Display device, method of manufacturing window, and method of manufacturing display device

1. A method of manufacturing a window, comprising:

providing a source substrate;

forming a first preliminary substrate by etching the source substrate; and

forming a second preliminary substrate by etching a portion of the first preliminary substrate, wherein

the forming of the second preliminary substrate comprises:

forming an etching paste on the portion of the first preliminary substrate;

radiating heat having an uneven temperature gradient to the etching paste by using a lamp; and

forming a first substantially curved surface, a substantially flat surface extending from the first substantially curved surface, and a second substantially curved surface extending from the substantially flat surface by etching the portion of the first preliminary substrate, wherein

the lamp comprises multiple lamps that provide different temperatures from each other to produce the uneven gradient.

2. The method of claim 1 , wherein a part of the first preliminary substrate, to which heat is radiated by the lamp, has a surface area greater than a surface area of the portion of the first preliminary substrate on which the etching paste is formed.

3. The method of claim 1 , wherein

the lamp comprises:

at least one first lamp;

at least one second lamp; and

at least one third lamp,

the at least one second lamp has a temperature greater than a temperature of each of the at least one first lamp and the at least one third lamp,

the first substantially curved surface is formed by the at least one first lamp,

the substantially flat surface is formed by the at least one second lamp, and

the second substantially curved surface is formed by the at least one third lamp.

4. The method of claim 3 , wherein

the at least one first lamp comprises a plurality of first lamps,

the at least one third lamp comprises a plurality of third lamps, and

each of the plurality of first lamps and the plurality of third lamps has a temperature gradient that gradually decreases in a direction away from the at least one second lamp.

5. The method of claim 3 , wherein

the at least one second lamp comprises a plurality of second lamps, and

the plurality of second lamps each have a same temperature.

6. The method of claim 1 , wherein the forming of the etching paste comprises screen-printing the etching paste on the portion of the first preliminary substrate.

7. A method of manufacturing a display device, comprising:

forming a display panel which includes a first non-folding area, a second non-folding area, and a folding area disposed between the first non-folding area and the second non-folding area, wherein the first non-folding area, the second non-folding area, and the folding area each include pixels;

forming a window which include a folding portion comprising a first substantially curved surface, a substantially flat surface extending from the first substantially curved surface, and a second substantially curved surface extending from the substantially flat surface; and

disposing the window on the display panel such that the folding portion of the window overlaps the folding area of the display panel, wherein

the window includes a top surface and a bottom surface opposing the top surface, the window being disposed on the display panel such that the top surface faces away from the display panel, and

the first substantially curved surface, the substantially flat surface, and the second substantially cured surface are etched in the top surface.

8. The method of claim 7 , wherein the forming of the window comprises:

providing a source substrate;

forming a first preliminary substrate by etching the source substrate; and

forming a second preliminary substrate by etching a portion of the first preliminary substrate, wherein

the forming of the second preliminary substrate comprises:

forming an etching paste on the portion of the first preliminary substrate;

radiating heat to the etching paste by using a lamp; and

forming the first substantially curved surface, the substantially flat surface, and

the second substantially curved surface by etching the portion of the first preliminary substrate.

9. The method of claim 8 , wherein a part of the first preliminary substrate, to which heat is radiated by the lamp, has a surface area greater than a surface area of the portion of the first preliminary substrate, on which the etching paste is formed.

10. The method of claim 8 , wherein

the lamp comprises:

at least one first lamp;

at least one second lamp; and

at least one third lamp, the at least one second lamp has a temperature greater than a temperature of each of the at least one first lamp and the at least one third lamp,

the first substantially curved surface is formed by the at least one first lamp,

the substantially flat surface is formed by the at least one second lamp, and

the second substantially curved surface is formed by the at least one third lamp.

11. The method of claim 10 , wherein

at least one first lamp comprises a plurality of first lamps,

the at least one third lamp comprises a plurality of third lamps, and

each of the plurality of first lamps and the plurality of third lamps has a temperature gradient that gradually decreases in a direction away from the at least one second lamp.

12. The method of claim 7 , wherein

each of the folding area of the display panel and the folding portion of the window is folded and unfolded with respect to a folding axis extending in a first direction,

the first substantially curved surface, the substantially flat surface, and the second substantially curved surface are in sequence in a second direction intersecting the first direction, and

each of a first width of the first substantially curved surface, parallel to the second direction, and a second width of the second substantially curved surface, parallel to the second direction, is greater than a third width of the substantially flat surface, parallel to the second direction.

13. The method of claim 7 , wherein

the window includes a top surface and a bottom surface facing the top surface, and

the top surface of the window comprises the first substantially curved surface, the substantially flat surface, and the second substantially curved surface,

wherein the disposing of the window on the display panel comprises:

aligning the bottom surface of the window between the top surface of the window and the display panel; and

disposing the bottom surface of the window on the display panel.

14. The method of claim 7 , further comprising:

disposing a first adhesive layer on the top surface of the window, the top surface of the window being attached to the first adhesive layer, wherein

the first adhesive layer has a shape substantially corresponding to that of the top surface of the window.

15. The method of claim 14 , further comprising:

disposing a second adhesive layer between the bottom surface of the window and the display panel, wherein

an edge of the second adhesive layer overlaps the window.