ULTRATHIN GLASS WITH HIGH IMPACT RESISTANCE

Abstract

An ultrathin chemically toughened and subsequently etched glass article is provided. The article has a thickness of less than or equal to 0.4 mm and a breakage height (given in mm) of more than 200 multiplied by the thickness (t given in mm)). Further, the article has a breakage bending radius (given in mm) of less than 100000 multiplied by the thickness (t given in mm) and divided by a surface compressive stress (in MPa) measured at a first surface.

Claims

1. A chemically toughened and subsequently etched glass article, comprising: glass having a first surface and a second surface; a thickness (t) of less than 0.4 mm between the first and second surfaces; a compressive stress region extending from the first surface to a first depth of layer (DoL), the compressive stress region having a compressive stress (CS) at the first surface that is at least 100 MPa; a breakage height (given in mm) of at least the thickness (t in mm) multiplied by a height factor of 200; and a breakage bending radius (given in mm) of less than the thickness (t in mm) multiplied by a radius factor of 100,000 and divided by the compressive stress (in MPa) at the first surface, and wherein the breakage height is determined in a pen drop test, wherein, during the pen drop test, the second surface is attached to substrate, wherein the substrate is 100 m thick and consists of a first layer of polyethylene (PE) material that is 50 m thick and second layer of a pressure sensitive adhesive (PSA) material that is 50 m thick layer, wherein the second surface is in contact with the second layer, and wherein, during the pen drop test, the substrate and the glass article are placed on a rigid support with the first surface orientated upwards and impacted until breakage by a 4.5 g pen with a ball-point made from tungsten carbide having a diameter of 300 m.

2. The article of claim 1, wherein the radius factor is 60,000 and/or the height factor is 300.

3. The article of claim 1, wherein the breakage height at B10 (given in mm) has a height factor of 150.

4. The article of claim 1, wherein the thickness selected from a group consisting of less than or equal to 0.33 mm, less than or equal to 0.25 mm, less than or equal to 0.21 mm, less than or equal to 0.18 mm, less than or equal to 0.15 mm, less than or equal to 0.13 mm, less than or equal to 0.1 mm, less than or equal to 0.08 mm, less than or equal to 0.07 mm, less than or equal to 0.05 mm, less than or equal to 0.03 mm, and less than or equal to 0.01 mm.

5. The article of claim 1, wherein the thickness is greater than or equal to 0.005 mm.

6. The article of claim 1, wherein the first surface is an etched surface caused by an etching that removed from the first surface, after toughening, less than or equal to 0.005 mm and/or greater than or equal to 0.0002 mm.

7. The article of claim 6, wherein the pen drop height is greater than 20% after the etching.

8. The article of claim 6, wherein the etching comprising etching with an acidic solution selected from a group consisting of HF, H.sub.2SO.sub.4, HNO.sub.3, HCl, NH.sub.4HF.sub.2, and any combinations thereof or etching with an alkaline solution selected from a group consisting of LiOH, NaOH, KOH, and any combinations thereof.

9. The article of claim 1, further comprising a central tensile stress (CT) selected from a group consisting of more than or equal to 2 MPa, more than or equal to 28 MPa, more than or equal to 43 MPa, more than or equal to 66 MPa, more than or equal to 79 MPa, and more than or equal to 100 MPa.

10. The article of claim 1, further comprising a coating material forming a coating layer on the first surface and/or the second surface.

11. The article of claim 10, wherein the coated layer is on the first surface and has a thickness (t2) of t2(0.3t) and wherein the height factor is 500.

12. The article of claim 10, wherein the coating material is selected from a group consisting of a silicone polymer, a sol-gel polymer, polycarbonate (PC), polyethersulphone, polyacrylate, polyimide (PI), an inorganic silica/polymer hybrid, a cycloolefin copolymer, a polyolefin, a silicone resin, polyethylene (PE), polypropylene, polypropylenepolyvinyl chloride, polystyrene, styrene-acrylonitrile copolymer, thermoplastic polyurethane resin (TPU), polymethyl methacrylate (PMMA), ethylene-vinyl acetate copolymer, polyethylene terephthalate (PET), polybutylene terephthalate, polyamide (PA), polyacetal, polyphenyleneoxide, polyphenylenesulfide, fluorinated polymer, a chlorinated polymer, ethylene-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyethylene naphthalate (PEN), a terpolymer made of tetrafluroethylene, a terpolymer made of hexafluoropropylene, and a terpolymer made of vinylidene fluoride (THV) or polyurethane, duroplastic reaction resin, phenoplasts, phenol formaldehyde resins, aminoplasts, urea formaldehyde resins, melamine formaldehyde resins, epoxide resins, unsaturated polyester resins, vinyl ester resins, phenacrylate resins, diallyl phthalate resins, silicone resins, crosslinking polyurethane resins, polymethacrylate reaction resins, and polyacrylate reaction resins, acrylic resin, acrylic-siloxane hybrid, and epoxy siloxane hybrid.

13. The article of claim 1, further comprising an edge surface between the first surface and/or the second surface and a coating material forming a coating layer on the edge surface.

14. The article of claim 1, further comprising a second compressive stress region extending from the second surface to a second depth of layer (DoL), the second compressive stress region having a compressive stress (CS) at the second surface that is at least 100 MPa.

15. The article of claim 14, the second surface is a second etched surface caused by an etching that removed from the second surface, after toughening, less than or equal to 0.005 mm and/or greater than or equal to 0.0002 mm.

16. The article of claim 14, wherein the compressive stress (CS) at the second surface is selected from a group consisting of more than 200 MPa, more than 300 MPa, more than 400 MPa, more than 500 MPa, more than 600 MPa, more than 700 MPa, and more than 800 MPa.

17. The article of claim 1, wherein the compressive stress (CS) at the first surface is selected from a group consisting of more than 200 MPa, more than 300 MPa, more than 400 MPa, more than 500 MPa, more than 600 MPa, more than 700 MPa, and more than 800 MPa.

18. The article of claim 1, wherein the glass comprises (in wt. %): TABLE-US-00024 SiO.sub.2 40-75 Al.sub.2O.sub.3 10-30 B.sub.2O.sub.3 0-20 Li.sub.2O + Na.sub.2O + K.sub.2O 4-30 MgO + CaO + SrO + BaO + ZnO 0-15 TiO.sub.2 + ZrO.sub.2 0-15 P.sub.2O.sub.5 0-10.

19. The article of claim 1, wherein the glass comprises (in wt. %): TABLE-US-00025 SiO.sub.2 60-85 Al.sub.2O.sub.3 0-10 B.sub.2O.sub.3 5-20 Li.sub.2O + Na.sub.2O + K.sub.2O 2-16 MgO + CaO + SrO + BaO + ZnO 0-15 TiO.sub.2 + ZrO.sub.2 0-5 P.sub.2O.sub.5 0-2.

20. The article of claim 1, wherein the glass comprises (in wt. %): TABLE-US-00026 SiO.sub.2 40-81 Al.sub.2O.sub.3 0-10 B.sub.2O.sub.3 0-5 Li.sub.2O + Na.sub.2O + K.sub.2O 5-30 MgO + CaO + SrO + BaO + ZnO 5-30 TiO.sub.2 + ZrO.sub.2 0-7 P.sub.2O.sub.5 0-2.

21. The article of claim 1, wherein the glass comprises (in wt. %): TABLE-US-00027 SiO.sub.2 55-69 Al.sub.2O.sub.3 15-25 Li.sub.2O 3-7 Na.sub.2O + K.sub.2O 0-30 MgO + CaO + SrO + BaO 0-5 ZnO 0-4 TiO.sub.2 0-5 ZrO.sub.2 0-5 TiO.sub.2 + ZrO.sub.2 + SnO.sub.2 2-6 P.sub.2O.sub.5 0-8 F 0-1 B.sub.2O.sub.3 0-2.

22. The article of claim 1, wherein the glass article is configured for a use selected from a group consisting of a cover film for a resistance screen, an expendable protective film for a display screen, a foldable/flexible phone, a camera, a gaming gadget, a tablet, a laptop, a TV, a mirror, a window, an aviation widows, furniture, a white good, a display substrate, display cover, a fragile sensor, a fingerprint sensor module substrate, a fingerprint sensor module cover, a semiconductor package, a thin film battery substrate, and a foldable display, and a camera lens cover.

23. A method of producing a chemically toughened and subsequently etched glass article, comprising: providing a composition of raw materials for the glass article; melting the composition; producing the glass article in a flat glass process with a first surface and a second surface; chemically toughening the first surface of the glass article; and surface etching first surface of the glass article so that the glass article has a thickness (t) of less than 0.4 mm, a compressive stress region extending from the first surface to a first depth of layer (DoL), the compressive stress region having a compressive stress (CS) at the first surface that is at least 100 MPa, a breakage height (given in mm) of at least the thickness (t in mm) multiplied by a height factor of 200, and a breakage bending radius (given in mm) of less than the thickness (t in mm) multiplied by a radius factor of 100,000 and divided by the compressive stress (in MPa) at the first surface, wherein the breakage height is determined in a pen drop test, wherein, during the pen drop test, the second surface is attached to substrate, wherein the substrate is 100 m thick and consists of a first layer of polyethylene (PE) material that is 50 m thick and second layer of a pressure sensitive adhesive (PSA) material that is 50 m thick layer, wherein the second surface is in contact with the second layer, and wherein, during the pen drop test, the substrate and the glass article are placed on a rigid support with the first surface orientated upwards and impacted until breakage by a 4.5 g pen with a ball-point made from tungsten carbide having a diameter of 300 m.

24. The method of claim 23, further comprising coating at least one surface of the glass article with a coating layer.

25. The method of claim 23, wherein the flat glass process is selected from a group consisting of a down draw process, a redraw process, an overflow fusion process, and chemical slimming process.

26. The method of claim 23, wherein the chemically toughening step comprises immersing the first surface into a salt bath containing monovalent cations comprising potassium ions and/or soda ions.

27. The method of claim 26, wherein the step of immersing in the salt bath comprising immersing at a temperature between 340 C. to 480 C. for 30 seconds to 48 hours.

28. The method according to claim 23, wherein chemical toughening comprises two consecutive toughening steps having a first chemical toughening with a first toughening agent and a second chemical toughening with a second toughening agent.

Description

BREIF DESCRPTION OF THE DRAWINGS

[0139] FIG. 1 shows a simplified schematic illustration of the pen drop test.

[0140] FIG. 2 shows an average pen drop height (breakage height) of comparison examples and inventive working examples of glass different glass types.

[0141] FIG. 3 shows a pen drop height (breakage height) of comparison examples and inventive working examples of different glass types.

DETAILED DESCRIPTIONS

[0142] Table 1 shows the compositions of several typical embodiments (types 1-5) of direct hot-forming ultrathin glasses which are chemically toughenable.

TABLE-US-00016 TABLE 1 Embodiments of direct hot-forming UTG composition of different glass types Composition (wt %) Type 1 Type 2 Type 3 Type 4 Type 5 SiO.sub.2 61 62 64 70 80 Al.sub.2O.sub.3 17 18 4 3 Li.sub.2O 5 Na.sub.2O 12 10 6 10 4 K.sub.2O 4 1 7 8 MgO 4 CaO 1 6 BaO 2.5 ZnO 6 4 ZrO.sub.2 2 3 B.sub.2O.sub.3 1 8 0.1 12 TiO.sub.2 4

[0143] Glass articles 1 of the different glass types were produced in a down draw process and chemically toughened to form ultrathin chemically toughened glass articles. Each ultrathin glass article has a first surface 2 and a second surface 3. In the embodiments shown each sample representing a glass article is toughened on both sides. So, there is a compressive stress region with a certain depth (DoL) on each side of the glass article. All samples were cut out of a larger glass article by using diamond cutting wheel. The samples were tested with surface etching as far as the inventive working examples are concerned.

[0144] The impact resistance of comparison and inventive working examples was tested with the pen drop test which was described in detail above. A simplified illustration of that test is shown in FIG. 1. As can be seen, a glass article 1 is placed with its second surface 3 on a 100 m substrate 4, which consists of a 50 m thick PE-layer 5 and a 50 m thick PSA-layer 6. The substrate 4 with attached glass article 1 is placed on a rigid support 7. The first surface 2 of the glass article 1 is orientated upwards and impacted until breakage by a 4.5 g pen 8 with a ball-point made from tungsten carbide having a diameter of 300 m. Step by step the drop height of the pen is increased until the glass article 1 breaks. The pen drop test is performed on small samples of 20 mm50 mm.

[0145] The breakage bending radius of comparison and inventive working examples was tested with the 2-point bending method as describes above. The bending test is performed on small samples of 20 mm70 mm.

Comparison EmbodimentGlass Types 1-5

[0146] Many samples of glass types 1-5 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.05, 0.07, 0.1 and 0.145 mm were prepared and chemically toughened. After ion-exchange, the toughened samples were cleaned and measured with FSM 6000.

[0147] Thirty (30) toughened samples of each thickness and each DoL were tested and evaluated in respect of impact resistance using the pen drop test as described above. The average breakage height was calculated as described above, and the B10 height was calculated using Weibull method.

[0148] Further, for determining a breakage bending radius 30 toughened samples of each thickness and DoL were tested in the 2-point bending method described above. The average breakage bending radius was calculated as described above.

[0149] Table 2 shows the test results concerning pen drop resistance and bending radius for the comparison examples A to F (average values and calculated B10 values using Weibull method). In FIG. 2 the results of the pen drop test (average breakage height) are given for the comparison examples A to F. A vertical line indicates the spread of the measured values around the corresponding average value (x) in each case. In FIG. 3 the calculated B10 heights are given for the comparison examples A to F.

TABLE-US-00017 TABLE 2 Glass types, toughening conditions and results (comparison examples) A B C D E F Glass Glass Glass Glass Glass Glass Comparison example Type 1 Type 1 Type 2 Type 3 Type 4 Type 5 Thickness (mm) 0.05 0.07 0.07 0.07 0.1 0.145 Toughening Temperature/ C. 390 390 420 400 420 430 condition Time/min or h 20 20 240 90 120 15 h CS/MPa 710 724 674 300 372 97 DoL/m 10.5 11.3 8 10.5 10.6 12 CT/MPa 257 173 100 64 50 10 Pen drop height/mm 13.2 20.1 20.3 19.1 27.4 41.3 B10 for pen drop/mm 9.1 12.3 11.1 10.4 18.2 23.2 Average Breakage Bending <3 <4 <6 <10 <15 <50 radius/mm

Embodiment 1Glass Type 1:

[0150] Many samples of glass type 1 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.05 mm and 0.07 mm were prepared and chemically toughened. Different etching conditions (table 3) are employed (table 3). After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000.

[0151] Thirty (30) toughened samples of each thickness and each DoL were tested and evaluated in respect of impact resistance using the pen drop test as described above. Table 3 shows the average pen drop height (=average breakage height, in the unit mm) that can be applied until the glass sample breaks corresponding to different etching condition. Further the calculated B10 (in mm) are given. FIG. 2 shows the average breakage heights (the results of the pen drop test) of samples having a thickness of 0.05 mm, 0.07 mm. A vertical line indicates the spread of the measured values around the corresponding average value (x) in each case. In FIG. 3 the calculated B10 heights (pen drop test) are given for the inventive working examples 1 to 7.

[0152] Further, for determining an average breakage bending radius 20 toughened samples of each thickness and each DoL were tested in the 2-point bending method described above and evaluated as described above. As the samples are measured as cut (that means without any edge treatment) the bending radii of glass articles having treated edges will be even smaller.

TABLE-US-00018 TABLE 3 Glass type 1, toughening conditions and results Working ex. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Thickness (mm) 0.05 0.05 0.07 0.07 0.07 0.07 0.07 Toughening Temperature/ C. 390 390 390 390 390 390 390 condition Time/min 2 5 10 20 2 5 20 CS/MPa 715 734 710 724 710 DoL/m 3.2 5.3 7.5 11.3 3.2 5.3 11.3 Etching condition 0.2% 0.5% 0.2% 0.5% 1% 1% 3 mol/L NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 + NaOH + 3 7 min 7 min 7 min 7 min 10 min 1% HNO.sub.3 mol/l KOH 1 min 16 h CS after etching/MPa 424 620 604 474 650 DoL after etching/m 1.8 3.3 6.2 9.1 2.2 4.3 10.3 CT/MPa 29 67 106 33 136 Pen drop height/mm 18.7 9.7 40 31 23 43.7 38.7 B10 for pen drop/mm 11.6 6.8 28.3 20.5 13.4 29.4 25.8 Average Breakage <4 <3 <5 <5 <5 <5 <5 Bending radius/mm

[0153] Comparing the inventive working examples (in the following just called examples) 1 to 7 with each other and with the comparison examples A and B the following can be seen:

[0154] Examples of glass type 1 with an etching treatment after chemically toughening predominantly show an increase in the pen drop height compared with comparison examples of the same glass type without etching treatment. The pen drop height can be raised by more than 30% up to more than 100%. E.g. the pen drop height of 0.05 mm thick example 1 is about 40% higher than the pen drop height of comparison example A of the same thickness, and the pen drop height of 0.07 mm thick example 4 is about 55% higher than the pen drop height of comparison example B of the same thickness. Example 6 even show an increase of pen drop height of more than 100%.

[0155] Regarding etched samples of the same glass type the pen drop height that can be reached depends on the applied etching medium. For 0.07 mm thick glass (glass type 1) the best result is achieved using a mixture of NH.sub.4HF.sub.2 and HNO.sub.3 (example 6).

[0156] Further, within the use of one specific etching medium, the resulting pen drop height is dependent on the applied etching conditions (time, temperature, concentration). If the conditions are insufficient, the pen drop height of etched glass will get worse, as can be seen by comparing example 1 with example 2 or by comparing example 3 to 5 with each other. Here, lower concentrations of etching medium seem to lead to better results regarding pen drop height. In the worst case the pen drop height of an etched toughened glass can even be lower than that of an unetched glass (e.g. example 2 in comparison to comparative example A).

[0157] Other aluminosilicate glasses, for example a glass comprising (in wt. %) about: 62% SiO.sub.2, 20% Al.sub.2O.sub.3, 4% B.sub.2O.sub.3, 13% Na.sub.2O, 1% MgO, or a glass comprising (in wt%) about: 56% SiO.sub.2, 24% Al.sub.2O.sub.3, 1% B.sub.2O.sub.3, 3% Li.sub.2O, 10% Na.sub.2O, 1% ZnO, 5% P.sub.2O.sub.5 may show similar results when prepared and tested under corresponding conditions.

Embodiment 2Glass Type 2

[0158] Many samples of glass type 2 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.07 mm were prepared and chemically toughened. Different etching conditions (table 4) are employed. Example 7 was toughened in one step, while examples 8 and 9 are toughened in two steps. After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000.

[0159] Thirty (30) toughened samples of each thickness and each DoL were tested and evaluated in respect of impact resistance using the pen drop test as described above. Table 4 shows the average pen drop height (=average breakage height, in the unit mm) that can be applied until the glass sample breaks corresponding to different etching condition. In addition, the breakage bending radius was measured by the 2-point bending method described above. In each test/experiment a plurality of 30 samples of each thickness and each DoL-type were tested and evaluated as described above. Table 4 shows the sample conditions and results of the experiments.

TABLE-US-00019 TABLE 4 Glass type 2 (0.07 mm), toughening, etching conditions and results Work. ex. Ex. 8 Ex. 9 Ex. 10 Thickness 0.07 0.07 0.07 (mm) Toughening Step 1 420 C. 4 h 380 C. 0.5 h 380 C. 0.5 h condition (100% KNO.sub.3) (45% NaNO.sub.3 + 55% KNO.sub.3) (45% NaNO.sub.3 + 55% KNO.sub.3) Step 2 380 C. 0.5 h 380 C. 0.5 h (20% NaNO.sub.3 + 80% KNO.sub.3) (20% NaNO.sub.3 + 80% KNO.sub.3) CS/MPa Layer 1 674 470 470 Layer 2 43 43 DoL/m Layer 1 7.4 2.9 3.9 Layer 2 14 14 Etching 0.2% HF 1 min 0.2% HF 1 min 0.5% NH.sub.4HF.sub.2 + 0.1% condition/min HNO.sub.3 10 min CS after Layer 1 643 431 etching/MPa Layer 2 43 43 DoL after Layer 1 7.0 2.5 1.9 etching/m Layer 2 14 14 CT/MPa 80 32 Average pen drop 40.1 37.4 18.2 height/mm B10 for pen 29.5 25.8 11.8 drop/mm Average breakage <8 <8 <10 bending radius/mm

[0160] As can be seen from comparing example 8, example 9 and comparison example C the pen drop height can be raised by more than about 80% (example 9) because of the etching treatment. Example 8 has an even higher increase in pen drop height. However, using unsuitable etching conditions the pen drop height can be even lower compared with unetched samples (see example 10 compared to comparison example C).

Embodiment 3Glass Type 3

[0161] Many samples of glass type 3 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.07 mm were prepared and chemically toughened. Different etching conditions (table 5) are employed. After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000. The impact resistance was tested with the pen drop test which was described in detail above. In addition, the breakage bending radius was measured by the 2-point bending method described above. In each test/experiment a plurality of 30 samples of each DoL were tested and evaluated as described. Table 5 shows the sample conditions and results of the experiments.

TABLE-US-00020 TABLE 5 Glass type 3 (0.07 mm), toughening conditions and results Working ex. Ex. 11 Ex. 12 Ex. 13 Thickness (mm) 0.07 0.07 0.07 Toughening Temperature/ C. 400 400 400 condition Time/h 1.5 3 3 CS/MPa 310 301 294 DoL/m 10.2 14.1 14.1 Etching condition/min 0.5% HF 0.5% HF 1% HF 1 min 1 min 2 min CS after etching/MPa 289 287 255 DoL after etching/m 9.7 13.7 12.1 CT/MPa 55 92 67 Average pen drop height/mm 32.4 33.8 27.3 B10 for pen drop/mm 21.2 21.8 18.4 Average breakage bending radius/mm <12 <12 <12

[0162] As can be seen from comparing example 11, example 12, example 13 with comparison example D the pen drop height can be raised by more than about 40% (example 13) and at least 70% (example 11) because of the etching treatment. Example 12 has an even higher increase in pen drop height. By appropriately selecting the etching conditions using the same etching medium the pen drop height can be improved.

Embodiment 4Glass Type 4

[0163] Many samples of glass type 4 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.1 mm were prepared and chemically toughened. Different etching conditions (table 6) are employed. After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000. The impact resistance was tested with the pen drop test which was described in detail above. In addition, the breakage bending radius was measured by the 2-point bending method described above. In each test/experiment a plurality of 20 samples of each DoL were tested and evaluated as described. Table 6 shows the sample conditions and results of the experiments.

TABLE-US-00021 TABLE 6 Glass type 4 (0.1 mm), toughening conditions and results Working ex. Ex. 14 Ex. 15 Ex. 16 Thickness (mm) 0.1 0.1 0.1 Toughening Temperature/ C. 420 420 420 condition Time/h 1 2 4 CS/MPa 389 372 360 DoL/m 7.8 10.6 15.1 Etching condition/min 1% 1% 1% NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 2 min 2 min 6 min CS after etching/MPa 367 352 324 DoL after etching/m 7.1 10 13.4 CT/MPa 30 44 59 Average pen drop height/mm 52.1 58.4 37.2 B10 for pen drop/mm 28.7 36.3 22.6 Average breakage bending radius/mm <20 <20 <20

[0164] As can be seen from comparing example 14, example 15, example 16 with comparison example E the pen drop height can be raised by more than about 35% (example 16) and more than 90% (example 14) because of the etching treatment. Example 15 has an even higher increase in pen drop height (more than 110%). By appropriately selecting the etching conditions using the same etching medium the pen drop height can be improved.

Embodiment 5Glass Type 5

[0165] Many samples of glass type 5 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.145 mm were prepared and chemically toughened. Different etching conditions (table 7) are employed. After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000. The impact resistance was tested with the pen drop test which was described in detail above. In addition, the breakage bending radius was measured by the 2-point bending method described above. In each test/experiment a plurality of 20 samples of each DoL were tested and evaluated as described. Table 7 shows the sample conditions and results of the experiments.

TABLE-US-00022 TABLE 7 Glass type 5 (0.145 mm), toughening conditions and results Working ex. Ex. 17 Ex. 18 Ex. 19 Thickness/mm 0.145 0.145 0.145 Toughening Temperature/ C. 420 430 430 condition Time/h 2 6 15 CS/MPa 118 112 97 DoL/m 4.3 7.7 12 Etching condition/min 1% 2% 5% NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 NH.sub.4HF.sub.2 7 min 7 min 10 min CS after etching/MPa 104 93 88 DoL after etching/m 4.1 7.2 10.5 CT/MPa 3 5 7 Average pen drop height/mm 43 70 65 B10 for pen drop/mm 28 46 42 Average breakage bending radius/mm <70 <60 <50

[0166] As can be seen from comparing example 18, example 19 with comparison example F the pen drop height can be raised by more than about 55% (example 19) and more than 65% (example 18) because of the etching treatment. However, example 17 has a comparatively low increase in pen drop height. This shows that it is necessary to appropriately select the etching conditions using the same etching medium for optimizing pen drop height.

[0167] In general, the strength of the ultrathin chemically toughened and etched glass articles according to the invention which is determined by the pen drop test follows Weibull distribution. B10 values defining the heights when 10% of the samples are broken are given in the figures.

[0168] From embodiments 1 to 5 it can be seen that chemically toughened and subsequently etched ultrathin glass articles of different glass types have an improved impact resistance, overall flexibility and reliability (even without an additional coated/polymeric layer provided on the first surface of the glass article which can get in contact with hard objects) compared to only chemically toughened glass articles.

Embodiment 6Glass Type 1

[0169] Many samples of glass type 1 having a length of 50 mm, a width of 20 mm and such having a length of 70 mm, a width of 20 mm and thicknesses of 0.05 mm and 0.07 mm were cut, chemically toughened and subsequently etched. After ion-exchange and after etching, the samples were cleaned and measured with FSM 6000. Different coated layers (polymer layers and/or hard coating layers) are laminated/coated on the first surface (top coating), (table 8). Some examples were prepared having a coated layer both on the first surface and on the second surface (see example 27) . The different coated layer-types of different thicknesses were applied to the glass articles by different methods:

[0170] The glass article was coated with a liquid polyimide (PI)-material via bar coating method and subsequently solidified for Examples 22, 24, and 28. After coating with PI material on the first surface, a 20 m hard coating layer (epoxy-siloxane hybrid materials) was deposited on top of the PI-material layer using a roller to roller coating method to generate example 28.

[0171] Example 20 was laminated with a polyethylene (PE)-material via a commercial lamination machine.

[0172] Example 21 was laminated with a commercial polyethylene terephthalate (PET)-material via a commercial lamination machine.

[0173] Examples 23 and 25 were laminated with a commercial thermoplastic polyurethane (TPU)-material via a commercial lamination machine.

[0174] Examples 26 and 27 were prepared as follows: A 20 m hard coating layer (epoxy-siloxane hybrid materials) was deposited on the first surface of the glass article using a known roller to roller coating method. In addition, in example 27 another 20 m hard coating layer (epoxy-siloxane hybrid materials) was deposited on the second surface of the glass article using a known roller to roller coating method. Thus example 27 has both top coating and bottom coating.

[0175] Comparison examples G and H (glass type 1) were prepared and measured corresponding to examples 26 and 28, however a subsequent etching step after chemically toughening was not performed.

[0176] Thirty (30) toughened samples of each thickness and coated layer type were tested and evaluated in respect of impact resistance using the pen drop test as described in detail above. The coated first surface was impacted by the pen. For performing the impact test for example 27, the hard coating of the second surface of the glass article was placed on the 100 m thick substrate. Table 7 shows the average pen drop height (=average breakage height, in the unit mm) that can be applied until the glass sample breaks corresponding to different polymer layers and hard coating layers. Further the calculated B10 (in mm) are given.

TABLE-US-00023 TABLE 7 Glass type 1, toughening conditions, different coated layers and results Working ex. Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Thickness (mm) 0.05 0.05 0.05 0.05 0.07 0.07 Toughening Temperature/ C. 390 390 390 390 390 390 condition Time/min 20 20 20 20 20 20 CS/MPa 710 710 710 710 724 724 DoL/m 10.5 10.5 10.5 10.5 11.3 11.3 Etching conditions 1% NH.sub.4HF.sub.2 + 1% HNO.sub.3 1 min CS/MPa 684 684 684 684 698 698 DoL/m 9.8 9.8 9.8 9.8 10.7 10.7 Polymer layer 50 m 60 m 80 m 100 m 50 m 100 m PE PET PI TPU PI TPU Hard Coating Pen drop height/mm 54.3 69.1 78.4 86.1 67.3 99.8 B10 for pen drop/mm 29.1 32.2 44.5 48.1 35.1 55.8 Glass type 1, toughening conditions, different coated layers, results and Comparison examples (G, H) Working ex. Ex. 26 Ex. 27 Ex. 28 G H Thickness (mm) 0.05 0.05 0.07 0.05 0.07 Toughening Temperature/ C. 390 390 390 390 390 condition Time/min 20 20 20 20 20 CS/MPa 710 710 724 710 724 DoL/m 10.5 10.5 11.3 10.5 11.3 Etching conditions 1% NH.sub.4HF.sub.2 + 1% HNO.sub.3 1 mm CS/MPa 684 684 698 DoL/m 9.8 9.8 10.7 Polymer layer 50 m PI 50 m PI Hard Coating 20 m hard 20 m hard 20 m hard 20 m hard 20 m hard coating on coating on coating on coating on coating on the first both the PI layer on the first PI layer on surface first and the first surface the first second surface surface surface Pen drop height/mm 32.1 39.1 74.2 31.4 63.4 B10 for pen drop/mm 22.7 24.8 43.1 18.7 38.5

[0177] As can be seen from comparing the coated examples of embodiment 6 (glass type 1) with examples 1 to 7 (glass type 1) having comparable thicknesses the pen drop height can be raised to a very high extent (at least 50%) by a coated layer. Both polymer layers and hard coating layers improve impact resistance. An additional bottom coating in addition to a top coating can further improve the impact resistance (see examples 26, 27). An additional hard coating layer on top of a polymer top coating can further improve the impact resistance (see examples 28, 24). When comparing comparison example G with working example 26 and comparison example H with working example 28, it can be seen that the etching treatment after chemically toughening improves the impact resistance of the coated ultrathin glass articles. In addition, the coated polymer layer and hard coating layer can protect the glass article from external scratches, which may improve the reliability of the glass cover. A coated layer can also be advantageous for other UTG of other glass types.