Window panel, electronic apparatus including same, and method for manufacturing window panel

1. A window panel comprising:

a substrate having a thickness of less than 100 μm and including a first surface and a second surface facing each other in a thickness direction;

first ions dispersed in the substrate and each having a first ion radius; and

second ions dispersed in the substrate and each having a second ion radius which is greater than the first ion radius, wherein

the second ions generate a compressive stress,

the compressive stress is reduced with depth from the first surface or the second surface within a range from the first surface or the second surface to a ½ point of the thickness,

a depth of compression satisfies:

0.15 T ≤DOC≤0.3 T,

where T is the thickness of the substrate, and DOC is the depth of compression defined as a depth at which the compressive stress becomes 0 (zero),

wherein a slope of a rate of change of the compressive stress changes at a transition point between the first surface and the DOC,

a depth of layer which is defined as a maximum depth in which the second ions are spaced from the first surface or the second surface is 0.3 T or greater, and

a tensile stress increases continuously from the depth of compression to the ½ point of the thickness.

2. The window panel of claim 1 , wherein the depth of layer is 0.5 T or greater.

3. The window panel of claim 2 , wherein a surface compressive stress at each of the first surface and the second surface is 200 MPa or greater.

4. The window panel of claim 1 , wherein a surface compressive stress is 100 MPa or greater.

5. The window panel of claim 1 , wherein a surface compressive stress at each of the first surface and the second surface is 500 MPa or greater.

6. The window panel of claim 5 , wherein the transition point is 0.2 T away from the first surface or less.

7. The window panel of claim 1 , wherein the second ions contain alkali metal ions.

8. The window panel of claim 1 , wherein the substrate is foldable about a folding axis extending along a direction intersecting the thickness direction.

9. An electronic apparatus comprising:

a display panel configured to display an image on a front surface thereof; and

a window panel on the front surface of the display panel, the window panel including a first surface and a second surface which is opposite to the first surface in a thickness direction and faces the display panel, wherein

the window panel and the display panel are foldable about a folding axis extending along a direction intersecting the thickness direction,

internal stress of the window panel has a stress behavior which varies according to a depth from each of the first surface and the second surface to a ½ point of a thickness of the window panel,

the stress behavior includes a surface compressive stress, a depth of compression, a depth of layer which is defined as a maximum depth in which second ions are spaced from the first surface or the second surface, and a center tensile stress, and

the depth of compression satisfies:

0.15 T ≤DOC≤0.3 T,

where T is the thickness of the window panel, and DOC is the depth of compression defined as a depth at which a compressive stress becomes 0 (zero),

wherein a slope of a rate of change of the compressive stress changes at a transition point between the first surface and the DOC,

the depth of layer is 0.3 T or greater, and

a tensile stress increases continuously from the depth of compression to the ½ point of the thickness.

10. The electronic apparatus of claim 9 , wherein the stress behavior changes in a depth range not less than the depth of compression.

11. The electronic apparatus of claim 10 , wherein the depth of layer is 0.5 T or greater, and the surface compressive stress at each of the first surface and the second surface is 200 MPa or greater.

12. The electronic apparatus of claim 9 , wherein the surface compressive stress is 500 MPa or greater.

13. The electronic apparatus of claim 12 , wherein an initial transition point at which a slope of the stress behavior changes is less than 0.2 T.

14. A method for manufacturing a window panel, comprising:

providing an initial window panel including a first ion; and

reinforcing the initial window panel by impregnating the initial window panel with a metal salt including a second ion having a greater radius than the first ion such that a window panel is formed, wherein

a thickness of the window panel is less than 100 μm, and

a depth of compression of the window panel satisfies:

0.15 T ≤DOC≤0.3 T,

where T is the thickness of the window panel, and DOC is the depth of compression defined as a depth at which a compressive stress becomes 0 (zero),

wherein a slope of a rate of change of the compressive stress changes at a transition point between a first surface of the window panel and the DOC,

in the reinforcing the initial window panel, a depth of layer of the second ion is designed to be 0.3 T or greater, and

a tensile stress increases continuously from the depth of compression to a ½ point of the thickness.

15. The method of claim 14 , wherein the metal salt comprises a single salt and the metal salt comprises an alkali nitrate salt, and

in the reinforcing the initial window panel, the depth of layer of the second ion is 0.5 T or greater.

16. The method of claim 14 , wherein the metal salt comprises a mixed salt and the metal salt comprises at least two different alkali nitrate salts.

17. The method of claim 14 , wherein reinforcing the initial window panel further comprises:

immersing the initial window panel in a mixed salt, and

immersing the initial window panel in a single salt, wherein

the depth of compression of the window panel is less than 0.2 T.

18. The method of claim 17 , wherein in the immersing of the initial window panel in the mixed salt, the depth of layer of the second ion is 0.3 T or greater.

19. The method of claim 17 , wherein a surface compressive stress of the window panel is 500 MPa or greater.