Foldable display device and manufacturing method thereof

1. A foldable display device, comprising:

at least a folding area and a plurality of non-folding areas disposed on and adjoining opposite two sides of the at least a folding area;

a flexible display panel provided in a first pre-folded state, wherein when the flexible display panel is in the first pre-folded state, part of the flexible display panel corresponding to the folding area is under a stress less than or equal to a first predetermined threshold ranging between 8 megapascals (MPa) and 12 MPa, wherein part of the flexible display panel corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle greater than zero degrees and less than 180 degrees with respect to each other.

2. The foldable display device of claim 1 , wherein when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the folding area is under the stress equal to 0 MPa.

3. The foldable display device of claim 1 , wherein when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle greater than or equal to 10 degrees and less than or equal to 170 degrees with respect to each other.

4. The foldable display device of claim 1 , wherein when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle greater than or equal to 60 degrees and less than or equal to 120 degrees with respect to each other.

5. The foldable display device of claim 4 , wherein when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle equal to 90 degrees with respect to each other.

6. The foldable display device of claim 1 , further comprising a functional layer, wherein the functional layer is provided in a second pre-folded state, and when the functional layer is in the second pre-folded state, part of the functional layer corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle greater than zero degrees and less than 180 degrees with respect to each other, wherein the part of the functional layer corresponding to the folding area is under a stress less than or equal to a second predetermined threshold.

7. The foldable display device of claim 6 , wherein the second predetermined threshold ranges between 0.8 MPa and 11 MPa, and the functional layer comprises at least one of a rear cover, a protection cover, a polarizer, a rigid support layer, and a touch layer.

8. The foldable display device of claim 6 , wherein the functional layer is a touch layer, and the touch layer comprises a plurality of first touch units corresponding to position of the folding area, and a plurality of second touch units corresponding to position of the non-folding areas;

wherein when the touch layer is in the second pre-folded state, adjacent two of the first touch units are spaced apart at a distance different from a distance between adjacent two of the second touch units;

wherein when the touch layer is in a fully expanded state, adjacent two of the first touch units are spaced apart at a distance equal to a distance between adjacent two of the second touch units.

9. The foldable display device of claim 1 , wherein when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the folding area has a circular arc shape or an oval arc shape, or when the flexible display panel is in the first pre-folded state, the part of the flexible display panel corresponding to the folding area has a drip-like curve shape, wherein the drip-like curve shape has an inward-bent curved segment and two outward-bent curved segments connected to two ends of the inward-bent curved segment, wherein part of the flexible display panel having the outward-bent curved segments are connected between the part of the flexible display panel corresponding to the non-folding areas and part of the flexible display panel having the inward-bent curved segment.

10. A method of manufacturing a foldable display device, comprising:

providing a jig, the jig comprising a first inclined surface, a second inclined surface, and a curved surface connecting the first inclined surface and the second inclined surface, wherein the first inclined surface and the second inclined surface are disposed at an angle greater than zero degrees and less than 180 degrees with respect to each other;

forming a flexible substrate on the first inclined surface, the second inclined surface, and the curved surface of the jig, such that the flexible substrate is in a pre-folded state;

obtaining, by forming a light-emitting device layer on a surface of the flexible substrate in the pre-folded state away from the jig, a flexible display panel in the pre-folded state; and

forming a functional layer in the pre-folded state on the first inclined surface, the second inclined surface, and the curved surface of the jig;

wherein the flexible display panel in the pre-folded state comprises a bending portion under a stress less than or equal to a first predetermined threshold, and the functional layer in the pre-folded state comprises a bending portion under a stress less than or equal to a second predetermined threshold.

11. The method of manufacturing the foldable display device of claim 10 , further comprising:

placing one of the flexible display panel in the pre-folded state or the functional layer in the pre-folded state on the first inclined surface, the second inclined surface, and the curved surface of the jig;

forming an adhesive layer away from the jig on a surface of the flexible display panel in the pre-folded state or on a surface of the functional layer in the pre-folded state whichever is placed on the jig; and

laminating one of the flexible display panel in the pre-folded state or the functional layer in the pre-folded state whichever is not placed on the jig to the adhesive layer so that the foldable display device is obtained.

12. The method of manufacturing the foldable display device of claim 10 , further comprising:

fully expanding the flexible display panel in the pre-folded state and the functional layer in the pre-folded state, so that the flexible display panel in a fully expanded state and the functional layer in a fully expanded state are obtained;

forming an adhesive layer on a surface of one of the flexible display panel in the fully expanded state or the functional layer in the fully expanded state; and

laminating one of the flexible display panel in the fully expanded state or the functional layer in the fully expanded state whichever is in exclusion of the adhesive layer to the adhesive layer, so that the foldable display device in the fully expanded state is obtained.

13. The method of manufacturing the foldable display device of claim 10 , wherein the functional layer comprises at least one of a rear cover, a protection cover, a polarizer, a rigid support layer, and a touch layer.

14. The method of manufacturing the foldable display device of claim 10 , wherein the first predetermined threshold ranges between 8 MPa and 12 MPa, and the second predetermined threshold ranges between 0.8 MPa and 11 MPa.

15. The method of manufacturing the foldable display device of claim 10 , wherein the angle formed by the first inclined surface and the second inclined surface is equal to 90 degrees, and the bending portion of the flexible display panel in the pre-folded state is under the stress equal to 0 Mpa.

16. A foldable display device, comprising:

at least a folding area and a plurality of non-folding areas disposed on and adjoining opposite two sides of the at least a folding area; and

a flexible display panel provided in a first pre-folded state, wherein when the flexible display panel is in the first pre-folded state, part of the flexible display panel corresponding to the folding area is under a stress less than or equal to a first predetermined threshold, wherein part of the flexible display panel corresponding to the non-folding areas located on the opposite two sides of the folding area is disposed at an angle greater than zero degrees and less than 180 degrees with respect to each other;

wherein the flexible display panel comprises a plurality of first pixels disposed corresponding to position of the folding area, and a plurality of second pixels disposed corresponding to position of the non-folding areas;

wherein when the flexible display panel is in the first pre-folded state, adjacent two of the first pixels are spaced apart at a distance different from a distance between adjacent two of the second pixels, and when the flexible display panel is in a fully expanded state, adjacent two of the first pixels are spaced apart at a distance equal to a distance between adjacent two of the second pixels.

17. The foldable display device of claim 16 , wherein the foldable display device is an inward-folded display device, and when the flexible display panel is in the first pre-folded state, adjacent two of the first pixels are spaced apart at a distance less than a distance between adjacent two of the second pixels.

18. The foldable display device of claim 16 , wherein the foldable display device is an outward-folded display device, and when the flexible display panel is in the first pre-folded state, adjacent two of the first pixels are spaced apart at a distance greater than a distance between adjacent two of the second pixels.