Composite glass panes with improved color effects

Abstract

The present invention relates to a composite glass pane (100) comprising an outer glass pane (1) and an inner glass pane (2) connected to each other via a thermoplastic interlayer (3), characterized in that the composite glass pane (100) has at least one functional film (5) comprising at least one metal layer (6), and the thermoplastic interlayer (3) is formed using at least one thermoplastic film (4B) comprising a refractive index-reducing medium and the refractive index of the thermoplastic film (4B) in the optically visible range between 380 nm and 780 nm is reduced by at least 0.05 by the refractive index-reducing medium.

Description

[0001] The invention relates to a composite glass pane having improved optical properties, in particular improved color effects in reflection, as well as a method for producing such a composite glass pane and its use.

[0002] Composite glass panes consist of two or more single glass panes firmly bonded together under heat and pressure using one or more interlayers. The interlayers are usually made of thermoplastics such as polyvinyl butyral (PVB) or ethylene vinyl acetate (EVA).

[0003] High demands are placed on the glazing of motor vehicles. The following legal regulations apply with regard to the viewing area and structural stability of the glass panes:

[0004] - ECE R 43: "Uniform provisions for the approval of safety glass and composite glazing materials" and

[0005] - Technical requirements for vehicle components during type testing § 22a StVZO, "Safety glass".

[0006] These requirements are usually met by composite vitreous glass panes. To date, thermoplastic films, particularly polyvinyl butyral (PVB) films, have been used to produce composite glass panes, which have a refractive index as close as possible to that of the outer and inner glass panes used. The refractive index of the PVB films used to date is usually approximately 1.48 in the visible light range, which is usually specified at a fixed value, for example, at 500 or 550 nm. (DC Miller, Optical Engineering 50(1), 013003, 2011).

[0007] Windshields are known to have transparent functional films, such as conductive coatings. These coatings can be used, for example, as IR-reflecting coatings to reduce heating of the vehicle interior, thereby improving thermal comfort. However, these coatings can also perform other functions and, for example, be used as heatable coatings by connecting the coating to a voltage source so that current flows through the coating. Suitable coatings include, for example, silver-based conductive metal layers. Because these layers are susceptible to corrosion, they are typically applied to the surface of the outer or inner glass panes facing the intermediate layer to protect them from atmospheric contact. However, so-called low-E coatings are also applied to the inner surface of the inner glass pane. Silver-containing transparent coatings are known, for example, from WO 03 / 024155, US 2007 / 0082219 A1, US 2007 / 0020465 A1, WO 2013 / 104438, or WO 2013 / 14439.

[0008] WO 2019 / 206493 A1 describes a composite glass pane having a conductive coating and an anti-reflective coating as a projection surface for a head-up display.

[0009] WO 2012 / 052315 describes a transparent composite glass pane with an electrically heatable coating, wherein at least one electrically heatable coating comprises at least four stacked functional layers. Each functional layer comprises at least one layer of an optically high-refractive-index material with a refractive index ≥ 2.1. The functional layers comprise multiple silver-containing layers and matching and smoothing layers disposed therebetween. The overall transmittance of the transparent glass pane is >70%.

[0010] DE 202019102388 U1 describes a composite glass pane comprising a transparent conductive coating and a dielectric superlattice. The superlattice is preferably formed from alternating layers with different refractive indices and, in this case, consists of a large number of individual layers, with layers having a high refractive index (preferably greater than 1.8 at a wavelength of 550 nm) and layers having a low refractive index (preferably less than 1.8 at a wavelength of 550 nm) arranged alternately one above the other. The superlattice reduces transmittance in the spectral range of 400 to 500 nm. The area containing the superlattice is arranged outside the central field of view of the composite glass pane, so that the reduced transmittance has no negative impact on vehicle occupants, particularly with respect to overall transmittance and possible color distortion.

[0011] When using functional films in composite glass panes, those skilled in the art must consider various requirements when designing the coating, particularly in vehicle construction. Transmission in the visible spectral range is reduced by the metal-containing conductive layers typically found in functional films. Larger amounts of conductive material used in the individual layers also lead to reduced transparency in the composite glass pane. For example, since windshields must meet strict minimum transparency requirements (at least 70% transmittance in the visible spectral range according to UN Economic Commission for Europe Regulation 43 (ECE R 43), the amount of conductive material and the number of functional film layers are limited.

[0012] In addition to transparency, the reflection spectrum and other boundary conditions of the composite glass pane must also be taken into account. This particularly concerns the color effects of the composite glass pane, as often only glass panes with a greenish-blue tint are required, but not yellow or red tints (for the reflection color).

[0013] The greater the number of conductive layers, the better the coating can generally be optimized with respect to the desired transmittance, coloration, or desired surface resistance. However, coatings as functional films, particularly those with one or more precious metal layers, are relatively expensive and also limited in their ability to adjust the desired color impression in combination with the desired transparency. Therefore, alternative approaches are being sought to optimize the color effects of composite glass panes that are to be equipped with one or more functional films.

[0014] The object of the present invention is therefore to provide a transparent composite glass pane having at least one functional film, wherein, along with the functionality provided by the film, an improved aesthetic appearance can also be achieved, in particular with minimal undesirable reflection tints of the composite glass pane.

[0015] According to the invention, the object of the invention is achieved by the composite glass pane according to the invention. Preferred embodiments emerge from the further description.

[0016] According to the present invention, a composite glass pane is provided, comprising an outer glass pane and an inner glass pane connected to one another via a thermoplastic interlayer, wherein the composite glass pane has at least one functional film comprising at least one metal layer, in particular a transparent metal layer, and forming a thermoplastic interlayer with at least one thermoplastic film, which contains a refractive index-lowering medium, and the refractive index of the thermoplastic film in the optically visible range of 380 nm to 780 nm is reduced by at least 0.05 (nΔ-0.05) by the refractive index-lowering medium.

[0017] In other words, according to the present invention, the interlayer of the composite glass pane is formed at least by a thermoplastic film, the refractive index of which is reduced by at least 0.05 (nΔ-0.05) by the refractive index-lowering agent compared to the refractive index n of a thermoplastic film of comparable composition but without the refractive index-lowering agent used according to the present invention. At the same time, the other properties of the film and the resulting composite glass pane, such as optical or mechanical properties, such as the desired transparency, light transmittance, breaking strength / impact value, or processability, remain essentially unchanged. Consequently, the composite glass pane according to the present invention surprisingly exhibits an improved color impression in reflection without adversely affecting its other properties.

[0018] The composite glass pane according to the present invention comprises an outer glass pane and an inner glass pane connected to one another via a thermoplastic interlayer. The composite glass pane is used to separate an interior from the exterior environment at a window opening, particularly a window opening in a vehicle. Within the meaning of the present invention, the inner glass pane is the glass pane of the composite glass pane that faces the interior (particularly the vehicle interior). The outer glass pane is the glass pane that faces the exterior environment. The composite glass pane is preferably a vehicle windshield (particularly a windshield of a motor vehicle, such as a passenger car or truck), a side window, or a sunroof.

[0019] As a windshield, a composite glass pane has an upper edge and a lower edge, as well as two side edges extending therebetween. The upper edge is the edge intended to point upward in the installed position. The lower edge is the edge intended to point downward in the installed position. The upper edge is often also referred to as the roof edge, and the lower edge as the engine edge. The outer and inner glass panes each have an outer side and an inner side surface, as well as a circumferential side edge extending therebetween. Within the meaning of the present invention, the outer surface is the main surface intended to face the external environment in the installed position. Within the meaning of the present invention, the inner side surface is the main surface intended to face the interior in the installed position. The inner side surface of the outer glass pane and the outer side surface of the inner glass pane face each other and are connected to each other by a thermoplastic interlayer.

[0020] The surfaces of glass panes are generally referred to as follows: the outside of the outer pane is called Side I. The inside of the outer pane is called Side II. The outside of the inner pane is called Side III. The inside of the inner pane is called Side IV.

[0021] The outer pane and the inner pane are preferably independently formed from glass or plastic, preferably soda-lime glass, alkali aluminosilicate glass, polycarbonate or polymethyl methacrylate. In a particularly preferred embodiment, the outer pane and the inner pane are composed of glass.

[0022] The outer and inner glass panes are preferably not mechanically prestressed, but in further embodiments they may be thermally prestressed or partially prestressed or chemically prestressed.

[0023] Suitable vitreous glass sheets include vitreous glass sheets sold under the trade name of Saint-Gobain and (each a clear glass), VG 10, VG 20, VG 40 or TSANx, TSA3+, TSA4+, wherein the glass of the VG series is a gray tinted glass and the glass of the TSA series is a green tinted glass.

[0024] The outer pane and / or the inner pane independently of one another preferably have a thickness of 0.1 to 4 mm, preferably 1 to 4 mm, particularly preferably 1.6 mm to approximately 2.1 mm.

[0025] The composite glass pane according to the invention further comprises at least one functional film, preferably a transparent functional film, which comprises at least one metal layer. According to the invention, the functional film therefore comprises at least one metal or metal alloy, for example silver, aluminum, copper, palladium, platinum or gold, and is preferably formed on the basis of a metal or metal alloy, i.e., consists essentially of the metal or metal alloy, apart from any dopants or impurities.

[0026] The functional film is applied, for example, to the outer surface of the inner glass pane facing the interlayer (side III) or to the inner surface of the outer glass pane facing the interlayer (side II). Alternatively, the functional film can be arranged as a coating within the interlayer. For this purpose, the functional film can also be applied to a carrier foil, for example made of polyethylene terephthalate (PET), with a thickness of approximately 20 μm to 100 μm, for example 50 μm, which is arranged between two layers of thermoplastic material, for example, two polymer films, such as PVB films.

[0027] A transparent functional film is understood to mean a layer or layer system (coating) with an average transmittance in the visible spectral range of at least 70%, preferably at least 75%. Therefore, it does not substantially restrict the view through the glazing and thus provides or enables functions such as reflection for HUD displays or IR reflection for sun protection coatings. Functional films can also be implemented as heatable coatings that are electrically contacted and heat up when current flows. The transmittance in the visible spectral range is determined according to the method for testing the light transmittance of glazing panels for motor vehicles specified in ECE-R 43, Annex 3, §9.1.

[0028] In another embodiment of the composite glass pane according to the invention, the functional film comprises at least one silver, aluminum, copper, palladium, platinum, or gold layer as a transparent metal layer. According to the invention, the at least one metal layer is preferably a silver layer. Silver is considered a preferred metal for the metal layer because it has a relatively neutral color and, for example, when used as a solar protection layer, selectively reflects infrared radiation outside the visible range of solar radiation.

[0029] In another preferred embodiment of the composite glass pane, the functional film comprises two to four metal layers, preferably two, three, or four silver layers. For example, layer systems with two silver functional layers or three or four silver functional layers are used for solar protection, as their efficiency (i.e., the reflection of infrared radiation outside the visible range in relation to the transmittance of visible radiation) is greater. Furthermore, the adjustability of certain properties, such as color effects, increases with the number of layers.

[0030] The metal-containing layer (metal layer), preferably a silver layer, is usually embedded between dielectric layers in the functional film. In other words, the metal layer is arranged in a sandwich-like manner between the dielectric layers.

[0031] The dielectric layer of the functional film may contain suitable materials known to those skilled in the art, for example at least one metal oxide such as ZnO, ZnSnOx or a metal nitride such as Si3N4 or SiZrNx or NiCr. The dielectric material may also have dopants, for example aluminum.

[0032] Each metal layer, for example a silver layer, is preferably arranged between two dielectric layers. The metal and dielectric layers are arranged such that, for example, at least one dielectric layer, preferably two or more dielectric layers, is arranged between two adjacent silver layers without a further silver layer arranged therebetween, and at least one further dielectric layer is arranged above the uppermost metal layer facing the outer glass pane in the installed position, and at least one further dielectric layer is arranged below the lowermost metal layer facing the inner glass pane. According to the invention, the dielectric layers preferably have a thickness of 0.1 nm to 100 nm, particularly preferably 0.2 nm to 50 nm, for example 0.3 nm to 45 nm.

[0033] The functional film according to the present invention can be applied, for example, as a coating to the inner glass pane by physical vapor deposition (PVD) using cathode sputtering ("sputtering"), particularly preferably magnetic field-assisted cathode sputtering. The functional film is preferably applied to the glass pane as a coating before lamination. Instead of applying the coating to the surface of the glass pane, it can also be provided on a carrier film arranged in the interlayer. This can be achieved, for example, by positioning the functional film between at least two thermoplastic polymer films during the production of the composite glass pane. The polymer films are then thermally fused to each other, for example during lamination, and the thermoplastic material of the films flows around and evenly seals the IR-reflecting film. This protects the functional film from environmental influences.

[0034] In another embodiment of the composite glass pane, the refractive index of the thermoplastic film is reduced by 0.05 to 0.15 in the optically visible range (380 nm-780 nm) due to the refractive index-reducing agent contained therein. By reducing the refractive index of the thermoplastic film, an improved aesthetic appearance of the composite glass pane can be achieved according to the invention, in particular, with minimal undesirable tints in reflections. It has been shown that with a greater reduction in the refractive index of the thermoplastic film, the color effect can be more strongly influenced towards the desired color neutrality or towards reducing or avoiding undesirable yellow and red tints in the composite glass pane.

[0035] In a preferred embodiment of the present invention, the refractive index-reducing medium is a nanoparticle having a refractive index in the optically visible range of <1.4, preferably <1.3 at a wavelength of 550 nm. This means that the refractive index values given are measured at a wavelength of 550 nm. The refractive index can be determined, for example, by ellipsometry. Ellipsometers are commercially available.

[0036] In another preferred embodiment, the refractive index-reducing medium comprises or includes metal fluoride nanoparticles, in particular MgF2, CaF2, or hollow SiO2 nanoparticles. For example, K. Scheurell, Inorganics 6, 128, 2018, describes alkali metal fluorides with a refractive index <1.4 and methods for preparing alkali metal fluorides, such as the mentioned MgF2 and CaF2. For example, M. Gorsd, Procedia Materials Science 8, 567-576, 2015, and T. Gao, Appl. Phys. A110, 65-70, 2013, disclose alternative hollow SiO2 nanoparticles.

[0037] In another embodiment according to the invention, the thermoplastic film comprises at least 1% by weight of a refractive index-lowering agent, in particular nanoparticles, based on the total weight of the film in the thermoplastic film volume. Preferably, the amount is 0.5-50% by weight; preferably 1-25% by weight, 1-10% by weight, for example up to 5% by weight of a refractive index-lowering agent, in particular nanoparticles, based on the total weight of the film in the thermoplastic film volume.

[0038] According to the present invention, the refractive index reducing medium is preferably a nanoparticle with an average diameter of 5nm to 200nm. The average particle size of the particles is 5nm to 200nm, preferably <150nm, particularly preferably <100nm, for example <90nm, <80nm<70nm or <50nm. The particle size distribution is preferably as uniform as possible, that is, the particles used have approximately the same diameter as much as possible. In the sense of the present invention, particles with an average diameter less than or equal to 500nm are referred to as nanoparticles. Nanoparticle size can be measured by means of dynamic light scattering (DLS).

[0039] In another embodiment of the composite glass pane according to the present invention, the thermoplastic film is a polyvinyl butyral (PVB) film, an ethylene vinyl acetate (EVA) film, or a polyurethane (PU) film, preferably a PVB film. In other words, according to the present invention, the thermoplastic film is designed as a thermoplastic polymer film comprising polyvinyl butyral (PVB), ethylene vinyl acetate (EVA), or polyurethane, and / or mixtures and / or copolymers thereof. Polyvinyl butyral is particularly preferred. The thermoplastic film is preferably formed based on the aforementioned materials, but may contain other components, such as plasticizers. The aforementioned polymer film types are particularly well-suited for use in the automotive industry.

[0040] Advantageously, a refractive index-lowering medium, in particular nanoparticles, can be introduced into such polymer films without adversely affecting other properties of the film, such as mechanical properties. The thermoplastic film can be a standard film having a refractive index reduced by at least 0.05 in the optically visible range between 380 nm and 780 nm by the refractive index-lowering medium according to the invention. The thermoplastic film can be transparent, tinted / dyed (for example, in the case of sunroof glazing), have color bands, or can also be designed with other special properties or functions, either individually or in combination. For example, the thermoplastic film can be a wedge film or an acoustic film used as a projection surface for a head-up display.

[0041] The thermoplastic film of the composite glass pane according to the invention preferably has a thickness of at least 0.1 mm and a maximum of 2 mm, preferably 0.2 mm to 1 mm, and particularly preferably 0.3 mm to 0.8 mm. The polymer film of the interlayer, in particular a PVB film, has a thickness of, for example, 0.38 mm, 0.76 mm, or 0.81 mm. Other properties of the composite vitreous glass pane can be influenced by the thickness of the film. For example, thicker PVB films provide better sound insulation (especially if they contain an acoustically effective core), increase the burglary resistance of the composite vitreous glass pane, and also enhance protection against ultraviolet radiation (UV protection).

[0042] In another preferred embodiment of the composite glass pane, the interlayer is formed from two or more thermoplastic films having mutually different refractive indices. This allows the optical properties, in particular the color effects of the outer and inner sides in reflection, to be advantageously influenced and optimized to the desired values for the composite glass pane.

[0043] The present invention further comprises a method for producing a composite glass pane according to the invention, as described above in various embodiments, comprising an outer glass pane and an inner glass pane connected to one another via a thermoplastic interlayer, wherein the composite glass pane comprises at least one functional film comprising at least one transparent metal layer, and the thermoplastic interlayer is formed with at least one thermoplastic film containing a refractive index-lowering medium, and the refractive index of the thermoplastic film in the visible light range is lowered by at least 0.05 by the refractive index-lowering medium, comprising the steps of:

[0044] S1: providing a thermoplastic film containing a refractive index reducing medium;

[0045] S2: Providing a functional film on the outer glass pane, the inner glass pane, on the thermoplastic film and / or on the carrier film;

[0046] S3: Forming a stacking sequence from an outer glass pane with a functional film, an inner glass pane and a thermoplastic film, optionally a carrier film

[0047] S4: Connecting the stacked sequence under the action of pressure, heat and / or vacuum.

[0048] The thermoplastic film can be produced in step 1 by methods known per se. In a preferred embodiment, the film is produced using refractive index-lowering nanoparticles having a refractive index of <1.4, preferably <1.3, in the optically visible range. In other words, the nanoparticles are dispersed throughout the bulk of the film. Films with dispersed nanoparticles can be produced, for example, in a manner similar to the methods described in JP 2002326846A, US 2003 / 0054160 A1, or EP 1227070 B1.

[0049] Advantageously, a refractive index-lowering agent, in particular nanoparticles, can be introduced into such polymer films without adversely affecting other properties of the film, such as mechanical properties. The thermoplastic film can be a standard film, such as a PVB film, to which the refractive index-lowering agent according to the invention has been added, which lowers the film's refractive index by at least 0.05 in the optically visible range (380 nm-780 nm). The thermoplastic film can be transparent, tinted / dyed, or have color bands, but can also be designed with other special properties or functions, either alone or in combination. For example, the thermoplastic film can be a wedge film or an acoustic film used as a projection surface for a head-up display.

[0050] In a preferred embodiment, the refractive index-reducing medium comprises or includes metal fluoride nanoparticles, in particular MgF2, CaF2 or hollow SiO2 nanoparticles.

[0051] In step S2, the functional film can be applied to the inner or outer glass pane, for example, by physical vapor deposition (PVD), by cathode sputtering (sputtering), or by magnetic field-assisted cathode sputtering. The functional film is preferably applied to the inner side II of the outer glass pane or the outer side III of the inner glass pane. The coating is preferably applied to the glass panes before lamination.

[0052] Preferably, at least 80% of the glass pane surface is coated with the functional film. In particular, the composite glass pane has a coating over its entire surface, with the exception of a surrounding edge region and an optional localized region serving as a communication, sensor, or camera window, which is intended to ensure the transmittance of electromagnetic radiation through the composite glass pane and is therefore uncoated. The width of the surrounding uncoated edge region can be up to 20 cm, for example. This prevents direct contact of the coating with the surrounding atmosphere, thereby advantageously protecting the coating in the interior of the composite glass pane from corrosion and damage.

[0053] Instead of applying the functional film as a coating to the surface of the glass pane, it can also be provided on a carrier film, for example made of polyethylene terephthalate (PET), which is arranged in an interlayer. This can be achieved, for example, by positioning the functional film between at least two thermoplastic polymer films of the composite glass pane in step S3 of laminating the glass pane.

[0054] In step S3 : the outer glass pane with the functional film, the inner glass pane and the thermoplastic film, optionally a carrier film, are arranged flatly one on top of the other in the usual manner.

[0055] If the composite glass pane is bent, the outer and inner glass panes are preferably subjected to a bending process before step S4 and preferably after any coating process in step S2. The outer and inner glass panes are preferably bent together (i.e., simultaneously and using the same tool) because this allows the shapes of the glass panes to be optimally matched to each other for the subsequent lamination. Typical temperatures for the glass bending process are, for example, 500° C. to 700° C.

[0056] The outer and inner glass panes are joined to form a composite glass pane via the thermoplastic interlayer formed from the stacked sequence in step S4, preferably by lamination under the action of heat, vacuum, and / or pressure. Known methods for producing composite glass panes can be used. During lamination, the heated, flowable thermoplastic material flows around the functional film, creating a stable bond and encapsulating the sun protection coating in the interlayer, protecting it from damage and environmental influences.

[0057] For example, the so-called autoclave method can be carried out at an elevated pressure of approximately 10 to 15 bar and a temperature of 130°C to 145°C for approximately 2 hours. The known vacuum bag or vacuum ring methods operate, for example, at approximately 200 mbar and 80°C to 110°C. The outer glass sheet, thermoplastic interlayer, and inner glass sheet can also be pressed into a glass sheet in a calender between at least one pair of rollers. This type of equipment is known for producing glass sheets and typically has at least one heating channel preceding the pressing device. The temperature during the pressing process is, for example, 40°C to 150°C. A combination of the calender and autoclave methods has proven particularly useful in practice. Alternatively, a vacuum laminator can be used. These consist of one or more heatable and evacuable chambers in which the glass sheets are laminated, for example, over a period of approximately 60 minutes at a reduced pressure of 0.01 to 800 mbar and a temperature of 80°C to 170°C.

[0058] In a preferred embodiment of the method, the thermoplastic film (4B) provided in step S1 is formed using metal fluoride nanoparticles, in particular MgF2, CaF2 or hollow SiO2 nanoparticles as the refractive index reducing medium. The nanoparticles can be incorporated into the film using conventional methods without adversely affecting other properties.

[0059] Another embodiment of the method provides for using two or more thermoplastic films (4B, 4, 4A) with different refractive indices in step S1. In other words, the interlayer is formed from two or more thermoplastic films with mutually different refractive indices. This again allows the optical properties, in particular the color effects in reflection of the outer and inner sides of the composite glass pane, to be advantageously influenced and optimized to the desired values for the composite glass pane.

[0060] The invention further comprises the use of the composite glass pane according to the invention in vehicles for land, air or water transport, in particular in motor vehicles, for example as windshield, rear window, side windows and / or sunroof.

[0061] All references to standards refer to the version in force on the filing date.

[0062] The various embodiments of the present invention can be implemented individually or in any combination. In particular, the features described above and those to be explained below can be used not only in the combinations given, but also in other combinations or alone, without departing from the scope of the present invention. Unless explicitly mentioned or mutually exclusive, the exemplary embodiments and / or their features are intended only as alternatives.

[0063] The present invention is described in more detail below with reference to the examples and accompanying drawings. It should be noted that various aspects are described, each of which can be used individually or in combination. In other words, each aspect can be used with various embodiments of the present invention, unless explicitly stated as a purely alternative.

[0064] The drawings are simplified schematic representations and are not true to scale. The drawings do not limit the invention in any way. Example

[0065] Table 1

[0066]

[0067] Table 1 shows the integrated values for a composite glass pane having a surface resistance of about 0.7 ohm, which has standard PVB, which is available under the trade name The following values were obtained by Saint Gobain and compared to the values obtained for composite glass sheets of the same construction and comparable laminates, but once with low-index PVB (0.05 reduction relative to standard PVB) and once with ultra-low-index PVB (0.13 reduction relative to standard PVB). The reflectance values were determined by simulation using common optical simulation programs.

[0068] The color values specified describe the reflected color of the respective composite glass pane and relate to the L*a*b* color space (also known as Lab color space) standardized in EN ISO 11664-4 "Colorimetry - Part 4: CIE 1976 L*a*b* Color space" and the updated DIN EN 410. The specified color values a*, b* relate at least to the reflected color of the outer side under illumination with illuminant D65 and angles of incidence of 8° and 60° (angle to the surface normal), measured with mixed polarization (50% s, 50% p) radiation irradiating the outer pane under the measuring conditions specified in the aforementioned standard using D65 / 10.

[0069] It is shown that the outer reflection becomes less blue at 8° and less red at 60° as the refractive index decreases. The differences in color values compared to a composite glass pane with a standard PVB film are each more than one point and can therefore be considered a significant improvement. The discernible trend towards color neutrality with decreasing refractive index of the PVB film allows the assumption that further reductions in the refractive index of the PVB film used can further enhance this effect of improved color effects in the reflection of the composite glass pane 100.

[0070] Table 1-1 Layer structure of the composite glass pane of Table 1 with four metal layers

[0071]

[0072]

[0073] Table 1-1 shows the layer structure of three composite glass panes with four silver layers, the values of which were determined by simulation, wherein the layer sequence and layer thicknesses remained constant, differing only in the different refractive indices of the PVB1 (standard / reference n at 500 nm 1.48), PVB2 (n (Δ-0.05) and PVB3 (n (Δ-0.13)) used in each composite glass pane.

[0074] Table 2

[0075]

[0076] Table 2 shows the integrated values for a composite glass pane having a surface resistance of about 0.9 ohm, with standard PVB, which is available under the trade name The following can be obtained from Saint Gobain, compared to a composite glass sheet laminate of the same construction and comparable but once with a low refractive index PVB (0.05 reduction relative to standard PVB). The simulation shows the same trend in the reflectance values of the simulated measurements as reproduced in Table 1, but less pronounced.

[0077] Table 2-1 Layer structure of the composite glass sheet in Table 2

[0078]

[0079] Table 2-1 shows the layer structure of two composite glass panes with three silver layers, wherein the layer sequence and layer thickness remain unchanged and differ only in the different refractive indices of the PVB1 (standard / reference n at 500 nm 1.48) and PVB2 (n (Δ-0.05)) used in each composite glass pane.

[0080] Table 3 Layer structure of HUD composite glass laminate

[0081]

[0082] Table 3 shows the integral values for HUD-compatible composite glazings (HUD composite glazings) with a silver layer (with standard PVB (PVB1)) compared to composite glazings of the same construction and comparable laminates but with PVB of a lower refractive index n. For PVB2, n is reduced by 0.05 (nΔ -0.05) compared to PVB1.

[0083] The layer structure of the composite glass laminate studied by simulation was reproduced using an optical simulation program Figure 1 and in the description.

[0084] The simulation also shows the significant effect of the composite glass pane on the color effect in the reflection at virtually unchanged light transmittance TL(A) and identical TTS values (total solar transmittance). The reflection color at 8° and 60° is shifted into the green range by the PVB film with a reduced refractive index. The HUD p-pol reflection color also becomes more neutral with the PVB with a reduced refractive index. This means that disruptive color shifts in the HUD projection can be reduced or avoided. The closer the color values a* and b* are to zero, the more neutral the color effect in the reflection. Surprisingly, a comparison of the two HUD composite glass pane laminates with the use of PVB with a reduced refractive index also revealed an increase in the polarization ratio (p-polarization / s-polarization) of 0.007. For the functioning of a camera system integrated into the windshield, this ratio should be as high as possible.

[0085] The values reproduced in Tables 1 to 3 are obtained by simulation using an optical simulation program.

[0086] in:

[0087] RL(A) stands for visible external reflectivity [%]. The external reflectivity describes the proportion of visible radiation incident from the external environment that is reflected.

[0088] TL(A) represents the visible light transmittance of the composite glass panel [%]

[0089] TTS stands for total transmitted thermal radiation [%]

[0090] RL(A)60° represents the visible reflection at an observation angle of 60° [%]

[0091] RL(A)p-pol indicates visible p-pol reflection [%]

[0092] L*, a*, b* color coordinates (color space CIE, International Commission on Illumination)

[0093] The values of light transmittance (TL) and reflectance (RL) relate to light type A, ie the visible part of sunlight at a wavelength of 380 nm to 780 nm.

[0094] in:

[0095] Figure 1 shows a schematic cross section through the layer structure of a composite glass pane according to the invention, taking as an example a HUD-compatible composite glass pane laminate (HUD composite glass pane / HUD laminate);

[0096] Figure 2 Graph showing the refractive index n and wavelength of PVB films with different reduced refractive indices

[0097] Figure 3 The color diagram shows the color values a*b* of the composite glass panes from Table 1 with the thermoplastic films PVB1, PVB 2 and PVB 3.

[0098] Figure 1 A schematic cross section through the layer structure 10 of a composite glass pane 100 according to the invention, using the example of a HUD laminate, is shown, as investigated using an optical simulation program. Table 3 reproduces the values used for the comparative optical simulation measurements, once for a composite glass pane 100 with a transparent standard PVB film 4A (prior art) and once for a transparent PVB film 4B with a reduced refractive index n according to the invention. The layer structure 10 of the composite glass pane 100 comprises an outer glass pane 1, an inner glass pane 2, and an intermediate layer 3. In the exemplary embodiment on which the optical simulation (Table 3) is based, the inner glass pane 2 and the outer glass pane 1 are transparent vitreous glass panes with a thickness of 2.1 mm, such as are available, for example, under the trade name GLASS. . In the comparative example of Table 3, the interlayer 3 comprises a thermoplastic film 4 (4A prior art / 4B according to the present invention with a reduced refractive index n), with the PVB film 4A (PVB1 standard / prior art) and the PVB film 4B (PVB2 / with a reduced refractive index) each having a thickness of 0.76 mm. A multilayer functional film 5 having a transparent silver layer 6 is arranged in the interlayer 3 on the outer side III of the inner glass pane 2, facing the thermoplastic film 4 (4A / 4B). The functional film 5 of the exemplary composite glass pane 100 comprises a silver layer 6 having a thickness of 12.5 nm and further dielectric layers (5a, 5b, 5c, 5d, 5e, 5f). The layer structure used for the optical simulation in Table 3 is reproduced in detail in Table 4. The functional film 5 can be applied to the inner glass pane, for example, by conventional methods such as sputtering. It has been shown that the composite glass pane 100 according to the present invention exhibits a significant positive effect on the color effect in reflection at approximately the same transmittance values TL(A). The reflected color of the composite glass pane 100 is shifted into the green range by the PVB film 4B according to the invention with a reduced refractive index n (Table 3, PVB2). The HUD p-pol reflected color is also rendered more color-neutral by the PVB film 4B with a reduced refractive index n (PVB2). This means that, in the case of a composite glass pane 100 manufactured according to the invention with the PVB film 4B with a reduced refractive index n, disruptive color shifts in HUD projection can be reduced or avoided compared to the prior art (using standard PVB film 4A). The closer the color values a* and b* are to zero, the more neutral the color effect in the reflection. Surprisingly, when comparing two HUD composite glass pane laminates 100 using PVB24B with a reduced refractive index, an additional increase in the polarization ratio (p-polarization) of 0.007 was observed.

[0099] Table 4 Comparison of the structure of the composite glass panel 100 using a HUD composite glass panel with a silver layer as an example and PVB1 (4A) and PVB2 (4B) as the thermoplastic film 4 (4A / 4B)

[0100]

[0101] Figure 2 A graph of the refractive index n and wavelength is shown for four PVB films having different reduced refractive indices. Simulations were performed with PVB 1 (standard / reference / refractive index at 500 nm approximately 1.48), PVB 2 (refractive index at 500 nm approximately 1.43; Δ-0.05), and PVB 3 (refractive index at 500 nm approximately 1.35; Δ-0.13), which gave the values reproduced in Tables 1 to 3. Another PVB film having a refractive index at 500 nm of approximately 1.39 is graphically presented using PVB 4.

[0102] Figure 3 The color values a* and b* of the composite glass pane 100 from Table 1 with the different thermoplastic films PVB1 (standard / reference), PVB 2 (refractive index Δ-0.05) and PVB 3 (refractive index nΔ-0.13 at 500 nm) are shown in the color coordinate diagram a*b*, obtained using an optical simulation program.

[0103] It is shown that the outer reflection becomes less blue at 8° as the refractive index decreases, and less red at 60°. The trend towards color neutrality with decreasing refractive index of the PVB film 4, indicated in the figure by arrows X (values for reflection at 8°) and Y (values for reflection at 60°), allows one to assume that a further reduction in the refractive index n of the PVB film used can also enhance this effect of improving the color effect of the composite glass pane 100 in reflection.

[0104] The composite glass pane according to the invention surprisingly has good optical and aesthetic properties, wherein in particular undesirable color tones in the reflection of the composite glass pane can be minimized or even avoided.

[0105] According to the invention, this is possible without negatively affecting the other properties of the composite glass pane.

[0106] According to the invention, the composite glass pane thus provides an improved color impression in reflection. Advantageously, an improved color effect and the resulting improved aesthetic visual impression can be achieved without negatively affecting other properties of the composite glass pane.

[0107] Reference Signs List

[0108] 100 composite glass panels

[0109] 10-layer structure

[0110] 1 outer glass panel

[0111] 2 inner glass panels

[0112] 3 Middle Layer

[0113] 4 Thermoplastic film

[0114] 4A Standard PVB film (existing technology)

[0115] 4B PVB film 4B (PVB2 / with a reduced refractive index according to the present invention).

[0116] 5 Functional membrane

[0117] 5a, 5b, 5c, 5d, 5e, 5f dielectric layers

[0118] 6 Metal Layer

[0119] I The outside of the outer glass plate 1

[0120] II Inner surface of outer glass plate 1

[0121] III Outside of inner glass plate 2

[0122] IV Inner surface of inner glass plate 2

[0123] X Trend value of reflection at 8° as the refractive index of PVB decreases

[0124] Y Trend value of reflection at 60° as the refractive index of PVB decreases.

Claims

1. A composite glass pane (100) comprising an outer glass pane (1) and an inner glass pane (2) connected to one another via a thermoplastic intermediate layer (3), characterized in that The composite glass pane (100) comprises at least one functional film (5), the functional film (5) comprising at least one metal layer (6), and the thermoplastic interlayer (3) is formed with at least one thermoplastic film (4B) comprising a refractive index-lowering medium and the refractive index of the thermoplastic film (4B) in the optically visible range between 380 nm and 780 nm is lowered by at least 0.

05. wherein the refractive index-reducing medium is a nanoparticle having a refractive index n of <1.4 in the optically visible range, The thermoplastic film (4B) is a polyvinyl butyral (PVB) film, an ethylene vinyl acetate (EVA) film or a polyurethane (PU) film. wherein the thermoplastic film (4B) contains at least 1 wt% of a refractive index-lowering medium based on the total weight of the thermoplastic film, and The functional film is applied on the outer side surface of the inner glass pane facing the intermediate layer or on the inner space side surface of the outer glass pane facing the intermediate layer.

2. The composite glass plate according to claim 1, wherein The functional film (5) comprises at least one silver layer, aluminum layer, copper layer, palladium layer, platinum layer or gold layer as the metal layer (6).

3. The composite glass plate according to claim 1 or 2, characterized in that The functional film (5) has two to four metal layers (6).

4. The composite glass panel according to claim 3, wherein: The functional film (5) has 2, 3 or 4 silver layers.

5. The composite glass panel according to any one of claims 1 to 2, characterized in that The functional film (5) comprises at least two dielectric layers, and the metal layer (6) is embedded in the dielectric layers in a sandwich shape.

6. The composite glass panel according to any one of claims 1 to 2, characterized in that The refractive index of the thermoplastic film (4B) is reduced by 0.05 to 0.15 in the optically visible range by the refractive index-reducing medium contained therein.

7. The composite glass panel according to any one of claims 1 to 2, characterized in that The refractive index-reducing medium is a nanoparticle having a refractive index n of <1.3 in the optically visible range.

8. The composite glass panel according to any one of claims 1 to 2, characterized in that The refractive index-reducing medium comprises or includes metal fluoride nanoparticles or hollow SiO2 nanoparticles.

9. The composite glass panel according to claim 8, characterized in that The refractive index-reducing medium contains or includes MgF2 and CaF2 nanoparticles.

10. The composite glass panel according to any one of claims 1 to 2, characterized in that The thermoplastic film (4B) contains at least 1 wt% of nanoparticles based on the total weight of the thermoplastic film.

11. The composite glass panel according to any one of claims 1 to 2, characterized in that The refractive index-reducing medium is nanoparticles with an average diameter of 5 nm to 200 nm.

12. The composite glass panel according to any one of claims 1 to 2, characterized in that The thermoplastic film (4B) is a PVB film.

13. The composite glass panel according to any one of claims 1 to 2, characterized in that The thermoplastic film (4B) has a thickness of at least 0.1 mm to a maximum of 2 mm.

14. The composite glass panel according to claim 13, characterized in that The thermoplastic film (4B) has a thickness of 0.2 mm to 1 mm.

15. The composite glass panel according to claim 13, wherein The thermoplastic film (4B) has a thickness of 0.3 mm to 0.8 mm.

16. The composite glass panel according to any one of claims 1 to 2, characterized in that The intermediate layer (3) is formed of two or more thermoplastic films (4B) having refractive indices different from each other.

17. A method for producing a composite glass pane (100) according to any one of claims 1 to 16, the composite glass pane (100) comprising an outer glass pane (1) and an inner glass pane (2) connected to one another via a thermoplastic interlayer (3), wherein the composite glass pane (100) has at least one functional film (5), the functional film (5) comprising at least one metal layer (6), and the thermoplastic interlayer (3) is formed using at least one thermoplastic film (4B) comprising a refractive index-lowering medium and the refractive index of the thermoplastic film (4B) in the optically visible range is lowered by at least 0.05 by the refractive index-lowering medium, the method comprising the steps of: S1: providing at least one thermoplastic film (4B) containing a refractive index-lowering medium; S2: providing a functional film (5) on the outer glass plate (1), the inner glass plate (2), the thermoplastic film (4B) or the carrier film; S3: forming a stacking sequence from an outer glass pane (1) with a functional film (5), an inner glass pane (2), a thermoplastic film (4B) and an optional carrier film; S4: Connecting the stacking sequence under the action of pressure and / or heat and / or vacuum.

18. The method according to claim 17, characterized in that In step S1, the thermoplastic film (4B) contains metal fluoride nanoparticles or hollow SiO2 nanoparticles as a refractive index-lowering medium.

19. The method according to claim 18, characterized in that In step S1, the thermoplastic film (4B) contains MgF2 and CaF2 nanoparticles as refractive index reducing media.

20. The method according to claim 17 or 18, characterized in that In step S1 , two or more thermoplastic films having different refractive indices are used.

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