present technology a glazing unit having a dimension of 2 m, preferably 1 m in diagonal are possible.

As the available distance between the projector and the glazing, in the orthogonal direction to the glass surface (projection distance), is usually between 2 cm and 60 cm, preferably between 7 cm and 40 cm, a preferential option is to use a short-throw projector. The throw ratio (size of the image/distance between projector and screen) is usually larger for short-throw projectors. In a short-throw projector, there is often a folding optics so that the projector image can be displayed in a plane that is perpendicular to the output lens. The projector may be a projector having a conventional lamp, a LED or a LASER as illumination means.

In the present case the projector is preferably arranged in a frame element of the vehicle or a box, more preferably in a frame element arranged above, below or laterally of the side window or partition window being adapted as vehicle compound glazing unit. Preferably the projector is arranged in a frame element or box of the vehicle above or below the window or the projector is arranged in a spacing, in particular below the partition window. There may be two or more projectors arranged side by side and/or opposite to each other. In the case of several projectors projecting on the same vehicle compound glazing unit the projectors may be calibrated to project a common unitary image. The number of projectors is chosen depending of the size and geometry of the vehicle compound glazing unit. Instead of a side window, in particular in the case of autonomous vehicles or public transport, a back window could be used. The side window, back window or partition window are extended vertically or inclined by a small angle of for example 5 to 20° from the vertical direction.

If a position above the side, partition or back window is chosen, passengers inside the car will be less likely to reach to the projector and get harmed or damage the projector. The same applies to an arrangement between a driver seat or another seat and the partition window. If the partition window is arranged behind a backrest of a seat, the space, there is typically some space where a projector can be arranged and which is not well accessible to passengers. Even if explanations are given by mentioning a driver’s seat, it could be as well another seat, which has a partition window arranged behind a backrest.

The above mentioned calibration is as well necessary, if the vehicle compound glazing unit is not flat. For calibration the projector(s) is/are connected to a projector compound unit which optionally comprises a camera.

The above-referenced generation of hot spots in the glazing unit can, to a certain extent, be suppressed by a suitable arrangement of the respective (first side and second side) surfaces of the glazing unit and, in particular, of the diffuse reflective sheet coating or surface, respectively. In a preferred embodiment, a hot spot is at least directed to a ground of the vehicle, where it does not trouble the occupants of the vehicle. For the positioning of the projector between a driver seat and the partition window a hot spot might in principal arise at the ceiling above the driver’s seat. However, by applying a dark fabric at the ceiling, the hot spot may not glare the driver. As an additional means for suppressing the hot spots at least one local blind can be arranged close to the output lens of the projector, in a suitably pre-defined position.

The image projected on the transparent screen is due to diffuse reflection. The reflection of a glazing is defined as diffuse reflection when incident radiation on the glazing with a given angle of incidence is reflected in a plurality of directions. Specular reflection occurs when incident radiation on the glazing with a given angle of incidence is reflected with an angle of reflection equal to the angle of incidence. Likewise, transmission is defined as specular when incident radiation with a given angle of incidence is transmitted with an angle of transmission equal to the angle of incidence. However, to keep transparency on the whole glazing, the first side face and second side face of the glazing are flat and therefore induce specular reflection from the projector beam. For a side window or back window of the vehicle the first side is defined to be the inner side directed towards an inside of the vehicle and the outside is the second side. For a partition window, first side is the one facing the projector. To achieve the experience, the light reaching the eye of the vehicle passengers should be given by the “diffuse reflection” of the projected image on the glass. The specular reflection on the first side and second side face of the glazing should be avoided. The specular reflection is also referred to as “hot-spot”, which glares the observer when it is directed to the viewer. The direction of the hot-spot is available via the law of reflection saying that the angle of reflection equals the incidence angle. To avoid glaring the viewer by the hot-spot, the hot-spot and the observation direction of all passengers of the vehicle show preferably an angle distance of at least 5°, more preferably at least 10°, most preferably at least 20°.

Regarding the configuration of the vehicle compound glazing unit, according to a first aspect of the invention, the glazing unit comprises a first side glass or plastic pane, a second side glass or plastic pane and a diffusely reflective plastic sheet laminated between the first side and second side glass or plastic panes. The glazing is switchable between a first state, wherein incident light is diffusely reflected, and a second state, wherein incident light is transmitted comparable to a clear window glass. The first state might be an active state and the second state a passive state or vice versa. Thus, the glazing unit has a transparent and a translucent state.

In an embodiment of this aspect, the diffusely reflective sheet is an adhesive sheet or is embedded between two adhesive films or layers, for bonding the first side glass or plastic pane to the second side glass or plastic pane.

In an embodiment, the diffusely reflective plastic sheet or diffusely reflective coating of the coated glass or plastic pane comprises nanoparticles or microparticles within transparent substrate. More specifically, the nanoparticles or microparticles are liquid crystal particles or comprise liquid crystal particles, in particular polymer dispersed liquid crystals. The nanoparticles or microparticles may further comprise silica or polymer. Metal or metal oxide particles can also be used. More specifically, the nanoparticles or microparticles can have spherical shape and/or are transparent or translucent.

The diffusely reflective plastic sheet may in particular be a PDLC (polymer dispersed liquid crystal) or a reverse PDLC layer. A PDLC layer is in particular translucent, if no current is applied, and transparent, if a current is applied. A reverse PDLC layer is in particular is transparent, if no current is applied, and translucent, if a current is applied. Under comparable projection properties, a PDLC layer shows a better contrast and a higher brightness of the projected image than a reverse PDLC layer. However, the application of a reverse PDLC layer might be favorable, if the vehicle compound glazing unit is used only in special situations and most of the time a clear view through the vehicle compound glazing unit is desired. In contrary, if the vehicle compound glazing unit should be used predominantly for projecting an image or if high contrast and/or brightness is desired, a PDLC layer is advantageous.

In an embodiment, the vehicle compound glazing unit comprises a first area which comprises the switchable glazing and a second area which is non-switchable. In particular, the first side glass or plastic pane and the second side glass or plastic pane extend over the first and the second area, while in the first area the diffusely reflective sheet is sandwiched between first side glass or plastic pane and the second side glass or plastic pane and in the second area a second polymer film, in particular comprising a polyethylene (PE), polyethylene terephthalate (PET), poly methyl methacrylate (PMMA), polyvinyl butyral (PVB), triacetyl cellulose (TAC) or polycarbonate, having a similar or the same thickness as the diffusely reflective sheet is sandwiched. The first area and the second area might be optically distinguishable by a printed frame.

Plastic sheets with a diffusely reflective coating comprising titanium oxides TiO_x particles or silver particles as well as plastic sheets with an organic diffusely reflective coating comprising cholesteric liquid crystals have turned out to be especially suitable for the screen applications according to the invention. Most preferably the diffusely reflective plastic sheet contains liquid crystal particles, which are oriented within a matrix.

Preferably the diffusely reflective plastic sheet comprises a polyethylene (PE), polyethylene terephthalate (PET), poly methyl methacrylate (PMMA), polyvinyl butyral (PVB), triacetyl cellulose (TAC) or polycarbonate sheet. Such sheets are basically commercially available or can be manufactured upon request of the manufacturer of the vehicle compound glazing unit, tailored to the specific optical requirements according to the invention.

Diffusive reflective plastic sheets have the advantage that they can be inserted only at the screen location and thus more easily tailored. At least in embodiments, the system of the invention results in significant advantages which open a wide range of applications in future mobility concepts, including driver- driven or autonomous cars, buses, train or subway cars, boats, airplanes and aerocabs.

In the framework of such concepts, the users will require that a broad range of information be displayed to all of them (not only a driver) in a convenient and flexible way, and big size displays implemented by means of the invention will be highly attractive in this regard. On the other hand, the glazing which is used for the display of information is still fully transparent, and the projection of light to outside the vehicle - which might disturb persons outside or even be dangerous - can be directed outside the expected eye boxes of other road users.

The main application of the invention is to display contents on glass in a vehicle (also autonomous vehicles, buses, taxicabs, trains, tractors, airplanes). This can be to provide information internally for vehicle passengers and also externally for pedestrians, cyclists, bus & train passengers, others road users or for external users.

Also we can think of an infotainment system integrated into the glass enabling for a mixed reality environment: this means that the occupant’s eye will see the image of the outer environment combined with the image projected on the glazing. This is kind of “augmented-reality”.

In the same way, safety information, touristic information, divertissement, like videos, and advertisement can be shown on the glass panes. This can lead to a usage of the glazing surface of the vehicle as an advertisement surface, while maintaining transparency.

Some safety features can be introduced by this technology: the image being surprisingly visible from inside and outside the vehicle, some information can be displayed to inside or outside users, depending on the need. It is to be noted that such an image visible from outside the vehicle corresponds to diffuse light and therefore not glaring the other road users and thus not contradictory with inventions requirements.

Likewise, also external users can, therefore, benefit from the presented system. The awareness of the outside traffic participants can be enhanced, e.g. by displaying safety-supporting features (blinking lights etc.) on the windshield or side windows. This can increase confidence in autonomous vehicles for other road users or for the occupants. In the context of public transport, we can think of information on routes, transport purpose, next stop, final destination on the windows of buses, trains, etc.

Likewise, it will be of huge interest for the advertisement industry regarding customer targeting and context enhancement.

The invention can be combined with other technologies as e.g. HUD, any specific coating, Smart-WS etc. It is possible to include this technology (transparent display in glazing) in other more complex system, for example integrating a camera for interaction with the vehicle occupants (e.g. skype call with call partner projected on glass).

In the following some preferred embodiments of the invention are described.

The vehicle glazing and display system comprises a vehicle compound glazing unit comprising a layer or surface switchable between an first state and a second state, which, in an first state, diffusely reflects incident light directed to the glazing unit from vehicle first side of the vehicle compound glazing unit (10, 10’, 10”) and having a maximum gain in the range of 0.03 to 0.8, preferably between 0.3 and 0.6 and preferably a viewing angle for a real image element generated within the glazing plane of more than 60°, preferably more than 90° and more preferably of 120° or more, in a first direction and of more than 30°, preferably more than 45°, in a second direction, perpendicular to the first direction, and which, in a second state is transparent, a projector for projecting an image to the vehicle glazing unit to generate a real image in the plane of the glazing unit, and a projector control unit for switching the layer or surface and controlling the projector.

Preferably, vehicle glazing and display system is adapted to observe the projected image in transmission geometry, i.e. from a second side of the vehicle compound glazing unit facing the first side of the vehicle compound glazing unit.

The first side of the vehicle compound glazing unit is preferably at an interior of the vehicle.

Preferably, the projector control unit is adapted to switch the vehicle compound glazing unit mandatory to the first state if the projector is turned on. Preferably, the projector control unit is adapted to calibrate the projection of the image on a pixel base. The projector control unit may comprise a camera.

Preferably, the glazing unit has a typical haze value in the range of 1 % to 6 %, preferably between 2.5 % and 4.5 %, and/or the reflective layer or surface within the glazing unit has a transmission of visible light of higher than 70 %, preferably of 80 % or more.

Preferably, the vehicle glazing and display system is adapted as a side window or partition window in a car, boat or airplane/aerocab.

Preferably, the vehicle glazing and display unit is adapted for viewing from the first side of the vehicle.

Preferably, the projector is adapted to be arranged in a vehicle frame part of the vehicle, in particular above the side window of partition window.

Preferably, the vehicle glazing and display system comprises at least a second projector adapted to be arranged beside or opposite to the projector. The at least second projector is preferably connected to the projector control unit and adapted to be calibrated by the projector control unit.

Preferably, projector control unit is connected or connectable to a camera or comprises a camera.

Preferably, at least one local blind is arranged close to the output lens of the projector, such that the generation of hot spots in the glazing plane of the glazing unit is avoided.

Preferably, the projector is adapted to provide an output flux of at least 1 ,000 Lumen, preferably of 3000 Lumen or more.

Preferably, the vehicle glazing and display system is adapted to generate, in its assembled state, a real image in the glazing plane with a horizontal extension of at least 25 cm, preferably between 40 cm and 200 cm, preferably between 50 cm and 150 cm. Preferably, the glazing unit comprises a first side glass or plastic pane, a second side glass or plastic pane and a diffusely reflective plastic sheet laminated between the first side and second side glass or plastic panes.

Preferably, the diffusely reflective sheet is an adhesive sheet or is embedded between two adhesive films or layers, for bonding the first side glass or plastic pane to the second side glass or plastic pane.

Preferably, the glazing unit comprises a first side glass or plastic pane, a second side glass or plastic pane and an adhesive film or layer for bonding the first side glass or plastic pane to the second side glass or plastic pane, wherein the first side surface of the first side or second side glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating.

Preferably, the diffusely reflective plastic sheet or diffusely reflective coating of the coated glass or plastic pane comprises nanoparticles or microparticles within transparent substrate.

Preferably, the nanoparticles or microparticles comprise liquid crystal particles and optionally further comprise silica or polymer.

Preferably, the diffusely reflective plastic sheet is a PDLC layer or reverse PDLC layer.

Preferably, the nanoparticles or microparticles have spherical shape and/or are transparent or translucent.

Preferably, the diffusely reflective plastic sheet comprises a PE, PET, TAC, PVB, PMMA or polycarbonate sheet.

Preferably, the glazing unit comprises a first switchable area and a second non- switchable area.

Preferably, the vehicle glazing and display system is integrated inside a car. Embodiments and aspects of the invention are illustrated in the drawing. In the drawing shows

Fig. 1 a first schematic view of a first embodiment of a vehicle glazing and display system according to an embodiment of the invention,

Fig. 2 a second schematic view of a vehicle glazing and display system according to an embodiment of the invention,

Fig. 3 an illustration for explaining definitions of the term “gain” in the context of the invention, and

Fig. 4A-4C schematic cross-sectional illustrations of embodiments of vehicle compound glazing units.

Fig. 1 and Fig. 2 show an exemplary arrangement of a vehicle glazing and display system 1 within a bus 2, for projecting images onto a partition window 3 of the bus by means of a projector 4 which is arranged in a spacing between a driver’s seat 5 and the partition window 3. The projector 4 is arranged at a first side of the partition window while an observer 20, in particular an occupant of the vehicle is located at the second side of the partitions window. An image generated by the projector in the glazing plane is shown and designated with numeral 6.

In an exemplary geometrical configuration, the projector can be a commercially available short-throw lamp projector which has a brightness of 3500 Lumen and a contrast ratio of 13Ό00: 1 and which is arranged inside between the driver’s seat 5 and the partition window 3 about 20 cm below the window and with a distance orthogonal to the window of about 20 cm.

An exemplary structure of the partition window 3 is: a stack of two clear glasses with a PVB layer laminated in between in a non-projection area and a polymer dispersed liquid crystal (PDLC) sheet laminated in between two clear glass layers in the projection area. The projection area and the non-projection are may be divided by a printed black frame.

The screen in the present embodiment has a width of 80 cm and a height of 100 cm. The viewing area has in the presented case only a height of 40 cm but may be higher.

In the present embodiment it is as well possible to observe the projected image from a sitting position as well as from a stand position. It is also possible to project the screen only on a part of the glass pane including the switchable area, using an optical element, directly controlling the light from the source (projector) or changing the projector features. In particular, only at the inside of the thick black frame a diffuse elastic sheet 14, e.g. a PDLC layer is sandwiched between to glass panes. Thus the area inside the frame is a first area. The area outside the frame is a second area, where a thermoelastic interlayer 13 is sandwiched between the two glass panes, wherein the thermoelastic interlayer 13 and the diffuse elastic sheet 14 have the same thickness in order to avoid mechanical stress. Layer stacking examples are depicted in Fig. 4 A-C The invention can include the use of a darker interlayer foil or any darker element that would help to increase the contrast by lowering the transmission while keeping transparency.

The required brightness and flux of light to be sent by the projector varies, depending on the projection direction.

In case the system has to be integrated in an existing bus, due to packaging and space constraints, it is sometimes impossible to avoid hot-spot, and therefore it is needed to recur to other methods to avoid the hot-spot for the passengers.

As the hotspot is caused by the specular reflection of the light projected by the projector and reaching the eyes of the driver or occupant, one way to eliminate the hot-spot, is to interfere in some light rays come from the projector, for example placing an opaque, non-reflecting obstacle, which partially reduces or traps the projected surface on the glass. The hotspot can also be avoided by reducing the image size, so that the angular area where the observer can hit a specular reflection is reduced.

In an embodiment, the elimination of the hot-spot is performed identifying the hot-spot positions for all the occupants, and then placing a non-reflecting optical surface (piece of dark paper or of dark material) between the projector and the portion of the window where the hotspot is appearing.

However, a glare of the driver or any sitting or standing passenger is not possible in the current position of the projector as the projector mainly projects towards the ceiling of the vehicle in a back side of the driver.

The image projected on the transparent screen is due to diffuse reflection. However, to keep transparency on the whole glazing, the first side face (face 4) and second side face (face 1) of the glazing are smooth and therefore induce specular reflection from the projector beam. In this context a smooth surface is a surface without 3-dimensional structuring. Of course, the second side pane and the first side pane show a 3- dimensional bending. To achieve the experience, the light reaching the eye of the vehicle passengers should be given by the “diffuse reflection” of the projected image on the glass and the specular reflection (on the first side (face 4) and second side (face 1) face of the glazing) should be avoided. Depending on the embodiment of the transparent screen, the first side faces of the glazing (face 2 and face 3) can be textured or smooth, wherein smooth surfaces induce specular reflection and structured surfaces lead to diffuse reflection (see embodiments of figures 4A, 4B and 4C).

In the depicted embodiment glaring of the occupants is further avoided by switching the PDLC layer to the first state, i.e. translucent state, when the projector is turned on by the projector control unit (not shown). By this security feature a turning on of the projector while the partition window is transparent is avoided.

Fig. 3 shows diagrams for explaining the important parameter “gain” with respect to a screen, e.g. the window 3 in Fig. 1 , referring to the explanations further above. The gain measurements were carried out using a luminance meter, and a video projector. The luminance is measured at various observation angles for a given incidence angle of the projected light. The projection angle was set as close as possible to 0° (normal to the screen). When the projection angle is held fixed, the gain depends only on the observation angle Q. The luminance meter position is consequently adjusted so that when the observation angle is set to 0° in the horizontal plane, the luminance meter is aligned with specular reflection; the observation angle is therefore really equal to 0° as the specular direction is taken as the reference for observation angle measurement. Luminance measurements were carried out every five degrees 5° to 75° (measured in the horizontal plane) in an unlit environment isolated from any light source other than the video projector. A Spectralon measured under the same conditions was used to standardize the luminance measurements and to extract the gain therefrom. The intrinsic viewing angle a can be derived from these measurements as the full width half maximum of the gain curve and depicts the angular width for which the gain is superior to half the peak gain.

Fig. 4A-4C show exemplary embodiments of the vehicle compound glazing unit (or: laminated glazing unit) according to the invention. Fig. 4A shows a glazing unit 10 which basically has a conventional structure, i.e. consists of a first side glass pane 11 and a second side glass pane 12 which are bonded together by means of an interlayer containing liquid crystal particles as switchable diffuse elastic sheet 14. The diffuse elastic sheet 14 is switchable between an active state and a passive state. The second side glass pane 12 comprises a second side surface (also denoted as face I) and a first side surface (also denoted as face II). The second side glass may be a clear glass or a tinted glass as well as the first side glass may be a clear glass or a tinted glass. The first side glass pane 11 also comprises a first side surface (face III) and a second side surface (face IV). To achieve a high transparency of the glazing in the transparent state an index-matching of the refractive indices between glass and interlayer is necessary. These two dielectric materials should have substantially the same refractive index, or their refractive indices should be substantially equal, which is defined as the absolute value of the difference between their refractive indices at 550 nm being less than or equal to 0.15. Preferably the absolute value of the difference in refractive index at 550 nm between the constituent materials of the two layers is less than 0.05, more preferably less than 0.015. This applies not only for the specific embodiment of fig. 4a with PVB as interlayer and a structured glass surface as diffusive layer, but also to other embodiments analog to this.

Fig. 4B shows a glazing unit 10’ which, corresponding to a conventional laminated glazing unit, comprises a first side glass pane 11 and a second side glass pane 12 and an intermediate layer bonding the glass panes 11 , 12 together. However, the intermediate layer 13 is a multilayer comprising a first thermoplastic interlayer 13.1 , preferably a PVB sheet, and a second thermoplastic interlayer 13.2, preferably a PVB sheet and, embedded between the two thermoplastic interlayers (PVB sheets), e.g. a diffusely reflective sheet 14 of PET or PMMA.

The reflectivity of the sheet 14 is due to transparent or semi-transparent nanoparticles or microparticles which are randomly distributed in the material of the sheet. These can e.g. be in particular liquid crystal particles. In a modified embodiment, the sheet 14 can additionally have one of its surfaces provided with a nanostructure or microstructure, similar to the surface 12a of the second side glass pane 12 in Fig. 3A and is also, as mentioned for surface 12a coated with a thin reflective coating.

Fig. 4C shows a further exemplary laminated glazing unit 10”, comprising a first side glass pane 11 and a second side glass 12 laminated to each other by means of a thin PVB sheet as thermoplastic interlayer 13. In this example, the first side surface 12a of the second side glass pane 12 has a diffusely reflective coating 12b. Such coating can contain nanoparticles or microparticles, in particular liquid crystal particles, as mentioned above with respect to Fig. 4B in a clear matrix.

Reference numerals

1 Vehicle glazing and display system

2 Vehicle

3 window 4 Projector

5 Drivers seat

6 Image on glazing unit

10; 10’; 10” Vehicle compound glazing unit

11 First side glass pane 12 Second side glass pane

12a First side surface of second side glass pane

12b Coating on second side glass pane

13; 13.1 , 13.2 thermoplastic interlayers, preferably PVB sheets

14 Diffuse reflective sheet 15 reflective coating

20 observer

Claims

1. Vehicle glazing and display system (1) comprising a vehicle compound glazing unit (10; 10’; 10”) comprising a layer or surface (12a; 12b; 14) switchable between active first state and a second state, which, in the first state, diffusely reflects incident light directed to the glazing unit from a first side of the vehicle compound glazing unit (10; 10’; 10”) to a second side of the vehicle compound glazing unit (10; 10’; 10”) and having a maximum gain in the range of 0.03 to 0.8, preferably between 0.3 and 0.6 and preferably an intrinsic viewing angle a for a real image element generated within the glazing plane of more than 60°, in a first direction and of more than 30°, in a second direction, perpendicular to the first direction in a reflection geometry, and which in the second state, is transparent, a projector (4) for projecting an image to the vehicle glazing unit to generate a real image in the plane of the glazing unit and wherein the vehicle compound glazing unit (10; 10’; 10”) is a side window or partition window (3) and a projector control unit for controlling the projector and the switching of the layer or surface.

2. Vehicle glazing and display system (1) of claim 1 , the glazing unit comprises an electrochromic or polymer dispersed liquid crystal layer.

3. Vehicle glazing and display system (1) of claim 1 or 2, wherein the projector (4) is adapted to be arranged in a frame or compartment above or below a side window or above or below a partition window.

4. Vehicle glazing and display system (1) of claims 1 to 3, wherein the projection distance given as orthogonal direction to the glass surface, is between 2 cm and 60 cm.

5. Vehicle glazing and display system (1) of one of the preceding claims, wherein comprising at least a second projector adapted to be arranged beside or opposite to the projector (4).

6. Vehicle glazing and display system (1) of one of the preceding claims, wherein the projector (4) is adapted to provide an output flux of at least 1 ,000 Lumen, preferably of 3000 Lumen or more.

7. Vehicle glazing and display system (1) of one of the preceding claims, adapted to generate, in its assembled state, a real image in the glazing plane with a horizontal extension of at least 25 cm, preferably between 40 cm and 200 cm, preferably between 50 cm and 150 cm.

8. Vehicle glazing and display system (1) of one of the preceding claims, wherein the vehicle compound glazing unit (10; 10’, 10”) comprises a first side glass or plastic pane (11), a second side glass or plastic pane (12) and a diffusely reflective plastic sheet (14) laminated between the first side glass or plastic panes and second side glass or plastic panes, wherein the diffusely reflective plastic sheet can be switched between a first state and a transparent second state.

9. Vehicle glazing and display system (1) of claim 8, wherein the diffusely reflective sheet (14) is an adhesive sheet or is embedded between two adhesive films (13.1 , 13.2) or layers, for bonding the first side glass or plastic pane (11) to the second side glass or plastic pane (12).

10. Vehicle glazing and display system (1) of claim 8 or 9, wherein the glazing unit comprises a first side glass or plastic pane (11), a second side glass or plastic pane (12) and an adhesive film (13) or layer for bonding the first side glass or plastic pane to the second side glass or plastic pane, wherein the first surface (12a) of the first side or second side glass or plastic pane, contacting the adhesive film or layer, respectively, comprises a diffusely reflective coating (12b) or is treated to make the surface a diffuse reflector.

11 . Vehicle glazing and display system (1) of one of claims 8-10, wherein the diffusely reflective plastic sheet (14) or diffusely reflective coating (12b) of the coated glass or plastic pane (12) comprises nanoparticles or microparticles within transparent substrate.

12. Vehicle glazing and display system (1) of claim 11 , wherein the nanoparticles or microparticles are silica or polymer or liquid crystal particles.

13. Vehicle glazing and display system (1) of claim 12, wherein the nanoparticles or microparticles have spherical shape and/or are transparent or translucent.

14. Vehicle glazing and display system (1) of one of claims 8-10, wherein one surface of the diffusely reflective plastic sheet (14) comprises a random nanostructure or microstructure and, in particular, the other surface is polished.

15. Vehicle glazing and display system (1) of one of claims 8, 9 or 10-14, wherein the diffusely reflective plastic sheet (14) comprises a PE, PET, TAC, PVB, PMMA or polycarbonate sheet.