Composite pane for a motor vehicle

Abstract

The invention relates to a composite pane (1) for a motor vehicle, comprising an outer pane (2), an inner pane (3), a connecting layer (5), and photovoltaic cells (7), the photovoltaic cells (7) being embedded in the connecting layer (5). The connecting layer (5) is provided between the outer pane (2) and the inner pane (3), the composite pane (1) comprises a reflective film (6) which is formed between the inner pane (3) and the connecting layer (5), the reflective film (6) is designed to reflect infrared radiation which passes through the connecting layer (5) and is incident on the reflective film (6), and the region between the reflective film (6) and the inner pane (3) is free of electro-functional elements.

Description

[0001] Composite disc for a motor vehicle

[0002] The present invention relates to a composite disc for a motor vehicle according to the preamble of claim 1.

[0003] Composite windscreens for motor vehicles with integrated photovoltaic cells are known in the prior art. They are typically used as roof windows. CN 214 799 405 U discloses a composite windscreen with photovoltaic cells embedded in a bonding layer comprising two adhesive films. This bonding layer connects an outer pane to an inner pane. Both the outer and inner panes have an infrared-reflecting coating applied to them, intended to reflect incident infrared radiation back to the photovoltaic cells.

[0004] From EP 2 958 150 A1, a laminated windscreen for a motor vehicle is known in which a light-modulating film is arranged between the inner and outer panes. Photovoltaic cells are also arranged between the outer pane and the light-modulating film. To reduce the heating of the light-modulating film by externally incident infrared radiation, an infrared-reflecting film is arranged between the photovoltaic cells and the light-modulating film. In this way, the infrared radiation is used to generate electrical energy, while at the same time the heating of the light-modulating film by the infrared radiation is kept to a minimum.

[0005] In contrast, the present invention aims to simplify the production of the composite disc. Furthermore, it seeks to create a motor vehicle equipped with such a composite disc.

[0006] This problem is solved by a composite disc for a motor vehicle according to claim 1 and a motor vehicle according to claim 14. Embodiments of the invention are specified in the dependent claims.

[0007] The composite panel according to claim 1 comprises an outer panel, an inner panel, a bonding layer, and photovoltaic cells. The composite panel can, for example, be configured as a roof panel for a motor vehicle. In its intended use, the outer panel can, for example, face the exterior of the motor vehicle. In its intended use, the inner panel can, for example, face the interior of the motor vehicle.

[0008] The bonding layer can be based, for example, on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane (PU), or on mixtures, copolymers, or derivatives thereof, particularly preferably on PVB. This means that the bonding layer comprises films that can contain a large proportion of the aforementioned polymer (greater than 50 wt%). In addition to the polymer, the bonding layer can contain other additives, such as plasticizers, UV absorbers, or stabilizers. The thickness of the bonding layer is preferably from 0.2 mm to 2 mm. For example, the bonding layer can comprise one or more PVB films with standard thicknesses of 0.38 mm or 0.76 mm.

[0009] The outer and inner panes are preferably made of glass, particularly preferably of soda-lime glass, as is common for window panes. However, one or both panes can also be made of other types of glass, such as quartz glass, borosilicate glass, or aluminosilicate glass, or of rigid, clear plastics, such as polycarbonate or polymethyl methacrylate. The thicknesses of the outer and inner panes are preferably from 0.5 mm to 5 mm, and particularly preferably from 1 mm to 3 mm, and are independent of each other.

[0010] The photovoltaic cells are embedded in the bonding layer. For example, the photovoltaic cells can be arranged between two thermoplastic films of the bonding layer. It is particularly possible that the photovoltaic cells are in direct contact with the thermoplastic films and are connected to the outer and inner panes via the thermoplastic films, especially by a material bond. The thermoplastic films can be, in particular, PVB films. For the purposes of this description, a photovoltaic cell can be understood to be, in particular, the smallest possible photovoltaic unit, comprising a single photovoltaically active absorber layer between a single front electrode and a single back electrode. The photovoltaic cell does not necessarily have to be further subdivided structurally, although this is possible. The photovoltaic cell can also be referred to as a solar cell.For the purposes of this description, a photovoltaic module can be, in particular, a single-piece component comprising a plurality of interconnected or electrically connected photovoltaic cells. The photovoltaic cells can be connected in series or in parallel, or there can be groups of series-connected photovoltaic cells that are connected in parallel, or groups of parallel-connected photovoltaic cells that are connected in series. The series connection of all photovoltaic cells is preferred.

[0011] The bonding layer is located between the outer pane and the inner pane. In particular, the outer pane can be bonded to the inner pane via the bonding layer.

[0012] The laminated glass pane includes a reflective film positioned between the inner pane and the bonding layer. It is particularly possible for the reflective film to be in direct contact with the bonding layer. The reflective film can, for example, be attached to the inner pane via a thermoplastic film. The reflective film is designed to reflect infrared radiation passing through the bonding layer and striking the reflective film, especially in the direction of the photovoltaic cells. For the purposes of this description, this means in particular that the reflective film can be designed to reflect more than 90% of the infrared radiation passing through the bonding layer and striking the reflective film. This, in particular, reduces the heating of the vehicle's interior.Furthermore, for example when using bifacial photovoltaic cells, more electrical energy is generated with the same amount of sunlight.

[0013] For the purposes of this description, infrared radiation refers specifically to electromagnetic radiation with a wavelength of 780 nm and above. Optionally, the reflective film can also be designed to reflect a portion of visible light. This applies particularly to visible light with a wavelength greater than 700 nm. Using a reflective film instead of a coating on the surface of the inner pane facing the bonding layer is particularly advantageous because it allows a coating to be applied to the interior surface of the inner pane without complicating its handling. A pane coated on both sides is difficult to transport and store without risking damage to one of the coatings. Furthermore, when using the reflective film, the surface of the inner pane facing the reflective film can also be coated.

[0014] The area between the reflective film and the inner pane is free of electrofunctional elements. For the purposes of this description, an electrofunctional element is understood to be, in particular, an element that performs a function when an electrical voltage is applied to it. For example, an electrofunctional element can be switched from a first state to a second state by applying an electrical voltage to it. The electrofunctional element may exhibit different optical properties in the first state than in the second state. An example of an electrofunctional element is an electrochromic element, as known from EP 2 958 150 A1. Due to the reflective film, infrared radiation reflected by the reflective film can be utilized by the photovoltaic cells.This applies in particular to the embodiment described below, in which the photovoltaic cells are designed as bifacial photovoltaic cells.

[0015] Omitting an electrofunctional element is advantageous in reducing the costs and effort involved in manufacturing the laminated glass. However, although an electrofunctional element is omitted in the area between the reflective film and the inner pane, the reflective film is still included, even though, according to EP 2 958 150 A1, it serves no purpose other than to protect the electrofunctional element from overheating.

[0016] According to one embodiment of the invention, it is possible for only one or more thermoplastic films to be arranged between the reflective film and the inner pane. This is advantageous for a stable, material-bonded connection between the reflective film and the inner pane. Furthermore, infrared radiation can penetrate the thermoplastic film(s) to a particularly high degree, so that a large proportion of the infrared radiation striking the inner pane from outside the composite pane is transmitted to the reflective film and from there forwarded to the photovoltaic cells.

[0017] Furthermore, it is advantageous to arrange the reflective film between the inner pane and the photovoltaic cells, even though the electrofunctional element known from EP 2 958 150 A1 is omitted, so that infrared radiation reflected by the reflective film can be utilized by the photovoltaic cells. This applies in particular to the embodiment described below, in which the photovoltaic cells are designed as bifacial photovoltaic cells.

[0018] The thermoplastic film(s) can be based, for example, on polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane (PU), or on mixtures, copolymers, or derivatives thereof, particularly preferably on PVB. This means that the thermoplastic film(s) can contain the aforementioned polymer to a large extent (proportion greater than 50% by weight). In addition to the polymer, the thermoplastic film(s) can contain other additives, such as plasticizers, UV absorbers, or stabilizers. The thickness of the thermoplastic film(s) is preferably between 0.2 mm and 2 mm. For example, the thermoplastic film(s) can be or comprise one or more PVB films with standard thicknesses of 0.38 mm or 0.76 mm.

[0019] According to one embodiment of the invention, the reflective film can comprise a carrier film and a reflective coating. The reflective coating can be arranged on the carrier film. The reflective coating preferably comprises at least one infrared-reflecting layer based on a metal, particularly silver. The infrared-reflecting layer preferably contains at least 90 wt.% silver, more preferably at least 99 wt.% silver, and most preferably at least 99.9 wt.% silver. The silver layer can have dopants, for example, palladium, gold, copper, and / or aluminum dopants. The thickness of the silver layer can be, for example, from 5 nm to 20 nm. In addition to the metallic layer, the reflective coating can typically contain dielectric layers or sequences of layers.Dielectric layers or layer sequences are also referred to as dielectric layer modules in the following. The reflective coating can comprise n metallic layers and (n+1) dielectric layer modules, where the dielectric layer modules and the metallic layers can be arranged alternately, such that each metallic layer is positioned between two dielectric layer modules and one layer module is positioned between adjacent metallic layers. The number n is a natural number greater than or equal to 1 (n > 1).

[0020] In a preferred embodiment, the reflective coating comprises at least two metallic layers (n > 2), for example, exactly two metallic layers (n = 2), or even at least three metallic layers (n > 3), for example, exactly three metallic layers (n = 3). A greater number of metallic layers improves the infrared light reflectivity without significantly reducing light transmission, because the individual metallic layers can be made thinner. On the other hand, the number of metallic layers should not be too large in order to keep production costs low.

[0021] The layer modules can be configured independently as single dielectric layers or as dielectric layer sequences (i.e., a plurality of successive dielectric layers). Common dielectric layers in such a thin-film stack include, for example:

[0022] Anti-reflective coatings, which reduce the reflection of visible light and thus increase the transparency of the coated substrate film, for example based on silicon nitride (Si3N4), silicon-metal mixed nitrides such as silicon zirconium nitride (SiZrN), titanium oxide (TiO2), aluminum nitride (AlN) or tin oxide (ZnO), with layer thicknesses of, for example, 10 nm to 100 nm;

[0023] Adaptation layers that improve the crystallinity of the electrically conductive layer, for example based on zinc oxide (ZnO), with layer thicknesses of, for example, 3 nm to 20 nm; smoothing layers that improve the surface structure for the layers above, for example based on a non-crystalline oxide of tin, silicon, titanium, zirconium, hafnium, zinc, gallium and / or indium, in particular based on tin-zinc mixed oxide (ZnSnO), with layer thicknesses of, for example, 3 nm to 20 nm.

[0024] The reflective coating can optionally include blocker layers that protect the metallic layers from degradation. Blocker layers are typically very thin, metal-containing layers based on niobium, titanium, nickel, chromium, zirconium, or alloys thereof, with layer thicknesses of, for example, 0.1 nm to 0.5 nm.

[0025] The reflective coating is preferably applied across the entire surface of the carrier film. If the carrier film also extends into a circumferential edge region of the inner pane, it is possible for this circumferential edge region of the carrier film, and optionally local areas intended to ensure the transmission of electromagnetic radiation through the window pane as communication, sensor, or camera windows, to be free of the reflective coating. The circumferential uncoated edge region has, for example, a width of up to 20 cm. It prevents direct contact between the reflective coating and the surrounding atmosphere, thus protecting the reflective coating inside the laminated pane from corrosion and damage. Preferably, at least 80% of the carrier film is provided with the reflective coating.

[0026] In particular, it is possible that the reflective film is arranged between the bonding layer and another thermoplastic bonding film.

[0027] According to one embodiment of the invention, the carrier film can comprise or consist of polyethylene terephthalate (PET).

[0028] According to one embodiment of the invention, the reflective coating can be configured to reflect, in particular to a proportion of more than 90%, the infrared radiation passing through the bonding layer and striking the reflective film. According to another embodiment of the invention, the photovoltaic cells can be configured as bifacial photovoltaic cells. For the purposes of this description, a bifacial photovoltaic cell is understood to be, in particular, a photovoltaic cell configured to convert electromagnetic radiation incident from both sides into electrical energy. This is advantageous for generating more electrical energy with the same amount of solar radiation. Due to the reflection of the infrared radiation striking the reflective film through the bonding layer, a large proportion of this reflected infrared radiation can also be converted into electrical energy.The infrared radiation passing through the inner pane and being transmitted by the reflective film can also be largely converted into electrical energy.

[0029] According to one embodiment of the invention, the reflective film can be configured to transmit infrared radiation passing through the inner pane and striking the reflective film. In particular, it is possible for the reflective film to be configured to transmit more than 90% of the infrared radiation passing through the inner pane and striking the reflective film. This is particularly advantageous for generating more electrical energy in bifacial photovoltaic cells under the same solar irradiance.

[0030] According to one embodiment of the invention, the outer pane can be directly bonded to the bonding layer. This means, in particular, that no further reflective layer or film is arranged between the bonding layer and the outer pane. This embodiment is advantageous for transmitting a particularly large amount of electromagnetic radiation through the outer pane to the photovoltaic cells. Compared to embodiments in which a reflective layer or film is partially arranged between the outer pane and the bonding layer, this embodiment is advantageous because a more optically homogeneous image is achieved from the outside. Under certain lighting conditions, a reflective layer or film can influence the optical appearance of the composite pane from the outside.Therefore, for optical reasons, it is advantageous to completely dispense with a reflective film or layer between the outer pane and the bonding layer, instead of only partially providing one. According to one embodiment of the invention, the bonding layer can be transparent. This allows, particularly when the photovoltaic cells are designed as bifacial photovoltaic cells, more electrical energy to be generated under the same solar irradiance compared to a bonding layer that is at least partially tinted.

[0031] According to one embodiment of the invention, the bonding layer can comprise a first bonding film and a second bonding film. The photovoltaic cells can be arranged between the first bonding film and the second bonding film. The first bonding film can be arranged between the photovoltaic cells and the outer pane. The second bonding film can be arranged between the photovoltaic cells and the inner pane. It is particularly possible for the first bonding film and the second bonding film to each be in direct contact with the photovoltaic cells. The first and the second bonding films can each be designed as thermoplastic films.

[0032] According to one embodiment of the invention, a coating can be applied to a surface of the inner pane facing away from the reflective film. In the intended use of the laminated pane, this can particularly be the surface facing the interior of the vehicle. It is especially possible that the circumferential edge region of the inner pane is free of this coating.

[0033] The use of such a coated inner pane is particularly feasible when the surface of the inner pane facing the reflective film is free of any coating. In this case, the inner pane can still be handled and stored easily because one of the two surfaces is free of any coating.

[0034] According to one embodiment of the invention, the coating can be emissivity-reducing. Emissivity-reducing coatings are also known as heat-radiation-reflecting coatings, low-emissivity coatings, or LowE (low emissivity) coatings. Emissivity is the measure that indicates how much heat radiation the pane emits into an interior space in its installed position compared to an ideal heat radiator (a black body). Emissivity-reducing coatings serve to reduce the amount of heat entering the interior space (infrared components of solar radiation and, in particular, the thermal radiation of the pane itself) and also to reduce the amount of heat emitted from the interior space. They exhibit reflective properties with respect to infrared radiation, especially heat radiation in the spectral range of 5 pm to 50 pm (see also standard DIN EN 12898:2019-06).This effectively improves thermal comfort in the interior. At high outside temperatures and with strong sunlight, the emissivity-reducing coatings can at least partially reflect the heat radiation emitted from the entire pane towards the interior. At low outside temperatures, they can reflect the heat radiation emitted from the interior, thus reducing the effect of the cold pane as a heat sink. The emissivity-reducing coating further enhances thermal comfort in the interior. It is typically a transparent stack of thin films. The emissivity-reducing coating has at least one, preferably exactly one, electrically conductive layer that provides infrared radiation reflective properties.The conductive layer is preferably based on a transparent conductive oxide (TCO), in particular indium tin oxide (ITO), or alternatively indium zinc mixed oxide (IZO), gallium-doped tin oxide (GZO), fluorine-doped tin oxide (FTO, SnO₂:F), antimony-doped tin oxide (ATO, SnO₂:Sb), or niobium-doped titanium oxide (TiO₂:Nb). Unlike metals, TCOs are not susceptible to corrosion, so they can be used on the exposed inner surface of the inner disk. In addition to the conductive layer, the coating typically includes dielectric layers (for example, based on silicon oxide or nitride), which serve in particular to optimize the optical properties (e.g., light transmission) or act as barrier layers to regulate oxygen diffusion during coating deposition.

[0035] According to one embodiment of the invention, the coating can be a metal coating or a metal oxide-containing coating. The metal coating can, for example, comprise silver. The metal oxide-containing coating can, for example, comprise indium tin oxide (ITO) and / or nickel chromium oxide. According to one embodiment of the invention, there can be a gap between the photovoltaic cells that is free of photovoltaic cells. In other words, there is a plurality of photovoltaic cells with a gap between adjacent photovoltaic cells, i.e., the adjacent photovoltaic cells are spaced apart from one another. However, it is possible that a thermoplastic film or another component is present in the gap. The gap therefore does not have to be component-free. The gap can be transparent to infrared radiation. In particular, it is possible that the gap transmits more than 90% of the infrared radiation.The gap can also be transparent to visible light. This gap is advantageous because it allows a user to see through the laminated glass. The photovoltaic cells can, for example, be arranged in the form of spaced-apart strips or in a checkerboard pattern.

[0036] The motor vehicle according to claim 14 comprises a composite disc according to an embodiment of the invention.

[0037] According to one embodiment of the invention, the composite panel can be part of the roof of the motor vehicle. This is advantageous because a particularly large amount of electromagnetic radiation falls on the roof during operation of the motor vehicle, a large proportion of which is converted into electrical energy by the photovoltaic cells.

[0038] Further features and advantages of the present invention will become clear from the following description of a preferred embodiment with reference to the accompanying figure. This figure shows

[0039] Fig. 1 shows a schematic sectional view of a composite disc according to one embodiment of the invention.

[0040] The composite panel 1 comprises an outer panel 2, an inner panel 3, several thermoplastic films 4 and 5, a reflective film 6, and bifacial photovoltaic cells 7. The photovoltaic cells 7 are arranged between the outer panel 2 and the inner panel 3. The photovoltaic cells 7 are embedded in a bonding layer. The bonding layer can be formed by two thermoplastic films 5 or by a single thermoplastic film 5. The reflective film 6 is arranged between the thermoplastic film 4 and the bonding layer. The reflective film 6 is bonded to a surface of the inner panel 3 facing the photovoltaic cells 7 by means of the thermoplastic film 4. The thermoplastic films 4 and 5 can, for example, consist of or comprise polyvinyl butyral.The reflective film 6 can, for example, be a PET film as a carrier film with a reflective coating that reflects infrared radiation.

[0041] Both the outer pane 2 and the inner pane 3, as well as the thermoplastic films 4 and 5, are transparent to infrared radiation, and preferably also to visible light. This can mean, in particular, that the respective panes and films each transmit more than 90% of the infrared radiation.

[0042] The photovoltaic cells are designed to convert infrared radiation incident on both the surface facing the outer pane 2 and the surface facing the inner pane 3 into electrical energy. When the laminated pane 1 is used as a roof window of a motor vehicle, a particularly large amount of infrared radiation typically passes through the outer pane 2 and the outer part of the bonding layer when exposed to sunlight, striking the surface of the photovoltaic cells 7 facing the outer pane 2. Some of the infrared radiation passes through the gap between the photovoltaic cells and is transmitted by the inner part of the bonding layer, thus striking the reflective film 6. Due to the reflective coating of the reflective film 6, which reflects the infrared radiation, the infrared radiation is reflected and at least a large portion of it strikes the surface of the photovoltaic cells 7 facing the reflective film 6.Thus, compared to a composite disc without bifacial photovoltaic cells, 7 more electrical energy is generated with the same solar irradiance.

[0043] The reflective film 6 is also advantageous because the surface of the inner pane 3 facing the photovoltaic cells 7 is free of any coating. This allows a coating to be applied to the other surface of the inner pane 3, which faces away from the photovoltaic cells 7 and, for example, towards the interior of the vehicle, without significantly complicating the handling and storage of the inner pane 3. This coating on the inner pane 3 can, for example, be an emissivity-reducing coating. Preferably, the reflective coating of the reflective film 6 is not reflective but rather transmits infrared radiation that passes through the inner pane 3 and the thermoplastic film 4 onto the reflective film 6. This infrared radiation then also reaches the photovoltaic cells 7 and can be used to generate electrical energy.

[0044] In addition to the thermoplastic film 4, one or more further thermoplastic films can also be arranged between the reflective film 6 and the inner pane 3. A particular advantage is that the area between the reflective film 6 and the inner pane is free of electrofunctional elements. In this way, the advantages described above are achieved with a cost-effectively manufactured laminated pane.

[0045] Reference symbol list

[0046] 1 composite disc

[0047] 2 Outer pane 3 Inner pane

[0048] 4 thermoplastic film

[0049] 5 thermoplastic film

[0050] 6 reflective foil

[0051] 7 photovoltaic cells

Claims

Patent claims 1. Composite window (1) for a motor vehicle, comprising an outer window (2), an inner window (3), a bonding layer (5) and photovoltaic cells (7), wherein the photovoltaic cells (7) are embedded in the bonding layer (5), wherein the bonding layer (5) is arranged between the outer window (2) and the inner window (3), wherein the composite window (1) comprises a reflective film (6) arranged between the inner window (3) and the bonding layer (5), wherein the reflective film (6) is configured to reflect infrared radiation passing through the bonding layer (5) and striking the reflective film (6), characterized in that the area between the reflective film (6) and the inner window (3) is free of electrofunctional elements.

2. Composite disc (1) according to claim 1 , characterized in that only one or more thermoplastic films (4) are arranged between the reflective film (6) and the inner disc (3).

3. Composite disc (1) according to one of the preceding claims, characterized in that the reflective film (6) has a carrier film and a reflective coating, wherein the reflective coating is arranged on the carrier film.

4. Composite disc (1) according to the previous claim, characterized in that the carrier film comprises polyethylene terephthalate.

5. Composite disc (1) according to one of the two preceding claims, characterized in that the reflective coating is designed to reflect the infrared radiation passing through the bonding layer (5) and striking the reflective film (6).

6. Composite disc (1) according to one of the preceding claims, characterized in that the photovoltaic cells (7) are designed as bifacial photovoltaic cells.

7. Composite disc (1) according to one of the preceding claims, characterized in that the reflective film (6) is designed to transmit infrared radiation passing through the inner disc (3) and striking the reflective film (6).

8. Composite disc (1) according to one of the preceding claims, characterized in that the outer disc (2) is directly connected to the bonding layer (5).

9. Composite disc (1) according to one of the preceding claims, characterized in that the bonding layer (5) is transparent.

10. Composite disc (1) according to one of the preceding claims, characterized in that the bonding layer (5) comprises a first bonding film (5) and a second bonding film (5), wherein the photovoltaic cells (7) are arranged between the first bonding film (5) and the second bonding film (5), wherein the first bonding film (5) is arranged between the photovoltaic cells (7) and the outer disc (2), wherein the second bonding film (5) is arranged between the photovoltaic cells (7) and the inner disc (3).

11. Composite disc (1) according to one of the preceding claims, characterized in that a coating is applied to a surface of the inner disc (3) pointing away from the reflective film (6), which is preferably emissivity-reducing.

12. Composite disc (1) according to the previous claim, characterized in that the coating is a metal coating or a metal oxide-containing coating.

13. Composite disc (1) according to one of the preceding claims, characterized in that there is a gap between the photovoltaic cells (7) which is free of photovoltaic cells, wherein the gap is permeable to infrared radiation.

14. Motor vehicle comprising a composite disc (1) according to any of the preceding claims.

15. Motor vehicle according to the previous claim, characterized in that the composite disc (1) is a part of the roof of the motor vehicle.

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