Glass, especially as a cover plate

Abstract

This document describes a chemically temperable or chemically tempered LABS glass. It also describes a method for its manufacture, a cover plate made of such glass and its use, as well as a digital display device that includes such a cover plate.

Description

[0001] The present invention relates to a chemically toughenable or chemically toughened glass, a method for its production, a cover plate made of such a glass and its use, as well as a digital display device comprising such a cover plate.

[0002] The use of glass or glass-ceramics as cover plates for electronic components and displays, especially for smartphones, has long been known. These glass-based materials are preferably chemically toughened to increase their mechanical strength.

[0003] Glasses made from the Li2O-Al2O3-SiO2 system, so-called LAS glasses, have proven particularly suitable for this purpose. They have SiO2, Li2O, and Al2O3 as their main components. A subgroup of LAS glasses is boron-containing LAS glasses, also known as LABS glasses.

[0004] Compared to AS glasses, i.e., Li-free glasses, they have the advantage, particularly with regard to their use as cover materials, that they can be chemically tempered very well by means of an ion exchange of Li ions for Na ions or by means of a combined ion exchange, namely Li ions for Na ions and Na ions for K ions. They therefore possess high mechanical strength both against so-called "sharp impact loads," i.e., against the effects of rough surfaces and pointed objects, as well as against the effects of blunt or smooth surfaces, so-called "blunt impact loads." LABS glasses are preferred over LAS glasses because the addition of B2O3 leads to stronger interconnection of the glass network and further improves mechanical properties, such as scratch resistance.

[0005] Such glasses are known from the state of the art.

[0006] For example, US 2017 / 197869 A describes LABS glasses which, according to the examples, have a relatively high coefficient of expansion and a low Li2O content of the total alkali oxide content.

[0007] US 2018 / 186685 A also describes LABS and LAS glasses. LABS glasses, in particular, have a low Li2O content in the total alkali oxide content.

[0008] US 2018 / 127302 A describes LABS glasses with rather low Li2O contents relative to the total alkali oxide content and / or high boron contents.

[0009] US 2020 / 317558 A describes AS, i.e. Li-free glasses or LA(B)S glasses, these with rather low Li contents and / or without B2O3.

[0010] DE 10 2019 121 146 A describes LAS glasses with a minimum content of the nucleating agents ZrO2, SnO2 and TiO2.

[0011] DE 10 2019 121 143 A describes LAS glasses with rather high alkali oxide, especially Na2O, contents.

[0012] The various state-of-the-art glasses with the good product properties described above have in common that they are difficult to process. This applies to the behavior of the glass melt during refining, as well as the glass itself during forming and cooling, as well as its susceptibility to crystallization.

[0013] The object of the present invention is therefore to provide a chemically toughenable or tempered glass, particularly for use as a cover glass, which, due to its viscosity properties, is easy to melt, refine, and heat-form, and can be produced economically. Of course, the glass should also exhibit the product properties necessary for its intended use in the tempered state.

[0014] Further aspects relate to a method for producing such a glass and a cover plate made of such a glass and its use as well as a digital display device comprising such a cover plate.

[0015] The object of the invention is achieved by the subject matter of the independent claims. Specific and preferred embodiments can be found in the dependent claims and in the description of the present disclosure.

[0016] The chemically toughenable or chemically toughened glass according to the invention comprises the components SiO2, Al2O3, Li2O and B2O3 and optionally Na2O and optionally K2O.

[0017] The following applies to the B2O3 content (in mol-% on an oxide basis): 0.1 < B2O3 ≤ 8.5; preferably 0.1 < B2O3 < 8.5

[0018] The stated minimum B2O3 content is necessary for a low upper devitrification limit. The upper devitrification limit is the temperature at which the glass is free of crystals after being heated from room temperature and held for one hour. LABS glasses usually crystallize when heated in a temperature range above the glass transition temperature Tg. If the temperature is increased further, the crystals dissolve again. Since dissolution can be slow due to the viscosity of the glass, the temperature is held for 1 hour. The upper devitrification limit is a measure of a glass's susceptibility to crystallization. If it is low, this advantageously means that the glass is less prone to crystallization (the crystals are rather "unstable" and dissolve even at low temperatures) and is therefore easier to produce.

[0019] Higher B2O3 contents than those mentioned can lead to demixing and are detrimental to ion diffusion, especially of K ions.

[0020] The following applies to the alkali oxides Li2O, Na2O and K2O (all contents in mol%): 0.8 < Li2O / (Li2O + K2O + Na2O) ≤ 1

[0021] This condition can be fulfilled by the presence of all three alkali oxides mentioned or by Li2O together with K2O or with Na2O or by the sole presence of Li2O (Li2O / (Li2O + K2O + Na2O) = 1).

[0022] A ratio of Li2O / (Li2O + K2O + Na2O) < 1 is preferred.

[0023] The chemically toughenable or chemically toughened glass according to the invention has an upper devitrification temperature (OEG) that is less than 10 K above, and preferably below, the processing temperature (VA). This prevents uncontrolled crystallization of undesirable crystal phases, such as spodumene, keatite, forsterite, baddeleyite, or gahnite, during the manufacturing process, particularly during hot forming.

[0024] The processing temperature is VA, i.e. the temperature at viscosity 10 4 dPas, preferably less than 1300 °C, preferably less than 1260 °C, particularly preferably less than 1220 °C. This facilitates shaping, in particular enabling the establishment of a low, homogeneous glass thickness, particularly in the float bath.

[0025] The glass has a temperature at viscosity 10 2dPas, designated as T2, of at most 1800 °C, preferably less than 1750 °C, particularly preferably less than 1720 °C. This makes the glass easy to refine and, as a product, exhibits good optical quality without gas inclusions, i.e., without scattering.

[0026] The glass has a CTE20-300 thermal expansion coefficient of less than 5.4 ppm / K. This allows for stress-free cooling after the hot forming process. The glass preferably has a CTE20-300 thermal expansion coefficient of more than 3.8 ppm / K.

[0027] The glass according to the invention with the described properties can be realized by a LABS glass with a composition with the described features 0.1 < B2O3 ≤ 8.5 and 0.8 < Li2O / (Li2O + K2O + Na2O) ≤ 1.

[0028] Preferably, the glass has good chemical resistance in both the non-tempered and tempered state, namely • a hydrolytic resistance H according to DIN 52296: Glass and glass ceramics: Water resistance of the surface of glass and glass-ceramic plates at 98°C, test method and classification (modification: determination of other cations by ICP) (1989-12) • a resistance to alkalis L according to DIN ISO 695: Glass: Resistance to a boiling aqueous mixed alkali, test methods and classification (1994 02) • and an acid resistance S according to DIN 12116: Testing of glass resistance to a boiling aqueous hydrochloric acid solution, test method and classification (2001 03) each of class 3 or better.

[0029] In the present disclosure, the components of the glass are given in mol% on an oxide basis.

[0030] In preferred embodiments, the proportions of these components are in mol% on an oxide basis: SiO2 62 - 72, preferably 65 - 70 and / or Al2O3 7 - 14, preferably 8 - 12 and / or B2O3 0.1 - 8.5, preferably < 8.5 or ≤ 8, preferably 4 - 7, particularly preferably ≥ 5, most particularly preferably > 5.5 and / or Li2O 5 - 12, preferably 7 - 10 and / or Na2O 0 - 2, preferably 0 - 1, particularly preferably ≥ 0.1 and / or < 1, very particularly preferably ≥ 0.3 and / or < 0.8 and / or K2O 0 - 2, preferably 0 - 1

[0031] The presence of SiO2, preferably at a minimum content of 62 mol% or even 65 mol%, is necessary for the formation of a stable glass network, which increases mechanical and chemical resistance. SiO2 increases the viscosity of the melt. Excessively high contents should be avoided to enable meltability and maintain a sufficiently low viscosity for bubbles to rise during refining. Therefore, its maximum content is preferably limited to 72 mol%, particularly preferably to 70 mol%.

[0032] The presence of Al2O3, preferably at a minimum content of 7 mol% or even 8 mol%, is necessary to enable rapid alkali diffusion in the glass and high compressive stresses (CS30 and CS50 values). Excessively high Al2O3 contents significantly increase the glass's tendency to crystallize. Therefore, its maximum content is preferably limited to 14 mol%, particularly preferably to 12 mol%.

[0033] The presence of B2O3, preferably at a minimum content of 4 mol% or 5 mol% or more than 5 mol% or even 5.5 mol% or more than 5.5 mol%, has a positive effect on meltability. Content levels above the preferred upper limit of 8.5 mol% can lead to a slight reduction in chemical resistance and the CS30 and CS50 values. Therefore, the B2O3 content is preferably limited to less than 8.5 or at most 8 mol%, particularly preferably to at most 7 mol%.

[0034] The presence of Li2O, preferably with a minimum content of 5 mol%, particularly preferably with a minimum content of 7 mol%, enables chemical tempering of the glass in a sodium-containing salt bath. Its content is preferably limited to 12 mol%, particularly preferably to 10 mol%, since otherwise the tendency to crystallization increases significantly, especially with the precipitation of Li2O- (and Al2O3-)-containing crystal phases such as spodumene or keatite.

[0035] The presence of Na2O, particularly preferably at a content of at least 0.1 mol%, most preferably at least 0.3 mol%, is beneficial for meltability and suppresses crystallization. Due to its negative influence on compressive stresses (CS30 and CS50 values) and the increase in the thermal expansion coefficient, its maximum content is preferably limited to 2 mol%, particularly preferably to 1 mol%, most preferably to less than 1 mol%.

[0036] The presence of K2O has a positive effect on meltability. Furthermore, K2O in the glass increases K diffusion and allows for deeper tempering (K-DoL) in the final tempering step during multi-stage tempering. The K2O content is preferably limited to 1 mol%, as excessive K2O contents negatively affect K-induced tempering (KCS).

[0037] In further preferred embodiments, the glass may comprise the following components (in mol% on an oxide basis): MgO 0 - 5, preferably 0.5 - 3 and / or CaO 0 - 8, preferably 1- 6 and / or SrO 0 - 5, preferably 0 - 1 and / or BaO 0-2 and / or ZnO 0 - 5, preferably 0 - 1 and / or P2O5 0 - 5, preferably 0.5 - 2 and / or ZrO2 0 - 5, preferably 0 - 3

[0038] To reduce the viscosity of the glass and thus improve its manufacturability, alkaline earth oxides and / or ZnO can be used.

[0039] If ZnO is present, its content is preferably limited to 5 mol%, particularly preferably to 1 mol%, since higher contents may lead to evaporation during the melting process and corrosion of the refractory material in glass production.

[0040] The presence of MgO, preferably at a minimum content of 0.5 mol%, has a positive effect on meltability. Content above 5 mol% promotes crystallization and is therefore preferably avoided. In some embodiments, the content is therefore limited to a maximum of 3 mol%.

[0041] If CaO is present, preferably at a minimum content of 1 mol%, this supports the desired low upper devitrification temperature UEG.

[0042] If SrO is present, its content is preferably limited to 5 mol%, particularly preferably to 1 mol%, since higher contents reduce alkali diffusion in the glass during chemical toughening and very long toughening times are necessary or only low DoCL values ​​can be achieved.

[0043] If BaO is present, its content is preferably limited to 2 mol%. Preferably, the glass is essentially free of BaO.

[0044] The presence of P2O5, preferably at a minimum content of 0.5 mol%, has a positive effect on alkali diffusion in the glass. This is advantageous because it can shorten the duration of ion exchange. The P2O5 content should preferably not exceed 5 mol%, particularly preferably 2 mol%, as excessively high levels can lead to corrosion of the refractory material during glass production.

[0045] The presence of ZrO2 has a positive effect on the chemical resistance of the glass. However, in high concentrations, ZrO2 promotes devitrification. Therefore, its maximum content is preferably limited to 5 mol%, more preferably to 3 mol%, most preferably to 2 mol%, or even just 1 mol%.

[0046] The glass may, for example, also contain TiO2. If TiO2 is present, its content is preferably limited to 2 mol%. Preferably, the glass is essentially free of TiO2.

[0047] “Essentially free” means that only impurities that are unavoidable in normal economic practice (e.g. from raw materials) are present.

[0048] Certain ratios of the components have proven to be very advantageous for the glass and its manufacturability and chemical toughenability. Therefore, its composition is preferably chosen so that the following applies to the components (in mol% on an oxide basis): 0.9 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.7; preferably 1< (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.6; particularly preferably 1.1 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.5 and / or 0.5 < Al2O3 / (R2O + RO) < 1.1; preferably 0.6 < Al2O3 / (R2O + RO) < 0.9; particularly preferably 0.7 < Al2O3 / (R2O + RO) < 0.85where R2O = Li2O + K2O + Na2O and RO = MgO + CaO + SrO + BaO + ZnO.

[0049] A ratio of 0.5 < Al2O3 / (R2O + RO) < 1.1 is advantageous for glass formation. If the ratio Al2O3 / (R2O + RO) is greater than 1.1, the tendency to crystallize with the formation of Al2O3-containing crystals increases significantly, as there is no longer sufficient R2O and RO to "dissolve" all of the Al2O3 in the glass. At a ratio of Al2O3 / (R2O + RO) less than 0.5, too many non-bonding bridging oxygens are present and alkali diffusion is reduced, as the negative charges are concentrated on individual oxy anions and are no longer delocalized over an entire AlO4 tetrahedron. This leads to a stronger electrostatic bond of the mobile alkali cations to the glass matrix, and the chemical temperability suffers.

[0050] A ratio of 0.9 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.7 has a positive effect on the connectivity of the glass network and thus on its mechanical stability. Furthermore, such a ratio ensures that boron cations are preferentially coordinated with oxygen in trigonal coordination rather than as tetragonal BO4 units. Tetragonal BO4 units have a strongly negative effect on alkali diffusion, especially of potassium cations.

[0051] In embodiments, the glass may contain 0 to 1 mol% SnO2, preferably 0.1 to 0.5 mol% SnO2, and / or 0 to 1 mol% CeO2 and / or 0 to 1 mol% Cl, wherein the sum of CeO2 + SnO2 + Cl is preferably at most 2 mol%.

[0052] In certain embodiments, the glass may contain up to 2 mol%, preferably up to 1 mol%, of conventional refining agents such as As2O3, Sb2O3, SnO2, CeO2, halides, preferably chlorides, or sulfur-containing compounds. For environmental and occupational safety reasons, and especially when produced using the float process, the glass is preferably essentially free of arsenic and antimony. This also applies to other toxic or environmentally harmful components such as PbO, TeO2, and CdO.

[0053] The glass is also preferably, especially when it is to serve as a front cover, essentially free of coloring components, in particular free of coloring rare earths, in particular Nd2O3, Er2O3 and coloring metal oxides, in particular V2O5, CoO, NiO, Cr2O3, CuO.

[0054] Such a colorless glass preferably has an average transmission in the range from 365 to 640 nm of at least 85% at a thickness of 0.6 mm.

[0055] In particular, if the glass is to serve as a rear cover pane, i.e. as a so-called back cover, it preferably contains coloring components, e.g. at least 0.1 mol% and at most 5 mol% of at least one coloring component, in particular preferably selected from the group CoO, Fe2O3, TiO2, Cr2O3 and / or MnO and / or mixtures thereof.

[0056] The iron content of the glass, expressed as weight percent Fe2O3, should preferably be less than 1000 ppm, particularly preferably less than 500 ppm, to avoid undesirable coloring of the material. The iron content of the glass results from unavoidable impurities in the raw materials. By using low-iron raw materials, the amount of iron can be reduced and a better (more neutral) intrinsic color of the glass can be achieved; however, this is generally associated with higher raw material costs.

[0057] The glass according to the invention is suitable for the production of a cover plate, for example in electronic devices, in particular in electronic display devices, in particular in mobile electronic display devices, for example in mobile touch panels and / or mobile digital display devices such as smartphones or smartwatches and touch panels in general.

[0058] The cover plate preferably has a thickness of 0.3 mm to 1 mm, preferably 0.35 mm to 0.7 mm, particularly preferably 0.4 mm to 0.65 mm.

[0059] The process for producing a glass includes the following steps: - Producing a silicate glass by a melting process and - Refining of the glass melt and - subsequent hot forming.

[0060] Hot forming can be carried out, without restriction of generality, for example by a drawing process, in particular a float process or a down-draw process, for example an overflow fusion or a drawing nozzle process.

[0061] To produce a toughened glass, in particular according to an embodiment for use as a cover plate, the above steps are followed by the following: - Carrying out at least one ion exchange in an exchange bath having a composition of 100 wt% to 0 wt% KNO3 and 0 wt% to 100 wt% NaNO3 and 0 wt% to 5 wt% LiNO3 at a temperature of the exchange bath between 370°C and 500°C and a duration between 1 hour and 50 hours.

[0062] An ion exchange in more than one exchange bath, for example, first carrying out an ion exchange in an exchange bath with a composition of 50 wt% to 0 wt% KNO3 and 50 wt% to 100 wt% NaNO3 and 0 wt% to 5 wt% LiNO3 at a temperature of the exchange bath between 370°C and 500°C and a duration between 1 hour and 20 hours, then carrying out a further ion exchange in an exchange bath with a composition of 100 wt% to 50 wt% KNO3 and 0 wt% to 50 wt% NaNO3 and 0 wt% to 5 wt% LiNO3 at a temperature of the exchange bath between 370°C and 500°C and a duration between 1 hour and 20 hours, is possible.

[0063] In addition, ion exchange in three or more exchange baths is also possible.

[0064] The cover panel made of tempered glass is high-strength.

[0065] The high proportion of Li2O in the total alkali content of the LABS glass, expressed by Li2O / (Li2O+K2O+Na2O) > 0.8, makes it possible to achieve good tempering values ​​in the tempering process even with low glass thickness, i.e. high prestresses CS not only at the surface but also near the surface, namely CS30 > 100 MPa, and near the depth of the compressive stress zone, namely CS50 > 80 MPa, and a deep compressive stress zone DoCL, namely DoCL > 0.17 * t, where t is the thickness of the sheet.

[0066] This is CS30, expressed in MPa, is the compressive stress at a distance of 30 µm from the surface of a main side, CS50, expressed in MPa, is the compressive stress at a distance of 50 µm from the surface of the same main side and DoCL, as the thickness of the disc given in µm, the depth of the compressive stress zone of the same main side.

[0067] Main sides are those sides of the glass pane that are the largest in terms of surface area compared to the other sides. In addition to the two main sides, a pane preferably has four sides connecting the two main sides, called edge sides. In the case of non-rectangular panes, the pane may also have fewer edge sides, e.g., only one edge side.

[0068] The toughening process is a chemical toughening process, which preferably takes place by immersing the disc in a tempering bath, but can also take place by applying pastes to the disc.

[0069] An exchange bath is understood to be a molten salt bath used in an ion exchange process for a glass or a glass article. In the context of this disclosure, the terms "exchange bath" and "ion exchange bath" are used synonymously.

[0070] As a rule, salts of technical purity are used for exchange baths. This means that even if, for example, only sodium nitrate is used as the starting material for an exchange bath, certain impurities are still present in the exchange bath. The exchange bath is a melt of a salt, for example sodium nitrate, or a mixture of salts, for example a mixture of a sodium and a potassium salt. The composition of the exchange bath is specified in such a way that it refers to the nominal composition of the exchange bath without taking into account any impurities that may be present. Therefore, if reference is made to a 100% sodium nitrate melt in the context of this disclosure, this means that only sodium nitrate was used as the raw material.However, the actual sodium nitrate content of the exchange bath can and usually will vary, as technical raw materials in particular contain a certain amount of impurities.

[0071] However, this is usually less than 5% by weight, based on the total weight of the exchange bath, in particular less than 1% by weight.

[0072] Similarly, for exchange baths containing a mixture of different salts, the nominal contents of these salts are specified without taking into account technically induced impurities in the starting materials. A exchange bath containing 90 wt.% KNO3 and 10 wt.% NaNO3 may therefore also contain minor impurities, which, however, are due to the raw materials and should generally be less than 5 wt.%, based on the total weight of the exchange bath, and in particular less than 1 wt.%.

[0073] Furthermore, the composition of the exchange bath also changes during the ion exchange process, as the continued ion exchange causes lithium ions, in particular, to migrate from the glass or glass article into the exchange bath. However, such a change in the composition of the exchange bath due to aging is also not considered here, unless expressly stated otherwise. Rather, in the context of the present disclosure, the nominal original composition is used when specifying the composition of an exchange bath.

[0074] The invention is explained in more detail below using examples.

[0075] The compositions of examples of glasses according to the invention can be found in Table 1 (all data in mole percent on an oxide basis). The compositions of comparison glasses (designations beginning with V) can be found in Table 2 (all data in mole percent on an oxide basis).

[0076] The materials listed in Tables 1 and 2 were melted and refined at temperatures ranging from 1550°C to 1680°C using raw materials commonly used in the glass industry. The batch was initially melted in a Pt / Rh crucible at 1550°C to 1620°C. The melt was then refined at 1650°C to 1680°C and then homogenized by stirring for 30 minutes. After standing at 1550°C to 1650°C for 2 hours, castings measuring approximately 140 mm x 100 mm x 30 mm were cast and relaxed in a lehr at approximately 500°C to 650°C and cooled to room temperature. Test specimens for measuring the properties in the untempered state were prepared from the castings. The samples for the prestressing tests had a thickness of approximately 0.5 mm.

[0077] In Tables 1 and 2 the following properties are given for both the glasses according to the invention and the comparison glasses: • the thermal expansion coefficient CTE20-300, determined by dilatometry and expressed in ppm / K; • the transformation temperature Tg, determined by dilatometry and expressed in °C; • the temperature at viscosity 10 2 dPas, denoted as T2, expressed in °C and calculated from the Vogel-Fulcher-Tammann (VFT) equation; where the VFT curve describes the decimal logarithm of viscosity using three parameters A, B and T0 as a function of temperature T: Ig(|η|)=A+B / (T−T0) where VFT parameters (A, B, T0) are determined by fitting the measured data of viscosity vs. temperature using the VFT function; • the density ρ, given in g / cm 3 ; • the temperature at viscosity 10 4 dPas, referred to as processing temperature VA, given in °C and determined using a stirring viscometer; • the temperature at viscosity 10 3dPas, designated as T3, expressed in °C and determined using a stirring viscometer • The upper devitrification temperature, referred to as the upper devitrification temperature (UET), is expressed in °C and determined using gradient annealing. Glass grit on a platinum support is placed in a gradient furnace and annealed for one hour. The platinum support containing the glass is then removed. The temperature at the hot end of the gradient, above which the glass is crystal-free, is referred to as the upper devitrification temperature. The glass samples are inspected for crystals using an optical microscope. • the decimal logarithm of the liquidus viscosity, denoted as Ig (liquidus viscosity), expressed in dPa*s, is the viscosity at the upper devitrification temperature and is determined from the VFT parameters A, B, T0 and the UEL according to Ig (|η|) = A + B / (UEL - T0).

[0078] The abbreviation “nb” in the table stands for “not determined”. Examples of implementation: Table 1 composition [mol-%] 1 2 3 4 5 6 7 8 9 10 11 12 13 SiO2 71,25 68,45 67,75 68,25 68,05 68,05 67,75 67,75 67,75 68,45 67,55 67,95 67,25 Al2O3 8,50 11,00 11,00 11,00 11,00 11,00 11,00 11,00 11,50 11,00 11,40 11,00 11,40 B2O3 8,00 4,00 7,00 6,60 6,60 6,60 6,60 6,60 5,80 4,00 5,70 5,80 5,70 Li2O 8,00 8,00 8,00 8,20 8,20 8,20 8,20 8,20 8,20 8,00 8,20 8,70 8,20 Na2O 0,70 0,70 0,70 0,70 0,70 0,70 0,70 0,40 0,70 0,70 0,70 0,70 0,70 K2O 0,20 0,20 0,20 0,20 0,20 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 MgO 1,00 1,50 1,00 1,00 0,50 0,50 0,50 0,50 0,70 1,00 1,10 0,50 1,40 CaO 0,50 4,30 2,50 2,50 3,20 2,90 2,90 3,20 3,00 4,50 3,00 3,00 3,00 SrO BaO ZnO 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 P2O5 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 0,50 Fe2O3 TiO2 ZrO2 0,40 0,40 0,40 0,10 0,10 0,10 0,40 0,40 0,40 0,40 0,40 0,40 0,40 CeO2 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 SnO2 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 SO3 F CI 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 0,55 Continuation of Table 1 Characteristics 1 2 3 4 5 6 7 8 9 10 11 12 13 CTE20-300 [ppm / K] 4,33 4,76 4,55 4,61 4,68 4,76 4,76 4,67 4,77 4,9 4,78 4,91 nb Tg [°C] 557 596 588 580 586 577 585 586 593 589 595 581 nb T2 (from VFT) [°C] 1799 1693 1680 1702 1702 1705 1687 1682 1687 1688 1678 1689 nb ρ [g / cm 3 ] 2,3134 2,4056 2,3593 2,3549 2,3613 2,3581 2,367 2,3684 2,375 2,4053 2,38 2,3758 nb VA [°C] 1242 1219 1214 1227 1220 1215 1212 1212 1223 1215 1216 1208 nb T3 [°C] 1465 1412 1405 1422 1417 1414 1407 1404 1413 1408 1406 1404 nb VFT A -1,994 -2,373 -2,555 -2,584 -2,467 -2,325 -2,532 -2,494 -2,590 -2,399 -2,598 -2,382 nb VFT B 6670,3 6597,9 6962,8 7171,5 6958,7 6700,9 7017,7 6849,5 7024,7 6654,5 7006,2 6728,1 nb VFT T0 129,0 184,0 151,5 137,4 144,5 155,3 138,2 157,6 156,7 175,2 154,0 153,8 nb UEL [°C] 1235 1225 1205 1230 1185 1185 1195 1195 1205 1185 1190 1210 nb Ig (Liquidus Viscosity) [dPa*s] 4,04 3,97 4,05 3,98 4,22 4,18 4,11 4,11 4,11 4,19 4,16 3,99 nb Comparison examples: Table 2 composition [mol-%] V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 V14 V15 SiO2 68,96 69,51 66,51 66,09 68,09 67,09 63,22 68,88 67,68 70,98 68,65 68,65 68,45 68,95 73,40 Al2O3 10,44 10,00 13,00 13,00 11,00 11,00 15,10 11,00 11,50 8,50 11,00 11,00 11,00 11,00 11,50 B2O3 3,60 3,80 3,80 3,80 3,80 3,80 4,00 4,00 3,00 4,00 4,60 4,60 4,60 3,60 Li2O 8,45 8,70 8,70 8,70 8,70 8,70 9,70 8,00 8,00 8,00 8,20 8,20 8,20 8,20 8,50 Na2O 2,35 0,50 0,50 0,70 0,70 0,70 0,70 0,70 0,70 0,70 1,20 0,70 0,70 0,70 2,00 K2O 0,20 0,20 0,20 0,20 0,20 0,20 0,20 0,20 0,20 0,20 0,20 0,50 0,50 0,50 0,10 MgO 2,00 3,70 3,70 2,50 2,50 2,50 2,00 2,50 6,00 5,50 1,30 1,30 0,50 0,50 0,80 CaO 2,80 2,50 2,50 4,30 4,30 4,30 4,50 3,30 1,50 0,50 3,30 3,50 4,50 5,00 2,00 SrO 0,24 0,80 BaO ZnO 0,11 0,10 0,10 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,11 0,15 P2O5 0,26 0,25 0,25 0,27 0,27 0,27 0,27 0,27 0,27 0,27 0,50 0,50 0,50 0,50 0,50 Fe2O3 TiO2 1,00 ZrO2 0,11 0,25 0,25 0,15 0,15 0,15 0,15 0,20 0,20 0,40 0,10 0,10 0,10 0,10 CeO2 0,16 0,15 0,15 0,15 0,15 0,15 0,02 0,15 0,15 0,15 0,15 0,15 0,15 0,15 0,15 SnO2 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,14 0,10 SO3 0,03 0,03 0,03 0,03 0,03 F CI 0,20 0,20 0,55 0,55 0,55 0,55 0,55 0,55 0,55 Continuation of Table 2 Characteristics V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 V13 V14 V15 CTE20-300 [ppm / K] 5,49 4,77 4,73 4,96 5 5,05 5,18 4,69 4,63 4,53 4,91 4,86 4,95 4,99 5,16 Tg [°C] 560 586 620 608 581 592 614 601 622 585 586 587 585 594 638 T2 (from VFT) [°C] 1697 1691 1649 1620 1663 1619 1569 1703 1664 1723 1705 1706 1704 1700 1841 ρ [g / cm 3 ] 2,404 2,3955 2,4125 2,4191 2,4093 2,4222 2,4268 2,3954 2,4118 2,3724 2,3826 2,3829 2,3908 2,4004 2,404 VA [°C] 1190 1201 1214 1190 1185 1165 1168 1234 1219 1224 1217 1217 1213 1210 1328 T3 [°C] 1394 1399 1393 1367 1376 1353 1334 1426 1402 1426 1415 1415 1412 1408 1539 VFT A -2,129 -2,178 -2,664 -2,646 -2,278 -2,105 -2,752 -2,567 -2,603 -2,230 -2,307 -2,257 -2,221 -2,162 -2,580 VFT B 6417,5 6312,1 6760,5 6642,9 6353,3 5810,3 6430,3 7039,4 6754,0 6566,9 6624,7 6519,9 6444,4 6285,2 7732,7 VFT T0 142,7 179,9 199,0 190,5 178,0 203,2 216,1 162,1 196,3 170,2 166,5 174,9 177,3 190,0 152,8 OEG [°C] 1185 1260 1260 1235 1215 1195 1275 1255 1255 1265 1260 1240 1240 1245 1285 Ig (Liquid Viscosity) [dPa*s] 4,03 3,67 3,71 3,71 3,85 3,75 3,32 3,87 3,78 3,77 3,75 3,86 3,84 3,80 4,25

[0079] Comparative example V1 has a thermal expansion coefficient that is too high, so that higher stresses occur during cooling, which can lead to warping and / or cracking of the glass, especially in the case of thin glass.

[0080] Comparative example V15 has a T2 temperature that is too high, so that at the temperatures used in industrial glass production the melt is too viscous and bubbles can only be incompletely removed in the refining step, which leads to a low yield.

[0081] Comparative examples V2 to V14 exhibit an unfavorable relationship between the OEG and VA. As a result, the viscosity range in which crystals can form begins earlier from the hot melt, and the overall tendency to devitrification is increased. This is detrimental to producing such a glass with good yields.

[0082] The data on OEG, VA, T2 and CTE of the working examples show that the glass according to the invention is very easy to process.

[0083] It can be produced with good yield, especially at low thicknesses, e.g., in the range of 0.3 mm to 0.7 mm. It is not prone to crystallization. Stresses in the cooling belt, which often occur in the float process due to the different cooling rates of the thin net glass and the thick border, can be largely avoided.

[0084] The glass according to the invention is easily chemically tempered.

[0085] If samples with the composition of the working examples are subjected to ion exchange under the following conditions: - ion exchange in an exchange bath with a composition of 20 wt% KNO3 and 80 wt% NaNO3 at an exchange bath temperature of 420 °C and a duration of 7.5 hours and - a further ion exchange in an exchange bath with a composition of 100 wt.% KNO3 and 0 wt.% NaNO3 at an exchange bath temperature of 390 °C and a duration of 3 hours, they exhibit the following properties, as shown in the following table, which lists not only the values ​​for CT (= Center Tension), CS30, CS50 and DoCL, but also for K-CS and K-DOL, for the example glasses 6, 7, 8 and 9: Table 3 A6 A7 A8 A9 Glass thickness [mm] 0,479 0,477 0,472 0,509 CS30 [MPa] 137 133 139 154 CS50 [MPa] 108 108 115 126 DoCL [µm] 111 108 109 117 CT [MPa] 133 135 142 144 K-CS [MPa] 810 828 810 893 K-DOL [µm] 3,8 3,6 3,4 3,6

[0086] The chemically toughened glass according to the invention therefore has the following properties: CT>80 MPa, preferably CT>100 MPa, CS30>100 MPa, CS50>80 MPa and DoCL>0.17*t.

[0087] The glass according to the invention is therefore very well suited for use as a cover plate for the applications mentioned in the tempered state; It combines good product properties with very good manufacturing and processing properties. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2017 / 197869 A

[0006] US 2018 / 186685 A

[0007] US 2018 / 127302 A

[0008] US 2020 / 317558 A

[0009] DE 10 2019 121 146 A

[0010] DE 10 2019 121 143 A

[0011] Cited non-patent literature

[0000] DIN ISO 695

[0028] DIN 12116

[0028]

Claims

[1] Chemically toughenable or chemically toughened glass comprising SiO2, Al2O3, Li2O and B2O3 and optionally Na2O and optionally K2O, characterized by that the following applies to the components (in mol-% on an oxide basis): 0.8 < Li2O / (Li2O + K2O + Na2O) ≤ 1 0.1 < B2O3 ≤ 8.5 [2] Chemically toughenable or chemically toughened glass, preferably according to claim 1, characterized by , • that the upper devitrification temperature OEG is less than 10 K above the processing temperature, preferably below the processing temperature VA, wherein the processing temperature VA is preferably less than 1300°C, preferably less than 1260°C, particularly preferably less than 1220°C, and • that the temperature at a viscosity of 10 2 dPas is not more than 1800 °C and • that the thermal expansion coefficient CTE20-300 is less than 5.4 ppm / K [3] Glass according to claim 1 or 2 characterized bythat it contains the following components (in mol% on an oxide basis): SiO2 62 - 72, preferably 65 - 70 Al2O3 7 - 14, preferably 8 - 12 B2O3 0.1 - 8.5, preferably < 8.5 or ≤ 8, preferably 4 - 7, particularly preferably ≥ 5, most particularly preferably > 5.5 Li2O 5 - 12, preferably 7 - 10 Na2O 0 - 2, preferably 0 - 1, particularly preferably ≥ 0.1 and / or < 1, very particularly preferably ≥ 0.3 and / or < 0.8 K2O 0 - 2, preferably 0 - 1 [4] Glass according to one of the preceding claims characterized by that it contains the following components (in mol% on an oxide basis): MgO 0 - 5, preferably 0.5 - 3 CaO 0 - 8, preferably 1 - 6 SrO 0 - 5, preferably 0 - 1 BaO 0 - 2 ZnO 0 - 5, preferably 0-1 P2O5 0 - 5, preferably 0.5 - 2 ZrO2 0 - 5, preferably 0 - 3 [5] Glass according to one of the preceding claims characterized by that the following applies to the components (in mol-% on an oxide basis): 0.9 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.7; preferably 1 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.6; particularly preferably 1.1 < (Al2O3 + B2O3 + ZrO2) / (R2O + RO) < 1.5 and / or 0.5 < Al2O 3 / (R2O + RO) < 1.1; preferably 0.6 < Al2O3 / (R2O + RO) < 0.9; particularly preferred 0.7 < Al2O3 / (R2O + RO) < 0.85 where R2O = Li2O + K2O + Na2O and RO = MgO + CaO + SrO + BaO + ZnO means [6] Glass according to one of the preceding claims characterized bythat it contains 0 to 1 mol% SnO2, preferably 0.1 to 0.5 mol% SnO2, and / or 0 to 1 mol% CeO2 and / or 0 to 1 mol% Cl, the sum of CeO2 + SnO2 + Cl preferably being at most 2 mol%. [7] Glass according to one of the preceding claims characterized by that it is essentially free from coloring components, in particular free from coloring rare earths, in particular Nd2O3, Er2O3 and coloring metal oxides, in particular V2O5, CoO, NiO, Cr2O3, CuO. [8] Glass according to one of claims 1 to 6, characterized by that it contains coloring components, in particular at least 0.1 mol% and at most 5 mol% of at least one coloring component, in particular preferably selected from the group CoO, Fe2O3, TiO2, Cr2O3 and / or MnO and / or mixtures thereof. [9] A method for producing a tempered glass according to any one of claims 1 to 8, comprising the steps - Production of LABS glass through a melting process, refining of the glass melt and subsequent hot forming - Carrying out at least one ion exchange in an exchange bath with a composition of 100 wt% to 0 wt% KNO3 and 0 wt% to 100 wt% NaNO3 and 0 wt% to 5 wt% LiNO3 at a temperature of the exchange bath between 370°C and 500°C and a duration between 1 hour and 50 hours. [10] Method according to claim 9, wherein the hot forming is carried out by a drawing process, in particular a float process or a down-draw process, for example an overflow fusion or a drawing nozzle process. [11] Cover plate with a thickness of 0.3 mm to 1 mm made of a toughened glass according to one of claims 1 to 8 or by a method according to claim 9 or 10. [12] Use of a cover plate according to claim 11 and / or of a tempered glass according to one of claims 1 to 8 in electronic devices, in particular in electronic display devices, in particular in mobile electronic display devices, for example in mobile touch panels and / or mobile digital display devices such as smartphones or smartwatches. [13] Display device, in particular digital display device, comprising at least one cover plate according to claim 11.