Long-term bendable glass material, and methods for producing a long-term bendable glass material

Abstract

Long-term bendable glass material in the form of a glass material wound onto a roll, with a thickness of less than 500 µm and a minimum thickness of 3 µm, characterized in that the long-term bendable glass material is such that the number of fractures N of the bent glass developing over time with a bending radius R in the range of 1 mm to 10 7 mm after a storage period of at least one day, a residual breakage probability Φ (σ) = 1- exp{-(L-LO)·(σ / σ0) m ) for a storage period of at most half a year less than 0.1, where σ0 the characteristic fracture stress for specimens with length L0 and m is the Weilbull modulus determined by destructive testing, and L is the length of the specimen subjected to a tensile stress σ. characterized by the fact that The long-term bendable glass material has a crack depth that is less than a specified crack depth, and the specified crack depth is determined by ac = ((K1c+R) / (E+d))2. where K 1c the fracture toughness of a glass material, R is the bending radius of a glass material E is the modulus of elasticity of a glass material d is the thickness of a glass material.

Description

[0001] The invention relates generally to a long-term bendable glass material, preferably in the form of a glass material wound on a roll, in particular a glass ribbon with thicknesses below 500 µm, which are also referred to as thin glasses. In particular, the invention also relates to a method for producing a long-term bendable glass material.

[0002] Thin glass with thicknesses below 500 µm is used in many areas of technology. Examples include displays, windows for optoelectronic components, encapsulations, and electrical insulation layers.

[0003] To handle thin glass for further processing, as well as for storage and transport, it is advantageous to coil thin glass into a strip. This allows the glass to be unwound and processed directly from the coil. However, a problem arises from the fact that glass strips can be damaged after production, for example, with edge damage or cracks. During coiling, the glass strip is also subjected to stresses, such as bending stresses within the glass. These damages and stresses, especially bending stresses, can cause the coiled glass strips to break. Even a single break can cause a significant problem, as further processing must be interrupted at the break point when uncoiling the strip. The breakage of the coiled glass strip occurs because, for example, it is damaged by a crack in the glass surface.Cracks may appear in the edge area of ​​the glass strip, leading to crack propagation and even breakage. Furthermore, such thin glass is also used as a curved glass substrate, where it is permanently subjected to tensile stress on one side, e.g., as the cover glass of a curved display.

[0004] It must be ensured that crack growth, which could lead to a crack or fracture, is excluded.

[0005] US 2013 / 0196163A1 describes a method for bending glass in which a sheet of glass is laminated onto a reinforcing film such that, during bending, the neutral plane of the bending line lies within the reinforcing film and the entire glass sheet is located within the bending-induced compressive stress zone. This requires reinforcing films with a thickness several times greater than the glass thickness, and the use of a low-creep, and therefore brittle-curing, high-strength adhesive for the laminate. However, this high strength can cause problems if the adhesive is difficult to remove or cannot be completely removed. In any case, removing the adhesive constitutes an additional process step required before cutting. Furthermore, the winding direction is specified. Regarding the fracture strength of the wound glass, creep in the adhesive bond and stress relaxation in the reinforcing film must be taken into account.If the neutral plane migrates into the glass web due to stress relaxation, the glass is subjected to tensile stress, which can even increase during unwinding.

[0006] US 8,241,751 B2 describes a glass roll with a low instantaneous breakage probability when a minimum bending radius is maintained. However, the document neglects the aspect of delayed breakage. In particular, breaks occurring at the edges of the glass roll are also disregarded. Based on the dimensioning rules described in the document, glass breakage is to be expected after a very short time.

[0007] WO 2012 / 176 594 A1 proposes that, to prevent breakage during transfer from one roll to another, a relative humidity of 40% RH or less should be maintained. This is intended to significantly reduce the likelihood of breakage. The method proposed in WO 2012 / 176 594 A1 indicates the best results for relative humidity levels ≤ 1% RH. However, the method according to WO 2012 / 176 594 A1 only serves to stabilize the glass ribbon in the short term during processing under significant humidity reduction. It does not achieve a long-term improvement in the stability of the thin glass in general further processing or as a finished product.

[0008] US Patent 9,321,679 B2 discloses a glass element with a thickness of 25 µm to 125 µm. US Patent 9,321,679 B2 shows that, at a radius of curvature of 3 mm to 20 mm, the glass material does not break for at least 60 minutes at 25°C. Weilbull distributions demonstrating the effectiveness of the etch step are also shown in US Patent 9,321,679 B2. However, US Patent 9,321,679 B2 does not disclose a proof test for a long-term bendable glass material, nor does it provide criteria that can be applied to such a material.

[0009] DE 10 2013 110 803 A1 describes a process for further processing thin glass, wherein the thin glass is subjected to tensile stress through further processing.

[0010] WO 2014 / 171 247 A1 describes a method for thin glass, which at a thickness of less than 0.2 mm is typically wound onto rolls, wherein the glass is subjected to testing after manufacture by bending the glass around a winding core and checking after 30 days whether or not there is a break.

[0011] As a rule, glass materials with a thickness ≤ 500 µm, so-called thin glasses, are not processed directly. Instead, the glass material is wound into rolls and stored for a certain period. The subsequent transport to a processing facility causes additional dynamic loads.

[0012] In coiled glass rolls, the glass is typically under tension, for example, bending stress. Additionally, glass strips often exhibit edge damage or cracks. This can cause the coiled glass strips to break, rendering further processing impossible. Therefore, it is desirable to provide a criterion, a proof test, or a verification test that allows conclusions to be drawn about whether a glass material is bendable over the long term. A proof test, i.e., a verification test, is an instantaneous test characterized by the following: a target value is specified, an actual value is determined, and the actual value is compared to the target value. For example, if, in a proof test for a glass material that is bendable over the long term, the actual value, the crack depth, and the crack depth are all smaller than a target value (e.g., a specified crack depth), then the coiled glass material is classified as bendable over the long term.

[0013] The object of the invention is to avoid the problems in the prior art and in particular to provide a long-term bendable glass material as thin glass which is stored or used under a long-term tensile stress acting on one side and which has a very low probability of breakage during further processing of a stored glass roll or in the course of long-term use, or in which breakage is avoided.

[0014] Furthermore, a method for producing a long-term bendable glass material, its use, and a proof test for long-term bendable glass material will be described. In a proof test for a long-term bendable glass material, the actual value, namely the crack depth, is compared with a target value, namely a predetermined crack depth. If the actual value is smaller than the target value, the glass material is classified as long-term bendable. For a glass material characterized in this way, the probability of breakage is below 0.1. The crack depth is a measure of edge stability. Specifically, the crack depth is a measure of the fracture stress. The critical crack depth for a glass material, beyond which breakage occurs under stress, is determined by the glass parameters: the fracture toughness of the glass material, the modulus of elasticity of the glass material, the thickness of the glass material, and the bending radius of the glass material.For the crack depth a. c applies, ac=((K1c+R) / (E+d))2 where K 1cThe fracture toughness is denoted by ρ, R by the bending radius, E by the modulus of elasticity, and d by the thickness of the glass material. For common glass materials, the fracture toughness ranges from 0.1 to 1.5 MPa · √m. With a modulus of elasticity of 75 GPa, a thickness of 100 µm, and a bending radius of 75 mm, a critical or predetermined crack depth of 49 µm results. Any glass roll with a crack depth greater than 49 µm, for example, 60 µm, is classified as not suitable for long-term bending after such a proof test.If the crack depth is less than 49 µm, for example 30 µm, the glass material is classified as long-term bendable, since even after storage for a longer period of at least 1 day, in particular at least 5 days, preferably at least 10 days, in particular at least 50 days, most preferably at least 300 days, a residual fracture probability of less than 0.05, in particular less than 0.01, is achieved for a storage period of a maximum of half a year, in particular one year, preferably 2 years, most preferably a maximum of 5 years.

[0015] Generally, a glass will break as soon as the specified crack depth is exceeded.

[0016] According to the invention, this problem is solved by a long-term bendable glass material, according to claim 1.

[0017] In addition to the long-term bendable glass material according to claim 1, the invention also provides a method for producing a long-term bendable glass material according to claim 4, as well as a proof test for a long-term bendable glass material according to claim 13. Further developments and preferred embodiments are the subject of the dependent claims.

[0018] The long-term bendable glass material is preferably a glass material wound onto a roll, in particular a glass strip with a thickness of less than 500 µm, preferably less than 350 µm and a minimum thickness of 5 µm, particularly in the range of 20 µm to 200 µm, wherein the long-term bendable glass material is such that the number of fractures N(t) developing over time of a bent glass with a bending radius R in the range of 1 mm to 10 7 mm, preferably 5 mm to 10 6 mm, especially 10 to 10 3mm after a storage period of at least one day, in particular at least three days, preferably at least five days, in particular at least seven days, most preferably at least ten days, in particular at least 50 days, in particular preferably at least 150 days, and most preferably at least 300 days, exhibits no or only a low probability of breakage. Low probability of breakage or residual probability of breakage, as defined in this application, means a probability of breakage Φ less than 0.1, preferably less than 0.05, in particular less than 0.01 for a storage period of at most half a year, in particular one year, preferably two years, and most preferably five years. These probabilities of breakage are achieved if the crack depth in the glass material does not exceed certain values. The critical crack depth at which breakage occurs is, as described above, ac=((K1c+R) / (E+d))2.

[0019] In a proof test, this critical crack depth is the specified crack depth (target value). Surprisingly, it has been shown that a failure probability of less than 0.1 is achieved according to the invention when the crack depth is less than specified above.

[0020] Glasses exhibiting such properties are characterized by a very low probability of breakage during long-term bending, as well as long-term storage in roll form or long-term use as a bent substrate.

[0021] Preferably, the glass material has a thickness of less than 500 µm, preferably less than 350 µm, and a minimum thickness of 3 µm. The glass thickness is particularly in the range of 20 µm to 200 µm. Preferred glass film thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm.

[0022] If the glass is wound onto a roll, the core diameter of the roll is preferably more than 75 mm, in particular more than 100 mm, more preferably more than 150 mm, in particular more than 300 mm, in particular more than 400 mm, most preferably more than 500 mm, in particular more preferably more than 600 mm.

[0023] Surprisingly, it has been found that the glasses according to the invention, particularly in the form of thin glass strips or thin glass laminate strips that are bent, for example wound into rolls, are significantly more stable in further processing than bent glasses, particularly in the form of glass rolls, which do not achieve the specified breakage probabilities of less than 0.1 after the specified times. A further advantage of the invention is that thin glass strips or thin glass laminate strips with problematic damage, especially with critical cracks and edges, can be very easily identified and rejected.

[0024] To increase the stability of the glass rolls, it may be necessary to rewind the wound glass rolls after a certain storage period. For example, this rewinding can be done in a roll-to-roll process.

[0025] Surprisingly, it was found that glass ribbons exhibiting the specified fracture behavior and, during the specified storage period of at least one day, preferably at least three days, preferably five days, particularly at least seven days, preferably ten days, most preferably at least 50 days, particularly preferably at least 150 days, most preferably at least 300 days, have a fracture probability Φ of less than 0.1, preferably less than 0.05, particularly less than 0.01 for a storage period of a maximum of six months, particularly one year, preferably two years, most preferably a maximum of five years, and exhibit significant stabilization and a longer service life in subsequent processing and further processing. In particular, they also demonstrated long-term bendability. The fracture probability denotes the likelihood of fracture.Here, 0.1 corresponds to a probability of 10%, 0.05 to a probability of 5%, 0.03 to a probability of 3%, and 0.01 to one.

[0026] A probability of 1%. It is particularly advantageous if the glass strips are rolled onto glass cylinders.

[0027] The strengths of a sample set follow a Weibull distribution. This is due to the static distribution of microcrack lengths, i.e., the microcrack depth. Once the underlying distribution is known, a failure probability can be determined for each sample under a given load. This failure probability also depends on the sample length, as the longer a sample, the more likely it is to have a long crack. The parameters of a Weibull distribution, measured by destructive testing on a sample set (all samples with the same length L0), are: σ = characteristic fracture stress m = Weilbull modulus.

[0028] If these two parameters and the size of the samples used to determine them are known for edge or surface machining, then the probability of fracture Φ(σ) for a sample of length L subjected to a tensile stress σ can be calculated using: ϕ(σ)=1−exp{−(L / L0)⋅(σ / σ0)m}

[0029] In the proof test, subcritical crack growth occurs under tensile stress in the glass samples. This means that any cracks reaching the critical crack length during the proof test period will result in fracture. Storage, therefore, serves as a test to eliminate all microcracks that are not shorter than the critical crack length. Cracks that do not cause fracture during the proof test will not cause fracture subsequently.

[0030] Surprisingly, glass material classified as sufficiently stable in the proof test has been found to exhibit an increase in strength. This is due to a rounding of the crack tips, which in turn increases the glass's strength. As has been surprisingly discovered, glass that has passed the proof test can be subjected to a significantly higher stress than that used in the proof test without breaking, due to this increased strength. The stress applied to the glass can be 5–20% higher than the stress determined by the bending radius in the proof test.

[0031] The coiled glass ribbons can be applied directly to a core after production and then stored, whereby edges of the glass ribbon can be trimmed off before application to the core, if present. The storage period of the coiled glass ribbons for the proof test is at least one day and preferably at most 60 days, particularly preferably 8 to 30 days.

[0032] Preferably, the storage of the roll according to the invention takes place at a relative humidity (RH) in the range of 40% to 100% RH, more preferably 50% to 95% RH, and particularly between 60% and 90% RH. It is especially preferred if the stored glass rolls are stored in an enclosed space at temperatures in the range of 10°C to 30°C, more preferably 15°C to 25°C, and particularly between 18°C ​​and 23°C.

[0033] As previously described, the long-term flexible glass material comprises not only thin glass but also a thin glass laminate, in particular a polymer-coated thin glass film as described, for example, in WO 00 / 66 507 A1, the full disclosure of which is included in the present application. In the thin glass laminate according to WO 00 / 66 507 A1, a polymer layer of a silicone polymer, a sol-gel polymer, a polycarbonate, a polyethersulfone, a polyacrylate, a polyimide, a cycloolefin copolymer, a polyarylate, or a silicone resin is applied to a thin glass film made of aluminosilicate glass, aluminoborosilicate glass, or borosilicate glass, preferably alkali-free borosilicate glass.

[0034] Particularly preferred glass materials suitable for the production of glass ribbons with a thickness of less than 500 µm are glasses with the following composition in wt.%. SiO2: 40-75 Al2O3 1-25 B2O3: 0-16 Alkaline earth oxides: 1-30 Alkali oxides: 0-20, especially 0-2.

[0035] In general, all glass compositions within the aforementioned composition range are suitable. Glasses with a low alkali oxide content are particularly preferred, i.e., glasses with an alkali content in the range of 0-2 wt%, such as the glasses AF32, AF37 and AF45 from Schott AG, Mainz.

[0036] In one embodiment, the thin glass is a lithium aluminosilicate glass with the following composition (in wt.%): composition (wt.%) SiO2 55-69 Al2O3 18-25 Li2O 3-5 Na2O + K2O 0-30 MgO + CaO + SrO + BaO 0-5 ZnO 0-4 TiO2 0-5 ZrO2 0-5 TiO2 + ZrO2 + SnO2 2-6 P2O5 0-8 F 0-1 B2O3 0-2

[0037] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon, or optical functions into the glass layer or plate, with the total amount of the composition being 100 wt%.

[0038] The lithium aluminosilicate glass of the present invention preferably has the following composition (in wt.%): composition (wt.%) SiO2 57-66 Al2O3 18-23 Li2O 3-5 Na2O + K2O 3-25 MgO + CaO + SrO + BaO 1-4 ZnO 0-4 TiO2 0-4 ZrO2 0-5 TiO2 + ZrO2 + SnO2 2-6 P2O5 0-7 F 0-1 B2O3 0-2

[0039] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0040] The lithium aluminosilicate glass of the present invention most preferably has the following composition (in wt.%): composition (wt.%) SiO2 57-63 Al2O3 18-22 Li2O 3.5-5 Na2O + K2O 5-20 MgO + CaO + SrO + BaO 0-5 ZnO 0-3 TiO2 0-3 ZrO2 0-5 TiO2 + ZrO2 + SnO2 2-5 P2O5 0-5 F 0-1 B2O3 0-2

[0041] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon, or optical functions into the glass layer or plate, with the total amount of the composition being 100 wt%.

[0042] In one embodiment, the thin glass is a soda-lime glass with the following composition and comprises (in wt.%): composition (wt.%) SiO2 40-81 Al2O3 0-6 B2O3 0-5 Li2O + Na2O + K2O 5-30 MgO + CaO + SrO + BaO + ZnO 5-30 TiO2 + ZrO2 0-7 P2O5 0-2

[0043] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0044] The soda-lime glass of the present invention preferably has the following composition (in wt.%): composition (wt.%) SiO2 50-81 Al2O3 0-5 B2O3 0-5 Li2O + Na2O + K2O 5-28 MgO + CaO + SrO + BaO + ZnO 5-25 TiO2 + ZrO2 0-6 P2O5 0-2

[0045] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0046] The soda-lime glass of the present invention most preferably has the following composition (in wt.%): composition (wt.%) SiO2 55-76 Al2O3 0-5 B2O3 0-5 Li2O + Na2O + K2O 5-25 MgO + CaO + SrO + BaO + ZnO 5-20 TiO2 + ZrO2 0-5 P2O5 0-2

[0047] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0048] In one embodiment, the thin glass is a borosilicate glass with the following composition (in wt.%): composition (wt.%) SiO2 60-85 Al2O3 0-10 B2O3 5-20 Li2O + Na2O + K2O 2-16 MgO + CaO + SrO + BaO + ZnO 0-15 TiO2 + ZrO2 0-5 P2O5 0-2

[0049] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0050] The borosilicate glass of the present invention preferably has the following composition (in wt.%): composition (wt.%) SiO2 63-84 Al2O3 0-8 B2O3 5-18 Li2O + Na2O + K2O 3-14 MgO + CaO + SrO + BaO + ZnO 0-12 TiO2 + ZrO2 0-4 P2O5 0-2

[0051] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0052] The borosilicate glass of the present invention most preferably has the following composition (in wt.%): composition (wt.%) SiO2 63-83 Al2O3 0-7 B2O3 5-18 Li2O + Na2O + K2O 4-14 MgO + CaO + SrO + BaO + ZnO 0-10 TiO2 + ZrO2 0-3 P2O5 0-2

[0053] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0054] In one embodiment, the thin glass is an alkali metal aluminosilicate glass with the following composition (in wt.%): composition (wt.%) SiO2 40-75 Al2O3 10-30 B2O3 0-20 Li2O + Na2O + K2O 4-30 MgO + CaO + SrO + BaO + ZnO 0-15 TiO2 + ZrO2 0-15 P2O5 0-10

[0055] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0056] The alkali metal aluminosilicate glass of the present invention preferably has the following composition (in wt.%): composition (wt.%) SiO2 50-70 Al2O3 10-27 B2O3 0-18 Li2O + Na2O + K2O 5-28 MgO + CaO + SrO + BaO + ZnO 0-13 TiO2 + ZrO2 0-13 P2O5 0-9

[0057] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0058] The alkali aluminosilicate glass of the present invention most preferably has the following composition (in wt.%): composition (wt.%) SiO2 55-68 Al2O3 10-27 B2O3 0-15 Li2O + Na2O + K2O 4-27 MgO + CaO + SrO + BaO + ZnO 0-12 TiO2 + ZrO2 0-10 P2O5 0-8

[0059] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0060] In one embodiment, the thin glass is a low alkali aluminosilicate glass with the following composition (in wt.%): composition (wt.%) SiO2 50-75 Al2O3 7-25 B2O3 0-20 Li2O + Na2O + K2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-25 TiO2+ZrO2 0-10 P2O5 0-5

[0061] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0062] The low alkali aluminosilicate glass of the present invention preferably has the following composition (in wt.%): composition (wt.%) SiO2 52-73 Al2O3 7-23 B2O3 0-18 Li2O + Na2O + K2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-23 TiO2+ZrO2 0-10 P2O5 0-5

[0063] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0064] The low alkali aluminosilicate glass of the present invention most preferably has the following composition (in wt.%): composition (wt.%) SiO2 53-71 Al2O3 7-22 B2O3 0-18 Li2O + Na2O + K2O 0-4 MgO + CaO + SrO + BaO + ZnO 5-22 TiO2 + ZrO2 0-8 P2O5 0-5

[0065] If desired, coloring oxides such as Nd2O3, Fe2O3, CoO, NiO, V2O5, MnO2, TiO2, CuO, CeO2, Cr2O3 may be added; 0-2 wt% As2O3, Sb2O3, SnO2, SO3, Cl, F and / or CeO2 may be added as a refining agent; and 0-5 wt% rare earth oxides may also be added to introduce magnetic, photon or optical functions into the glass layer or plate, and the total amount of the composition is 100 wt%.

[0066] The glass material is primarily a thin glass strip or film with a thickness of less than 500 µm, preferably less than 350 µm, and a minimum thickness of 3 µm. Preferably, the thickness is in the range of 20 µm to 200 µm. Preferred glass film thicknesses are 5, 10, 15, 20, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm.

[0067] Stability can be further increased by rewinding the glass strips, changing the direction of curvature after a quarter or half of the total storage time. The glass is rewound using a roll-to-roll process.

[0068] Preferably, the curved glass, especially the rolled glass, is subjected to a moderate tensile stress σ. app set which is smaller than the following term: 1.15⋅Min(σ¯a−Δa0.4⋅(1−ln(ArefAAppΦ)),σ¯e−Δe0.4⋅(1−ln(LrefLAppΦ))), where σ̅ a and σ̅ e Mean values ​​of the tensile stress during fracture of thin glass samples under bending stress are, where L ref the edge length and A ref denote the area of ​​the samples, where σ̅ a the mean value of the tensile stress at fracture in the area of ​​the specimen and σ̅ e are the mean value of the tensile stress in a fracture originating from the edge of the specimen, and where Δ e and Δ athe standard deviations of the means σ̅ e , or σ̅ a designate, and where A app the surface area of ​​the thin glass and L app the added edge length of opposite edges of the thin glass and Φ a predetermined maximum breakage rate within a period of at least half a year.

[0069] The curved glass sheets, especially those rolled into rolls, particularly thin glass sheets, have a thickness of less than 500 µm, most preferably less than 350 µm. The minimum thickness is preferably 3 µm. A particularly preferred thickness range is between 20 µm and 200 µm. Preferred glass sheet thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm.

[0070] The specification of the maximum tensile stress for the curved glass, particularly the glass coils in a preferred embodiment, is based on the understanding that fractures at the edges and in the surface of the glass are due to different types of defects in the glass and that the fracture probabilities are statistically independent of each other. Therefore, the glass strengths with respect to fracture strength at the edges and in the surface are considered independently. The actual fracture strength is calculated according to the term specified above by the minimum of the tensile stresses at fractures in the surface and at the edges. In this way, the typically different service lives of thin glass with respect to fractures occurring under bending at the edges and in the surface are also taken into account.Given a specified lifetime, the maximum probability of breakage Φ is preferably 0.1 or less (i.e., at most 10%), particularly preferably less than 0.05 (less than 5%), and most preferably less than 0.03 (less than 3%) for long-term storage in the rolled or bent state, or for use in the bent state.

[0071] A low probability of breakage under the given storage conditions is observed particularly in largely alkali-free borosilicate glasses. Borosilicate glasses with a composition containing the following oxide-based components (in wt% %) are especially preferred: SiO2 40-75 Al2O3 1-25 B2O3 0-16 Alkaline earth oxides 1-30 Alkali oxides 0-1.

[0072] Glasses with a composition containing the following components (in % by weight) based on oxides are particularly preferred: SiO2 45-70 Al2O3 5-25 B2O3 1-16 Alkaline earth oxides 1-30 Alkali oxides 0-1.

[0073] In addition to glass materials that can be stored or used under bending for extended periods, the invention also provides a method for producing a long-term bendable glass material, preferably in the form of a glass material wound onto a roll, in particular a glass ribbon with a thickness of less than 500 µm, preferably less than 350 µm, and a minimum thickness of 3 µm, particularly in the range of 20 µm to 200 µm. The method according to the invention comprises the following steps: - the glass material is first bent with a radius R in the range of 1 mm to 10 7 mm, 5 mm to 10 6 mm, 10 to 10 3 The bent glass material is stored for a period of at least 1 day, in particular at least 3 days, preferably at least 5 days, in particular at least 7 days, most preferably at least 10 days, preferably at least 50 days, in particular preferably at least 150 days, most preferably at least 300 days; - After storage for a period of at least 1 day, preferably 3 days up to a maximum of 500 days, preferably at least 50 days up to a maximum of 300 days, the bent glass material is examined for damage, in particular cracks, breaks, fractures, fractures, defects and - The bent glass material, or a section of bent glass material, is classified as rejectable, particularly with a defect mark, if damage, especially cracks, breaks, fractures, fractures, or defects are found. - The bent glass material is classified as long-term bendable glass material.

[0074] To increase the stability of the glass strips, one approach is to wrap the glass roll once or several times. This can be done using a roll-to-roll process.

[0075] Discarding also includes marking areas with damage, especially cracks, breaks, tears, fractures, and defects, and discarding or sorting them out in a later step.

[0076] The marking is made on the glass strip using a defect marker, which is placed, for example, at a defect point F. i at a position (x i , y i ) is attached to the glass strip.

[0077] Applying defect markers prevents entire sections of the glass ribbon from being discarded as rejects. Instead, applying a defect marker F allows for the identification of specific defects. iTo enable further processing, e.g., of glass coils, the section of the glass ribbon with the defect can be identified and not used for the production of products that could not be manufactured according to specifications due to the defect. The defect marks can be read, for example, during the further processing of the glass coil or ribbon as it is unwound and, in particular, taken into account when the continuous ribbon is cut. During further processing, a further defect inspection can be advantageously omitted. Furthermore, scrap can be reduced. Scrap due to impurities in the glass ribbon, which are mistakenly classified as defects, is avoided because the defect inspection takes place earlier, preferably directly after the glass ribbon is drawn from the melt and before it is wound or laminated.If the layers of the glass ribbon are separated by a removable separating layer bonded to the glass ribbon, the defect mark may also be located on the separating layer. If the glass ribbon also includes a metal or plastic layer bonded to the glass layer, the defect mark may also be located on this metal or plastic layer. The glass materials classified or characterized as described above are distinguished by long-term bendability, during which virtually no damage occurs during storage or use in a bent state, i.e., under tensile stress on one side of the glass material.

[0078] Long-term flexible glass materials can have bending radii of 1 to 10 mm when bent. 7 mm, preferably 5 to 10 6 mm, especially 10 to 10 3 mm.

[0079] The glass material is preferably one with a thickness of less than 500 µm, preferably less than 350 µm, and with a minimum thickness of 3 µm, particularly in the range of 20 µm to 200 µm. Preferred glass foil thicknesses are 5, 10, 15, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm. If a long-term bendable glass material is wound onto a roll, the core diameter of the roll is preferably more than 75 mm, in particular more than 100 mm, preferably more than 150 mm, in particular more than 300 mm, in particular more than 400 mm, most preferably more than 500 mm, in particular more preferably more than 600 mm.

[0080] The storage of the roll according to the invention preferably takes place at a relative humidity (RH) in the range of 40% to 100% RH, preferably 50% to 95% RH, and particularly between 60% and 90% RH. It is especially preferred if the roll has also been exposed to a temperature between 10°C and 30°C, preferably 15°C and 25°C, and particularly between 18°C ​​and 23°C, and to standard atmospheric conditions. Humid storage, compared to dry storage, has the advantage that cracks heal. Generally, one would expect the glass to break if stored indefinitely. However, this is counteracted by crack healing through the aging of the glass. Humid storage is particularly advantageous for crack healing because it is achieved through rapid crack rounding. In general, it has been found that the more humid the storage conditions, the faster the crack rounding occurs.Crack rounding prevents further fractures and crack propagation. Furthermore, it increases the strength of the glass or glass strip.

[0081] The effect of aging the glass is 0-40%, preferably 5%, particularly 5-20% of the increase in strength over time.

[0082] In the process for producing a glass with a low probability of breakage, after storage the glass material is rewound or processed into sheets from the stored roll and / or the roll is inspected for breaks in the glass, whereby a ray is passed from winding mirror or winding roll to winding mirror or winding roll with defect detection.

[0083] The glass material is primarily a thin glass strip or foil with a thickness of less than 500 µm, preferably less than 350 µm. The minimum thickness is 3 µm. A preferred thickness range is from 20 µm to 200 µm. Preferred glass foil thicknesses are 5, 10, 15, 20, 25, 30, 35, 50, 55, 70, 80, 100, 130, 145, 160, 190, 210, or 280 µm.

[0084] Regarding the different glass materials, reference is made to the explanations in the introductory part; glasses with a low alkali oxide content are particularly preferred, i.e. glasses with an alkali content in the range of 0-2 wt.%, such as the glasses AF32, AF37 and AF from Schott AG, Mainz.

[0085] In one embodiment, the use of a long-term bendable glass material classified according to the invention as a bent glass substrate is possible, in particular with a bending radius of 1 to 10. 7 mm, preferably 5 to 10 6 mm, particularly preferably from 10 to 103 mm. The long-term bendable glass materials are first wound onto a glass roll and stored for an extended period. Sections of glass are then unwound from the roll and subjected to permanent tensile stress. This bends the glass into a curved glass substrate with the previously specified bending radii. The curved glass substrate can then be used, for example, as a cover glass in a curved display or as the glass for a touch panel. Wrapping is also possible.

[0086] The invention further provides a proof test or a test method for characterizing a long-term bendable glass material. The test test comprises the storage of a glass material, preferably in the form of a glass material wound onto a roll, in particular a glass ribbon with a thickness of less than 500 µm, preferably less than 350 µm and a minimum thickness of 3 µm, particularly in the range of 20 µm to 200 µm, for a storage period of at least one day, in particular at least three days, preferably five days, in particular at least seven days, most preferably ten days, in particular at least 50 days, more preferably at least 50 days, and most preferably 300 days. After the storage period, a crack depth in the glass ribbon is determined and compared with a predetermined crack depth.The glass material is determined to be a long-term bendable glass material, in the case the crack depth is less than the specified crack depth, so that the residual fracture probability Φ is less than 0.005, in particular less than 0.01 for a storage period of a maximum of half a year, in particular one year, preferably 2 years, most preferably a maximum of 5 years.

[0087] The invention is explained in more detail below with reference to the accompanying drawings and the following descriptions, which are not intended to limit the invention.

[0088] They show: Fig. 1 the course of fracture development for a 50 µm thick thin glass foil of the glass AF32; Fig. 2 Fracture profile for a 100 µm thick thin glass foil of AF32 glass; Fig. 3 Weilbull diagram of strength (fracture stress) versus probability of failure; Fig.4a-4g Weilbull diagram of strengths (fracture stress) versus failure probability for differently loaded specimens.

[0089] In the Fig. 1 and Fig. Figure 2 specifies the breakage probability over time for a large number of glass rolls with a diameter of 85 mm, comprising a glass film with a thickness of 50 µm. Intermediate layers of a physically cross-linked, closed-cell polyolefin foam, such as that offered under the name Alveolit ​​by SEKISUI ALVEO BS GmbH / D-Bad Sobernheim, were inserted between the individual glass layers of the rolls. The glass rolls themselves were enclosed in plastic wrappings and stored at room temperature. The relative humidity was varied between 20% and 85%. Several observations were made over a total observation period of 300 days. The breakage development of a 50 µm thick thin glass film made of AF32 is shown in Figure 2. Fig.Figure 1 shows that the probability of breakage increases sharply at the beginning, then remains at a largely constant level; at most, a slight increase can be detected after a certain storage period.

[0090] The glass material tested consists of rolls of thin glass strips, 50 µm thick, made of alkali-free aluminoborosilicate glass. This glass, AF32, from Schott AG, Mainz, contains the following components (in wt%): SiO2 61,4 Al2O3 17,5 B2O3 10,5 Alkaline earth oxides 10,3 Alkali oxides 0

[0091] How Fig.As can be seen in Figure 1, the number of breaks initially increases sharply to 4 breaks / km of film length and then only slowly with longer storage periods. After 4 weeks, equivalent to 30 days, a quasi-steady state is reached and no significant increase in the number of breaks is detected. The breakage probability after 30 days of storage is less than 0.03, preferably less than 0.01. For several months of storage, the glass film shows no significant increase in the number of breaks at all.

[0092] The following applies to the voltage σ in the glass roll: σ=E⋅t2R here is - E of the Young module, which is 74 GPa at AF32, - t is the glass thickness, which is 50µm for AF32. - the core diameter R of the roller, which is 85 mm.

[0093] This results in a voltage σ of approximately 21 MPa for the roller made of 50 µm thick AF32 glass foil, and a voltage of 45 MPa for a 100 µm thick glass foil.

[0094] Fig. Figure 2 shows the results of the fracture test for a 100 µm thick glass foil made of AF32. How Fig. As can be seen in Figure 2, the number of fractures also increases rapidly within 25 days. In contrast to the 50 µm thick glass foil, the plateau, after which the number of fractures remains largely constant, is only reached after more than 100 days. As with the 50 µm thick glass foil, the probability of breakage after storage for more than 150 days is 0.01, i.e., less than 1%. A value of σ = 45 MPa is determined for the stress in the glass roll.

[0095] Glass rolls with a storage time of at least one day, in particular at least three days, preferably at least five days, most preferably at least seven days, in particular at least ten days, most preferably at least 50 days, in particular preferably at least 150 days, and most preferably at least 300 days, with a low probability of breakage, are characterized as being suitable for long-term storage stability, long-term bending, or use under bending conditions. The glass selected in this way is particularly suitable for use in curved display devices, as curved cover glasses, or as display glass.

[0096] Surprisingly, after performing the proof test, i.e., classifying the glass material as long-term bendable, an increase in strength is achieved by rounding the crack tips.

[0097] In glass undergoing a proof test, tensile stress causes subcritical crack growth; that is, any cracks that reach the critical crack length (i.e., the predetermined crack length) within a given timeframe will result in fracture. Storage according to the proof test is therefore a test used to eliminate microcracks that are not significantly shorter than the critical crack length (i.e., the target value or predetermined crack length). Cracks that do not fracture within the initial short period will not fracture even after a longer period.

[0098] This makes it possible to subject the glass roll to a higher load after the proof test. It has been found that the loads can be up to 20% higher than in the proof test. The range of possible load increases is therefore 0 to 20%. Values ​​of 5%, 10%, and 15% load increases are possible. The load is adjusted by the winding radius, as in the proof test. The following applies to the tensile stress: σ=E⋅t2R where t is the thickness of the glass material, R: the winding radius, E: the Young Modulist.

[0099] The following will be based on Fig. 3 - 4g will show the surprising fact that the glass becomes stronger during storage.

[0100] Fig. Figure 3 shows the Weilbull diagram as strengths of a reference sample.

[0101] In the Fig.4a - 4g are the Weilbull diagrams of glasses stored for longer periods after performing the proof test and under higher stress than in the proof test, compared to a reference sample. Fig. 3 shown. In Fig. 4a the sample under investigation has a radius of 30 mm, in Fig. 4b of 25 mm, in Fig. 4c of 22.5 mm, in Fig. 4d of 20 mm, in Fig. 4e of 17 mm, in Fig. 4f of 15 mm and in Fig. 4g of 14 mm. The lenses are held under constant tension for an extended period after the proof test has been performed.

[0102] What one can Fig. What can be surprisingly deduced from sections 4a-4g is that the samples with high strengths deteriorate significantly, while samples whose initial strength is not much above the load limit deteriorate significantly. However, if the stresses become too high, the effect is no longer so clearly discernible.

[0103] With this invention, the inventors have for the first time identified the necessary steps to enable long-term bendability of glass on a roll or in bent applications. Furthermore, a proof test is provided that makes it possible to classify long-term bendable glass samples.

Claims

[1] Long-term flexible glass material in the form of a glass material wound on a roll, with a thickness of less than 500 µm, and a minimum thickness of 3 µm, characterized by that the long-term bendable glass material is such that the number of fractures N of the bent glass developing over time with a bending radius R in the range 1 mm to 10 7 mm after a storage time of at least one day a residual fracture probability Φ (σ) = 1- exp{-(L-LO)·(σ / σ0) m ) for a storage period of a maximum of half a year less than 0.1, where σ0 the characteristic fracture stress for specimens of length L0 and m is the Weilbull modulus determined by destructive testing and L is the length of the specimen loaded with a tensile stress σ, characterized by that, the long-term bendable glass material has a crack depth which is less than a specified crack depth and the specified crack depth is determined by ac=((K1c+R) / (E+d))2. where K 1c the fracture toughness of a glass material, R is the bending radius of a glass material E is the elastic modulus of a glass material d is the thickness of a glass material. [2] Long-term bendable glass material according to claim 1, characterized by , that the glass material comprises the following components in wt.%: SiO2: 40-75 Al2O3 1-25 B2O3: 0-16 Alkaline earth oxides: 0-30 Alkali oxides: 0-20, especially 0-2 [3] Long-term bendable glass material according to one of claims 1 to 2, characterized by that glass material in the form of a glass material wound on a roll is subjected to tensile stress which is less than: 1.15⋅Min(σ¯a−Δa0.4⋅(1−ln(ArefAAppΦ)),σ¯e−Δe0.4⋅(1−ln(LrefLAppΦ))), where σ̅ a and σ̅ e Mean values ​​of the tensile stress at break of samples (10) of the glass material (1) under bending stress, where L ref the edge length and A ref denote the area of ​​a sample, where σ̅ a the mean value of the tensile stress at fracture in the area of ​​the sample and σ̅ e is the mean value of the tensile stress at a fracture originating from the edge of the specimen, and where Δ e and Δ a the standard deviations of the means σ̅ e or σ̅ a and where A app the area of ​​the glass material (1) and L app the added edge length of opposite edges (22, 23) of the glass material (1) and Φ (σ) = 1- exp{-(L-L0)·(σ / σ0) m ) a maximum breakage rate of 0.1 within a period of at least six months. [4] A process for producing a long-term bendable glass material according to any one of claims 1 to 3 in the form of a glass material wound on a roll with a thickness of less than 500 µm and a minimum thickness of 3 µm, the process comprising the following steps: - the glass material is processed with a bending radius R in the range 1 mm to 10 7 mm curved - the bent glass material is stored for a period of at least 3 days - after storage for at least 1 day, the bent glass material is examined for damage and - the bent glass material or a glass section of the material is classified as discardable if injuries are found or - the roll is classified as a long-term bendable glass material, where the long-term bendable glass material has a crack depth that is less than a specified crack depth, and the specified crack depth is determined by ac=((K1c+R) / (E+d))2 where K 1c the fracture toughness of a glass material, R is the bending radius of a glass material E is the elastic modulus of a glass material d is the thickness of a glass material. [5] Method according to claim 4, characterized by that the injuries, cracks, breaks, fissures, breaks or defects are. [6] Method according to claim 4 or 5, characterized by that the bent glass material or a glass section of the material with a defect mark is classified as discardable. [7] Method according to at least one of claims 4 to 6, characterized by that the glass material comprises the following components in wt.%: SiO2: 40-75 Al2O3 1-25 B2O3: 0-16 Alkaline earth oxides: 0-30 Alkali oxides: 0-20, especially 0-2 [8] Method according to one of claims 4 to 7, characterized by that the glass material comprises at least one coating. [9] Method according to one of claims 4 to 8, characterized by that the glass material includes pretreatment. [10] Method according to one of claims 4 to 9, characterized by that the glass material is formed as a composite material with a polymer film. [11] Method according to one of claims 4 to 10, characterized by that the glass material is rewound at least once from a first glass roll to a second glass roll. [12] Method according to one of claims 4 to 11, characterized bythat the glass is stored at a relative humidity rF in the range 40% rF to 100% rF, preferably 50% rF to 95% rF, in particular 60% rF to 90% rF and / or a temperature of 10° C to 30° C, preferably 15° C to 25° C, in particular 18° C to 23° C. [13] Proof test for a long-term bendable glass material according to one of claims 1 to 3 in the form of a glass material wound on a roll with a bending radius R and a thickness of less than 500 µm and a minimum thickness of 3 µm. wherein the glass material is stored for a storage period of at least 1 day, and after the storage period, a crack depth in the glass ribbon is determined and compared with a predetermined crack depth, characterized by , that the glass material is determined as a long-term bendable glass material, in case the crack depth is less than the specified crack depth, so that the residual fracture probability Φ (σ) = 1- exp{-(L-L0)·(σ / σ0) m) for a storage period of a maximum of half a year, of less than 0.1, where σ0 is the characteristic fracture stress for samples with length L0 and m is the Weilbull modulus determined by destructive testing and L is the length of the sample loaded with a tensile stress σ and the specified crack depth is determined by ac=((K1c+R) / (E+d))2. where K 1c the fracture toughness of a glass material, R is the bending radius of a glass material E is the elastic modulus of a glass material d the thickness of a glass material is. [14] Test according to claim 13, characterized by , that - the fracture toughness K 1c of the glass in the range 0.1 to 1.5 MPa + √m, preferably 0.55 to 0.9 MPa + √m and / or - the elastic modulus of the glass is in the range 40 to 150 GPa, preferably 50 to 100 GPa and / or - the bending radius R in the range 1 mm to 10 7mm, preferably 5 mm to 10 6 mm, particularly preferably 10 to 1000 mm, preferably 20 to 100 mm. [15] Test test according to one of claims 13 to 14, characterized by that the glass material comprises the following components in wt.%: SiO2 40-75 Al2O3 1-25 B2O3 0-30 Alkali oxides 0-20, especially 0-2. [16] Test test according to one of claims 13 to 15, characterized by that the glass material includes pretreatment. [17] Test test according to one of claims 16, characterized by that the pretreatment is a hardening or a chemical hardening.

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