CHEMICALLY STRENGTHENED GLASS SHEET AND METHOD FOR ITS PRODUCTION

Abstract

A chemically strengthened glass sheet is provided that has a thickness of at least 3.3 mm and at most 6.0 mm and a composition, in mol% on an oxide basis, comprising the following components: SiO.sub.2 65 to 85 B.sub.2O.sub.3 3 to 13 .Math. (R.sub.2O + RO) 3 to 19, wherein R.sub.2O represents any of Li.sub.2O, Na.sub.2O, and K.sub.2O, and any combination thereof, and wherein RO represents any of MgO, CaO, SrO and BaO, and any combination thereof.

Claims

1. A chemically strengthened glass sheet, comprising: a thickness of at least 3.3 mm and at most 6.0 mm; and a composition, in mol% on an oxide basis, comprising the following components: SiO.sub.2 65 to 85 B.sub.2O.sub.3 3 to 13 .Math. (R.sub.2O + RO) 3 to 19 wherein R.sub.2O represents any of Li.sub.2O, Na.sub.2O, and K.sub.2O, and any combination thereof, and wherein RO represents any of MgO, CaO, SrO and BaO, and any combination thereof.

2. The chemically strengthened glass sheet of claim 1, wherein the glass sheet shows no breakage after two cycles of gravel test according to VW80000 M-02 (ISO 20567-1.

3. The chemically strengthened glass sheet of claim 2, wherein the glass sheet has a size of 136 by 63 mm.sup.2.

4. The chemically strengthened glass sheet of claim 1, wherein the glass sheet has for a size of 136 by 63 mm.sup.2 and passes a ball drop test according to PV 3905 with a drop height of at least 30 cm using a 500 g steel ball with a diameter of 50 mm.

5. The chemically strengthened glass sheet of claim 1, wherein the thickness is at least 3.8 mm and at most 4.5 mm.

6. The chemically strengthened glass sheet of claim 1, further comprising: a sum of components SiO.sub.2, B.sub.2O.sub.3, and Al.sub.2O.sub.3 that is at least 80 and at most 98; and an oxide content of a network modifier, given in mol% on an oxide basis, of at least 3 and at most 19, wherein the network modifier is selected from a group consisting of Li.sub.2O, Na.sub.2O, K.sub.2O, MgO, CaO, SrO, BaO, and any combination thereof.

7. The chemically strengthened glass sheet of claim 6, wherein the sum of components SiO.sub.2, B.sub.2O.sub.3, and Al.sub.2O.sub.3 is at least 90 and at most 91 and/or wherein the oxide content of the network modifier is at most 11.

8. The chemically strengthened glass sheet of claim 1, further comprising a sum of SiO.sub.2 and B.sub.2O.sub.3 that is between at least 72 and at most 95.

9. The chemically strengthened glass sheet of claim 1, wherein the composition comprises, in mol% on an oxide basis: SiO.sub.2 79 to 85 Al.sub.2O.sub.30.5 to 4 B.sub.2O.sub.3 8 to 12 Na.sub.2O2.5 to 5.2 K.sub.2O0.3 to 1.8 MgO 0 to 3 CaO 1.3 to 2.9.

10. The chemically strengthened glass sheet of claim 1, wherein the composition comprises Li.sub.2O in an amount of not more than 500 ppm per weight.

11. The chemically strengthened glass sheet of claim 1, further comprising: a DoL between 8.5 and 13.5 .Math.m; and a compressive stress of 400 MPa or less and at least 140 MPa.

12. The chemically strengthened glass sheet of claim 1, wherein the composition comprises, in mol% on an oxide basis: SiO.sub.2 67 to 71 Al.sub.2O.sub.3 10 to 12 B.sub.2O.sub.3 3 to 5 Li.sub.2O7.5 to 9 Na.sub.2O41.0 to 2.4 K.sub.2O0.1 to 0.3 MgO 0 to 1.2 CaO2.5 to 5 SrO 0 to 0.4.

13. The chemically strengthened glass sheet of claim 1, further comprising: a DoCL between 8.5 and 13.5 .Math.m; and a compressive stress (CS30) of not more than 700 MPa and at least 250 MPa.

14. A method for producing a chemically strengthened glass sheet, comprising: providing a glass sheet; providing a bath comprising a molten alkali salt or a mixture of molten alkali salts; and immersing the glass sheet in the bath for a duration of at least 2 hours to at most 12 hours and at a temperature between at least 400° C. and at most 480° C. so that an ion exchange takes place.

15. The method of claim 14, wherein the temperature is between at least 420° C. and at most 460° C.

16. The method of claim 14, wherein the temperature is 420° C.

17. The method of claim 14, wherein the duration is between at least 2 hours and at most 8 hours.

18. The method of claim 14, wherein the duration is 4 hours.

19. The method of claim 14, wherein the molten alkali salt or the mixture of molten alkali salts comprises a nitrate or is a nitrate.

20. The method of claim 14, wherein the step of immersing consists of a single immersion.

Description

DESCRIPTION OF FIGURES

[0176] The present invention will now be further explained with reference to the following figures. In the figures, like reference numerals refer to the same or corresponding elements.

[0177] FIG. 1 schematically and not drawn to scale a test set up of a ball drop test,

[0178] FIG. 2 schematically and not drawn to scale a glass sheet according to embodiments of the disclosure, and

[0179] FIGS. 3 to 5 show photographs of samples according to the disclosure as well as of a comparative example after gravel testing.

DETAILED DESCRIPTION

[0180] FIG. 1 shows schematically and not drawn to scale glass sheet 1 according to an embodiment in a sectional view, placed onto sample holder 2 for the so-called ball drop test.

[0181] Sample holder 2 has an overall thickness of 10 mm of a phenolic resin. Further, in order to accurately position glass sheet 1 sample holder 2 comprises a step, characterized by a tread 21 with a width of about 10 mm and riser 22 of 3.4 mm.

[0182] Further, sample holder 2 comprises a middle portion step 23 (or depression 23) arranged under a central portion of glass sheet 1. Glass sheet 1 has, in the example depicted in FIG. 1, as size of about 136 by 63 mm.sup.2.

[0183] FIG. 2 shows a perspective view of a schematic and not drawn to scale glass sheet according to embodiments of the disclosure.

[0184] FIG. 3 shows in the upper part to photographs of samples 3 and 4, corresponding to samples of material no. 3. Here, sample 3 is a chemically strengthened sample after gravel testing, whereas sample 4 is a non-strengthened sample. Further, FIG. 3 shows reference surface according to DIN EN ISO 20567-1 for characteristic values of 1.0 (reference numeral 81), of 2.0 (reference numeral 82), of 2.5 (reference numeral 83), and of 3.0 (reference numeral 84), respectively. As can be seen upon comparison with these reference surface 81 to 84, sample 3 has lesser surface damage, resulting in a CV of 1.5, whereas the higher surface damage visible in non-strengthened sample 4 results in CV 2.0 to 2.5.

[0185] FIG. 4 shows in the upper part to photographs of samples 5 and 6, corresponding to samples of material no. 1. Here, sample 5 is again a chemically strengthened sample after gravel testing, whereas sample 6 is a non-strengthened sample. Further, FIG. 4 shows reference surface according to DIN EN ISO 20567-1 for characteristic values of 1.0 (reference numeral 81), of 2.0 (reference numeral 82), of 2.5 (reference numeral 83), and of 3.0 (reference numeral 84), respectively. As can be seen upon comparison with these reference surface 81 to 84, sample 5 has lesser surface damage, resulting in a CV of 1.5, whereas the higher surface damage visible in non-strengthened sample 6 results in CV 2.0 to 2.5.

[0186] Further, FIG. 5 shows a photograph of sample 7 corresponding to the comparative example after gravel testing. This gravel testing results in a higher amount of deteriorated surface area that in samples 3 and 5 according to the disclosure. The corresponding CV is. 3.0.

[0187] Whereas even samples that have not been chemically strengthened (see samples 4 and 6 in FIGS. 3 and 4, respectively) show a lesser degree of surface defects in comparison sample 7, this already good performance can be optimized by strengthening, as can be seen for samples 3 and 5, as explained above.

LIST OF REFERENCE NUMERALS

[0188] 1 Glass sheet [0189] 2 sample holder [0190] 21 step tread 21 [0191] 22 riser 22 [0192] 23 middle portion, depression of sample holder [0193] 3 sample for material no. 3, chemically strengthened [0194] 4 sample for material no. 3, not strengthened [0195] 5 sample for material no. 1, not strengthened [0196] 6 sample for material no. 1, chemically strengthened [0197] 7 comparative example, chemically strengthened [0198] 81 CV example according to DIN EN ISO 20567-1, CV 1.5 [0199] 82 CV example according to DIN EN ISO 20567-1, CV 2.0 [0200] 83 CV example according to DIN EN ISO 20567-1, CV 2.5 [0201] 84 CV example according to DIN EN ISO 20567-1, CV 3.0