Ultrathin glass ceramic article and method for producing an ultrathin glass ceramic article
An ultrathin glass-ceramic article is provided having an article thickness (t) of equal to or less than 0.3 mm and an outer surface followed towards the inside of the article by an outer layer and a central part. The glass-ceramic has a crystal phase and an amorphous phase and the outer layer includes the crystal phase. The article has a gradient structure or a layered structure.
1. An ultrathin glass-ceramic article, comprising:
a crystal phase and an amorphous phase;
a thickness t of the article that is equal to or less than 0.3 mm;
a first outer surface of the article;
a central portion of the article;
a first outer portion adjacent to the first outer surface and the central portion, the first outer portion having a thickness t 1 in a range of 5 to 40 μm;
a gradient structure in the first outer portion,
wherein the gradient structure is such that a crystal volume fraction decreases along the gradient structure from the first outer surface towards the central portion;
a ratio t 1 /t that is greater than 0.007; and
a coefficient of thermal expansion (CTE) difference between the first outer portion and the central portion,
wherein the first outer portion has a CTE that is less than 13*10 −6 in a temperature interval of 20° C. to 300° C.
2. The article of claim 1 , wherein the crystal phase has a crystal volume fraction in the first outer portion that is in a range of 0.1 to 99 vol. %.
3. The article of claim 1 , further comprising a glassy zone in which there are no crystals in the central portion.
4. The article of claim 1 , further comprising a second outer surface and a second outer portion, the second outer surface being opposite to the first outer surface and the second outer portion being adjacent to the second outer surface and the central portion.
5. The article of claim 1 , further comprising chemical toughening ions exchanged via an ion exchange process.
6. The article of claim 5 , further comprising a compressive stress region extending from the first outer surface towards the central portion to a depth, wherein the compressive stress region has a surface compressive stress at the first outer surface of at least 100 MPa.
7. The article of claim 6 , wherein the depth is greater than 0.01*t, wherein t is in microns.
8. The article of claim 5 , further comprising a pen drop breakage height that is higher than t 2 /800 mm, wherein t is in microns.
9. The article of claim 5 , further comprising a ball drop breakage height that is higher than (t 2 /600)*mm, using a 20 g steel ball, wherein t is in microns.
10. The article of claim 5 , further comprising a bending radius that is less than 900*t mm, wherein t is in millimeters.
11. The article of claim 1 , wherein the article comprises a glass system selected from a group consisting of: a lithium-aluminate-silicate (LAS), magnesium-alum inate-silicate (MAS), zinc-aluminate-silicate (ZAS), sodium-aluminate-silicate (NAS), and lithium-disilicate (LDS).
12. The article of claim 1 , further comprising a compressive stress on the first outer portion that extends into the central portion due to the CTE difference.
13. The article of claim 1 , wherein the central portion has a CTE that is greater than 1*10 −6 in the temperature interval of 20° C. to 300° C.
14. The article of claim 1 , wherein the crystal volume fraction in the gradient structure varies by 3% per μm.
15. The article of claim 1 , further comprising a ratio t 1 /t that is greater than 0.01.
16. The article of claim 1 , further comprising a ratio t 1 /t that is greater than 0.02.
17. The article of claim 1 , wherein the first outer portion has a thickness t 1 in a range of 5 to 20 μm.
18. The article of claim 1 , further comprising a ratio t 1 /t that is greater than 0.02.