DE202015003739U1 - Laminated glass for protective glazing with functional coating - Google Patents

Abstract

Laminated pane for protective glazing, preferably an image, showcase, or showcase glazing, comprising a first and a second mineral glass pane and at least one organic UV-absorbing layer A, which is arranged between the first and the second mineral glass pane, characterized in that the basis weight of the composite disc has a lower limit of 0.6 kg / m2 and an upper limit of 7.5 kg / m2, the quotient of the total thickness of all organic layers to the total thickness of the first and second mineral glass is 0.1 to 31 the total thickness of all organic layers is less than or equal to 3.1 mm, the composite pane has an antireflective coating, in particular an interference-optical coating, the composite pane comprises a coating and / or film having a filtering effect and / or absorption for electromagnetic radiation in the wavelength range less than 380 nm and the UV Durc The permeability of the composite disc at a wavelength of 300 to 380 nm is preferably less than or equal to 3% and the general color rendering index Ra r composite disc is greater than or equal to 98.

Description

The present invention relates to a composite pane for protective glazing, in particular for picture, showcase or shop window glazing with an interference-optical coating and a coating or film for reducing the UV transmission at a wavelength below 380 nm.

Pictures, art objects or displays are often displayed behind a glass. In this glazing, it is important to make these objects largely visible without visually disturbing influences through the glazing and at the same time to protect them from harmful electromagnetic waves such as infrared and UV radiation. Thus, the glazing should have the highest possible transparency and low reflection and allow a faithful, unadulterated color reproduction of the objects. Furthermore, these objects should also be protected from broken glass, if the glass should break. In this case, the thickness of the glass pane is limited by weight specifications and specifications in connection with the use of conventional and thus inexpensive building modules, such as frames. So a protective glazing should be as easy as possible and also by the thickness z. For example, in standard picture frames or standard showcase frames or standard frames. Usually, the standard thickness for picture glazings, corresponding to the standard grooves in the picture frames, is less than or equal to 3 mm. At the same time, the glazing should be stable and shatterproof enough to meet the requirements of use. If the glazing could be made thinner and lighter without sacrificing safety, the building modules could also be made lighter, thinner and cheaper, which would provide good savings in terms of static, space and cost.

From the DE 10 2010 037 150 a transparent composite material has become known as a multi-layer composite for safety glazing, for example for glazing of processing machines. As the inner layer, a 3 to 9 mm thick polycarbonate plate is proposed. Glass sheets are proposed as outer layers, the sum of the thickness of the outer layers being smaller than the thickness of the inner layer. Thicknesses between 0.5 and 4 mm are specified as glass thicknesses. To reduce UV radiation, a transparent film is suggested. However, such a composite material is unsuitable for picture, showcase or shop window glazing, since the transparency and the quality of the color reproduction of the objects displayed does not meet the high requirements due to the high proportion of plastic alone. The total thickness of the glazing is also unsuitable for a standard picture frame, for example.

From the US 2010/0151210 has become known a composite pane for automobile or building slices, which is also proposed for showcases. The composite consists of a plurality, ie 4 to 10 glass sheets, which are connected to a composite polymer to form a laminated glass. This composite pane should have a higher resistance to mechanical impact or impact to a monolithic glass pane by elastically absorbing the energy. However, a solution for high-quality image, object or color reproduction with simultaneously high UV protection is not specified.

From the WO 2015/058885 A1 For example, a laminated glass having at least one chemically tempered disc has become known wherein the thickness of the prestressed disc is 2.1 mm or less. The intermediate layer comprises at least one thermoplastic compound layer and a thermoplastic carrier layer, wherein the carrier layer has a functional coating or functional inclusions.

The functional coating according to the WO 2015/058885 A1 arranged in the finished laminated glass between the carrier layer and a connecting layer. In principle, the functional coating can be any functional coating known to the person skilled in the art which is suitable for being applied to a carrier film. The functional coating can be, for example, an IR-reflecting or absorbing coating, a UV-reflecting or absorbing coating, a coloring coating, a low-emissivity coating (so-called low-E coating), a heatable coating, an antenna function coating, a coating with splinter-binding effect (splinter-binding coating) or a coating for shielding electromagnetic radiation, such as radar radiation, be.

From the WO 2015/058885 A1 Composite disks are not known which have two mineral glass panes with a basis weight of between 0.6 kg / m ² and 7.5 kg / m ² and require a maximum thickness of 3.1 mm for the organic layers.

The object of the invention is therefore to provide a glazing, in particular a picture, showcases, shop window glazing which, in addition to a weight reduction compared to a monolithic glazing and the properties of high UV protection and low reflectivity in the visible wavelength range, as unadulterated as possible Color reproduction of the displayed objects allows.

The invention solves this problem with the features of the independent claims. Advantageous embodiments and further developments of the invention are specified in the dependent claims.

According to the invention, the composite pane for protective glazing, in particular for picture glass showcase glazing, comprises a first and a second mineral glass pane and at least one organic UV absorbing layer A, which is arranged between the first and the second mineral glass pane. The inventive composite disk is characterized in that its basis weight has a lower limit of 0.6 kg / m ² and an upper limit of 7.5 kg / m ² . In preferred embodiments, the basis weight has a lower limit of greater than or equal to 1.0 kg / m ² , preferably greater than or equal to 2.2 kg / m ² , in particular greater than or equal to 4.3 kg / m ² , in particular greater than or equal to 5, 2 kg / m ² and an upper limit of less than or equal to 7.1 kg / m ² , preferably of less than or equal to 6.5 kg / m ² .

In this case, the quotient of the total thickness of all organic layers to the total thickness of the first and second mineral glass pane is 0.1 to 31. In preferred embodiments, the quotient is 0.1 to 20, preferably 0.1 to 8, in particular 0.1 to 4 , in particular 0.1 to 1, in particular 0.15 to 0.4. The selection depends in particular on the desired weight saving in conjunction with a minimum rigidity of the composite pane required by the application. For example, for smaller image glazing, a higher ratio quotient glass and a smaller basis weight laminated glass can be used to achieve greater weight savings.

In this case, the total thickness of all organic layers is less than or equal to 3.1 mm. In preferred embodiments, the total thickness of all organic layers is less than or equal to 2 mm, in particular less than or equal to 0.8 mm

The composite disc has an interference-optical coating which reduces the reflection of the disc for wavelengths in the visible wavelength range and thus allows a free and undisturbed view through the disc on the images, art objects or displays for the viewer. The reflectivity in the visible wavelength range is defined as the spectral reflectance of a glass sheet weighted with the eye sensitivity and a standard illumination (D65). This is within the meaning of the invention less than 2%, in particular less than 1%. The composite pane furthermore comprises a coating and / or foil which has a filtering action and / or absorption for electromagnetic radiation in the wavelength range less than 420 nm, in particular in the range smaller than 380 nm. This is preferably the organic UV-absorbing layer A. The thickness of this layer is less than or equal to 3.1 mm, preferably less than or equal to 1.9 mm, preferably less than or equal to 0.8 mm, at 0.76 mm. The thickness of the UV transmission or the UV transmission can be adjusted via the layer thickness, ie. H. the thicker this layer the lower the UV transmission and the higher the UV protection for the displayed images, art objects or displays. Simultaneously with the thickness of the organic layer, the weight savings of the composite disc. Such a layer can be composed of one or more films and consists of a hot melt adhesive, in particular a polyvinyl butyral (PVB) or a thermoplastic urethane-based elastomer (TPE-U) or an ionomer or a polyolefin, or a polyethylene (PE) or a polyethylene acrylate (EA) or a cyclo-olefin copolymer (COC) as an adhesive film or a thermoplastic silicone. The polymers are preferably provided with a UV-absorbing doping.

The composite disc according to the invention should ensure a high splinter protection in case of breakage, d. H. no splinters should be emitted to the environment and the displayed images or objects should be protected against damage by splinters. Therefore, the first and second mineral glass sheets are combined with at least one organic layer. This layer advantageously has a high adhesion to the glass panes, so that in case of breakage it holds or holds together the fractions of the glass pane and which also increases the elasticity and reliability of the composite pane.

As an alternative or in addition to the organic UV-absorbing layer A, a UV-absorbing coating B can be applied to the inwardly directed surface of the first mineral glass pane and / or a UV-absorbing coating can be applied to the inwardly directed surface of the second mineral glass pane. absorbent coating C be attached. Instead of a UV-absorbing coating, it is also possible to provide a UV-absorbing film.

The UV transmittance of the composite disc, defined as the average transmission in the range of the wavelength spectrum from 380 to 300 nm, is less than or equal to 3%. In preferred embodiments, the UV transmittance is less than or equal to 1%, preferably less than or equal to 0.8%, more preferably less than or equal to 0.5%, even more preferably less than or equal to 0.3%, in particular less than or equal to 0.1%. In particularly estimable applications, the part of the protection extends to the visible spectral range. In this case, for example, the absorption properties up to 420 nm are significantly noticeable. An example of such films are the Semasorb UV absorbing films of Sema Gesellschaft für Innovations mbH, Industriestr. 12, 06869 Coswig, where the absorption within the PVB layer is changed by doping.

To produce the composite disk by means of a polymeric material as mentioned above, this or the film or film layers is liquefied or softened by pressure and bonded to the first and second mineral glass sheets to form the composite.

For a realistic reproduction of displayed pictures, art objects or displays an unadulterated color reproduction is very important, ie the composite pane must not falsify the color spectrum of the incident light and the light reflected by the objects. Thus, according to the invention, the general color rendering index R _{a of} the composite pane is greater than or equal to 98. In preferred embodiments, the general color rendering index R _{a is} greater than or equal to 99 to 100.

Furthermore, for high-quality reproduction of displayed images, art objects or displays, the transparency of the composite pane is greater than or equal to 97%, preferably greater than or equal to 98%, particularly preferably greater than or equal to 99%, particularly preferably greater than or equal to 99.5%. Transparency is understood to mean the transmission of the light in the visible wavelength range from 380 nm to 900 nm, in particular from 420 nm to 800 nm.

Furthermore, for a high-quality reproduction of displayed images, art objects or displays, there is also an excellent freedom from streaking, low haze or low haze. Again, the ratio of the total thickness of all organic layers to the total thickness of the first and second mineral glass is advantageous. Thus, the optical scattering behavior (haze) of the lightweight composite disk is less than or equal to 1.5%, preferably less than or equal to 1.0%, particularly preferably less than or equal to 0.5%, measured with a HazeGard, measurement after ASTM D1003 D1044 ,

General color rendering index R _a is understood to be a photometric quantity with which the quality of the color reproduction of light sources of the same correlated color temperature can be described through the composite pane. The color rendering index R _a only includes the values of the first eight test colors according to DIN. Color rendering refers to the relationship between the color stimulus and the color impression, ie the reproduction of colors of displayed objects, which are illuminated through the composite disc with different light sources and then compared with respect to a reference light source. The reference is a black body with a color temperature of up to 5,000 Kelvin and light with a daylight-like spectrum above 5,000 Kelvin.

Cheap glass panes, such as commercial soda-lime glasses usually lead due to the impurities contained, especially z. Of iron and chromium ions, to a lower overall color rendering index. However, by using a small thickness of such a glass sheet, the general color rendering index can be significantly increased again. If, in a particular embodiment, a largely contamination-free soda lime glass or borosilicate glass is used, a very high general color rendering index can be achieved with the use of a small glass thickness. The first and / or the second mineral glass pane of a composite pane according to the invention consists of a lithium-aluminum silicate glass, soda lime silicate glass, borosilicate glass, alkali aluminosilicate glass, alkali-free or low-alkali aluminosilicate glass, in particular of a chemically and / or thermally hardened lithium aluminum silicate glass, lime Sodium silicate glass, borosilicate glass, alkali aluminosilicate glass, alkali-free or low-alkali aluminosilicate glass. Such glasses are obtained, for example, by means of drawing methods, such as a downdraw drawing method, overflow fusion or by means of float technology.

Advantageously, a low-iron or iron-free glass, in particular with a Fe ₂ O ₃ content of less than 0.05 wt .-%, preferably less than 0.03 wt .-%, more preferably less than or equal to 0.01 wt .-% because it allows for increased transparency and in particular a high overall color rendering index. An optical glass may also be used, such as a heavy flint glass, lanthanum flint glass, flint glass, light flint glass, crown glass, borosilicate crown glass, barium crown glass, heavy glass or fluorocarbon glass.

Preference is given to using lithium aluminosilicate glasses of the following glass compositions for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 55-69 Al ₂ O ₃ 19-25 Li ₂ O 3-5 Total Na ₂ O + K ₂ O 0-3 Sum of MgO + CaO + SrO + BaO 0-5 ZnO 0-4 TiO ₂ 0-5 ZrO ₂ 0-3 Total TiO ₂ + ZrO ₂ + SnO ₂ 2-6 P ₂ O ₅ 0-8 F 0-1 B ₂ O ₃ 0-2, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-1 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ from 0-2 wt .-%.

Preference is furthermore given to using soda-lime silicate glasses of the following glass compositions for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 40-80 Al ₂ O ₃ 0-6 B ₂ O ₃ 0-5 Total Li ₂ O + Na ₂ O + K ₂ O 5-30 Sum of MgO + CaO + SrO + BaO + ZnO: 5-30 Total TiO ₂ + ZrO ₂ 0-7 P ₂ O ₅ 0-2, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-5 wt .-% or for "black glass" of 0-15 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ of 0 -2% by weight.

Borosilicate glasses of the following glass compositions are preferably also used for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 60-85 Al ₂ O ₃ 1-10 B ₂ O ₃ 5-20 Total Li ₂ O + Na ₂ O + K ₂ O 2-16 Sum of MgO + CaO + SrO + BaO + ZnO: 0-15 Total TiO ₂ + ZrO ₂ 0-5 P ₂ O ₅ 0-2, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-5 wt .-% or for "black glass" of 0-15 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ of 0 -2% by weight.

Preference is furthermore given to using alkali aluminosilicate glasses of the following glass compositions for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 40-75 Al ₂ O ₃ 10-30 B ₂ O ₃ 0-20 Total Li ₂ O + Na ₂ O + K ₂ O 4-30 Sum of MgO + CaO + SrO + BaO + ZnO: 0-15 Total TiO ₂ + ZrO ₂ 0-15 P ₂ O ₅ 0-10, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-5 wt .-% or for "black glass" of 0-15 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ of 0 -2% by weight.

Preference is furthermore given to using alkali-free aluminosilicate glasses of the following glass compositions for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 50-75 Al ₂ O ₃ 7-25 B ₂ O ₃ 0-20 Total Li ₂ O + Na ₂ O + K ₂ O 0-0.1 Sum of MgO + CaO + SrO + BaO + ZnO: 5-25 Total TiO ₂ + ZrO ₂ 0-10 P ₂ O ₅ 0-5, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-5 wt .-% or for "black glass" of 0-15 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ of 0 -2% by weight.

Preference is furthermore given to using low-alkali aluminosilicate glasses of the following glass compositions for the first and / or the second mineral glass pane, consisting of (in% by weight) SiO ₂ 50-75 Al ₂ O ₃ 7-25 B ₂ O ₃ 0-20 Total Li ₂ O + Na ₂ O + K ₂ O 0-4 Sum of MgO + CaO + SrO + BaO + ZnO: 5-25 Total TiO ₂ + ZrO ₂ 0-10 P ₂ O ₅ 0-5, and optionally additives of coloring oxides, such as. B. Nd ₂ O ₃ , Fe ₂ O ₃ , CoO, NiO, V ₂ O ₅ , Nd ₂ O ₃ , MnO ₂ , TiO ₂ , CuO, CeO ₂ , Cr ₂ O ₃ , rare earth oxides in contents of 0-5 wt .-% or for "black glass" of 0-15 wt .-%, and refining agents such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Cl, F, CeO ₂ of 0 -2% by weight.

For example, thin glasses such as those sold by Schott AG, Mainz under the designations D263, D263 eco, B270, B270 eco, B270i, Borofloat, Xensation Cover, Xensation cover 3D, AF45, AF37, AF32 or AF32 eco are particularly preferred. Alternative thin glasses are made by the company Pilkington under the Optiwhite or Optifloat, sold by the company Corning under the name Gorilla glass, and the company Asahi under the brand name "Dragontail".

According to the invention, the thickness of the first and / or the second mineral glass pane is less than or equal to 3 mm, preferably less than or equal to 1.3 mm, more preferably less than or equal to 1.1 mm and greater than or equal to 50 μm, in particular greater than or equal to 100 μm, preferably greater than or equal to 250 μm, particularly preferably greater than or equal to 450 μm, particularly preferably greater than or equal to 700 μm, the sum of the thickness of the first and the second mineral glass pane being less than or equal to 3.1 mm. Advantageous thicknesses are 0.2 mm, 0.21 mm, 0.3 mm, 0.4 mm, 0.55 mm, 0.7 mm, 0.9 mm, 1.0 mm or 1.1 mm. To improve especially the breaking strength and the scratch resistance of the first and / or the second mineral glass pane, it is thermally and / or chemically prestressed in one embodiment of the invention. As a result, an increased strength over the unbiased base glass is achieved. Thermal and chemical tempering processes are known. In thermal tempering processes, the entire glass article is heated, and then the glass surface quenched rapidly by blowing cold air. As a result, the surface solidifies immediately, while the glass interior continues to contract. This results in a tension inside and correspondingly on the surface a compressive stress. However, thermal tempering processes are generally less suitable for thin glasses having a thickness of less than 1 mm or 0.5 mm.

In one embodiment of the invention, the first and / or second mineral glass pane is advantageously thermally pre-stressed prior to chemical tempering.

The first and / or second mineral glass pane is preferably chemically tempered in one embodiment. Chemical tempering can be carried out in one or more stages. In particular, alkali or lithium-containing glasses are used in which sodium ions are exchanged for potassium ions or lithium ions for sodium ions. By exchanging smaller ions for larger ions, a compressive stress is generated in the surface of the glass sheet in this way. The ion exchange takes place, for example, in a corresponding salt bath, such as KNO ₃ or NaNO ₃ or AgNO ₃ or any mixture of the salts or in a multistage process using KNO ₃ and / or NaNO ₃ and / or AgNO ₃ . The tempering temperatures are in the range of 350 ° C to 490 ° C with an annealing time of 1 to 16 hours. The ion exchange in an AgNO ₃ salt bath takes place in particular in order to design the surface antibacterial by incorporation of silver ions.

In the embodiment of the invention with a single-stage tempered glass sheet of aluminosilicate glass, the compressive stress at the surface is at least 600 MPa, preferably at least 800 MPa at a penetration depth of the exchanged ions of greater than or equal to 30 microns, in particular greater than or equal to 40 microns. In an alternative embodiment of the invention, the tempered glass is soda-lime glass. The compressive stress on the surface of the prestressed soda-lime glass is at least 200 MPa, preferably 400 MPa at a penetration depth of the exchanged ions of greater than or equal to 10 μm.

In the context of chemical changes by ion exchange as described above, it is advantageous if the glasses coated with an anti-reflective layer are diffusion-open for ion exchange. This applies in particular to the antireflecting layer described further on in the application, which is also referred to as AR layer for short and which is applied to the glass pane by means of a sol-gel process.

In the embodiment of the invention with a multi-stage chemically tempered glass, the compressive stress at the surface may be lower, but in the multi-stage biasing the penetration depth of the exchanged ions is increased, so that the strength of the tempered glass can be higher overall. In particular, the compressive stress at the surface of the glass pane is at least 500 MPa at a penetration depth of greater than or equal to 50 μm, in particular greater than or equal to 80 μm. With multi-stage tempering, the penetration depth can also be over 100 μm.

The ion exchange depth of a chemical hardening for a glass pane in a composite pane according to the invention is greater than or equal to 30 μm, preferably greater than or equal to 40 μm, particularly preferably greater than or equal to 50 μm, particularly preferably greater than or equal to 80 μm, and the surface compressive stress is greater than or equal to 500 MPa, preferably greater than or equal to 600 MPa, preferably greater than or equal to 700 MPa, particularly preferably greater than or equal to 800 MPa, particularly preferably greater than or equal to 900 MPa.

But even with float or drawing glasses based on soda-lime glasses, a significant increase in glass strength can be achieved by the chemical pretensioning. Characteristic of these glasses, for example, a lower ion exchange depth of about 10 microns for float glass such as Optifloat or Optiwhite from Pilkington and about 20 microns for a glass of B270 SCHOTT AG.

The penetration depth of the exchanged ions and thus the surface zones of a higher compressive stress in the glass pane increase the strength of the glass pane. However, it is to be adjusted in each case to the total thickness of the glass, because if the tensile stress generated in the interior of the glass sheet during chemical curing is too high, the glass would break. When the glass sheet is subjected to flexing due to an external force, the disk is more sensitive due to its internal tension. The internal tensile stress in the glass or glass-ceramic disc is therefore less than or equal to 50 MPa, preferably less than or equal to 30 MPa, particularly preferably less than or equal to 20 MPa, particularly preferably less than or equal to 15 MPa. The surface compressive stress of the glass sheet is greater than or equal to 500 MPa, preferably greater than or equal to 600 MPa, more preferably greater than or equal to 700 MPa, particularly preferably greater than or equal to 800 MPa, especially greater than or equal to 900 MPa.

The 4-point bending tensile strength after DIN EN 843-1 respectively. DIN EN 1288-3 the first and / or the second mineral glass pane is greater than or equal to 550 MPa, preferably greater than or equal to 650 MPa, particularly preferably greater than or equal to 800 MPa.

The Young's modulus or elastic modulus of the first and / or the second mineral glass pane is greater than or equal to 68 GPa, preferably greater than or equal to 73 GPa, particularly preferably greater than or equal to 74 GPa, particularly preferably greater than or equal to 80 GPa.

The shear modulus of the first and / or the second mineral glass pane is greater than or equal to 25 GPa, preferably greater than or equal to 29 GPa, particularly preferably greater than or equal to 30 GPa, particularly preferably greater than or equal to 33 GPa. Above all, a tempered glass sheet has a high surface hardness and offers a high resistance to scratching and scratching by external force. The Vickers hardness of a non-tempered first and / or second mineral glass sheet in a non-prestressed condition DIN EN 843-4 respectively. EN ISO 6507-1 is greater than or equal to 500 HV 2/20, preferably greater than or equal to 560 HV 2/20, particularly preferably greater than or equal to 610 HV 2/20, or the Vickers hardness of the first and / or the second mineral glass pane in a prestressed state is greater than or equal to 550 HV 2 / 20, preferably greater than or equal to 600 HV 2/20, particularly preferably greater than or equal to 650 HV 2/20, particularly preferably greater than or equal to 680 HV 2/20 at a test force of 2 N (corresponding to a mass of 200 g).

To avoid unwanted bending or bulging of the composite disc, the thermal expansion coefficients of the first and second glass are matched. The difference in the thermal expansion coefficient of the first and second glass sheets is less than or equal to 10 × 10 ^-6 K ^-1 , preferably less than or equal to 7 × 10 ^-6 K ^-1, preferably less than or equal to 5 × 10 ^-6 K ^-1 , preferably less than or equal to 3 × 10 ^-6 K ^-1 , preferably less than or equal to 2.5 × 10 ^-6 K ^-1 , preferably less than or equal to 2 × 10 ^-6 K ^-1 , particularly preferably less than or equal to 1 × 10 ^-6 K ^-1 , particularly preferably equal.

In order to ensure the good optical properties of the composite pane, in a preferred embodiment the refractive indices of all materials of a composite pane are matched to one another. The difference in the refractive index of the materials arranged in each case in one embodiment of a composite pane is less than or equal to 0.3, preferably less than or equal to 0.25, preferably less than or equal to 0.2, more preferably less than or equal to 0.15, particularly preferably less than or equal to 0.09 , For example, typical refractive indices or refractive indices for the first and / or second glass pane are 1.50 to 1.53 (at 588 or 633 nm) for an aluminosilicate glass, or in its compressive stress layer after chemical tempering 1.51 to 1.54 (at 588 or 633 nm) or for a borosilicate glass 1.523 (at 588 nm) or for an alkali-free aluminosilicate glass 1.510 (at 588 nm) or for a soda-lime glass 1.52 (at 588 nm). The refractive index of the organic layer A in the PVB version is 1.48. The indicated refractive indices refer to the laminated glass pane and explicitly not to the multilayer layer or multiple layer for antireflection coating, which is considered separately. In terms of structure, layer thicknesses and refractive indices, this multiple layer or multilayer layer must be adapted separately to the laminate described in order to allow good antireflection.

For the determination of the thickness of the individual layers in a composite pane according to the invention while maintaining the ratio of the total thickness of all organic layers to the total thickness of the first and second mineral glass pane and the basis weight, the following examples are given Indicative values given: for an aluminosilicate glass a density of 2.39 to 2.48 g / cm ³ , for a borosilicate glass a density of 2.51 g / cm ³ , for an alkali-free aluminosilicate glass a density of 2.43 g / cm ³ , for a soda-lime glass, a density of 2.5 g / cm ³ , for a lithium-aluminosilicate glass-ceramic, a density of 2.5 g / cm ³ , for an organic layer A in the version with PVB a density of 1 , 07 g / cm ³ .

In order to meet the high optical requirements for a faithful reproduction of displayed images, art objects or displays, the composite pane on the outwardly facing surface of the first and / or the second mineral glass pane has an interference-optical coating with antireflective properties, which by a Coating of one or more layers on the first and / or the second mineral glass pane is realized.

By coating at least one surface of the composite pane with an antireflection coating or antireflection coating, in particular the reflection in the visible wavelength range of 350 nm to 780 nm is significantly reduced so that the objects displayed can be perceived without disturbing reflections. The degree of reflection R _vis is preferably reduced by the antireflection coating by a factor of 4 to 50 compared with a composite pane not provided with an antireflection coating. If the reflectance R _{vis of} the composite pane without antireflection coating is, for example, 8%, then the reflectance R _{vis can be} reduced to 0.1% to 6%, preferably to 0.2% to 4%, by the antireflection coating. The above-mentioned reflectance R _vis is a reflectance under standard light D65 (artificial daylight) folded with the eye sensitivity. Although the reflection for individual wavelengths may be greater than, for example, 2%, the standard light D65 may have a value R _vis of 1% or less.

According to the invention, the term "antireflection coating" is understood as meaning a layer which, at least in a part of the visible, ultraviolet and / or infrared spectrum of electromagnetic waves, causes a reduction of the reflectivity at the surface of a carrier material coated with this layer. It should thereby be prevented in particular that superimposed on the surface of the laminated glass radiation from light sources in space the image impression and thus trouble-free viewing is difficult.

As anti-reflection coatings interference layer systems are preferably used. In such systems, light is reflected at the interfaces of the anti-reflective coating. The waves reflected at the interfaces can even completely cancel each other out by interference if phase and amplitude conditions are fulfilled. Such anti-reflection coatings are realized, for example, in the products MIROGARD from Schott AG. Regarding an interference layer system for broadband antireflection is also on the EP-A-1248959 the disclosure of which is incorporated in full in the present application.

In addition to the reduction of the reflection R _vis in the optically visible spectral range from 380 nm to 780 nm, it is also possible to achieve an increase in the transmission of up to 10% by the antireflection coating.

• a) Die Entspiegelungsbeschichtung wird mit Hilfe der Flüssigtechnologie aufgebracht, wobei die mit Hilfe der Flüssigtechnologien aufgebrachte Schicht mit Hilfe einer der nachfolgenden Techniken zur Verfügung gestellt wird:
• – die Entspiegelungsbeschichtung wird mit Hilfe der Sol-Gel-Technologie aufgebracht;
• – die Entspiegelungsbeschichtung wird als Einfachinterferenzbeschichtung, insbesondere als poröse Einfachinterferenzbeschichtung aus der Sol-Gel-Technologie hergestellt;
• – die Entspiegelungsbeschichtung wird als Mehrfach-Interferenzbeschichtung aus der Sol-Gel-Technologie hergestellt;
• – die Entspiegelungsbeschichtung wird als Dreifach-Interferenz-Beschichtung aus der Sol-Gel-Technologie hergestellt, wobei die erste Schicht eine Brechzahl zwischen 1,6 und 1,8 aufweist, die zweite Schicht eine Brechzahl zwischen 1,9 und 2,5 aufweist und die Brechzahl der dritten Schicht zwischen 1,4 und 1,55 liegt.
• b) Die Entspiegelungsbeschichtung wird mit Hilfe einer Hochvakuumtechnologie hergestellt, wobei die mit Hilfe der Hochvakuumtechnologie aufgebrachte Schicht mit einer der nachfolgenden Techniken zur Verfügung gestellt wird:
• – die Entspiegelungsbeschichtung wird mit Hilfe einer Hochvakuumtechnologie als Mehrfach-Interferenzschichtsystem hergestellt;
• – die Entspiegelungsbeschichtung wird mit Hilfe einer Hochvakuumtechnologie als Einfachschichtsystem hergestellt;
• – die Entspiegelungsbeschichtung wird aus einem Sputterprozess unter Hochvakuum hergestellt;
• – die Entspiegelungsbeschichtung wird aus einem Aufdampfprozess unter Hochvakuum hergestellt.
• c) die Entspiegelungsbeschichtung wird mit Hilfe eines CVD-Verfahrens hergestellt, wobei die mit Hilfe eines CVD-Verfahrens aufgebrachte Schicht mit einer der nachfolgenden Techniken zur Verfügung gestellt wird:
• – die Entspiegelungsbeschichtung wird aus einem Online-CVD-Prozess hergestellt;
• – die Entspiegelungsbeschichtung wird aus einem Offline-CVD-Prozess hergestellt.

Suitable antireflection or antireflection coatings are layers which are produced by different processes. Such layers can be prepared by a sol-gel method, sputtering method or CVD method. Specifically, the anti-reflection coating can be applied using one of the following application methods:

• a) The antireflective coating is applied by liquid technology, the layer applied with the aid of liquid technologies being made available by one of the following techniques:
• - The anti-reflection coating is applied using the sol-gel technology;
• The anti-reflection coating is produced as a single-interference coating, in particular as a porous single-interference coating from the sol-gel technology;
• The anti-reflection coating is produced as a multiple interference coating from sol-gel technology;
• The antireflective coating is produced as a triple-interference coating from the sol-gel technology, the first layer having a refractive index between 1.6 and 1.8, the second layer having a refractive index between 1.9 and 2.5, and the refractive index of the third layer is between 1.4 and 1.55.
• b) The anti-reflection coating is produced by means of a high vacuum technology, whereby the layer applied by means of the high vacuum technology is provided by one of the following techniques:
• The anti-reflection coating is produced by means of a high-vacuum technology as a multiple interference layer system;
• The anti-reflection coating is produced by means of a high-vacuum technology as a single layer system;
• The anti-reflection coating is produced from a sputtering process under high vacuum;
• - The anti-reflection coating is produced from a vapor deposition process under high vacuum.
• c) the antireflective coating is produced by means of a CVD process, wherein the layer applied by means of a CVD process is provided by one of the following techniques:
• - the anti-reflection coating is made from an online CVD process;
• - The anti-reflective coating is made from an offline CVD process.

Such an antireflective coating in one embodiment consists of a layer which preferably constitutes a primer layer and has a low refractive index in the range of from 1.22 to 1.44, more preferably in the range of from 1.28 to 1.44.

In a further embodiment, the antireflective coating consists of two or more alternating high and low refractive index layers, the uppermost layer having a low refractive index and preferably being a primer layer.

In a further embodiment, the antireflective coating consists of three or more layers with alternating average, high and low refractive indices, wherein the uppermost layer has a low refractive index and preferably represents a primer layer. In an antireflective coating which is composed of several layers and the uppermost layer represents a primer layer, this has a low refractive index in the range of 1.22 to 1.70, more preferably in the range of 1.28 to 1.60, particularly preferably in the range of 1.28 to 1.56.

In a further embodiment, the antireflective coating in the form of at least one layer is designed in such a way that an incomplete antireflective coating is present, which, together with an adhesion promoter layer, has the complete antireflective effect in the spectral range.

In a further embodiment, the antireflective coating in the form of at least one layer is designed such that an incomplete antireflective coating is present which only has the complete antireflective effect in the spectral range together with an antifingerprint coating which is applied to this antireflective coating.

In a further embodiment, the antireflective coating in the form of at least one layer is designed in such a way that an incomplete antireflective coating is present, which has the complete antireflective effect in the spectral range only together with an adhesion promoter layer and an antifingerprint coating.

In a further embodiment, at least one layer of the antireflective coating, preferably the uppermost layer, which is present as an adhesion promoter layer, is subdivided into sublayers with one or more intermediate layers, the one or more intermediate layers preferably having almost the same refractive index as the sublayers.

The adhesion promoter layer represents a mixed oxide layer, preferably a silicon mixed oxide layer, which is an oxide of at least one of aluminum, zinc, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, tin, boron and / or magnesium fluoride, preferably at least an oxide of the element aluminum.

With respect to such an antireflective coating as a primer layer or with a primer layer is also on the WO 2012/163946 the disclosure of which is incorporated in full in the present application.

In a further embodiment, the outwardly directed surface of the first and / or the second mineral glass pane has a coating with antimicrobial and / or easy-to-clean properties. Here, the antimicrobial property is characterized by the presence of one or more antimicrobial metal ions, preferably selected from silver, copper, cadmium, zinc, iron, tin, cobalt, cerium, antimony, selenium, chromium, Magnesium and / or nickel ions in antimicrobial effective amount in the surface of the first and / or the second mineral glass sheet and a present realized antireflective coating. The easy-to-clean property or property of easy cleanability is achieved by a coating of one or more layers on the antireflectively coated first and / or second mineral glass pane or directly on its surface.

By "easy-to-clean (ETC) coating", in particular an "anti-fingerprint (AFP) coating", a coating is understood which has a high stain-resistant property, is easy to clean and can also show an anti-graffiti effect. The material surface of such an easy-to-clean coating shows a resistance to deposits z. From fingerprints such as liquids, salts, fats, dirt and other materials. This relates both to the chemical resistance to such deposits and to a low wetting behavior towards such deposits. Furthermore, it relates to the suppression, avoidance or reduction of the occurrence of fingerprints when touched by a user. Fingerprints contain mainly salts, amino acids and fats, substances such as talc, sweat, residues of dead skin cells, cosmetics and lotions and possibly dirt in the form of liquid or particles of various kinds.

Such an easy-to-clean coating must therefore be resistant to water with salt as well as to fat and oil deposits and have a low wetting behavior with respect to both. The wetting characteristics of a surface with an easy-to-clean coating must be such that the surface is both hydrophobic, ie. H. the contact angle between surface and water is greater than 90 ° as well as oleophobic identifies, d. H. the contact angle between surface and oil is greater than 50 °.

In one embodiment, the adhesion promoter layer as the uppermost layer or layer of an anti-reflection coating is a liquid-phase coating, in particular a thermally solidified sol-gel layer. However, the adhesion promoter layer can also be a CVD coating (layer application by plasma-enhanced chemical vapor deposition), which is produced for example by means of PECVD, PICVD, low-pressure CVD or chemical vapor deposition at atmospheric pressure. However, the adhesion promoter layer can also be a PVD coating (layer application by plasma-assisted physical vapor deposition), which is produced, for example, by sputtering, thermal evaporation, laser beam, electron beam or arc vapor deposition. The primer layer may also be a flame pyrolysis layer.

In particular, this is a silicon mixed oxide layer, wherein the admixture is preferably an oxide of at least one of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc, boron and / or magnesium fluoride is, wherein preferably at least one oxide of the element aluminum is contained.

For the purposes of this invention, silicon oxide means any silicon oxide between silicon mono- and silicon dioxide. Silicon in the sense of the invention is understood as metal and as semi-metal. Silicon mixed oxide is a mixture of a silica with an oxide of at least one other element, which may be homogeneous or non-homogeneous, stoichiometric or non-stoichiometric.

Such an adhesion promoter layer has a layer thickness of greater than 1 nm, preferably greater than 10 nm, particularly preferably greater than 20 nm. It is relevant here that, taking into account the depth of the interaction with the easy-to-clean coating, the adhesion promoter function of the layer can be fully utilized. Furthermore, the layer thickness interacts with the thickness of the remaining layers of the anti-reflection coating, resulting in a reduction of the reflection of light as far as possible. An upper limit in the thickness of the adhesion promoter layer results from the condition that it contributes at least as part of the uppermost layer of an antireflection coating to the antireflection effect of the overall layer or contributes to the antireflection effect of the overall package of an antireflection coating.

Such a primer layer has a refractive index in the range of 1.35 to 1.7, preferably in the range of 1.35 to 1.6, more preferably in the range of 1.35 to 1.56 (at 588 nm reference wavelength).

In principle, all known coatings can be used as anti-reflection coating. According to the invention, the uppermost layer is modified. Such an anti-reflection coating can be applied by means of printing technology, spraying or vapor deposition, preferably by means of a liquid-phase coating, particularly preferably by means of a sol-gel process. The anti-reflection coating may also be applied by means of a CVD coating, which may be, for example, a PECVD, PICVD, low pressure CVD or chemical vapor deposition at atmospheric pressure. The Anti-reflection coating can also be applied by means of a PVD coating, which may be, for example, sputtering, thermal evaporation, laser beam, electron beam or arc evaporation.

The primer layer and the remaining layers of the antireflection coating may also be made by a combination of various methods. Thus, a preferred embodiment that the anti-reflection layers, optionally without the top, the air side facing layer in the layer package are applied by sputtering, the primer layer is applied as the top layer in the coating design by means of a sol-gel process.

The layers of the anti-reflective coating can have any design. Particularly preferred are alternating layers of medium, high and low refractive index layers, in particular with three layers, wherein the uppermost adhesion promoter layer is a low refractive index layer. Also preferred are alternating layers of high and low refractive index layers, in particular with four or six layers, wherein the uppermost adhesion promoter layer is again a low refractive index layer. Further embodiments are monolayer anti-reflection systems or even layer designs, where one or more layers are interrupted by a very thin intermediate layer which is not optically effective. The adhesion promoter layer according to the invention, which has the adhesive property at least on the side facing the air; may also have a different composition with approximately the same refractive index relative to the underlying layer in order to produce a total of an optical reflection-reducing cover layer of an anti-reflection system.

In the overall design, the antireflection coating can initially also be embodied as an incomplete antireflecting layer package which is adapted such that the antireflective coating layer is optically completed by a supplementary coating with a primer layer and optionally later an easy-to-clean coating.

The antireflection coating can also be modified in the thickness of a single layer or a plurality of individual layers in such a way that the complete desired antireflection in the spectral range is achieved by a subsequent subsequent coating of the substrate element with an easy-to-clean coating. Here, the optical effect of the ETC layer is taken into account as part of the overall coating package.

One embodiment is an antireflection coating in the form of a thermally solid sol-gel coating, wherein the uppermost layer forms the adhesion promoter layer.

A further embodiment is also an adhesion promoter layer according to the invention which is applied as an optically non-or almost non-effective layer over an antireflective coating system of one or more layers. The layer thickness of this adhesion promoter layer is usually less than 10 nm, preferably less than 8 nm, particularly preferably less than 6 nm.

In a further embodiment, the adhesion promoter layer according to the invention itself also forms the anti-reflection layer as a single layer or as a layer interrupted with one or more intermediate layers. This is the case when the refractive index of the primer layer is less than the refractive index of the surface material of the carrier substrate, such. B. corresponding glasses with a higher refractive index or with an electrically conductive coating such. B. ITO (indium tin oxide) coated glasses.

The adhesion promoter layer according to the invention can preferably be applied by a sol-gel process or else by a process with chemical or physical vapor deposition, in particular by sputtering.

An antireflection coating may consist of several individual layers which have different refractive indices. Such a coating primarily acts as an antireflection coating, the topmost layer being a low-refractive-index layer and forming the adhesion promoter layer according to the invention.

In one embodiment, the anti-reflection coating consists of a change of high and low refractive layers. The layer system has at least two, but also four, six or more layers. In the case of a two-layer system, a first high-refraction layer T adjoins the carrier material and a low-refractive-index layer S applied thereto forms the adhesion promoter layer according to the invention. The high-index layer T usually comprises titanium oxide TiO ₂ , but also niobium oxide Nb ₂ O ₅ , tantalum oxide Ta ₂ O ₅ , Cerium oxide CeO ₂ , hafnium oxide HfO ₂ and mixtures thereof with titanium oxide or with one another. The low-refraction layer S preferably comprises a silicon mixed oxide, in particular a silica mixed with an oxide of at least one of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc, boron or magnesium fluoride, where preferably at least one oxide of the element aluminum is contained. The refractive indices of such individual layers are at a reference wavelength of 588 nm in the following range: the high-index layer T at 1.7 to 2.3, preferably at 2.05 to 2.15 and the low-index layer S at 1.35 to 1.7 , preferably at 1.38 to 1.60, more preferably at 1.38 to 1.58, especially at 1.38 to 1.56.

In a further particularly preferred embodiment, the anti-reflection coating consists of a change of medium, high and low refractive layers. The layer system has at least three, but also five or more layers. In the case of a three-layer system, such a coating comprises an anti-reflection layer for the visible spectral range. These are interference filters of three layers with the following structure of single layers:
Support material / M / T / S, where M denotes a middle refractive index layer, T denotes a high refractive index layer, and S denotes a low refractive index layer. The mid-refractive layer M mostly comprises a mixed oxide layer of silicon oxide and titanium oxide, but alumina is also used. The high-index layer T usually comprises titanium oxide and the low-index layer S comprises a silicon mixed oxide, in particular one with an oxide of at least one of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc, boron or mixed with magnesium fluoride silicon oxide, wherein preferably at least one oxide of the element aluminum is contained. The refractive indices of such individual layers are at a reference wavelength of 588 nm in the following range: the medium-refractive index layer M at 1.6 to 1.8, preferably at 1.65 to 1.75, the high-index layer T at 1.9 to 2.3 , preferably at 2.05 to 2.15 and the low refractive index layer S at 1.38 to 1.56, preferably at 1.42 to 1.50. The thickness of such individual layers is usually from 30 to 60 nm, preferably from 35 to 50 nm, more preferably from 40 to 46 nm for a medium-refractive layer, from 90 to 125 nm, preferably from 100 to 115 nm, particularly preferably from 105 to 111 nm, for a high-index layer for a low-refraction layer S 70 to 105 nm, preferably 80 to 100 nm, particularly preferably 85 to 91 nm.

In a further embodiment of the invention with a structure of the coating of several individual layers with different refractive indices, the individual layers of the antireflection coating comprise UV and temperature-stable inorganic materials and one or more materials or mixtures of the following group of inorganic oxides: titanium oxide, niobium oxide, tantalum oxide, cerium oxide , Hafnium oxide, silica, magnesium fluoride, alumina, zirconia. In particular, such a coating has an interference layer system with at least four individual layers.

In a further embodiment, such a coating comprises an interference layer system with at least five individual layers with the following layer structure:
Support material / M1 / T1 / M2 / T2 / S, wherein M1 and M2 each denote a middle refractive index layer, T1 and T2 denote a high refractive index layer and S denotes a low refractive index layer. The mid-refractive layer M mostly comprises a mixed oxide layer of silicon oxide and titanium oxide, but alumina or zirconia is also used. The high-index layer T usually comprises titanium oxide, but also niobium oxide, tantalum oxide, cerium oxide, hafnium oxide and mixtures thereof with titanium oxide or with one another. The low-refractive-index layer S comprises a silicon mixed oxide, in particular a silicon oxide mixed with an oxide of at least one of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc, boron or magnesium fluoride, with preference being given to this at least one oxide of the element aluminum is included. The refractive indices of such individual layers are usually at a reference wavelength of 588 nm for the mid-refractive layers M1, M2 in the range of 1.6 to 1.8, for the high-refractive layers T1, T2 in the range greater than or equal to 1.9 and for the low-refractive layer S in the range less than or equal to 1.58. The thickness of such layers is usually 70 to 100 nm for layer M1, 30 to 70 nm for layer T1, 20 to 40 nm for layer M2, 30 to 50 nm for layer T2 and 90 to 110 nm for layer S ,

Such coatings of at least four individual layers, in particular of five individual layers are in the EP 1 248 959 B1 "UV-reflecting interference layer system" described in the disclosure of which reference is made in its entirety and the disclosure of which is part of this application.

Component of the invention are further layer systems that can realize by combining different M, T and S layers anti-reflective systems that differ from the systems presented here. For the purposes of the invention, all reflection-reducing layer systems should be approved which have a Reduction of the optical reflection, at least in spectral regions, with respect to the substrate material with the property that the air-facing layer is always the adhesion promoting layer according to the invention, and the binding effect against ETC materials is influenced by this layer.

In one embodiment of the invention, at least one surface of a substrate element comprises an antireflection coating of a single layer, which is covered with a primer layer, which is then preferably very thin and optically not or almost not effective. The anti-reflection coating, which in this embodiment consists of one layer, is a low-refraction layer which, if appropriate, can still be interrupted by very thin, optically virtually non-effective intermediate layers. The thickness of such an intermediate layer is 0.3 to 10 nm, preferably 1 to 3 nm, more preferably 1.5 to 2.5 nm. In this embodiment, the adhesion promoter layer is a low-refraction layer with a layer thickness of less than 10 nm, preferably smaller It consists of a silicon mixed oxide, in particular of one with an oxide of at least one of the elements aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc, Boron or mixed with magnesium fluoride silicon oxide, wherein preferably at least one oxide of the element aluminum is contained.

The anti-reflection layer may consist of a porous single-layer anti-reflection, a magnesium fluorite layer or a magnesium fluorite silicon mixed oxide layer. In particular, the monolayer anti-reflection may be a porous sol-gel layer. Particularly good antireflection properties can be obtained, in particular in the case of single-layer antireflection coatings, if the volume fraction of the pores amounts to 10% to 60% of the total volume of the antireflection coating. Such a porous anti-reflection single layer has a refractive index in the range of 1.2 to 1.38, preferably 1.2 to 1.35, preferably 1.2 to 1.30, preferably 1.25 to 1.38, preferably 1 , 28 to 1.38 (at 588 nm reference wavelength). The refractive index depends inter alia on the porosity. This porous single-layer anti-reflection coating can also serve directly as a primer layer. In any case, at least in the surface region facing the air side, it comprises a mixed oxide which can interact with an easy-to-clean coating in such a way that a long-term stability of the easy-to-clean coating is achieved.

In another embodiment of the invention, a single-layer anti-reflection coating comprises a metal mixed oxide, preferably a silicon mixed oxide, in particular one with an oxide of at least one of aluminum, tin, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, zinc , Boron or mixed with magnesium fluoride silicon oxide, wherein preferably at least one oxide of the element aluminum is included. This single-layer anti-reflection coating is simultaneously the primer layer. In the case of a silicon-aluminum mixed oxide layer, the molar ratio of aluminum to silicon in the mixed oxide is between about 3% to about 30%, preferably between about 5% and about 20%, more preferably between about 7% and about 12%. This antireflective monolayer has a refractive index in the range of 1.35 to 1.7, preferably in the range of 1.35 to 1.6, more preferably in the range of 1.35 to 1.56 (at 588 nm reference wavelength).

This embodiment of an antireflection coating of a single layer is limited to applications in which the first and / or second glass pane has a correspondingly higher refractive index as carrier material, so that the antireflection effect of the single layer can unfold. The antireflective coating consists as a single layer of a layer which is the adhesion promoter layer and has a refractive index which corresponds to the square root of the refractive index of the carrier material or the carrier material surface ± 10%, preferably ± 5%, particularly preferably ± 2%. The antireflection coating may alternatively be covered with an optically virtually ineffective adhesion promoter layer.

It is advantageous if an antireflection coating, in particular in the uppermost air-facing layer, contains porous nanoparticles having a particle size of about 2 nm to about 20 nm, preferably about 5 nm to about 10 nm, particularly preferably about 8 nm , Porous nanoparticles advantageously comprise silica and alumina.

When the molar ratio of aluminum to silicon in the mixed oxide of the ceramic nanoparticles is from about 1: 4.0 to about 1:20, particularly preferably about 1: 6.6, so if the silicon-aluminum mixed oxide has a composition (SiO 2) _{1 x} (Al ₂ O ₃ ) _{x / 2} with x = 0.05 to 0.25, preferably 0.15, the coating has a particularly high mechanical and chemical resistance. The primer layer may also contain porous nanoparticles. With porous nanoparticles having a particle size of about 2 nm to about 20 nm, preferably about 5 nm to about 10 nm, more preferably about 8 nm, is advantageously achieves that the transmission and reflection properties of a layer or a layer system are only slightly deteriorated by scattering.

Also part of the invention are layer systems in which one or more layers are separated from one another by one or more very thin, optically non or hardly active intermediate layers. This is mainly used to avoid stress within a shift. For example, in particular, the uppermost low-index mixed oxide layer serving as the adhesion promoter layer may be divided by one or more pure intermediate silicon oxide layers. However, it is also possible to split a high or medium refractive layer. In any case, the refractive index is adjusted so that the partial layers and the one or more intermediate layers have almost the same refractive index. The thickness of such an intermediate layer is 0.3 to 10 nm, preferably 1 to 3 nm, particularly preferably 1.5 to 2.5 nm.

In a further embodiment of a composite pane according to the invention, the inwardly directed surface of the first and / or the second mineral glass pane has a coating with a heat-reflecting layer having a sheet resistance of less than or equal to 20 Ω, so that a thermal protection composite pane results.

The formation of an IR-reflecting coating, in particular a low-E coating based on silver layers, is disclosed in US Pat Hans-Joachim Gläser, "Thin Film Technology on Flat Glass", pp. 167-171 , the disclosure of which is incorporated in full in the present application, described in detail. While other metals such as gold or aluminum are possible as IR-reflective coatings, silver is preferred because of its good color effect.

Thermal protection glasses are based on the principle of reflection of the infrared heat radiation through a thin, visibly predominantly transparent, electrically conductive coating. As the heat-reflective coating, substantially tin oxide and silver-based layers are discussed.

Tin oxide can be used immediately after the glass production, z. As the float glass - and application of a diffusion-inhibiting SiOx precoat - be applied in the cooling phase at about 600 ° C by means of a spray process. By doping with fluorine or antimony surface resistances are achieved at about 300 nm layer thickness up to 15 ohms, whereby averaged over the distribution of 300 K heat radiation infrared reflectance of more than 80% is achieved.

As picture, showcase or shop window glazing, this glass thus reflects most of the heat radiation, thereby protecting the displayed objects from it. It is particularly preferred if the thermal insulation layer is constructed so that the layer has a low reflection when it is embedded on both sides in a film / glass. Typically, the refractive index of these materials is between 1.45 and 1.55, and the sunscreen must be adapted thereto; With adapted layer achieves Reflxionsgrade better than 4%, preferably better 3%, especially 2%.

Instead of doped tin oxide SnO ₂ : F, Sb, the transparent semiconductor materials zinc oxide ZnO: Al (aluminum-doped) and indium oxide In203: Sn (tin-doped, "ITO") can also be used.

However, deposition of the silver layers, which are more favorable in terms of heat reflection, must be carried out quite expensively by means of vacuum coating methods after glass production, wherein further dielectric layers enclosing the silver layer on both sides and possibly also metallic layers are required to increase transmission and long-term stability.

By applying an interference layer system according to the invention, it is possible to obtain a heat protection composite pane with very low transmission in the UV range and high transmission in the visible range, so-called UV-filtering heat protection composite disks.

The invention further comprises the use of such a composite pane, in one of the embodiments or a combination thereof, as protective glazing with a holder for fixing an object. This is in particular a picture glazing with a composite pane and a holder. The holder is preferably a frame or any known to those skilled fixation of a disc with the image to be protected.

However, the use also includes the composite pane as a protective glazing for an illuminated or a self-luminous object. An illuminated object is a lit picture or a lit one Object in a showcase or display, which is protected by the composite disc. A self-luminous object may be an organic light emitting diode, a lit display or a luminous body in a display or showcase.

The invention will be explained in more detail with reference to the following embodiments and figures, which are not intended to limit the invention.

Show it:

1 the basic structure of a disc according to the invention;

2 the course of the transmission / reflection of a composite pane according to the invention in the wavelength range 300 nm to 800 nm.

1 and shows a composite pane according to the invention 1 with a first mineral glass pane 11 and a second mineral glass sheet 12 , Both glass sheets have a thickness of 1.1 mm and consist of a low-iron lime-soda glass with a content of Fe ₂ O ₃ of less than 0.03 wt .-%. They are by lamination with a 0.76 thick PVB film as a UV-absorbing layer 13 to a composite disk 1 connected. With a 0.76 mm thick PVB film, a UV protection of 99.9% is achieved. Thinner PVB films, for example of 0.38 mm are also possible. Here, however, the UV protection is lower. Such a PVB film is obtained, for example, from Eastman Chem. Corp. offered under the trade name Saflex ^® .

The outward facing surfaces of a first mineral glass pane 11 and a second mineral glass sheet 12 are with an interference-optical coating 14 coated as antireflective coating or anti-reflection coating. As antireflection coating, for example, antireflection coatings produced by sol-gel processes or sputtering processes are used. Below, by way of example, three exemplary embodiments of such antireflective or antireflective coatings are given:

Example 1:

One-sided antireflection coating produced by the sol-gel method:
The coating consists in each case of three individual layers and has the structure: substrate + M + T + S. The individual layer marked T contains titanium dioxide TiO ₂ , the single layer marked S contains silicon dioxide SiO ₂ and the single layer marked M is respectively made of and T mixed solutions pulled. The float glass substrate is thoroughly cleaned before coating. The immersion solutions are each applied in air-conditioned rooms at 28 ° C at a humidity of 5-10 g / m3, the drawing speeds for the individual layers M / T / S about 275/330/288 mm / min. The pulling of each gel layer is followed by a bake process in air. The bake temperatures and bake times are 180 ° C / 20 minutes after preparation of the first gel layer and 440 ° C / 60 minutes after preparation of the second and third gel layers. In the case of the T-layers, the dipping solution (per liter) is composed of: 68 ml of titanium n-butylate, 918 ml of ethanol (abs.), 5 ml of acetylacetone and 9 ml of ethyl-butyl acetate. The dip solution for the preparation of the S-layer contains: 125 ml of silica methyl ester, 400 ml of ethanol (abs.), 75 ml H2O (dist.), 7.5 ml of acetic acid and is after a rest period of about 12 hours with 393 ml of ethanol diluted (abs.). The coating solutions for producing the intermediate refractive index oxides are prepared by mixing the S + T solutions. The layer marked M is drawn from a dipping solution having a silicon dioxide content of 5.5 g / l and a titanium dioxide content of 2.8 g / l. The applied wet-chemical sol-gel process allows the economic coating of large areas as a dipping process, whereby two slices are glued together before the dipping process, so that the necessary one-sided anti-reflection effect is achieved. The adhesive is chosen to burn at 440 ° C within the burn-in time described above so that the slices leave the process separately.

Example 2:

• A) Sputtern einer hochbrechenden Schicht A mit einem Vorschub von 1,7 m/min, wobei der Carrier vor der Sputterquelle pendelt und währenddessen eine Schicht von 30 nm Dicke abgeschieden wird. Die Schichtherstellung erfolgt durch Zugabe von Argon und Reaktivgas unter Regelung des Reaktivgases auf eine Plasmaimpedanz. Der Prozessdruck wird insbesondere durch die Menge an Argon bestimmt, welcher zu typischen Prozessdrücken im Bereich zwischen 1·E-3 und 1·E-2 mbar führt. Die Abscheidung im Plasma erfolgt über eine Pulsung.
• B) Sputtern einer niedrigbrechenden Schicht B mit einem Vorschub von 2,14 m/min. Hierbei wird eine Schicht der Dicke 30,5 nm hergestellt. Die Schichtherstellung erfolgt entsprechend der Abscheidung unter Schicht 1.
• C) Sputtern einer hochbrechenden Schicht entsprechend Schicht A. Hier wird bei einem Vorschub von 0,9 m/min eine Schicht der Dicke 54 nm hergestellt.
• D) Sputtern einer niedrigbrechenden Schicht gemäß Schicht B. Bei einem Vorschub von 0,63 m/min wird eine Schicht der Dicke 103 nm hergestellt. Anschließend wird das beschichtete Substrat mit dem Carrier über eine Transferkammer ausgeschleust.
• E) Herstellen eines Verbundes aus 2 Scheiben Antireflex System nach Schritt A–D, wobei die beschichtete Seite jeweils nach Außen zeigt, und zwischen die beiden Glasscheiben eine PVB Folie mit 0,38 mm Dicke in einem Rollenverbundverfahren laminiert wird.

One-sided antireflection coating produced by the sputtering method:
The coating is coated in a continuous flow system with an MF sputtering process by magnetron sputtering, wherein the substrate is positioned on a so-called carrier and transported on the latter by the sputtering system. Within the coating plant, the substrate is first used for "dewatering" the surfaces preheated to about 150 ° C. Subsequently, an antireflective system (as an example consisting of four layers) is prepared as follows:

• A) sputtering a high-index layer A at a feed rate of 1.7 m / min, wherein the carrier oscillates in front of the sputtering source and during which a layer of 30 nm thickness is deposited. The layer is produced by adding argon and reactive gas while controlling the reactive gas to a plasma impedance. The process pressure is determined in particular by the amount of argon, which leads to typical process pressures in the range between 1 · E-3 and 1 · E-2 mbar. The deposition in the plasma takes place via a pulsation.
• B) sputtering a low-refraction layer B at a feed rate of 2.14 m / min. In this case, a layer of thickness 30.5 nm is produced. The layer production takes place according to the deposition under layer 1.
• C) sputtering of a high-index layer corresponding to layer A. Here, a layer of thickness 54 nm is produced at a feed rate of 0.9 m / min.
• D) Sputtering of a low-refraction layer according to layer B. At a feed of 0.63 m / min, a layer of thickness 103 nm is produced. Subsequently, the coated substrate is discharged with the carrier via a transfer chamber.
• E) Making a composite of 2 slices of anti-reflection system after step A-D with the coated side facing outwards, and laminating a 0.38 mm thick PVB film between the two glass sheets in a roll-bonded process.

A composite pane produced in this way with two glass panes of low-iron soda-lime glass with a Fe ₂ O ₃ content of less than 0.03% by weight and a thickness of 1.1 mm and a layer of PVB film with a thickness of 0, 38 mm has a basis weight of 6.45 kg / m ² , a quotient of the total thickness of all organic layers to the total thickness of the first and second mineral glass of 0.17 and a total thickness of all organic layers of 0.38 mm. As a result, a weight reduction compared to a conventional monolithic glazing of 9% can be achieved. The general color rendering index R _a is greater than 99. The UV transmission of the composite disc at a wavelength of 380 to 300 nm is 2.2%. When using a 0.76 mm PVB film results in an R _a of 100 and a UV protection of 99.9% is achieved. Hereby, a weight-reduced composite pane can be provided as picture, showcases or shop window glazing, with a high UV protection and a low reflectivity in the visible wavelength range, as well as an unadulterated color reproduction of the objects displayed.

Example 3:

• A) Herstellen einer einseitig beschichteten Glasscheibe mit interferenzoptischer Entspiegelung gemäß Beispiel 2, Schritt A–D.
• B) Herstellen eines Verbundes aus 2 Scheiben Antireflex System nach Schritt A–D, wobei die beschichtete Seite jeweils nach Außen zeigt, und zwischen die beiden Glasscheiben zwei PVB Folie mit jeweils 0,38 mm Dicke in einem Rollenverbundverfahren laminiert wird.

One-sided antireflection coating produced by the sputtering method:

• A) Production of a glass sheet coated on one side with interference-optical antireflection coating according to Example 2, step A-D.
• B) A composite of 2 slices of antireflective system after step A-D, with the coated side facing outwards, and between the two glass sheets two PVB film each 0.38 mm thick in a roll-laminated process is laminated.

A composite pane produced in this way with two glass panes of low-iron soda-lime glass with a Fe ₂ O ₃ content of less than 0.03% by weight and a thickness of 1.1 mm and a layer of PVB film with a thickness of 0, 38 mm has a basis weight of 6.45 kg / m ² , a quotient of the total thickness of all organic layers to the total thickness of the first and second mineral glass of 0.17 and a total thickness of all organic layers of 0.76 mm. As a result, a weight reduction compared to a conventional monolithic glazing of 9% can be achieved. The general color rendering index R _a is greater than 99. The UV transmission of the composite disc at a wavelength of 380 to 300 nm is 0.11%. Hereby, a weight-reduced composite pane can be provided as picture, showcases or shop window glazing, with a high UV protection and a low reflectivity in the visible wavelength range, as well as an unadulterated color reproduction of the objects displayed.

In 2 is for a composite pane, comprising two 1.1 mm thick glass panes of a low-iron soda-lime glass and a PVB film of 0.38 mm between the glass sheets, the course of transmission / reflection between 300 nm and 800 nm. Both the outer surface of the first disc and the second disc comprises an antireflecting coating, which is preferably designed as an interference-optical coating as described in Examples 1 to 3. In addition, the composite pane comprises a coating and / or foil which has a filtering action and / or absorption for electromagnetic radiation in the wavelength range smaller than 380 nm. Such a PVB film is obtained, for example, from Eastman Chem. Corp. offered under the trade name Saflex ^® .

Clearly visible is the strongly decreasing transmission for wavelengths smaller than 380 nm and the high transmission over 90% for wavelengths from 400 nm to 800 nm. The transmission curve is designated 100. The reflection curve designated 200 also shows low values and reflections below 10% for the range 400 nm to 700 nm.

The combination of in 2 Proposed disc with an Easy to Clean (ETC) layer allows a further increase in the properties of the disc. The antri-reflective layer reduces the reflection of the disk by typically a factor of 10, as described above. Due to this effect, contamination appears to be visually enhanced as the contamination remains fully visible. This effect can be countered with an ETC layer. The very thin ETC layer is usually subsequently applied to the antireflection layer and forms a thin protective film, which is usually much thinner than the entire AR layer. The protection can be both hydrophobic and oleophobic. Solid bodies and greases adhere significantly less to this layer, so that they also remain less visible. Another advantage is better cleanability of the disc compared to untreated glass because of the low adhesion.

The invention can be used as picture glazing and showcase glazing. When used as picture glazing and showcase glazing there is increased protection against mechanical impact combined with increased UV protection.

The increase of the strength by a bias in the glass is particularly advantageous in these glasses. Antireflective coating also achieves a significantly higher contrast of a screen compared to uncoated glass surfaces, even in bright environments.

It is understood that the invention is not limited to a combination of the features described above, but that the skilled person will arbitrarily combine all features of the invention, as far as appropriate, or use it alone, without departing from the scope of the invention. Other embodiments are possible. LIST OF REFERENCE NUMBERS 1 laminated pane 11 first mineral glass pane 12 second mineral glass pane 13 UV absorbing layer 14 Interference-optical antireflective coating 100 transmission curve 200 reflection curve

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010037150 [0003]
• US 2010/0151210 [0004]
• WO 2015/058885 A1 [0005, 0006, 0007]
• EP 1248959A [0049]
• WO 2012/163946 [0060]
• EP 1248959 B1 [0083]

Cited non-patent literature

• ASTM D1003 D1044 [0020]
• DIN EN 843-1 [0040]
• DIN EN 1288-3 [0040]
• DIN EN 843-4 [0042]
• EN ISO 6507-1 [0042]
• Hans-Joachim Gläser, "Thin Film Technology on Flat Glass", pp. 167-171 [0093]

Claims (20)

Laminated pane for protective glazing, preferably an image, showcase, or showcase glazing, comprising a first and a second mineral glass pane and at least one organic UV-absorbing layer A, which is arranged between the first and the second mineral glass pane, characterized in that the basis weight of the composite disc has a lower limit of 0.6 kg / m ² and an upper limit of 7.5 kg / m ² , the quotient of the total thickness of all organic layers to the total thickness of the first and second mineral glass pane 0.1 to 31, the total thickness of all organic layers is less than or equal to 3.1 mm, the composite disc has an antireflective coating, in particular an interference-optical coating, the composite disc comprises a coating and / or film which has a filtering effect and / or absorption for electromagnetic radiation in the wavelength range smaller 380 nm and the UV Du roughness of the composite disc at a wavelength of 300 to 380 nm, preferably less than or equal to 3%, and the general color rendering index R _a r composite disc is greater than or equal to 98. The composite pane according to claim 1, wherein the basis weight has a lower limit of greater than or equal to 1.0 kg / m ² , preferably greater than or equal to 2.2 kg / m ² , in particular greater than or equal to 4.3 kg / m ² , in particular greater than or equal to 5.2 kg / m ² and the basis weight has an upper limit of less than or equal to 7.1 kg / m ² , preferably less than or equal to 6.5 kg / m ² and the quotient of the total thickness of old organic layers to the total thickness of the first and second mineral glass pane is 0.1 to 20, preferably 0.1 to 8, in particular 0.1 to 4, in particular 0.1 to 1, in particular 0.15 to 0.4 and the total thickness of all organic layers is less than or equal to 2 mm, in particular less than or equal to 0.8 mm, in particular less than or equal to 0.4 mm. A composite pane according to claim 1 or 2, wherein the UV permeability of the composite pane at a wavelength of 380 to 300 nm is less than or equal to 1%, preferably less than or equal to 0.8%, more preferably less than or equal to 0.5%, most preferably less than or equal to zero , 3%, in particular less than or equal 0.1%. Laminate according to one of the preceding claims, wherein the general color rendering index of the composite disc is greater than or equal to 99. Composite pane according to one of the preceding claims, wherein the transparency of the composite pane is greater than or equal to 97%, preferably greater than or equal to 98%, particularly preferably greater than or equal to 99%. Composite pane according to one of the preceding claims, wherein the optical scattering behavior of the composite pane is less than or equal to 1.5%, preferably less than or equal to 1.0%, particularly preferably less than or equal to 0.5%. Laminate according to one of the preceding claims, wherein the inwardly facing surface of the first glass sheet, a UV-absorbing coating B and / or the inwardly facing surface of the second glass sheet has a UV-absorbing coating C. Composite pane according to one of the preceding claims, wherein the antireflective coating is designed such that the reflectivity of each antireflective surface is less than 3%, preferably less than 2%, in particular less than 1% for wavelengths of 400 nm to 700 nm. A composite pane according to claim 8, wherein the antireflective coating of two or more layers consists of alternating high and low refractive indices, the uppermost layer having a low refractive index and preferably being a primer layer; or - The antireflective coating consists of three or more layers with alternating average, high and low refractive index and the top layer has a low refractive index, and preferably represents a primer layer. A composite pane according to claim 8 or 9, wherein The antireflective coating consists of a layer which is preferably a primer layer and has a low refractive index in the range of from 1.22 to 1.44, more preferably in the range of from 1.28 to 1.44; or - The antireflective coating is composed of several layers, wherein preferably the uppermost layer is an adhesive layer and a low refractive index in the range of 1.22 to 1.70, more preferably in the range of 1.28 to 1.60, particularly preferably in the range from 1.28 to 1.56. A composite pane according to any one of claims 8 to 10, wherein - the antireflective coating in the form of at least one layer is designed such that an incomplete antireflective coating is present, which only together with an antifingerprint coating has the complete antireflective effect in the spectral range; or - the antireflective coating in the form of at least one layer is designed such that an incomplete antireflective coating is present, which has the complete antireflective effect in the spectral range only together with a primer layer and an antifingerprint coating. Laminate according to one of claims 8 to 11, wherein at least one layer of the antireflective coating, preferably the top layer, which is present as a primer layer is subdivided into sub-layers with one or more intermediate layers, wherein the one or more intermediate layers preferably has almost the same refractive index as the sub-layers exhibit. A composite pane according to any one of claims 8 to 12, wherein the primer layer is a mixed oxide layer, preferably a silicon mixed oxide layer comprising an oxide of at least one of aluminum, zinc, magnesium, phosphorus, cerium, zirconium, titanium, cesium, barium, strontium, niobium, tin , Boron and / or magnesium fluoride, preferably at least one oxide of the element has aluminum and preferably has a thickness greater than 1 nm, preferably greater than 10 nm, more preferably greater than 20 nm. Laminate according to one of the preceding claims, wherein the outwardly facing surface of the first and / or the second glass sheet mineral having a coating with antimicrobial and / or easy-to-clean properties. A composite pane according to claim 14, wherein The antimicrobial property by the presence of one or more antimicrobial metal ions, preferably selected from silver, copper, cadmium, zinc, iron, tin, cobalt, cerium, antimony, selenium, chromium, Magnesium and / or nickel ions in antimicrobial effective amount in the surface of the first and / or the second mineral glass sheet and a present antireflective coating is realized; - The easy-to-clean property is realized by a coating of one or more layers on the antireflectively coated first and / or the second mineral glass pane or directly on the surface thereof. Composite pane according to one of the preceding claims, wherein the thickness of the first and / or the second mineral glass pane is less than or equal to 3 mm, preferably less than or equal to 1.3 mm, more preferably less than or equal to 1.1 mm and greater than or equal to 50 μm, in particular greater than or equal to 100 μm, preferably greater than or equal to 250 μm, particularly preferably greater than or equal to 450 μm, particularly preferably greater than or equal to 700 μm, and the sum of the thickness of the first and the second mineral glass pane is less than or equal to 3.1 mm. Composite pane according to one of the preceding claims, wherein the first and / or the second mineral glass pane of a lithium aluminum silicate glass, soda-lime silicate glass, borosilicate glass, alkali aluminosilicate glass, alkali-free or low-alkali aluminosilicate glass in particular from a chemically and / or thermally hardened lithium Aluminosilicate glass, soda lime silicate glass, borosilicate glass, alkali aluminosilicate glass, alkali-free or low-alkali aluminosilicate glass. Composite pane according to one of the preceding claims, wherein the thickness of the at least one organic UV-absorbing layer A is less than or equal to 3.1 mm, preferably less than or equal to 1.9 mm, preferably less than or equal to 0.8 mm, particularly preferably less than or equal to 0.4 mm is. Laminate according to one of the preceding claims, wherein the at least one organic UV-absorbing layer A of a hot melt adhesive, in particular a polyvinyl butyral (PVB) or a thermoplastic urethane-based elastomer (TPE-U) or an ionomer or a polyolefin, such as an ethylene vinyl acetate ( EVA), or a polyethylene (PE) or a polyethylene acrylate (EA) or a cyclo-olefin copolymer (COC) as an adhesive film or a thermoplastic silicone. A composite pane according to any one of the preceding claims, wherein the inwardly facing surface of the first and / or the second mineral glass sheet has a coating with a heat-reflecting layer having a sheet resistance of less than or equal to 20 Ω.

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