Sheetlike glass article, preferably for solar applications, and process for production thereof

Abstract

The present disclosure relates generally to sheetlike glass articles that can be used, for example, in solar applications as "frontside substrate", i.e. as a cover, as protection for photovoltaic modules, for example including in aerospace / outer space applications. In addition, the disclosure generally also relates to a process for producing such sheetlike glass articles and to the use thereof.

Description

[0001] Sheetlike glass article, preferably for solar applications, and process for production thereof

[0002] Field of the invention

[0003] The present disclosure relates generally to sheetlike glass articles that can be used, for example, in solar applications as “frontside substrate”, i.e. as a cover, as protection for photovoltaic modules, for example including in aerospace / outer space applications. In addition, the disclosure generally also relates to a process for producing such sheetlike glass articles and to the use thereof.

[0004] Background of the invention

[0005] In general, sheetlike glass articles, also referred to as glass panes or substrates, are used as covers (also referred to as cover glasses or cover panes) for solar modules. The sheetlike glass articles serve as protection for the photovoltaic cells that they cover, for example from mechanical stress, but also from corrosion. At the same time, however, the cover glasses must also be sufficiently transparent for enough light to pass through them in order to enable efficient power generation.

[0006] In the case of solar modules or solar panels for terrestrial applications, cover panes used may frequently have a thickness of up to several millimetres and are frequently specially configured to enable diffuse reflection, for example, for which the surface of the cover pane may have, for example, a specific rough or else pyramidal structure. Terrestrial solar modules are subject to weathering. By contrast, distinctly different demands are placed on cover panes intended specifically for use in space. It is true that glasses for cover panes for terrestrial solar modules should also have minimum propensity to solarization. However, these aspects are much more important in the case of use in space, since radiation is firstly distinctly increased here; on the other hand, because of the payload, i.e. the transport weight, the cover pane should be as thin as possible since the cover pane is not subject to any weathering in space - but this results in difficulties in adjusting the material of the cover pane such that sufficient protection of the solar cells beneath the cover pane is assured in spite of a low thickness, especially protection from harmful UV radiation. UV radiation can especially lead to ageing of the adhesive layers that are disposed between and connect cover glass and solar cells. In order to prevent this, components such as lead, titanium or cerium may be added to the glass that forms the cover pane, which improve the shielding effect to radiation, especially UV radiation. However, a general disadvantage of this is that such components are not able solely to improve the shielding effect against radiation, but will of course generally affect the glass properties. For example, known glasses having a sufficient shielding effect frequently have an unfavourable, excessively high refractive index, thermal expansion is not sufficiently adapted to the material of the solar module, for example the polymer layer and / or the material of the solar cells, and / or the fusion properties of the glass do not enable inexpensive production. In the case of lead, an additional factor is that this material increases the density of the glass - and hence the payload of the resulting cover pane - and is also toxic.

[0007] US patent specification US 6 207 603 B1 describes a glass suitable for covering solar cells. This glass has a sharp transmittance edge and is suitable even in a very thin glass article having a thickness between 50 pm and 500 pm, especially a thickness of 150 pm, for ensuring good protection of UV-curing materials that are used as adhesive between a solar cell and the cover glass, while simultaneously obtaining good overall transmittance of the glass material over the wavelength range of relevance for the solar spectrum. However, the glassy material has a relatively high coefficient of thermal expansion of about 7.4*106 / K.

[0008] European patent application EP 3 863 980 A1, filed by the applicant of the present application, names a broad composition range comprising up to 3% by weight of CeO2, but relates not to glass articles but to glass ceramics, and is thus very far removed from the subject-matter of the present application.

[0009] Japanese patent application JP2017 / 193464 A describes a radiation-resistant glass, but for nuclear applications. Very thin sheetlike glass articles are not addressed; instead, thicknesses of several millimetres are described. Japanese patent application JP 2014 / 141363 describes a chemically tempered glass having a broad composition range that can be used as cover glass for display applications. This glass is said to have a “blue light cut function” in order to prevent eye fatigue, such that transmittance in the visible spectral region is 60% or more, but at a wavelength of 437.5 nm is less than 90%. However, the application relates to very thin glass articles having thicknesses of 50 pm or less.

[0010] There is thus a need for an improved glass material and for sheetlike glass articles comprising said glass which at least partly alleviate the aforementioned shortcomings of the prior art. invention

[0011] It is an object of the invention to provide a sheetlike glass article, especially for use as cover pane, preferably as cover pane for a solar module, especially for extraterrestrial use. Further aspects of the invention relate to a corresponding glass from which such a sheetlike glass article can be formed or which comprises such a glass, and a process for producing such a glass article. Yet a further aspect is directed to the use of sheetlike glass articles according to embodiments of the disclosure.

[0012] Summary of the invention

[0013] The object is achieved by the subject matter of the independent claims. Preferred and specific embodiments can be found in dependent claims, the description and the drawings of the disclosure.

[0014] The invention thus relates generally to a sheetlike glass article which, at a thickness of the sheetlike glass article of 125 pm,

[0015] - has spectral transmittance at a wavelength of 330 nm of less than 2% and spectral transmittance at a wavelength of 400 nm of at least 87%, and the average transmittance in the wavelength range of 500 nm to 1800 nm, determined as the arithmetic average over the spectral transmittances measured in this wavelength range, is at least 92%, and optionally one of the further features: - spectral transmittance at a wavelength of 450 nm of at least 88%, preferably of at least 89%, more preferably of at least 90%,

[0016] - transmittance in the wavelength range of 320 nm to 340 nm of less than 1 %,

[0017] - transmittance in the wavelength range of 395 nm to 420 nm of at least 88%.

[0018] Such a configuration is very particularly advantageous. The sheetlike glass article according to the disclosure, as described above, is thus configured such that, even at a very low material thickness of only 125 pm, it already has a sufficient shielding effect against UV radiation. The low material thickness is advantageous since the sheetlike glass article is specifically also intended for extraterrestrial applications and should therefore be made as thin as possible to avoid a high payload.

[0019] In general, glass articles having a thickness other than 125 pm, in order to check whether they satisfy the aforementioned properties of the glass article, may be thinned or stacked one on top of another in order to arrive at the corresponding thickness of 125 pm, and the transmittance properties can then be measured accordingly. Alternatively or additionally, mathematical calculations are also possible in order to be able to undertake a corresponding calculation of transmittance values for glass articles at variance from 125 pm. This can be effected, for example, in accordance with the method described, for example, in DIN EN 410 in the annex starting from page 39 ff. This involves separating the transmittance losses of a glass pane via absorption in the glass and via reflection at the interfaces by calculation, such that conversion of the transmittance at a particular glass thickness to other glass thicknesses is possible.

[0020] In the context of the present disclosure, a glass article is generally understood to mean an article or product comprising a glass or formed from a glass.

[0021] In one embodiment, the sheetlike glass article comprises a glass comprising SiO2, AI2O3, B2O3 and CeO2. In particular, in one embodiment, this is understood to mean that the sheetlike glass article is formed from such a glass. For example, the sheetlike glass article according to the present disclosure may generally be regarded as a glass pane, wherein, in one embodiment, the glass pane is formed from a glass comprising SiO2, AI2O3, B2O3 and CeO2. A glass comprising SiO2, AI2O3, B2O3 and CeO2 may generally also be regarded as a cerium oxide- and aluminium oxide-containing borosilicate glass.

[0022] Such a configuration is advantageous since, in this way, the glass is first formed as a chemically stable glass comprising B2O3 and SiO2 as network formers and AI2O3 as interstitial oxide. In this way, a stable glass network is formed, and the glass thus therefore takes the form of a borosilicate glass, i.e. generally forms part of the class of the chemically stable glasses. AI2O3 as interstitial oxide is likewise advantageous since it can suppress or at least alleviate the known separation tendencies that occur in the area of borosilicate glasses. Advantageously, the glass may also comprise alkalis, especially in the form of alkali metal oxides. Finally, it is advantageous for the glass in the glass pane to have a CeO2 content because cerium oxide is a component that can also improve the shielding effect with respect to UV radiation, for example, and can simultaneously also improve the solarization stability of the glass.

[0023] In one embodiment, the glass preferably comprises at most 70% by weight of SiO2. Preferred upper limits are 69% by weight and 66% by weight. A preferred lower limit for the SiO2 content of the glass is at least 55% by weight, preferably at least 59% by weight, more preferably at least 60% by weight. Such an SiO2 content of the glass may be advantageous because, in this way, the glass is present in a composition in which it has good meltability since the SiO2 content of the glass, as stated, is indeed limited and is not too high. At the same time, however, it may likewise be advantageous not to lower the SiO2 content of the glass to too low a level, in order still to enable a glass network of maximum stability, especially good chemical and mechanical stability of the glass. The glass preferably therefore comprises at least 55% by weight of SiO2, preferably at least 59% by weight of SiC>2 and, as already stated above, preferably at least 60% by weight.

[0024] In one embodiment, the glass comprises at least 2% by weight of AI2O3. Such a content is advantageous because it has been found that, in this way, it is possible to effectively counteract separation of a glass comprising, as network formers, SiO2 and B2O3. However, AI2O3 increases the melting temperature and at the same time tends to lower the chemical stability of a glass and should therefore not be present in excessively high amounts in the glass. Preferred lower limits are 2.5% by weight, preferably 3% by weight. It has also been found that, for the glass, according to embodiments, a preferred upper limit for the AI2O3 content in the glass is at most 12% by weight. The glass preferably comprises at most 11% by weight, more preferably at most 10% by weight.

[0025] B2O3 is a component that generally lowers the melting temperature and simultaneously leads, in association with SiO2, to formation of chemically very stable glasses. However, excessively high contents of B2O3 promote separation and should be avoided. The glass according to the present disclosure therefore comprises, in one embodiment, at least 4% by weight of B2O3. For example, the glass may comprise at least 4.5% by weight or more preferably at least 5% by weight of B2O3. However, the B2O3 content in the glass is preferably limited and, in one embodiment, comprises at most 8% by weight, preferably at most 7.5% by weight and more preferably at most 7% by weight.

[0026] CeO2 is a component which, as also set out above, is advantageous for the development of good shielding of UV radiation and also increases solarization stability. The CeO2 content of the glass, in one embodiment, should therefore be at least 0.5% by weight. Preferred minimum contents are 1% by weight, 2% by weight, 3% by weight and 4% by weight. However, the CeO2 content of the glass is preferably limited. The following aspects are significant here: firstly, CeO2 is a component having a high density and therefore increases the payload. Furthermore, excessively high contents of CeO2 move the UV edge too far into the visible, and transmittance at a wavelength of 400 nm decreases. Finally, excessively high CeO2 contents can lead to an elevated tendency to crystallization of the glass. In one embodiment, the CeO2 content of the glass is therefore at most 8% by weight, preferably at most 6% by weight, more preferably at most 5.6% by weight and most preferably at most 5.2% by weight.

[0027] The form of the sheetlike glass article is preferably such that it comprises a glass comprising SiC>2, AI2O3, B2O3 and CeO2, where these components are preferably encompassed by glass in the following ranges, reported as % by weight based on oxide:

[0028] SiC>2 at most 70, preferably at most 69, more preferably at most 66, and preferably at least 55, preferably at least 59, more preferably at least 60,

[0029] AI2O3 at least 2, preferably at least 2.5 and more preferably at least 3, and preferably at most 12, preferably at most 11 , more preferably at most 10, B2O3 at least 4, preferably at least 4.5 and more preferably at least 5, and preferably at most 8, preferably at most 7.5 and more preferably at most 7,

[0030] CeO2 at least 0.5, preferably at least 1 , more preferably at least 4, and preferably at most 8, preferably at most 6, more preferably at most 5.6 and most preferably at most 5.2.

[0031] In general, it is pointed out that, in the context of the present disclosure, the components of the glass are specified in the form as typically obtained by analysis. The component is typically specified in the stable, usually in the highest, oxidation state. However, it is pointed out that this does not necessarily correspond to the form in which the component is actually present. For example, the iron in an oxidic glass may be present both in divalent and trivalent form, i.e. as Fe2+ / FeO or as Fe3+ / Fe20s. The figures relating to the contents of corresponding components in the context of the present disclosure thus relate to standard figures from the analysis, although it will be appreciated that the component may also be in a form at variance from the “ideal”, customarily reported oxidation state.

[0032] In a preferred embodiment of the sheetlike glass article, the glass comprises less than 1 .5% by weight of F (fluorine). It has been found that fluorine is advantageous in glasses that can be used as covers of solar modules, including in the extraterrestrial sector. Fluorine can be advantageous as a component in a glass because it lowers the melting temperature of a glass. However, it is preferable according to the present disclosure to limit the fluorine content of the glass if possible since fluorine is toxic and is problematic in relation to occupational safety and environmental protection in glass production. Advantageously, the glass therefore comprises at most 1.5% by weight or even less. In particular, the glass, in one embodiment, may even be free of fluorine apart from unavoidable traces. Unavoidable traces are generally at most 500 ppm of the corresponding component, based on weight.

[0033] In one embodiment, the glass has a coefficient of thermal expansion (GTE) in the temperature range from 20°C to 300°C, 020-300, of less than 7.5*106 / K, preferably of less than 7.4*106 / K, more preferably of less than 7.3*106 / K, most preferably of less than 7.2*106 / K, for example of even less than 7.1*106 / K or less than 7.0*106 / K and more preferably of at least 6.5*106 / K. The coefficient of thermal expansion here generally means the linear coefficient of thermal expansion. This may especially be determined by a method according to ISO 7991. In the context of the present disclosure, the terms “coefficient of expansion”, “(linear) coefficient of thermal expansion”, “GTE” and “020-300” or “a” are used synonymously.

[0034] The coefficient of thermal expansion is an important parameter of the sheetlike glass article according to the present disclosure. This is because the sheetlike glass article, as stated, is intended in particular for use as cover of solar cells, for example. An example of a material for solar cells that is used by way of example in this field is gallium arsenide. This material has a coefficient of thermal expansion of 6.5*106 / K . However, this generally does not correspond to the coefficient of thermal expansion of the resulting solar cell; instead, this is likely to be higher as a result of other components of a solar cell or solar module, for example metal contacts or the like. The glass should therefore have a coefficient of thermal expansion matched to the other components of the solar cell and / or solar module, such that the coefficient of thermal expansion of the solar cell is not too high overall, but, on the other hand, is nevertheless matched to the materials used to such an extent that there are no great thermal stresses between the components of the module that may occur, for example, on launching of a launch vehicle or else later in the operation of the module.

[0035] However, known glasses that are already used as cover panes usually have much higher coefficients of thermal expansion, for example of more than 8*106 / K. This is unfavourable because, owing to the difference in the coefficients of thermal expansion of the glass and further components, there may be delamination from the cover pane, i.e. a sheetlike glass article, and the further materials of the solar module and / or solar cell.

[0036] Advantageously, therefore, the coefficient of thermal expansion of the sheetlike glass article, in one embodiment, should be not more than 7.5*106 / K, preferably less than 7.4*106 / K, more preferably less than 7.3*106 / K, most preferably less than 7.2*106 / K, for example even less than 7.1*10"6 / K, or less than 7.0*106 / K and more preferably at least 6.5*106 / K. Advantageously, the coefficient of thermal expansion of the sheetlike glass article should not be too low either, but should advantageously be at least 6.5*106 / K , in order to have good compatibility with customary materials that are used in solar cells and solar modules. Good agreement of the coefficients of thermal expansion of the different materials is advantageous in particular in a solar cell structure in which glass and solar cell are bonded by the adhesive (generally Dow Corning 93-500 or a similar adhesive) at 150°C (fur 15 min), and in the ultimate application with the rapid changes in temperature in space, since warpage of the solar cells and hence possible detachment from the carrier substrate or damage to the solar cells can thus be avoided. It can also be advantageous for the possible use of cells other than the GaAs cells described to provide glasses having lower coefficients of thermal expansion. Other materials for solar cells could also be able to get round the disadvantage of arsenic-containing solar cells, but generally have lower coefficients of thermal expansion than modern, customarily used glasses for cover panes of known solar modules and solar cells.

[0037] In one embodiment of the sheetlike glass article, the glass comprises TiO2. The glass preferably comprises at most 2% by weight of TiO2, preferably at most 1 .0% by weight of TiC>2, preferably at most 0.9% by weight of TiC>2, more preferably at most 0.8% by weight of TiC>2.

[0038] An embodiment of the sheetlike glass article in such a form that the glass of the glass article comprises TiC>2 may be advantageous especially when the CeO2 content of the glass is to be limited. If, for example, the glass comprises a comparatively small proportion of CeO2 of 3% by weight or less, it is possible that cost targets can be achieved in production in this way. However, this is at the expense of solarization stability and especially at the expense of a sufficiently steep UV edge of the resulting glass or, correspondingly, of the resulting sheetlike glass article. The inventors have found that a relatively low CeO2 content of the glass can be compensated for, however, by interplay of TiO2 and CeO2, such that good solarization stability can then nevertheless also arise in the case of low contents of CeO2, i.e. , for example, in the case of contents of CeO2 of 3% by weight or less.

[0039] For this purpose, in one embodiment, it may generally be the case that the sum total of the Ti O2 and CeO2 components is between 2% by weight and 6% by weight, preferably between 2% by weight and 5% by weight, for example between 2% by weight and 4% by weight or between 2% by weight and 3% by weight.

[0040] It has also been found that it can be advantageous, especially in the case of relatively low CeO2 contents of the glass, when a particular ratio between TiO2 and CeO2 components of the glass is established. In particular, it may be the case that the ratio of TiC>2 to Ce02, especially in the case of small contents of CeO2 of 3% by weight or less and / or especially in the case of a sum total of the components in the range between 2% by weight and 6% by weight, preferably between 2% by weight and 5% by weight, for example between 2% by weight and 4% by weight or between 2% by weight and 3% by weight, is configured such that, based on weight, the glass always comprises more CeO2 than TiO2 or, in other words:

[0041] 0 s TiO2 / CeO2 1 .

[0042] It has also been found that the redox state of the cerium in the glass can be of particular significance. Cerium is an element that may be in both trivalent and tetravalent form in a glass, i.e., for example, as Ce3+or as Ce4+. It has been found that specifically a high proportion of Ce4+in the glass of the sheetlike glass article is advantageous since, in this way, the position and steepness of the UV edge can be adapted. For this purpose, it may generally be advantageous to melt the glass of the glass pane under oxidizing conditions. For this purpose, the glass may be melted with addition of antimony oxide and / or nitrate and / or sulfate and / or arsenic oxide.

[0043] However, arsenic oxide is not preferred because of its toxicity. In particular, therefore, it may thus be the case that the glass of the glass pane comprises Sb2O3, up to a content of about 0.6% by weight.

[0044] In general, for a glass according to embodiments, especially a glass comprising CeO2, solarization stability is very good. It has thus been found that, for glasses according to embodiments, average transmittance in the wavelength range of 450 nm to 1800 nm, as a result of irradiation for a duration of 100 h with UV-A light at 210 W / m2, with UV-B light at 170 W / m2and UV-C light at 250 W / m2, changes by less than 1 percentage point. The advantageous, very high solarization stability of the glasses or sheetlike glass articles according to embodiments is also shown by way of example further down with reference to different transmittance spectra before and after solarization.

[0045] In addition, it has been found that cerium not only affects solarization stability. As will be shown further down with regard to Fig. 1 , the redox ratio of cerium in the glass can have a major influence on the position of the UV edge and the profile thereof. For instance, it has been found that the presence of cerium predominantly in the tetravalent positive oxidation state, i.e. as Ce4+, has the effect that the steepness of the UV edge is more marked and spectral transmittances are at higher values overall.

[0046] In one embodiment, therefore, the present disclosure relates to a sheetlike glass article comprising a glass, where the relative proportion of Ce3+in the total cerium in the glass, determined as the sum total of Ce3+and Ce4+, is at most 50%, preferably at most 30% and more preferably at most 10%.

[0047] In a further embodiment of the sheetlike glass article, this comprises a glass where the ratio of Ce3+to Ce4+in the glass, Ce3+ / Ce4+, is less than 1 , preferably less than 0.4 and more preferably less than 0.1.

[0048] The redox ratio of cerium in a glass is preferably determined by X-ray photoelectron spectroscopy (XPS) or alternatively by electron paramagnetic resonance (EPR).

[0049] It is possible to obtain such an advantageous redox ratio via melting of the glass with maximum oxidation. This can be effected, for example, by adding antimony oxide and / or nitrate as oxidizing agent to the glass melt and / or by adding sulfate and / or fluorine.

[0050] In a further embodiment of the sheetlike glass article, it may be the case that the glass comprises less than 2% by weight of BaO, preferably less than 1 .5% by weight of BaO, more preferably less than 1 % by weight of BaO.

[0051] Barium oxide BaO is a component which is widely used even in borosilicate glasses of high chemical stability, and additionally also has a radiation-blocking effect, being a heavy element. However, it has also been found that, surprisingly, in the sheetlike glass articles according to embodiments of the present disclosure, there is no need for a high BaO content in order to assure advantageous properties for radiation shielding. Even relatively small amounts of less than 2% by weight of BaO, for example less than 1 .5% by weight of BaO and more preferably less than 1 % by weight of BaO, are therefore preferred, although it may also be the case that the glass or, correspondingly, the sheetlike glass article may be free of BaO apart from unavoidable traces, which are generally, depending on the component, not more than 500 ppm, based on weight. This is advantageous because BaO is a heavy component and hence increases the payload and, advantageously, the density of the glass of the sheetlike glass article should not be too high. Furthermore, a frequently used raw material for BaO, namely BaCOs, is classified as a hazardous substance, and so, for that reason too, the BaO content in the glass should be as small as possible.

[0052] In one embodiment of the sheetlike glass article, the glass has a density between 2.4 g / cm3and 2.6 g / cm3, preferably between 2.45 g / cm3and 2.6 g / cm3.

[0053] Such a configuration, which is particularly favourable with regard to extraterrestrial applications because of the payload that has to be considered here, may advantageously be combined with a low BaO content of the glass.

[0054] In one embodiment of the sheetlike glass article, the glass comprises less than 5% by weight of IJ2O, preferably less than 3% by weight of IJ2O and more preferably less than 1% by weight of U2O. IJ2O is a component that can lower the melting point in the glasses according to embodiments, but can be unfavourable because of high raw material costs and generally because of the tendency to separation and crystallization in glasses. It may therefore be preferable when the glass is free of IJ2O apart from unavoidable traces.

[0055] In a further embodiment of the sheetlike glass article, the glass comprises less than 10% by weight of Na2O and / or less than 5% by weight of CaO and / or at least 0.9% by weight of MgO. The components mentioned are one alkali metal oxide and two alkaline earth metal oxides that may be advantageous in glasses of the sheetlike glass article in embodiments, since these are components that improve the meltability of the glass. They also serve to achieve a corresponding matched coefficient of thermal expansion. However, these components should not be encompassed in excessively high contents by the glass of the sheetlike glass article, since they can firstly reduce the chemical stability of the glass and secondly, in excessively high contents, would also lead to excessively high thermal expansion. In one embodiment, the sheetlike glass article has a surface roughness, reported as Ra, of 1 nm or less. The surface of the sheetlike glass article is preferably fire-polished, i.e. is a native surface.

[0056] A low roughness of the sheetlike glass article is advantageous for the construction of a welladhering, non-delaminating composite with the further constituents of the solar module for which the sheetlike glass article is supposed to be suitable as cover. Such surfaces of the sheetlike glass article having only a very low roughness are also of very good suitability, as specified above, for any coatings to be applied to the sheetlike glass article, for example antireflection coatings. In addition, it is advantageous when this very low roughness can be obtained without further post-processing steps, i.e. provides such a low roughness already in native form, originating from the shaping method itself.

[0057] For example, such a low roughness of the sheetlike glass article may advantageously be obtained in a drawing process, especially in what is called a down-draw process, for example an overflow fusion process or a down-draw process through a slot, further preferably with melting of a glass melt by means of Sb20s and / or by means of a nitrate and / or by means of sulfate and / or by means of fluorine.

[0058] In particular, the present disclosure thus also relates to a glass article produced or producible in a process according to one embodiment.

[0059] In a further embodiment of the sheetlike glass article, the glass has a refractive index nd of at least 1 .51 and at most 1 .53 at a wavelength of 588 nm. A refractive index in this range is advantageous for avoidance of reflection losses at interfaces to other materials, for example of a solar module.

[0060] In a further embodiment of the glass article, the electrical resistivity of the glass is between more than 1013Q*cm and less than 1015Q*cm at a temperature of 20°C. The sheetlike glass articles according to the disclosure are generally suitable as cover glasses (or cover panes or frontside substrates) for solar panels for aerospace applications, for example for satellites or space vehicles or space stations.

[0061] The present disclosure thus also relates generally to a frontside unit for a solar module, especially for mobile applications, such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications, comprising a sheetlike glass article according to one embodiment of the present disclosure, and an adhesive layer preferably applied over the full area of one side of the sheetlike glass article, where the adhesive layer more preferably comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone.

[0062] EVA is generally understood to mean ethylene-vinyl acetate. PVB denotes the polymer polyvinyl butyral. SMP is an abbreviation for a silane-modified polymer.

[0063] In addition, the present disclosure generally also relates to a solar module, especially for mobile applications, such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications, comprising a sheetlike glass article in one embodiment, preferably a backside element, especially in the form of a module frame, a solar cell, preferably disposed between the backside element and the sheetlike glass article, and an adhesive layer that bonds the sheetlike glass article and the solar cell to one another, where the adhesive layer more preferably comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone.

[0064] The solar cell may especially take the form of a single junction, with use here of silicon cells in particular, or of a multi-junction, especially with use of gallium arsenide cells, but they may generally also take the form of gallium indium phosphide cells or thi n-film cells comprising or composed of amorphous silicon (a-Si) or comprising or composed of materials having what is called perovskite structure, cadmium telluride or copper indium gallium selenide (CIGS).

[0065] The present disclosure also relates to a use. In particular, the present disclosure relates to the use of a sheetlike glass article according to embodiments of the disclosure and / or of a frontside unit according to an embodiment for a solar module, especially for mobile applications, for example mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications. In addition, the present disclosure also relates to the use of a solar module according to the present disclosure for mobile applications, for example mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications. Examples

[0066] The invention is elucidated in detail hereinafter by examples. The table that follows shows the composition of two example glasses that meet the specifications according to the present disclosure. The figures in the table are given in % by weight. Sums at variance from 100% by weight are the result of rounding.

[0067] Description of drawings The invention is elucidated in detail hereinafter by drawings. The figures show:

[0068] Fig. 1 the effect of the redox ratio of cerium (the ratio of Ce3+to Ce4+) on the position of the UV edge, Fig. 2 and 3 transmittance spectra of different sheetlike glass articles, Fig. 4 a schematic diagram, not true to scale, of a sheetlike glass article according to embodiments of the disclosure,

[0069] Fig. 5 a schematic diagram, not true to scale, of a frontside unit comprising a sheetlike glass article according to embodiments, and

[0070] Fig. 6 a schematic diagram, not true to scale, of a solar module according to one embodiment.

[0071] Fig. 1 shows, by way of example and without restriction to a specific working example, the effect of the redox ratio of cerium, i.e. in the context of the present disclosure the ratio of the two oxidation states Ce4+and Ce3+to one another, on the position of the UV edge and the steepness thereof in a sheetlike glass article according to one embodiment.

[0072] Reference numeral 1 in Fig. 1 represents the transmittance curve of a sheetlike glass article at a thickness of 125 pm, where this glass article is not a glass article according to an embodiment. By contrast, reference numeral 2 denotes the transmittance curve of a sheetlike glass article within the specifications of sheetlike glass articles according to the present disclosure,

[0073] - with a spectral transmittance of less than 2% at a wavelength of 330 nm and a spectral transmittance of at least 87% at a wavelength of 400 nm, and average transmittance in the wavelength range of 500 nm to 1800 nm, determined as the arithmetic average over the spectral transmittances measured in this wavelength range, of at least 92% and optionally one of the further features:

[0074] - spectral transmittance at a wavelength of 450 nm of at least 88%, preferably of at least 89%, more preferably of at least 90%,

[0075] - transmittance in the wavelength range of 320 nm to 340 nm of less than 1 %,

[0076] - transmittance in the wavelength range of 395 nm to 420 nm of at least 88%.

[0077] Astonishingly, however, the compositions of these two sheetlike glasses barely differ from one another - except that the glass of the sheetlike glass article, the transmittance spectrum of which is identified by reference numeral 2, was melted under oxidizing conditions. This can be effected, for example, in that antimony oxide and nitrate as oxidizing agents are added to the glass melt. This leads to the presence of cerium predominantly in the tetravalent positive oxidation state, i.e. as Ce4+, the result of which is that the steepness of the UV edge is more marked and spectral transmittances are at higher values overall. It can therefore be very advantageous to melt the glasses of the glass panes according to embodiments under oxidizing conditions.

[0078] The inventors believe in general, without restriction to the aforementioned specific example, that the proportion of Ce4+, based on the sum total of the redox states Ce3+and Ce4+in question here, in a corresponding melting operation is at least 50% and preferably accounts for at least 70% and more preferably at least 90%. What this means in a corresponding manner is that the proportion of Ce3+, based on the sum total of the redox states Ce3+and Ce4+in question here, accounts for at most 50%, preferably at most 30% and more preferably at most 10%. Of particular technical relevance here is the low proportion of the Ce3+content based on the total content which, for the glasses in question here, is the sum total of the contents of Ce3+and Ce4+in the glass. This is because this broadens the transmittance edge. A high proportion of Ce4+, which results in particular from an oxidizing melting operation, is therefore particularly advantageous for the use in question here.

[0079] In general, without restriction to the specific example shown in Fig. 1, the sheetlike glass article in one embodiment is therefore in such a form that it comprises a glass where the relative proportion of Ce3+in the total cerium in the glass, determined as the sum total of Ce3+and Ce4+, is at most 50%, preferably at most 30% and more preferably at most 10%.

[0080] In general, without restriction to the specific example shown in Fig. 1, the sheetlike glass article in one embodiment is therefore in such a form that it comprises a glass where the ratio of Ce3+to Ce4+in the glass, Ce3+ / Ce4+, is less than 1, preferably less than 0.4 and more preferably less than 0.1.

[0081] Plotted by way of example in Fig. 2 are some transmittance spectra of different sheetlike glass articles having a thickness of 125 pm. The transmittance spectra of the sheetlike glass articles identified by reference numerals 3 and 4 are commercially available sheetlike glass articles having very high transmittance. However, these commercially available sheetlike glass articles have coatings, namely antireflection coatings, which increases the transmittance of the glasses or sheetlike glass articles. Transmittance spectra 1 and 2 and 5 to 7 in Fig. 2, by contrast, were obtained for sheetlike glass articles in uncoated form. Transmittance spectra 1 and 2 correspond to those that are already also shown in Fig. 1 . Although the sheetlike glass articles that result in transmittance spectra 1 and 5 are outside the specifications of a sheetlike glass article according to embodiments, this is not the case for the further glass articles, the transmittance spectra of which are labelled 2, 6 and 7. It is preferably the case in general, in one embodiment, that the sheetlike glass article is also uncoated, meaning that it does not have an antireflection coating. Antireflection coatings in the context of the present disclosure generally mean optically active coatings that may take the form of individual layers, in which case they have a low refractive index of less than 1 .4, or optical alternating layer systems comprising at least one layer with a high refractive index and at least one with a low refractive index. It is often the case that such alternating layer systems are formed from alternating layers of SiO2 as material of the layer of low refractive index and TiO2 as material of the layer of high refractive index, although other configurations are also possible and known. In any case, a coating, whether in the form of a single layer or of an alternating layer system, constitutes an additional cost factor. In addition, such antireflection coatings are also prone to damage. It is therefore advantageous that such coatings are not required for glass articles according to the present disclosure.

[0082] The sheetlike glass article for which the transmittance spectrum 5 arises does have high transmittance over and above a wavelength of, for example, 350 nm, as can be inferred from the diagram in Fig. 2. However, this glass article, as can likewise be inferred from the spectrum 5 shown, has excessively high transmittance at a wavelength of 330 nm and below and is therefore unsuitable for the applications addressed here.

[0083] For the advantageous sheetlike glass articles, the spectra of which are shown in Fig. 2 by reference numerals 2 and 7, and also for the glass articles with spectra 1 and 5, further solarization tests were implemented. The results of these solarization tests show that average transmittance in the wavelength range of 450 nm to 1800 nm, as a result of irradiation for a duration of 100 hours with UV-A light at 210 W / m2, UV-B light at 170 W / m2and UV-C light at 250 W / m2, changes by less than one percentage point. This is shown in detail in Fig. 3. The values reported here in the context of the solarization tests are generally the arithmetic average transmittance within the wavelength range specified.

[0084] Particularly advantageous configurations are the sheetlike glass articles (and the corresponding glasses from which these sheetlike glass articles are formed) which, in the unirradiated state, give transmittance spectra 2 and 7 that are likewise shown again in Fig. 3. Fig. 3 shows the transmittance curves before (reference numerals without letters) and after (reference numerals with letter “a”) UV solarization, i.e. after irradiation for a duration of 100 hours with UV-A light at 210 W / m2, UV-B light at 170 W / m2and UV-C light at 250 W / m2. The solid lines in each case correspond to the transmittance spectra of unirradiated sheetlike glass articles; the dotted lines in each case are the corresponding transmittance spectra after irradiation or solarization. These spectra obtained after solarization are correspondingly also identified by “a”. The two very advantageous sheetlike glass articles according to embodiments of the present disclosure with spectra 2 and 7, after solarization, show a decrease in average transmittance in the wavelength range of 400 nm to 450 nm of only 0.92 percentage point and 1 .06 percentage points respectively. In general, the loss of transmittance should be lower than 1.5 percentage points and should generally be as low as possible, and so these two sheetlike glass articles thus show very good performance. In the wavelength range of 450 nm to 1800 nm, the decrease in transmittance was 0.16 percentage point and 0.12 percentage point respectively, although a decrease in transmittance of up to one percentage point would still have been acceptable.

[0085] Fig. 4 shows, generally in schematic form and not to scale, a sheetlike glass article 10 according to embodiments. It is generally the case that the sheetlike glass article has two sides 11 , 12 that preferably lie opposite and parallel to one another; a parallel formation of the two sides 11 , 12 relative to one another means that the angle between the normal vectors to the sides 11 , 12 is not more than 5°. The lateral dimension of the glass article 10 in any spatial direction of a Cartesian coordinate system is at least one order of magnitude lower than the two other lateral dimensions in the two other spatial directions perpendicular to that first spatial direction. This first lateral dimension is also referred to as thickness d of the glass article, and the two other lateral dimensions as length and width. In other words, the thickness d of the glass article 10 is thus at least one order of magnitude lower than the length and width of the glass article 10. A pane or sheetlike form in the context of the present disclosure generally means that the faces 11 , 12 may have any desired shape, but are preferably rectangular. However, other forms are possible, albeit not preferred. The sides 11 , 12 may also be regarded as lateral faces or surfaces of the glass article 10, by contrast with the circumferential edge face 13.

[0086] Fig. 5 is a schematic diagram, not true to scale, of a section view through a frontside unit 100 for a solar module (not shown). The frontside unit is especially suitable for mobile applications such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications. The frontside unit 100 generally comprises a sheetlike glass article 10 according to one embodiment of the disclosure and an adhesive layer 21 . This has preferably been applied over the full area of one side 11 , 12 (not labelled here) of the sheetlike glass article 10. More preferably, the adhesive layer 21 comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone.

[0087] Finally, Fig. 6 shows a schematic diagram, not true to scale, of a section view of a solar module according to the disclosure. The solar module 20 is likewise especially suitable for mobile applications such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects. The solar module 20 is very particularly suitable for aerospace applications. It comprises a sheetlike glass article 10 according to embodiments of the present disclosure. In general, without restriction to the schematic example shown in Fig. 6, the solar module 20 may comprise a backside element 300. This may take the form, for example, of a module frame. The solar module 20 further comprises a solar cell 200. This is preferably disposed between the backside element 300, if present, and the sheetlike glass article 10. In general, the solar module 20 comprises the adhesive layer 21 that bonds the sheetlike glass article 10 according to embodiments and the solar cell 200 to one another. More preferably, the adhesive layer 21 comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone. List of reference numerals

Claims

Claims1. Sheetlike glass article (10) which, at a thickness (d) of the sheetlike glass article (10) of125 pm,- has spectral transmittance at a wavelength of 330 nm of less than 2% and spectral transmittance at a wavelength of 400 nm of at least 87%, and the average transmittance in the wavelength range of 500 nm to 1800 nm, determined as the arithmetic average over the spectral transmittances measured in this wavelength range, is at least 92%, and optionally one of the further features:- spectral transmittance at a wavelength of 450 nm of at least 88%, preferably of at least 89%, more preferably of at least 90%,- transmittance in the wavelength range of 320 nm to 340 nm of less than 1 %, transmittance in the wavelength range of 395 nm to 420 nm of at least 88%.

2. Sheetlike glass article (10) according to Claim 1 , having a thickness between at least 50 pm and at most 175 pm, preferably between at least 100 pm and at most 150 pm.

3. Sheetlike glass article (10) as claimed in either of Claims 1 and 2, wherein the sheetlike glass article (10) comprises a glass comprising SiO2, AI2O3, B2O3 and CeO2, where these components are preferably encompassed by glass in the following ranges, reported as % by weight based on oxide:SiO2 at most 70, preferably at most 69, more preferably at most 66, and preferably at least 55, preferably at least 59, more preferably at least 60,AI2O3 at least 2, preferably at least 2.5 and more preferably at least 3, and preferably at most 12, preferably at most 11 , more preferably at most 10,B2O3 at least 4, preferably at least 4.5 and more preferably at least 5, and preferably at most 8, preferably at most 7.5 and more preferably at most 7,CeO2 at least 0.5, preferably at least 1 , more preferably at least 4, and preferably at most 8, preferably at most 6, more preferably at most 5.6 and most preferably at most 5.2.

4. Sheetlike glass article (10) according to any of Claims 1 to 3, wherein the glass comprises less than 1.5% by weight of F.

5. Sheetlike glass article (10) according to any of Claims 1 to 4, wherein the glass has a coefficient of thermal expansion (CTE) within the temperature range from 20°C to 300°C, 020-300, of less than 7.5*106 / K, preferably of less than 7.4*106 / K, more preferably of less than 7.2*106 / K, more preferably of less than 7.1 *106 / K, most preferably of less than 7.0*106 / K, and preferably of at least 6.5*10-6 / K.

6. Sheetlike glass article (10) according to any of Claims 1 to 5, wherein the glass comprises TiO2, wherein the glass preferably comprises at most 2% by weight of TiO2, preferably at most 1.0% by weight of TiO2, more preferably at most 0.9% by weight of TiO2, especially preferably at most 0.8% by weight of TiO2.

7. Sheetlike glass article (10) according to any of Claims 1 to 6, wherein the glass comprises less than 2% by weight of BaO, preferably less than 1 .5% by weight of BaO, more preferably less than 1% by weight of BaO.

8. Sheetlike glass article (10) according to any of Claims 1 to 7, having a surface roughness, reported as Ra, of 1 nm or less.

9. Sheetlike glass article (10) according to any of Claims 1 to 8, wherein the glass has a refractive index nd of at least 1 .51 and at most 1 .53.

10. Sheetlike glass article (10) according to any of Claims 1 to 9, wherein the glass has a density between 2.4 g / cm3and 2.6 g / cm3, preferably between 2.45 g / cm3and 2.6 g / cm3.

11. Sheetlike glass article (10) according to any of Claims 1 to 10, wherein the glass comprises less than 5% by weight of IJ2O, preferably less than 3% by weight of IJ2O and more preferably less than 1 % by weight of IJ2O.

12. Sheetlike glass article (10) according to any of Claims 1 to 11 , wherein the glass comprises less than 10% by weight of Na2O and / or less than 5% by weight of CaO and / or at least 0.9% by weight of MgO.

13. Sheetlike glass article (10) according to any of Claims 1 to 12, wherein average transmittance in the wavelength range of 450 nm to 1800 nm, as a result of irradiation for a duration of 100 h with UV-A light at 210 W / m2, with UV-B light at 170 W / m2and UV-C light at 250 W / m2, changes by less than 1 percentage point.

14. Sheetlike glass article (10) according to any of Claims 1 to 13, comprising a glass, wherein the relative proportion of Ce3+in the total cerium in the glass, determined as the sum total of Ce3+and Ce4+, is at most 50%, preferably at most 30% and more preferably at most 10%.

15. Sheetlike glass article (10) according to any of Claims 1 to 14, comprising a glass, where the ratio of Ce3+to Ce4+in the glass, Ce3+ / Ce4+, is less than 1 , preferably less than 0.4 and more preferably less than 0.1.

16. Frontside unit (100) for a solar module (20), especially for mobile applications, such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications, comprising a sheetlike glass article (10) according to any of Claims 1 to 15 and an adhesive layer (21) preferably applied over the full area of one side (11, 12) of the sheetlike glass article (10), wherein the adhesive layer (21) more preferably comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone.

17. Solar module (20), especially for mobile applications, such as mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications, comprising a sheetlike glass article (10) according to any of Claims 1 to 15, preferably a backside element (300), especially in the form of a module frame, a solar cell (200), preferably disposed between the backside element (300) and the sheetlike glass article (10), and an adhesive layer (21) that bonds the sheetlike glass article (10) and the solar cell (200)to one another, where the adhesive layer (21) more preferably comprises at least one of the following materials: a butyl polymer, EVA, PVB, SMP or a preferably transparent silicone.

18. Use of a sheetlike glass article (10) according to any of Claims 1 to 15 and / or of a frontside unit (100) according to Claim 16 for a solar module (20), especially for mobile applications, for example mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications.

19. Use of a solar module (20) according to Claim 17 for mobile applications, for example mobile devices, modes of transport, modes of transportation and / or manned and / or unmanned flying objects, especially for aerospace applications.

20. Process for producing a sheetlike glass article (10), especially a sheetlike glass article (10) according to any of Claims 1 to 15, in a drawing process, especially in what is called a down-draw process, for example an overflow fusion process or a down-draw process through a slot.

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