Impact-damage-resistant glass sheet
Impact-damage-resistant glass sheet comprising at least one chemically etched surface in combination with a tempering surface compression layer, the glass sheet exhibiting a high standardized ball drop failure height and a high flexural modulus of rupture strength, useful to provide damage-resistant glass cover sheets for consumer electronic video display devices, is provided by subjecting thin glass sheet to a combination of a surface tempering treatment and a surface etching treatment that improves strength while maintaining the optical glass sheet properties required for video display applications.
1. An impact-damage-resistant glass sheet comprising at least one tempered and chemically-etched surface free of surface flaws of a depth greater than about 2 μm, said sheet exhibiting a standardized 128 g ball drop failure height of at least 120 cm and said tempered and chemically-etched surface incorporating a surface compression layer having a depth of at least 8 μm and a surface compressive stress level of at least 200 MPa, and at least one tempered and non-chemically-etched surface having a surface compression layer with a depth that is greater than the surface compression layer of the tempered and chemically-etched surface.
2. An impact-damage-resistant glass sheet in accordance with claim 1 wherein the glass sheet is a planar sheet of a uniform thickness not exceeding 2 mm, wherein the tempered and chemically-etched surface is an acid-etched surface, and wherein the surface compression layer of the tempered and chemically-etched surface has a depth of at least 15 μm and a surface compressive stress level of at least 400 MPa.
3. An impact-damage-resistant glass sheet in accordance with claim 2 wherein the glass sheet is composed of an alkali aluminosilicate glass and wherein the surface compression layer of the tempered and chemically-etched surface is an ion-exchanged surface layer having a layer depth of at least about 30 μm and a surface compressive stress level of at least about 500 MPa.
4. An impact-damage-resistant glass sheet in accordance with claim 3 having a thickness not exceeding 1 mm and an ion-exchanged surface layer having a layer depth of at least about 40 μm and a surface compressive stress level of at least about 650 MPa.
5. A video display cover sheet formed of alkali aluminosilicate glass, the sheet having a thickness not exceeding 1 mm, at least one tempered and chemically-etched surface defining a surface compression layer of at least 40 μm thickness, and a peak surface compressive stress level of at least about 650 MPa, wherein the sheet exhibits a standardized 128 g ball drop failure height of at least 120 cm, and the at least one tempered and chemically-etched surface is free of surface flaws of a depth greater than about 2 μm, and at least one tempered and non-chemically-etched surface having a surface compression layer with a depth that is greater than the surface compression layer of the tempered and chemically-etched surface.
6. A cover sheet in accordance with claim 5 having a thickness not exceeding 0.7 mm.
7. A video display device comprising an impact-damage-resistant glass cover sheet, wherein the glass cover sheet has (i) a thickness in the range of 0.2-2 mm, (ii) an alkali aluminosilicate glass composition, (iii) at least one surface compression layer incorporating a tempered and chemically-etched surface free of surface flaws of a depth greater than about 2 μm, and (iv) a standardized 128 g ball drop failure height of at least 120 cm, and at least one tempered and non-chemically-etched surface having a surface compression layer with a depth that is greater than a surface compression layer of the tempered and chemically-etched surface.
8. A display device in accordance with claim 7 wherein the glass cover sheet has a thickness not exceeding 1 mm, wherein the tempered and chemically-etched surface is an acid-etched surface, and wherein the surface compression layer incorporating the acid-etched surface has a depth of at least 30 μm and a surface stress level of at least 500 MPa.
9. An impact-damage-resistant glass sheet in accordance with claim 1 , wherein the depth of the surface compression layer of the tempered and non-chemically-etched surface is greater than the depth of the surface compression layer of the tempered and chemically-etched surface by between about 1 μm and about 2 μm.
10. An impact-damage-resistant glass sheet in accordance with claim 1 , wherein the impact-damage-resistant glass sheet has a bi-axial flexural strength test mean failure load of at least 651 kgf.
11. A cover sheet in accordance with claim 5 , wherein the depth of the surface compression layer of the tempered and non-chemically-etched surface is greater than the depth of the surface compression layer of the tempered and chemically-etched surface by between about 1 μm and about 2 μm.
12. A cover sheet in accordance with claim 5 , wherein the cover sheet has a bi-axial flexural strength test mean failure load of at least 651 kgf.
13. A display device in accordance with claim 7 , wherein the depth of the surface compression layer of the non-chemically-etched surface is greater than the depth of the surface compression layer of the chemically-etched surface by between about 1 μm and about 2 μm.
14. A display device in accordance with claim 7 , wherein the glass cover sheet has a bi-axial flexural strength test mean failure load of at least 651 kgf.