Plate-shaped chemically tempered glass product and preparation method thereof

Abstract

The invention relates to a plate-like, chemically tempered glass article and to a method for producing such a chemically tempered glass article.

Description

[0001] This application is a divisional application of patent application 202010769055.4, whose invention name is "Plate-shaped chemically tempered glass products and preparation methods thereof". Technical Field

[0002] The present invention relates to a plate-shaped, chemically toughened glass product and a method for producing such a chemically toughened glass product. Background Art

[0003] Known chemically tempered glass and / or chemically tempered or chemically tempered glass products and / or methods for preparing such products are described, for example, in the following patents: the patent family of US 2019 / 0016632 A1 having an already granted U.S. patent US 9,593,42 B2 as its patent family family patent, the patent family of US 2018 / 0057401 A1 having an already granted U.S. patent US 10,294,151 B2 as its patent family patent, the patent family of US 2018 / 0029932 A1 having an already granted U.S. patent US 10,259,746 B2 as its patent family patent, the patent family of US 2017 / 0166478 A1 having an already granted U.S. patent US 9,908,811 B2 as its patent family patent, the patent family of US 2017 / 0166478 A1 having an already granted U.S. patent US 9,908,811 B2, the patent family of US 10,239,784 B2 having an already granted U.S. patent US 10,239,784 B2 as its patent family patent, B2 is a patent family of US 2016 / 0122240 A1, which is a patent family of its own, US 10,150,698, US 10,271,442, US 2017 / 0295657 A1, which is a patent family of its own, US 8,312,739, US 2010 / 0028607 A1, which is a patent family of its own, US 9,359,251, US 2013 / 0224492 A1, which is a patent family of its own, US 9,718,727, US 2016 / 0023944, which is a patent family of its own A1's patent family, US 2012 / 0052271 A1's patent family with the granted patent family patent US10,227,253 B2, US 2015 / 0030840 A1's patent family with the granted US patent US 10,227,253 B2 as its patent family, US 2014 / 0345325 A1's patent family, US 2016 / 0257605 A1's patent family with the granted US patent US 9,487,434 B2 as its patent family, US 2015 / 0239776 A1's patent family with the granted US patent US 9,517,968 B2 as its patent family, US 2015 / 0239776 A1's patent family with the granted US patent US 9,567,254 B2 as its patent family 2015 / 0259244A1 patent family, with authorized US patent US 9,676,663 B2 is a patent family of US 2017 / 0036952 A1, which has a patent family of the same patent as US 10,266,447 B2, a patent family of US 2018 / 0002223 A1, which has a patent family of the same patent as US 9,517,968 B2, a patent family of US 2017 / 0129803 A1, which has a patent family of the same patent as US 10,266,447 B2, a patent family of US 2016 / 0102014 A1, which has a patent family of the same patent as US 10,266,447 B2, a patent family of US 2015 / 0368153 A1, which has a patent family of the same patent as US 9,676,663 B2, and a patent family of US 2015 / 0368148, which has a patent family of the same patent as US 9,902,648 B2. A1 patent family, US2015 / 0239775 A1 patent family with issued US Patent No. 10,118,858 B2, US 9,908,812 B2, US 2016 / 0264452 A1 and issued US Patent No. 9,902,648 B2 patent family, US 2016 / 102011 A1 and issued US Patent No. 9,593,042 B2 patent family, WO 2012 / 126394 A1 patent family; US 2014 / 0308526 A1 and issued US Patent No. 9,540,278 B2 patent family, US 2011 / 0294648 A1 and issued US Patent No. 8,759,238 B2 patent family, US 2010 / 0035038 A1 and the patent family of the authorized U.S. Patent US 8,075,999 B2, the patent family of US 4,055,703, the patent family of DE 10 2010 009 584 A1, the authorized German patent DE 10 2010 009 584 B4 and the U.S. application US2016 / 0347655 A1 with the authorized U.S. Patent US10351471 B2, the patent family of CN 102690059 A and the authorized Chinese patent CN 102690059 B, the patent family of US2016 / 0356760 A1 and the authorized U.S. Patent US 10,180,416 B2, the patent family of WO 2017 / 049028 A1 with the authorized U.S. Patent US 9,897,574 B2 as its equivalent patent, WO 2017 / 087742 A1 patent family, US 2017 / 0291849 A1 and the already granted US patent US 10,017,417 B2, US 2017 / 0022093 A1 and the granted US patent US 9,701,569 B2, US2017300088 (A1) and the granted US patent US 9,977,470 B2, EP 1 593 658 A1, the granted European patent EP 1 593 658 B1, and US applications US 2005 / 0250639 A1 and US 2018 / 0022638 A1 and the granted US patent US 10,183,887 B2. Chemically toughenable glasses can be distinguished between so-called aluminosilicate glasses (also known as AS glasses, aluminosilicate glasses or aluminosilicate glasses), which contain, in particular, Al2O3 and SiO2 as well as alkali metal oxides other than lithium oxide Li2O as components, and lithium-aluminosilicate glasses (also known as LAS glasses, lithium-aluminosilicate glasses or lithium-aluminosilicate glasses), which additionally contain Li2O as a component.

[0004] Other documents of the prior art are found in the following patents: the patent family of US 2019 / 0152838 A1, the patent family of US2013 / 0122284 A1 and the granted US patent US 9,156,724 B2; the patent family of US 2015 / 0079400 A1 with the granted US patent US 9,714,188 B2, the patent family of US 2015 / 0099124 A1 and the granted US patent US 9,701,574 B2, the patent family of WO 2019 / 085422 A1, the patent family of US 2017 / 0197869 A1 and the granted US patent US 10,131,567 B2, the patent family of US 2015 / 0030840 A1 and the granted US patent US 10,227,253 B2, the patent family of US 2015 / 0140325 A1 and the patent family of issued U.S. Patent No. 10,125,044 B2, US 2015 / 0118497 A1 and the patent family of issued U.S. Patent No. 9,822,032 B2, US 2012 / 0135852 A1 and the patent family of issued U.S. Patent No. 8,796,165 B2, US 2015 / 0147575 A1 and the patent family of issued U.S. Patent No. 10,000,410 B2, and US 2015 / 0376050 A1 and the patent family of issued U.S. Patent No. 9,783,451 B2.

[0005] Sheet glass products are often used in the electronics industry as cover glass (so-called cover glass or protective glass), specifically to protect mobile devices such as smartphones and / or tablet PCs. While glass offers excellent transparency across the entire optical spectrum and improved scratch resistance compared to transparent plastics, these electronic devices are, however, subject to extensive wear and tear in everyday life. Furthermore, compared to transparent plastics, glass is a brittle material prone to cracking. To further improve the abrasion resistance of sheet glass, it is often tempered, with chemical tempering often being the preferred method for very thin glass. This method can further improve abrasion resistance. For the protection of mobile devices, only sheet glass products with a very high degree of tempering are considered.

[0006] In the context of this document, abrasion loads are understood to be loads that may cause damage to the sheet glass article. These include, for example, friction loads (e.g., rubbing), scratching loads (e.g., due to contact with sharp objects, especially when such objects move over the surface of the sheet glass article), and impact loads (e.g., when the sheet glass article is dropped).

[0007] Within the scope of this disclosure, unless otherwise explicitly stated, the terms wear resistance and strength are used essentially synonymously as general terms for the resistance of a material or product to mechanical attack. Within the scope of this disclosure, specific strengths, such as set drop strength or flexural strength (also known as flexural tensile strength), are understood to be subsets of the (total) strength of a material, product, or article.

[0008] It has been shown that the actual loads to which sheet glass products are exposed cannot be adequately described and simulated by observing friction, scratching, and / or impact loads separately. Consequently, the actual loads that occur under practical conditions, such as friction with sharp particles on a surface, and the impact loads that are generated, for example, when a test specimen is dropped onto the sheet glass product for the purpose of determining the impact strength, can only partially (and sometimes not at all) resemble the loads that would occur when the assembled sheet glass product is dropped onto a surface.

[0009] It should be noted that the mechanical strength of products (such as glassware) depends not only on the material but also, in particular, on the type of load. Thus, known chemically tempered glassware exhibits, for example, high bending strength (measured using the four-point bending method) or high impact resistance (measured using the so-called drop ball test (a "blunt impact" load with a round object) or high strength under so-called "sharp impact" (a load with an acute angle). A particularly important test for mobile devices is the so-called drop test. This test investigates the loads a glassware will experience under conditions that it might encounter in real-world applications. To this end, the glassware is assembled in the same manner as it would later be assembled in a mobile device (such as a smartphone). A mockup of the device (e.g., a smartphone) is constructed, in which the glassware serves as a display cover. Without the use of corresponding components, the weight of the mockup roughly corresponds to that of the actual device, as does the assembly of the glassware. The mockup is then dropped, with the glassware facing downward, onto a surface, such as one containing particles with a small radius of curvature. This test method should therefore simulate real-world loads, such as those encountered when a smartphone is dropped on asphalt or concrete. It is generally known that rough surfaces (i.e., surfaces with sharp pebbles or sand particles protruding from them) are very dangerous to the integrity of the protective glass of mobile devices. For example, when the glass-equipped dummy device described is dropped onto a smooth surface (such as granite) or onto a rough surface covered with sandpaper (such as granite covered with sandpaper), the drop height of the dummy device is significantly different. The drop height on the rough surface simulated by the sandpapered granite is smaller than the drop height on a smooth surface. Alternative tests for studying the strength of such "sharp impacts" are, for example, so-called "sandpaper ball drop tests." For example, US Patent Application US 2015 / 0239775 A1 describes an exemplary configuration for a sandpaper ball drop test.

[0010] Glass or sheet glass suitable for use as cover glass for mobile devices is designed to be temperable, particularly chemically temperable. Within the scope of this disclosure, chemically temperable glass is understood to mean glass that can undergo an ion exchange process. In this process, alkali metal ions are exchanged in the surface layer of the glass article (e.g., a glass sheet). This is achieved by creating a compressive stress zone in the surface layer by exchanging ions with larger radii for ions with smaller radii. To this end, the glass article is immersed in a so-called ion exchange bath (e.g., a salt melt) containing ions with larger ionic radii, particularly potassium and / or sodium ions, so that these ions migrate into the surface layer of the glass article. During this exchange, ions with smaller ionic radii, particularly lithium and / or sodium ions, migrate from the surface layer of the glass article into the ion exchange bath.

[0011] This creates a compressive stress zone. This can be described by a characteristic value for the compressive stress (also called "compressive stress" or "CS") and the compressive stress depth (also called "depth of layer" or "DoL"). The compressive stress depth DoL is well known to those skilled in the art and, within the scope of this disclosure, refers to the depth at which the stress curve has a stress zero crossing. Alternatively or additionally, this DoL can be determined using a photoelastic zero-crossing measurement method, for example using a measuring device known as the FSM-6000 (which only determines the "imaginary" K DoL) or the SLP 1000 (which determines the "real" DoL).

[0012] For lithium-aluminosilicate and aluminosilicate glasses, the compressive stress at the surface of the glass sheet or sheet-shaped glass article as well as the maximum compressive stress CS can also be determined. The "hypothetical" Na CS or Na CS 30 (i.e., the compressive stress at a depth of 30 µm) can be determined using SLP.

[0013] The above-mentioned lithium-aluminum-silicate glasses and aluminosilicate glasses are known glass types which are generally notably chemically toughenable.

[0014] Aluminosilicate glass is also referred to as "AS glass" within the scope of this disclosure. Lithium-aluminosilicate glass is also referred to as "LAS glass" within the scope of this disclosure. Other names for AS glass include aluminosilicate glass or aluminosilicate glass; correspondingly, LAS glass is also referred to as "lithium-aluminosilicate glass" or "lithium-aluminosilicate glass."

[0015] Regarding the compositions of the two glass types, AS glass and LAS glass, aluminosilicate glass contains silicon dioxide (SiO2) and aluminum oxide (Al2O3) as components, as well as alkali metal oxides in addition to lithium oxide (Li2O), while lithium-aluminosilicate glass contains lithium oxide (Li2O) in addition to aluminum oxide and silicon dioxide. In other words, the difference between the glasses referred to as "aluminosilicate glass" and "lithium-aluminosilicate glass" is that lithium-aluminosilicate glass contains Li2O, while aluminosilicate glass does not. In addition to the aforementioned components, glasses often contain other components.

[0016] Typically, in the case of highly temperable glass (which is only considered for use, for example, as protective glass for mobile devices subject to high strength requirements), high compressive stress values ​​(between 700 MPa and 1000 MPa) are achieved at compressive stress depths between 40 µm and 200 µm. If not only one ion is exchanged, but a combined exchange of, for example, potassium and sodium ions is performed (as is typically the case with LAS glass), the variables CS and DoL, which characterize the compressive stress, are also typically given relative to the respective components or ions. This means, for example, that the compressive stress resulting from the potassium exchange is given as "CS Potassium" and the corresponding compressive stress depth is given as "Potassium DoL" or potassium compressive stress depth.

[0017] When the compressive stress depth is given relative to the respective exchanged component or ion, the compressive stress depth is also referred to as the so-called “exchange depth.” Within the scope of the present disclosure, the terms exchange depth, compressive stress depth and DoL are used synonymously.

[0018] However, it should be noted that the terms "potassium DoL" or "sodium DoL" are also commonly used. However, potassium DoL is a fictitious value in itself. Sodium DoL and DoL are therefore identical, just as potassium CS and CS are identical. For example, the value obtained by extending the intersection of the compressive stress curve obtained by potassium exchange with the X-axis is called "potassium DoL" or "potassium exchange depth". Therefore, whenever "potassium DoL" is mentioned, it is a value that can be obtained or has been obtained as described above within the scope of the present disclosure, but it is itself fictitious. The commonly used terms in the case of tempered glass with a combined stress characteristic curve will also be described below. Figure 7 This is explained with the aid of an exemplary stress characteristic curve.

[0019] LAS glass is advantageous over AS glass because it allows for greater compressive stress depths to be achieved more quickly. The compressive stress depth is given here as the value at which the stress curve has a value of 0 MPa, i.e., the compressive stress depth is indicated in the stress diagram by the stress curve crossing 0. In the case of LAS glass, the compressive stress depth is generally at least 100 µm or more at a treatment time of 1 to 3 hours.

[0020] Even with AS glass, large compressive stress depths are possible, for example, up to 125 µm or more. However, with this glass, very high tempering temperatures of 450°C or higher and / or very long tempering times of 8 hours or more must be selected to achieve such compressive stress depths. In contrast, LAS glass offers the advantage that high values ​​for compressive stress and compressive stress depth can be achieved under significantly more favorable conditions (i.e., at lower temperatures and / or shorter tempering times).

[0021] Compressive stress and compressive stress depth values ​​are determined metrologically using commercially available equipment, such as the FSM 6000 device for determining compressive stress (potassium CS) and compressive stress depth (potassium DoL) achieved through potassium exchange, and the SLP 1000 device for determining characteristic values ​​for stress achieved through sodium exchange, in particular the compressive stress at a depth of 30 μm achieved through sodium exchange (also referred to as "Na CS 30") and the compressive stress depth achieved through sodium exchange (sodium DoL). These devices are supplied by Orihara Co., Ltd.

[0022] Tempered glass products made from this type of material achieve high mechanical strength – either in terms of flexural tensile strength (e.g. double ring method according to DIN / EN 1288-5 or DIN EN 61747-5-3) or impact resistance (e.g. drop ball strength).

[0023] In the prior art, in addition to the classic compressive stress parameters CS and DoL, tensile stress is also correlated with strength, as can also be seen from the prior art detailed above. It has been shown that at excessively high compressive stress integrals (and therefore correspondingly very high tensile stress integrals, since the compressive stresses introduced into the surface of the glass article due to the tempering process are of the same magnitude as the tensile stresses generated within the glass article), strength growth lags behind and can even reverse course. This is attributed to a more intense triggering of crack growth or earlier glass breakage in strength tests (e.g., in the four-point bending method or tests investigating sharp impact resistance, such as the so-called drop test). This is particularly true when the DoL is correspondingly low. However, this also holds true for approximately equal DoL and non-combined (i.e., not optimized with respect to the storable tensile stress) tempering concepts or tempering methods. This can also be seen, for example, from the following table: Therefore, to optimize wear resistance, the applicant's own application, DE 10 2018 124 785, proposes providing a plate-shaped chemically tempered glass article that combines high surface compressive stress with high compressive stress, while simultaneously maximizing the stored or storable tensile stress to a value between a minimum of -20.6 MPa and a maximum of -30 MPa, preferably a maximum of -27.5 MPa, particularly preferably a maximum of -25 MPa, and very particularly preferably a maximum of -24 MPa. The glass article thus exhibits improved resistance to sharp impact loads. This high strength is derived from a storable tensile stress of at least -20.6 MPa. However, the applicant's own application assumes that the storable tensile stress should not be maximized, as experimental data suggests that even higher storable tensile stresses would result in lower strength against sharp impact loads. This approach resulted in a strength of 120 cm (average value) in a drop test. Sandpaper with a grit size of #180 (relatively fine) was used. Although good values ​​are achieved here, it has been shown that the drop strength deteriorates significantly at coarser grain sizes, corresponding to rougher ground surfaces.

[0024] There is therefore a need for glazing which at least alleviates the existing weaknesses of the prior art and which in particular always has sufficient wear resistance even under acute loads, such as when dropped onto rough surfaces. Summary of the Invention

[0025] The object of the present invention is to provide a plate glass product with high abrasion resistance, in particular when used as cover glass for mobile terminals, and to provide a method for producing such a glass product, which at least alleviates the existing weaknesses of the prior art.

[0026] This object is achieved by the subject matter of the independent claims. Preferred and particular embodiments are found in the dependent claims as well as in the description and the drawings.

[0027] Thus, according to a first aspect, the present disclosure describes a chemically tempered sheet-shaped glass product having a composition including the components SiO 2 , Al 2 O 3 , and Li 2 O, the glass product having at least one of the following features: at least 85 μm, preferably at least 100 μm and particularly preferably at least 115 μm, preferably a sodium exchange depth at a thickness of the glass article of at least 0.4 mm to less than 0.55 mm, at least 90 μm, preferably at least 120 μm and particularly preferably at least 125 μm, preferably a sodium exchange depth at a thickness of the glass article of 0.55 mm to less than 0.6 mm, at least 100 μm, preferably at least 125 μm and particularly preferably at least 135 μm, preferably a sodium exchange depth at a thickness of the glass article of 0.6 mm to less than 0.7 mm, at least 120 μm, preferably at least 140 μm and particularly preferably at least 160 μm, preferably a sodium exchange depth at a thickness of the glass article of 0.7 mm to less than 1 mm, and at least 170 μm, preferably a sodium exchange depth at a thickness of the glass article of 1 mm to 3 mm, preferably up to 2 mm, and / or a storable tensile stress of at most -15 MPa and preferably at least -45 MPa, preferably at least -35 MPa, particularly preferably at least -30 MPa and very particularly preferably at least -27.5 MPa, and / or a network former content of at least 82% by weight, and / or an alkali metal oxide content of up to 12% by weight, preferably up to 10% by weight, The plate-shaped glass article is preferably characterized by a drop strength given as a drop height in cm, wherein, when using sandpaper with a grit size of 60, a drop height of 50 to 150 is obtained as an average value of 15 samples. The grit size of the sandpaper is measured in mesh (#), i.e., the number of particles per inch (#60).

[0028] The storable tensile stress is understood to be the integral of the tensile stress in the normal direction along a straight line from the first main surface to the opposite main surface. To obtain comparable values ​​for substrates of different thicknesses, this integral is divided by the integration length (and therefore the substrate thickness). This tensile stress integral, normalized for thickness, thus has the dimension of stress and provides comparable values ​​for substrates of different thicknesses.

[0029] Such a design has a number of advantages.

[0030] A chemically tempered, sheet-like glass article having a composition comprising the components SiO 2 , Al 2 O 3 , and Li 2 O is thus formed as a glass article made of LAS glass. As already mentioned, such glass articles made of so-called LAS glass have advantages in terms of temperability, i.e., they are easier to handle, and also achieve very good mechanical strength.

[0031] However, compared to chemically tempered sheet glass products of the prior art, further advantages are achieved by the sheet glass products according to the present invention. In particular, it has been shown that the chemically tempered sheet glass products again have an increased resistance to so-called "sharp impact loads" (e.g., set drop tests). It has been shown that particularly good, i.e. particularly high, drop strength values ​​are achieved with an exchange depth, preferably a sodium exchange depth, of at least 85 μm, preferably at least 100 μm and particularly preferably at least 115 μm for a thickness of the glass article of at least 0.4 mm to less than 0.55 mm, an exchange depth, preferably a sodium exchange depth, of at least 90 μm, preferably at least 120 μm and particularly preferably at least 125 μm for a thickness of the glass article of 0.55 mm to less than 0.6 mm, an exchange depth, preferably a sodium exchange depth, of at least 100 μm, preferably at least 125 μm and particularly preferably at least 135 μm for a thickness of the glass article of 0.6 mm to less than 0.7 mm, an exchange depth, preferably a sodium exchange depth, of at least 120 μm, preferably at least 140 μm and particularly preferably at least 160 μm for a thickness of the glass article of 0.7 mm to less than 1 mm, and an exchange depth, preferably a sodium exchange depth, of at least 170 μm for a thickness of the glass article of 1 mm to 3 mm, preferably up to 2 mm. An exchange depth of 100 μm, preferably a sodium exchange depth, and / or a storable tensile stress of at most −15 MPa and preferably at least −45 MPa, preferably at least −35 MPa, particularly preferably at least −30 MPa and very particularly preferably at least −27.5 MPa.

[0032] Tensile stress is generally assigned a negative sign, while compressive stress, in contrast, has a positive sign, since compression and tension have correspondingly opposite directions. Whenever the magnitude of tensile stress is mentioned within the scope of this disclosure, without mentioning the sign, it should be understood that this refers to the numerical value of the stress. The definition of the sign of stress used here is the same as that commonly used by those skilled in the art (i.e., developers of tempered protective glass). This differs significantly from the common nomenclature commonly used in physics, for example (compressive stress is negative, tensile stress is positive). However, within the scope of this disclosure, as detailed herein, the definition of stress commonly used in the glass industry is used.

[0033] By working with sandpaper of varying particle sizes (e.g., grit sizes #60 to #180), it was discovered that the relationship between stored tensile stress and drop strength described in the applicant's own application, DE 10 2018 124 785, is linked to the minimum DoL requirement. This is attributed to the varying particle sizes of the respective sandpaper. It has been noted that particularly rough and sharp-angled surfaces are particularly hazardous for protective or cover glass. Depending on their size, sharp-angled small stones, or the stress fields they generate, can penetrate the DoL and penetrate into the tensile stress zone, thereby causing the glass to break. In this sense, the minimum required DoL (beginning with which the relationship between greater stored tensile stress and higher drop strength holds true) increases with the particle size of the abrasive paper used in the drop test. The larger the sharp-angled particles or stones, the greater this minimum DoL or minimum DoL. AS glass, which has a simple ion exchange characteristic curve, demonstrates this relationship particularly impressively. Thus, these glasses have a stored tensile stress of -33.07 MPa for a thickness of 0.7 mm in the standard tempering solution (where a DoL of 50 µm and a compressive prestress of 926 MPa are achieved). However, due to the small DoL, this stored tensile stress does not translate into good #60 drop strength, and these glasses fail at a minimum height of 25 cm.

[0034] The stored tensile stress is determined with a fluctuation of approximately 5% to 10% around the determined value.

[0035] For simplification purposes, the tensile stress integral is calculated assuming a linear compressive stress characteristic curve. Therefore, for aluminosilicate glass, the calculation is performed according to the following formula: CS * DoL / 2 * 1000 * d, Wherein CS is understood to be the maximum compressive stress at the surface of the glass article, DoL is the depth of compressive stress and d is the thickness of the glass article.

[0036] For LAS glasses with a combined compressive stress characteristic curve, the calculation is slightly more complex and is performed according to the following formula.

[0037] [K CS * K DoL / 2 * 1000 + Na CS intersection * ((Na DoL – K DoL) + ( Na DoL – K DoL intersection)) / 2 * 1000] / d.

[0038] Here, d also represents the thickness of the glass article. The "sodium-CS intersection" describes the compressive stress at the point in the compressive stress characteristic curve where the sodium and potassium compressive stress curves intersect. The "potassium-DoL intersection" is understood to be the depth in the glass article at the point in the compressive stress characteristic curve where the sodium and potassium compressive stress curves intersect.

[0039] Thus, as is apparent from the above, the stored tensile stress is as defined above a thickness-dependent quantity, ie the tensile stress relative to the thickness, such that the unit of the stored tensile stress is MPa.

[0040] Furthermore, it has been shown that such a chemically toughened plate-shaped glass article can alternatively also be described as comprising a network former content of at least 82% by weight and / or an alkali metal oxide content of not more than 12% by weight, preferably not more than 10% by weight.

[0041] A high content of at least 82% by weight of network formers is advantageous because a stable three-dimensional crosslinked network is thereby achieved. It has been shown that this also results in good temperability of such glasses, i.e., such glasses with a content of at least 82% by weight of network formers are sufficiently hard to store stresses, in particular tensile stresses, in the bulk without causing significant relaxation and without causing, for example, a decrease in the wear resistance of the glass or glass article over time.

[0042] Alternatively or additionally, the glass of the glass article can contain an alkali metal oxide content of up to 12% by weight, preferably up to 10% by weight. It has been shown that, surprisingly, good strength values ​​can be achieved in this way after chemical tempering. This is all the more surprising because it is precisely the exchange of alkali metal ions during chemical tempering that has previously assumed that a high alkali metal oxide content is required for good tempering. In other words, the more small ions are exchanged for larger ions, the greater the degree of tempering achieved by ion exchange.

[0043] Thus, a very high drop resistance can be achieved with this sheet glass design. While the absolute drop heights achieved here are comparable to those of known glass or glass products, the absolute drop heights obtained are for a drop onto a surface with a particle size of 180°. This relates to a relatively fine particle size. A more dangerous situation arises when a surface with larger, coarser particles is present. This is because, due to their size and the higher energy per particle (due to the smaller particle size per cm), 2The number of particles (the number of particles) can penetrate deeper into the glass product and even cause failure. Therefore, for plate-shaped chemically tempered glass products, the drop height onto such a rough surface (e.g., achieved with abrasive paper having a grit size of 60) is significantly lower than the drop height of the glass products according to the present disclosure. Within the range of experimental components used, the set drop value for grit size #60 should be approximately 3.5 to 4 times lower than the value achieved for grit size #180.

[0044] The drop test is preferably carried out as follows: The glass plate is fixed to the sample holder and lowered from a cumulative drop height to a defined floor. An overview of the entire structure is given in Figure 8 The glass article used in the drop test had a length of 99 mm and a width of 59 mm and was Figure 9 is shown magnetically fixed in the sample holding portion together with the sample replica.

[0045] Here, a plastic sheet is first glued to a metal housing with the aid of double-sided adhesive tape, which has the shape and weight of a holder for a mobile terminal (e.g., a smartphone). Plastic sheets with a thickness of, for example, 4.35 mm to 4.6 mm are particularly suitable (see Figure 10The adhesive bonding is preferably performed using double-sided adhesive tape having a thickness of approximately 100 µm. The plate-shaped glass article to be tested is then adhered to the plastic plate using double-sided adhesive tape, preferably 295 µm thick, in particular tesa®, product number 05338, so that a distance of between 350 µm and 450 µm is maintained between the upper edge of the housing or holder and the upper edge of the glass article. The glass article is raised above the housing frame, and direct contact between the glass body and the aluminum housing is not permitted. The resulting "set" weighing 177.5 g (emphasizing that the glass article is incorporated into a mobile terminal and is a kind of "imitation" of an actual mobile terminal (here, in particular a smartphone)) is then dropped downwards on its glass side onto a DIN A4 surface, the so-called impact surface, at an initial velocity of zero in the vertical direction (thus, in the direction of fall). The impact surface is prepared as follows: Sandpaper with the corresponding grit size (e.g. grit size 60 (#60)) is adhered to the base plate using double-sided adhesive tape, e.g. 100 µm thick. Transparent, double-sided Tesa (10 m / 15 mm) with product number 05338 is used as the adhesive tape. For the purposes of this disclosure, the particle size is defined in accordance with the standards of the European Union Abrasive Manufacturers (FEPA), examples of which can also be found in DIN ISO 6344, in particular DIN ISO 6344-2:2000-04, Abrasives on Substrates - Particle Size Analysis - Part 2: Determination of the Particle Size Distribution of Large Particles P12 to P220 (ISO 6344-2:1998). At the values ​​disclosed herein, the weight of the substrate (being an aluminum substrate) is approximately 3 kg.

[0046] The base plate must be solid and preferably made of aluminum or, alternatively, steel. The sandpaper must be completely covered with adhesive tape and attached in a bubble-free manner. The impact surface is only permitted for ten drop tests and must be replaced after the tenth drop test. The sample (i.e., the resulting set) is placed in the test apparatus and oriented with the aid of a 2D level (circular level) so that the set is mounted horizontally, with the plate-shaped glass facing the ground, i.e., in the direction of the impact surface (see Figure 11The first drop height is 25 cm, followed by a drop from 30 cm. As long as no cracking occurs, the drop height is increased in 10 cm increments until the glass breaks. Record the crack height, crack starting point, and crack type. Test 15 samples and calculate the average value.

[0047] It may be advantageous to attach the sheet glass to the plastic sheet in such a way that, in the event of a glass breakage, the sheet glass remains adhered to the foil, making it possible to remove it as easily as possible and also to examine the glass. For this purpose, it is recommended to arrange a self-adhesive foil between the plastic sheet and the sheet glass in addition to the adhesive tape used. The broken sheet glass can then be removed using this foil.

[0048] For the purposes of this disclosure, the following definitions apply: An exchange bath is understood to be a salt melt, wherein such a salt melt is used in an ion exchange process for glass or glass products. Within the scope of the present disclosure, the terms exchange bath and ion exchange bath are used as synonyms.

[0049] Technically pure salts are generally used for the exchange bath. This means that, for example, even if only sodium nitrate is used as the starting material for the exchange bath, the exchange bath still contains certain impurities. The exchange bath is a melt of a salt (e.g., sodium nitrate) or a salt mixture (e.g., a mixture of sodium and potassium salts). The composition of the exchange bath is given in such a way that it relates to the nominal composition of the exchange bath without taking into account the impurities actually present. Therefore, if a 100% sodium nitrate melt is mentioned in this disclosure, this means that only sodium nitrate is used as the raw material. However, the actual sodium nitrate content of the exchange bath can differ from this and generally will differ, because, in particular, technical raw materials have a certain proportion of impurities. However, this is generally less than 5% by weight, in particular less than 1% by weight, relative to the total weight of the exchange bath.

[0050] The nominal contents of these salts are given in corresponding manner for exchange baths containing mixtures of different salts, without taking into account technically related impurities of the starting materials. For example, an exchange bath containing 90% by weight of KNO and 10% by weight of NaNO also contains small amounts of impurities, which, however, are due to the starting materials and should generally be less than 5% by weight, in particular less than 1% by weight, relative to the total weight of the exchange bath.

[0051] Furthermore, the composition of the exchange bath may also change as the ion exchange proceeds, as lithium ions, in particular, migrate from the glass or glass product into the exchange bath. However, unless explicitly stated otherwise, such compositional changes of the exchange bath due to aging are not considered herein. Rather, within the scope of this disclosure, reference to the nominal starting composition is made when specifying the composition of the exchange bath.

[0052] Within the scope of the present disclosure, a stress characteristic curve is understood to be the stress in a glass article (e.g., a glass sheet) observed over the thickness of the glass article as recorded in a graph. When referring to a compressive stress characteristic curve within the scope of the present disclosure, this is understood to be the portion of the stress characteristic curve in which stresses have positive values ​​(i.e., greater than zero). Tensile stress, in contrast, has a negative sign.

[0053] Within the scope of the present disclosure, a combined compressive stress characteristic curve is understood to be a compressive stress characteristic curve in which the compressive stress generated in the corresponding product (eg, a glass product) is combined from at least two sub-regions.

[0054] The compressive stress stored in the tempered glass article is obtained as the integral of the compressive stress over the thickness of the glass article. Within the scope of the present disclosure, this integral is referred to as the compressive stress integral.

[0055] The stored tensile stress in a tempered glass article is determined as the average value of the tensile stress integrated over the total thickness of the glass article. Within the scope of this disclosure, this integral is referred to as the tensile stress integral. Therefore, within the scope of this disclosure, the stored tensile stress is understood to be the normalized tensile stress or a synonym for the normalized tensile stress integral, i.e., the tensile stress integral relative to the thickness. Within the scope of this disclosure, the stored tensile stress is synonymous with the terms normalized (or relative to thickness) tensile stress and normalized (or relative to thickness) tensile stress integral.

[0056] Within the scope of the present disclosure, a sheet-like glass article is understood to be a glass article in which the lateral dimensions in one spatial direction are at least an order of magnitude smaller than in the other two spatial directions, wherein the spatial directions are given with respect to a Cartesian coordinate system, wherein the spatial directions each extend perpendicularly to one another and wherein the thickness is measured in the normal direction of the largest or main surface from one main surface to the other main surface.

[0057] Since the thickness of the glass article is at least an order of magnitude smaller than its width and length, the width and length can be of the same order of magnitude. However, it is also possible for the length of the glass article to be significantly greater than its width. Within the meaning of the present disclosure, a sheet-like glass article can therefore also include a glass ribbon.

[0058] For the purposes of this disclosure, glass is understood to mean a material, and a glass product is understood to mean a product made from and / or containing a glass material. A glass product can, in particular, consist of glass or consist predominantly (i.e., at least 50% by weight) of a glass material. If, within the scope of this disclosure, a glass product having a certain composition is described, this is to be understood as meaning that the glass product contains glass having such a composition or consists predominantly (i.e., at least 50% by weight) or essentially (i.e., at least 90% by weight) of or contains such a material or glass.

[0059] Within the scope of this disclosure, chemical tempering is understood to be a process in which a glass article is immersed in a so-called exchange bath. This process results in ion exchange. Within the meaning of this disclosure, potassium exchange is understood to mean the migration (i.e., incorporation) of potassium ions from the exchange bath into the glass article, particularly into its surface, while simultaneously migrating small alkali metal ions (e.g., sodium) from the glass article into the exchange bath. Similarly, sodium exchange is understood to mean the migration of sodium ions from the exchange bath into the glass article's surface, while conversely, small ions (e.g., lithium ions) from the glass article (particularly from its surface) into the exchange bath. As already explained, this ion exchange creates compressive stress zones in the surface region of the glass article.

[0060] Within the scope of the present disclosure, the maximum tensile stress is understood to be the minimum stress value in the stress characteristic curve of the glass article.

[0061] In the context of the present disclosure, a so-called "sharp impact" is understood to be a load that causes damage by a small, sharp object or by a plurality of such small, sharp objects. In other words, it involves the action of one or more sharp objects (i.e., for example, particles with a very small radius of curvature or a tip angle of less than 100°).

[0062] When the grit size of abrasive paper is mentioned within the scope of this disclosure, it is specified in accordance with DIN ISO 6344 (preferably in accordance with the same). This grit size refers to the unit of measure, mesh. The larger the grit size, the smaller the abrasive particles. Within the scope of this disclosure, the terms "60 grit" and "#60" (here, exemplarily referring to a grit size of 60) are used synonymously to designate grit sizes. This, of course, applies in a corresponding manner to other grit sizes, such as 100 grit or 180 grit.

[0063] Surprisingly, it has been shown in chemically tempered sheet glass products according to the present disclosure that the exchange depth, in particular the sodium exchange depth, is a significant factor in terms of wear resistance. In other words, potassium exchange (although this allows for very high prestressing at the surface) surprisingly has only a minor effect on the observed drop strength. In particular, it is possible to achieve very good drop strength of glass products according to the present disclosure even with pure sodium exchange.

[0064] The underlying mechanisms here are not yet precisely understood.

[0065] However, it is assumed that even with the penetration of larger sharp particles (such as those contained in the 60 grit size of commercially available abrasive paper) the greater exchange depth may still be deep enough to avoid the sharp particles from possibly advancing into the core of the glass article which is under tensile stress.

[0066] In order to advantageously achieve the highest possible exchange depth, glasses having at least one of the following properties can be used: High ion (especially alkali metal ion) mobility, and / or A rigid network that uses resistance to offset deformation is called a hard network.

[0067] Such glasses can be obtained, for example, by using a glass composition with a high content of network formers. This results in a rigid, stiff network that subsequently counteracts deformation with resistance and can thus store the introduced compressive stresses accordingly. It may also be advantageous to limit the content of such network formers with low field strength, as such network modifiers are known to weaken the network structure.

[0068] Alternatively or additionally, it may be advantageous for the glass to have a high mobility of ions, in particular alkali metal ions, since in this case the alkali metal ions can be exchanged well, which should lead to a correspondingly large exchange depth.

[0069] It can also be very particularly advantageous if the glass has both a high mobility of ions (especially alkali metal ions) and a rigid, hard glass network. This is because in this case, not only can the ions be exchanged well, but each exchanged ion should also store or be able to store stress in the glass network (that is, in the glass or the resulting glass product).

[0070] Within the scope of the present disclosure, the term ionic field strength is used according to Dietzel. This term is used in particular with respect to oxidic glass matrices, it being understood that this value may vary depending on the coordination number of the ions involved.

[0071] With regard to the terms network modifier and network former, these terms are to be understood according to Zachariasen.

[0072] Within the scope of the present disclosure, network formers are referred to herein as, in particular, SiO 2 , Al 2 O 3 , B 2 O 3 , P 2 O 5 .

[0073] In particular, alkali metal oxides and alkaline earth metal oxides are referred to as network modifiers.

[0074] In particular, ZrO 2 is referred to as a so-called intermediate oxide.

[0075] An example of a particularly rigid, strong network is quartz glass, i.e., amorphous SiO2. Quartz glass SiO2 also has a number of advantageous properties, but due to the extremely high melting temperature of pure quartz glass, it cannot be economically used in a melting process with subsequent hot forming. Therefore, sheet-shaped glass products made of pure quartz glass are not economically viable, especially not within the relevant parameters for use as cover glass for mobile devices. Ion exchange tempering is also not possible with this type of glass, as it does not contain significant, more than trace, proportions of alkali metal ions.

[0076] It has been shown that a sufficiently hard, rigid glass network is achieved with a minimum content of at least 82% by weight of network formers. The sum of the Al2O3 and SiO2 contents of the glass and / or glass product should preferably not exceed 92% by weight, preferably 90% by weight. The total content of network formers in the glass should particularly preferably not exceed 92% by weight, very particularly preferably not exceed 90% by weight.

[0077] Alternatively or additionally, the chemically toughened plate-shaped glass product according to the present disclosure can be obtained by limiting the content of alkali metal oxides to a maximum of 12% by weight, preferably a maximum of 10% by weight.

[0078] The glass network becomes more rigid the fewer non-bridging oxygens it has. However, the addition of alkali metal oxides to network formers (e.g., SiO2 and / or Al2O3) creates non-bridging oxygens. The inventors have discovered that significantly better toughening properties are achieved when the alkali metal oxide content is kept as low as possible.

[0079] This is particularly surprising, since alkali metal ions are precisely the components of the glass that are exchanged during ion exchange. Therefore, it was previously assumed that the highest possible degree of toughening could be achieved when the glass network contained the highest possible content of exchangeable ions.

[0080] However, it is precisely the example of the so-called drop strength observed here that shows that the exchangeability of the alkali metal ions is not particularly decisive, but rather the physical properties of the glass network, which are hard and rigid, play a role in deformation.

[0081] Another aspect of the present disclosure relates to a chemically tempered plate-shaped glass product having a composition comprising SiO2, Al2O3 and Li2O, in particular the glass product according to the first aspect of the present disclosure, which can be obtained by ion exchange of lithium-aluminosilicate glass, wherein carrying out the ion exchange in an exchange bath comprising between at least 20% by weight and up to 100% by weight of sodium salt, preferably sodium nitrate NaNO , at a temperature of between at least 380° C. and at most 440° C. for a period of at least 2 hours, preferably at least 4 hours and at most 24 hours, wherein a potassium salt, in particular potassium nitrate, can optionally be added to the exchange bath, in particular in such a way that the sum of the contents of sodium salt and potassium salt adds up to 100%, and optionally carrying out a second ion exchange in an exchange bath comprising between 0% and 10% by weight of a sodium salt, preferably sodium nitrate NaNO 3 , relative to the total amount of salts, at an exchange bath temperature of at least 380° C. and at most 440° C. for a period of at least one hour and at most 6 hours, wherein a potassium salt, particularly preferably potassium nitrate KNO 3 , is added to the exchange bath, particularly in such a manner that the sum of the contents of sodium and potassium salts adds up to 100% by weight.

[0082] It is also possible to carry out further ion exchange steps.

[0083] The tempering process generally includes at least one, preferably at least two, and less often three or even four ion exchange steps. These steps can be performed with mixed salts (i.e., containing sodium and potassium salts, preferably sodium nitrate NaNO3 and potassium nitrate KNO3) or with only one salt (e.g., sodium nitrate NaNO3 and potassium nitrate KNO3). The first step generally contains a higher percentage of sodium salt than the second step, and the first step also lasts at least longer than the second step.

[0084] In the first exchange step, the exchange bath contains, for example, between 20% and up to 100% by weight of sodium salt, relative to the total amount of salt. The first step is carried out for a duration of, for example, at least 2 hours, preferably at least 4 hours and up to 24 hours, the temperature of the exchange bath being able to vary between 380° C. and 440° C.

[0085] In the second exchange step, the exchange bath contains, for example, between 0% and 10% by weight of sodium salt, relative to the total amount of salt. This second step can last between at least one hour and at most six hours. The temperature of the exchange bath can also vary between 380°C and 440°C.

[0086] By preparing the tempered glass article as described above, a glass article having a high strength can be produced in a particularly rapid manner.

[0087] According to a third aspect of the present disclosure, the present disclosure relates to a chemically tempered plate-shaped glass product, wherein the glass product has a composition including SiO2, Al2O3, and Li2O. The glass product is particularly the glass product according to the first and / or second aspects of the present disclosure, wherein the glass product has a composition including the following components in weight %: SiO257 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O30 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and at most 92, preferably at most 90.

[0088] As already mentioned, SiO2, as pure quartz glass, forms a particularly hard network. Therefore, the SiO2 content in the glass article according to the present disclosure is at least 57% by weight. A high SiO2 content also contributes to the highest possible chemical resistance. Excessively low SiO2 contents are also not permitted, as otherwise devitrification could occur. According to embodiments of the present disclosure, the SiO2 content is preferably at least 59% by weight, particularly preferably at least 61% by weight. However, the SiO2 content is limited in the present case, as otherwise it could result in excessively high melting temperatures. Therefore, the SiO2 content should preferably be at most 69% by weight. According to other embodiments having other composition ratios disclosed herein, the upper limit of the SiO2 content is preferably 67% by weight.

[0089] Al2O3 is a known network former, which is added in particular to alkali-containing silicate glasses. This is because the addition of Al2O3 reduces the amount of non-bridging oxygen, allowing a hard network to be achieved despite a given glass content. This means that the temperability of alkali-containing silicate glasses can be improved. Therefore, according to embodiments having other composition ratios disclosed herein, the minimum Al2O3 content in the glass is advantageously 17% by weight. However, excessively high Al2O3 contents reduce the chemical resistance, in particular the acid resistance, of the resulting glass or glass product. Therefore, according to further embodiments having other composition ratios disclosed herein, the Al2O3 content in the glass or glass product is limited and is preferably a maximum of 25% by weight, particularly preferably a maximum of 21% by weight.

[0090] The glass according to the present disclosure—or, in a corresponding manner, the glass product according to the present disclosure—also contains Li2O as a component. Li2O is an essential component of the glass or glass product according to the present disclosure, since this allows sodium exchange, i.e., the exchange of lithium ions from the glass with sodium ions from the exchange bath. As explained in detail with respect to the glass product according to the first aspect of the present disclosure, a particularly high sodium exchange depth can be a decisive feature of the glass product according to the present disclosure. The lithium content should therefore be at least 3% by weight, preferably at least 3.5% by weight, if possible. However, the Li2O content should not be too high, since Li2O is also a glass component known to cause or may cause delamination and / or crystallization of the glass. Therefore, the content of the glass or sheet glass product is advantageously at most 5.5% by weight.

[0091] B2O3 is only an optional component of glass articles according to the present disclosure, with other embodiments having the other composition ratios disclosed herein. B2O3 is a known network former and improves, among other things, the meltability of the glass because it lowers the melting point. B2O3 is also advantageous because it increases the scratch resistance of the glass. Therefore, a certain proportion of B2O3 can be advantageous, since scratching (e.g., so-called colliding) is also a burden on articles or products with sharp objects. However, the B2O3 content is advantageously limited and, according to embodiments having the other composition ratios disclosed herein, should be up to 7% by weight, preferably up to 5% by weight, and particularly preferably up to 4.5% by weight.

[0092] According to one embodiment, which otherwise has the other composition ratios disclosed herein, Na2O is another component of the glass or glass product. According to these embodiments of the present disclosure, sodium ions can be exchanged for potassium ions during the ion exchange. Therefore, in order to achieve the highest possible surface compressive toughening resulting from the potassium exchange, according to embodiments, which otherwise have the other composition ratios disclosed herein, the glass or glass product contains at least 0.8% by weight of Na2O. However, the sodium oxide content of the glass product or glass according to the present disclosure is preferably limited and is no more than 7% by weight, particularly preferably no more than 6% by weight, and very particularly preferably no more than 5.5% by weight. This is because a high sodium oxide content, for example, leads to a reduction in the chemical resistance of the glass or glass product, in particular the acid resistance.

[0093] PO is another optional component of glass and / or glass products according to embodiments having other composition ratios disclosed herein. The PO content of glass and glass products can be advantageous because PO can act as a glass component, allowing for deeper tempering in a shorter time. That is, PO can be advantageous because the exchange process can be accelerated in this way. However, a high PO content in glass is disadvantageous because PO may attack the materials of the melting equipment. Therefore, according to embodiments having other composition ratios disclosed herein, the PO content of glass and / or glass products should be a maximum of 3 wt%. The PO content of glass and / or glass products is preferably no more than 2 wt%, particularly preferably no more than 1.7 wt%.

[0094] The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and a maximum of 92, preferably a maximum of 90.

[0095] A content of at least 75% by weight of the network formers Al2O3 and SiO2 is particularly advantageous, since this ensures a sufficient amount of glass formers. In other words, this ensures that a glassy material is obtained without causing crystallization. On the other hand, the content of these network formers should not be too high, since otherwise the resulting glass would no longer melt well. Therefore, the content of Al2O3 and SiO2 is preferably limited and amounts to no more than 92% by weight, preferably no more than 90% by weight. The network former content of the glass or glass product is preferably no more than 92% by weight, particularly preferably no more than 90% by weight.

[0096] According to another embodiment, the glass article has a thickness of at least 0.4 mm and at most 3 mm.

[0097] The thickness of the glass article is preferably at least 0.5 mm.

[0098] The thickness of the glass article is further preferably limited and, according to one embodiment, is at most 2 mm, preferably at most 1 mm.

[0099] The present disclosure further relates to the use of the glass article according to the embodiment as a cover panel, in particular as a cover panel in an entertainment electronic device, in particular for a display device, a screen of a computing device, a measuring device, a television device, in particular as a cover panel for a mobile device, in particular for at least one device selected from the following group, the group comprising: a mobile terminal, a mobile digital processing device, in particular a mobile phone, a mobile computer, a PDA, a laptop computer, a tablet computer, a wearable device, a portable watch and a timing device, or as a protective glass window, in particular as a protective glass window for a machine, or as a glass window in a high-speed train, or as safety glass, or as a car glass window, or in a diving watch, or in a submarine, or as a cover panel for explosion-proof equipment, in particular for those explosion-proof equipment for which the use of glass is mandatory.

[0100] Another aspect of the present disclosure relates to a lithium-alumino-silicate glass comprising the following components in weight %: SiO257 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O30 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and at most 92, preferably at most 90.

[0101] This type of glass is advantageous because it is designed to be chemically toughened, resulting in a chemically toughened glass article with particularly high strength in the so-called drop test, even when using a coarse grain size (e.g., a grain size of 60). Despite a high glass former content (particularly preferably a content of at least 75% by weight of the glass formers SiO2 and Al2O3), the glass according to the present disclosure melts surprisingly well, making the addition of B2O3, a component known to improve meltability, unnecessary. Surprisingly, it has been shown that while the addition of B2O3 improves the scratch resistance of the glass or glass article, it is not absolutely necessary for achieving high drop strength and, surprisingly, can even be detrimental (although drop strength, like scratch resistance, is also a function of the loading of the article or product surface with a sharp object).

[0102] According to the inventors' understanding, this can probably be attributed to the fact that the glass with a composition within the above-mentioned limits is designed in such a temperable manner that a particularly large exchange depth, in particular achieved by sodium exchange (i.e., exchanging lithium ions from the glass for sodium ions from the sodium salt melt), is decisive for the development of good drop strength and surprisingly less decisive for the resistance of the surface to scratches or intrusions by sharp objects.

[0103] Here, despite the relatively small amount of Li2O in the glass according to the present disclosure, there is still sufficient temperability. This is all the more surprising because the Li2O content in the glass according to the embodiments having other composition ratios disclosed herein is significantly limited and does not exceed 5.5 wt%. It is also known that Li2O is a relatively small amount of Li2O in the glass according to the present disclosure. + Ions have ratios such as Na + The ions have a large field strength and are therefore more firmly bound to the glass network than the latter. Li + Sufficient ion mobility. It has been shown that it is the combination of the components of the glass according to the present disclosure, in particular the ratio of the three main components lithium oxide, aluminum oxide, and silicon dioxide, that leads to sufficient lithium ion mobility within the glass network. The glass network is clearly defined, and despite a certain content of sodium oxide, which, for example, also allows for an optional, but not mandatory, potassium exchange, it is sufficiently rigid for effective tempering and is also a known component for improving the meltability of the glass. However, it has been shown that sodium oxide, as a component of the glass network, can negatively affect temperability because it increases the number of non-bridging oxygens, resulting in a lower hardness and rigidity of the network. However, it has been shown that the combined effects of the individual components create a balance, so that the glass according to the present disclosure can achieve a very good compromise between drop strength, meltability, and temperability.

[0104] According to one embodiment of the lithium-aluminum-silicate glass, the embodiment has the following composition in wt. %: SiO257 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O30 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7, MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O50 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO20 to 3, preferably 0 to 2, Impurities and / or purifying agents and / or coloring components may also be present in amounts of up to 2% by weight.

[0105] Yet another aspect of the present disclosure relates to a method for preparing a glass article according to embodiments disclosed herein, the method comprising the steps of: carrying out the ion exchange in an exchange bath comprising between at least 20% by weight and up to 100% by weight of sodium salt, preferably sodium nitrate NaNO , at a temperature of between at least 380° C. and at most 440° C. for a period of at least 2 hours, preferably at least 4 hours and at most 24 hours, wherein a potassium salt, in particular potassium nitrate, can optionally be added to the exchange bath, in particular in such a way that the sum of the contents of sodium salt and potassium salt adds up to 100%, and optionally carrying out a second ion exchange in an exchange bath comprising between 0% and 10% by weight of a sodium salt, preferably sodium nitrate NaNO 3 , relative to the total amount of salts, at an exchange bath temperature of at least 380° C. and at most 440° C. for a period of at least one hour and at most 6 hours, wherein a potassium salt, particularly preferably potassium nitrate KNO 3 , is added to the exchange bath, particularly in such a manner that the sum of the contents of sodium salt and potassium salt adds up to 100% by weight, and optionally performing one or more additional ion exchange steps.

[0106] Example Exemplary compositional ranges for glasses and / or glass articles are given by the following compositions in wt %: SiO257 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O30 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7, MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O50 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO20 to 3, preferably 0 to 2, Impurities and / or purifying agents and / or coloring components may also be present in amounts of up to 2% by weight.

[0107] Exemplary compositions of the glass from which the plate-shaped glass product according to the embodiment can be produced and / or the glass product according to the embodiment are given by the following composition in wt. %: SiO257 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O30 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and a maximum of 92, preferably a maximum of 90. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] The present invention will be further explained below with the aid of the accompanying drawings. In the accompanying drawings: Figure 1 The relationship between the stored tensile stress and the drop strength of the aggregate at particle size 60 (#60) is shown. Figure 2 shows the minimum DoL in the set drop test depending on the particle size used, Figure 3 and Figure 4 Figure 2 shows images of glass article breakage depending on the stored tensile stress of two different glasses. Figure 5 shows a schematic and not to scale illustration of a glass article according to an embodiment of the present disclosure, Figure 6 shows a schematic and not to scale cross-sectional view through a glass article according to an embodiment of the present disclosure, Figure 7 shows an exemplary stress characteristic curve of a glass article, Figure 8 Shows the overall structure of the drop test set with the names of the individual components, Figure 9 The sample holding part and trigger mechanism of the drop test structure are shown. Figure 10 An aluminum housing and a plastic plate are shown as a sample holder and a sample replica. Figure 11 Alignment of the sample replicas with the aid of a 2D level is shown. DETAILED DESCRIPTION

[0109] Figure 1 The relationship between stored tensile stress and the resulting drop strength when using abrasive paper with a grit size of #60 is shown. This strength, given as an average value of the drop height in centimeters for 15 samples, differs from the drop strength presented, for example, in the applicant's own application DE 10 2018 124 785, which increases with increasing stored tensile stress (referred to within the present disclosure as TS / d, where "TS" stands for "tensile stress" and "d" represents the thickness of the glass article, with the stored tensile stress expressed in MPa).

[0110] However, this does not apply absolutely, but only when objects with smaller radii of curvature do not penetrate the DoL. Instead, it has been shown that the described relationship between stored tensile stress and set drop strength is linked to the condition of a minimum DoL. As already explained in detail above, this is due to the different grain sizes of the respective sandpaper. Figure 2The following is a schematic diagram showing the minimum DoL for glasses or glass articles having a certain composition according to embodiments of the present disclosure. In principle, this minimum DoL decreases with finer particle size (i.e., as the number of particles / surface area increases, i.e., toward larger values ​​of #). It has been noted that particularly rough and sharp-angled surfaces are particularly hazardous for protective or cover glass. Depending on their size, sharp-angled small stones or the stress fields they generate can penetrate the DoL and penetrate into the tensile stress zone, thereby causing the glass to break. In this sense, the minimum required DoL (beyond which the relationship between greater stored tensile stress and higher drop strength holds true) increases with the particle size of the abrasive paper used in the drop test. The larger the sharp-angled particles or stones, the greater this minimum DoL or minimum value DoL. AS glass, which has a simple ion exchange characteristic curve, demonstrates this relationship particularly impressively. Thus, these glasses have a stored tensile stress of 33.07 MPa for a thickness of 0.7 mm in the standard tempering solution (where a DoL of 50 µm and a pre-compressive stress of 926 MPa are achieved). However, due to the small DoL, this stored tensile stress does not translate into good #60 drop strength, and these glasses fail at a minimum height of 25 cm.

[0111] Figure 3 Figures show fracture patterns from a drop test of a glass article comprising LAS glass of the first composition according to one embodiment of the present disclosure, using glass #60. In the top image, the glass article has a storable tensile stress of -23.84 MPa, in the middle image -21.97 MPa, and in the bottom image -19.61 MPa. This demonstrates that the higher the stored tensile stress in the glass article, the finer the fracture pattern.

[0112] This can also be achieved with the help of Figure 4 This is further demonstrated by photographs of the glass. Shown here are the fracture patterns of a glass article comprising LAS glass of the second composition according to one embodiment of the present disclosure, using glass #60, in a drop test. In the top graph, the storable tensile stress is -19.02 MPa, in the middle graph -15.38 MPa, and in the bottom graph only -12.36 MPa.

[0113] Figure 5 is a schematic and not-to-scale illustration of a sheet-shaped glass article according to an embodiment of the present disclosure.

[0114] Figure 6A schematic and not to scale cross-sectional view of a glass article 1 according to an embodiment of the present disclosure is shown. The glass article 1 here has two zones 101 arranged at the two main surfaces of the glass article, which are under compressive stress and are also referred to as compressive stress zones. These compressive stress zones 101 also have Figure 6 The dimension "DoL" is schematically indicated in FIG. It is possible that the DoL on the two sides of the plate-shaped glazing differs in its value, but such a difference is generally within the range of measurement accuracy, so that the DoL of the plate-shaped glazing 1 is generally the same on both sides (at least within the range of measurement accuracy).

[0115] The region 102 under tensile stress is located between these compressive stress regions 101 .

[0116] exist Figure 7 In FIG. 2 , characteristic values ​​of a stress characteristic curve for a glass article containing LAS glass are shown in a diagram using an exemplary combined stress characteristic curve 2 of an exemplary glass article. The diagram plots the stress in MPa on the y-axis and the glass depth in μm on the x-axis. The stress over the total thickness of the glass article is not shown here, but rather only the stress up to approximately half the thickness of the glass article is shown as an example.

[0117] Point 201 indicates the stress present at the surface of the glass article (ie at a depth of 0 μm in the glass). This stress is essentially a compressive stress caused by potassium ion exchange (potassium CS). Point 202 indicates Figure 7 The compressive stress at the surface of the glass article caused by sodium exchange (also referred to as sodium CS) is shown in Figure 203 . This is a value obtained by extrapolation, as the stress characteristic curves attributable to sodium ion exchange and potassium exchange overlap. Point 203 schematically illustrates the value of the compressive stress due to sodium ion exchange at a glass depth of 30 µm (sodium CS-30). At point 205, the stress in the glass article is zero. This is the so-called sodium ion compressive stress depth, also referred to as sodium DoL (or simply DoL). The integral of the compressive stress due to sodium ion exchange is indicated at 204.

[0118] By extrapolating that portion of the stress characteristic curve 2 , the compressive stress depth of potassium (potassium DoL) is obtained, here indicated by 206 .

[0119] Finally, the area of ​​the normalized tensile stress integral is indicated by 207 , ie, the tensile stress stored in the glass product.

[0120] The term "potassium-DoL intersection point" is understood to mean the depth in the glass product at the point in the compressive stress characteristic curve where the sodium compressive stress curve and the potassium compressive stress curve intersect. Figure 7Indicated by reference numeral 208 in the accompanying drawings.

[0121] List of Reference Numerals 1 Plate-shaped glass products 101 compressive stress zone 102 Internal areas of glass products under tensile stress 2 Example stress characteristic curves of tempered LAS glass products 201 Compressive stress generated on the surface of glass products (roughly potassium CS) 202 Sodium CS 203 Compressive stress based on sodium ion exchange at a glass depth of 30 µm 204 Sodium compressive stress integral 205 Sodium DoL, compressive stress depth of sodium ions 206 Potassium ion compressive stress depth, potassium DoL 207 Stored tensile stress, normalized tensile stress integral 208 Na-CS-K-DoL intersection

Claims

1. A chemically tempered plate-shaped glass product (1), the glass product having a composition comprising SiO2, Al2O3 and Li2O, and the glass product having at least one of the following characteristics: - an exchange depth, preferably a sodium exchange depth, of at least 85 μm, preferably at least 100 μm and particularly preferably at least 115 μm for a thickness of the glass article of at least 0.4 mm to less than 0.55 mm, an exchange depth, preferably a sodium exchange depth, of at least 90 μm, preferably at least 120 μm and particularly preferably at least 125 μm for a thickness of the glass article of 0.55 mm to less than 0.6 mm, an exchange depth, preferably a sodium exchange depth, of at least 100 μm, preferably at least 125 μm and particularly preferably at least 135 μm for a thickness of the glass article of 0.6 mm to less than 0.7 mm, an exchange depth, preferably a sodium exchange depth, of at least 120 μm, preferably at least 140 μm and particularly preferably at least 160 μm for a thickness of the glass article of 0.7 mm to less than 1 mm, and an exchange depth, preferably a sodium exchange depth, of at least 170 μm for a thickness of the glass article of 1 mm to 3 mm, preferably up to 2 mm, and / or - a storable tensile stress of at most -15 MPa and preferably at least -45 MPa, preferably at least -35 MPa, particularly preferably at least -30 MPa and very particularly preferably at least -27.5 MPa, and / or - a network former content of at least 82% by weight, and / or - an alkali metal oxide content of up to 12% by weight, preferably up to 10% by weight, The plate-shaped glass article (1) is preferably characterized by a set drop strength of 50 to 150, given as a drop height in cm, when using a #60 grit size (#60), wherein the drop height is given as an average value of 15 samples.

2. Preferably, the chemically tempered plate-shaped glass product (1) according to claim 1 has a composition comprising SiO2, Al2O3 and Li2O, The glass product can be obtained by ion exchange of lithium-aluminosilicate glass, wherein carrying out the ion exchange in an exchange bath comprising between at least 20% by weight and up to 100% by weight of sodium salt, preferably sodium nitrate NaNO , at a temperature of at least 380° C. and at most 440° C. for a period of at least 2 hours, preferably at least 4 hours and at most 24 hours, wherein a potassium salt, in particular potassium nitrate, can optionally be added to the exchange bath, in particular in such a way that the sum of the contents of sodium salt and potassium salt adds up to 100%, and optionally carrying out a second ion exchange in an exchange bath comprising between 0% and 10% by weight of a sodium salt, preferably sodium nitrate NaNO 3 , relative to the total amount of salts, at an exchange bath temperature of at least 380° C. and at most 440° C. for a period of at least one hour and at most 6 hours, wherein a potassium salt, particularly preferably potassium nitrate KNO 3 , is added to the exchange bath, particularly in such a manner that the sum of the contents of sodium salt and potassium salt adds up to 100% by weight, This can optionally be followed by a further ion exchange step.

3. Preferably, the chemically tempered plate-shaped glass product (1) according to claim 1 or 2 has a composition comprising SiO2, Al2O3 and Li2O, The glass article has a composition including the following components in wt %: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and a maximum of 92, preferably a maximum of 90.

4. The glass product (1) according to any one of claims 1 to 3, comprising the following components in wt %: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7, MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O5 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO2 0 to 3, preferably 0 to 2, Impurities and / or purifying agents and / or coloring components may also be present in amounts of up to 2% by weight.

5. The glass article (1) according to any one of claims 1 to 4, wherein the glass article (1) has a thickness of at least 0.4 mm and at most 3 mm.

6. The glass article (1) according to any one of claims 1 to 5, wherein the glass article (1) has a thickness of at least 0.5 mm.

7. The glass article (1) according to any one of claims 1 to 6, wherein the glass article (1) has a thickness of at most 2 mm, preferably at most 1 mm.

8. Use of the glass product (1) according to any one of claims 1 to 7 as a cover panel, in particular as a cover panel in an electronic entertainment device, in particular for a display device, a screen of a computing device, a measuring device, a television device, in particular as a cover panel for a mobile device, in particular for at least one device selected from the following group: Mobile terminals, mobile digital processing devices, in particular mobile phones, mobile computers, PDAs, laptops, tablet computers, wearable devices, portable watches and timing devices, or as protective glass windows, in particular as protective glass windows for machines, or as glass windows in high-speed trains, or as safety glass, or as car glass windows, or in diving watches, or in submarines, or as cover panels for explosion-proof equipment, in particular for those explosion-proof equipment for which the use of glass is mandatory.

9. A lithium-aluminum-silicate glass comprising the following components in weight %: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, The sum of the contents of Al2O3 and SiO2 relative to the values ​​in wt. % is preferably between at least 75 and a maximum of 92, preferably a maximum of 90.

10. The glass according to claim 9, comprising the following components in weight %: SiO2 57 to 69, preferably 59 to 69, particularly preferably 61 to 69, wherein the upper limit can be preferably 67, Al2O3 17 to 25, preferably 17 to 21, B2O3 0 to 7, preferably 0 to 5, particularly preferably 0 to 4.5, Li2O 3 to 5.5, preferably 3.5 to 5.5, Na2O 0.8 to 7, preferably 0.8 to 6, particularly preferably 0.8 to 5.5, K2O 0 to 1, preferably 0 to 0.8, particularly preferably 0 to 0.7, MgO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, CaO 0 to 4.5, SrO 0 to 2, preferably 0 to 1.5, particularly preferably 0 to 1, ZnO 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.5, P2O5 0 to 3, preferably 0 to 2, particularly preferably 0 to 1.7, ZrO2 0 to 3, preferably 0 to 2, Impurities and / or purifying agents and / or coloring components may also be present in amounts of up to 2% by weight.

11. A method for preparing a glass product (1) according to any one of claims 1 to 7, the method comprising the following steps: - ion exchange in an exchange bath comprising between at least 20% by weight and up to 100% by weight of sodium salt, preferably sodium nitrate NaNO 3 , at a temperature of at least 380° C. and at most 440° C. for a period of at least 2 hours, preferably at least 4 hours and at most 24 hours, wherein potassium salt, in particular potassium nitrate, can optionally be added to the exchange bath, in particular in such a way that the sum of the contents of sodium salt and potassium salt adds up to 100%, and optionally carrying out a second ion exchange in an exchange bath comprising between 0% and 10% by weight of a sodium salt, preferably sodium nitrate NaNO 3 , relative to the total amount of salts, at an exchange bath temperature of at least 380° C. and at most 440° C. for a period of at least one hour and at most 6 hours, wherein a potassium salt, particularly preferably potassium nitrate KNO 3 , is added to the exchange bath, particularly in such a manner that the sum of the contents of sodium salt and potassium salt adds up to 100% by weight, - and optionally carrying out one or more further ion exchange steps.

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