Flexible display device and method for manufacturing the same

1. A flexible display device having a bending area and a non-bending area, the flexible display device comprising:

a display panel which displays an image on an front surface; and

a window member disposed on the front surface of the display panel,

wherein the window member comprises:

a first glass substrate disposed on the display panel;

a second glass substrate disposed on the first glass substrate; and

a bonding layer disposed between the first glass substrate and the second glass substrate, and the bonding layer attaching the first and second glass substrates to each other,

wherein the bonding layer comprises:

a first bonding part comprising a cured first bonding resin overlapping the bending area, the first bonding part comprising a first modulus; and

a second bonding part comprising a cured second bonding resin overlapping the non-bending area and having a second modulus greater than the first modulus of the first bonding part.

2. The flexible display device of claim 1 , wherein

the modulus of the first bonding part is equal to or greater than 0.1 MPa and equal to or less than 100 MPa, and

the modulus of the second bonding part is greater than 100 MPa and equal to or less than 700 MPa.

3. The flexible display device of claim 1 , wherein the bonding layer includes a polyurethane resin.

4. The flexible display device of claim 1 , wherein the first bonding part has a restoration rate equal to or greater than 70% and equal to or less than 100%.

5. The flexible display device of claim 1 , wherein each of the first glass substrate and the second glass substrate is a tempered glass substrate.

6. The flexible display device of claim 1 , wherein each of the display panel and the window member is bent to have a radius of curvature equal to or greater than 1 mm and equal to or less than 5 mm with respect to a bending axis extending in one direction.

7. The flexible display device of claim 6 , wherein

a width of the first bonding part in the one direction perpendicular to an extension direction of the bending axis satisfies the following inequation: πR≤W≤3×(πR),

wherein R denotes the radius of curvature, and W denotes the width of the first bonding part.

8. The flexible display device of claim 1 , wherein

the display panel and the window member are bent with respect to a bending axis in a first mode and spread in a second mode, and

the window member is disposed closer to the bending axis than the display panel in the first mode.

9. The flexible display device of claim 1 , wherein

the display panel and the window member are bent with respect to a bending axis in a third mode and spread in a fourth mode, and

the display panel is disposed closer to the bending axis than the window member in the third mode.

10. The flexible display device of claim 1 , wherein the first bonding part comprises:

a first sub-bonding portion overlapping the bending area; and

a second sub-bonding portion extending from the first sub-bonding portion and overlapping the non-bending area.

11. The flexible display device of claim 1 , wherein each of the first glass substrate and the second glass substrate has a thickness equal to or greater than 30 μm and equal to or less than 50 μm.

12. The flexible display device of claim 1 , wherein the bonding layer has a thickness equal to or greater than 5 μm and equal to or less than 30 μm.

13. A method for manufacturing a flexible display device, the method comprising:

providing a display panel comprising a bending part and a non-bending part;

providing a window member comprising a first glass substrate, a second glass substrate disposed opposite to the second glass substrate, and a bonding layer disposed between the first glass substrate and the second glass substrate; and

arranging the window member on the display panel,

wherein the providing the window member comprises:

providing a first bonding resin and a second bonding resin directly on the first glass substrate;

arranging the second glass substrate on the first and second bonding resins; and

curing the first and second bonding resins to form the bonding layer between the first glass substrate and the second glass substrate,

wherein:

the first bonding resin is provided in correspondence to the bending part,

the second bonding resin is provided in correspondence to the non-bending part, and

wherein the curing the first bonding resin and the second bonding resin to form the bonding layer comprises:

curing the first bonding resin to form a first bonding part having a first modulus; and

curing the second bonding resin to form the second bonding part having a second modulus greater than the first modulus.

14. The method of claim 13 , wherein each of the first bonding resin and the second bonding resin includes a polyol and a isocyanate, and

the polyol in the first bonding resin has a mean molecular weight less than a mean molecular weight of the polyol in the second bonding resin.

15. The method of claim 14 , wherein the mean molecular weight of the polyol in the first bonding resin is equal to or greater than 500 and equal to or less than 1000.

16. The method of claim 13 , wherein each of the first bonding resin and the second bonding resin provided on the first glass substrate is in a pre-cured film type.

17. The method of claim 13 , wherein the curing the first bonding resin and the second bonding resin to form the bonding layer comprises thermally curing the first bonding resin and the second bonding resin between the first glass substrate and the second glass substrate.

18. The method of claim 13 , wherein

each of the first glass substrate and the second glass substrate is a tempered glass substrate.

19. The method of claim 13 , wherein

the first modulus is equal to or greater than 0.1 MPa and equal to or less than 100 MPa, and

the second modulus is greater than 100 MPa and equal to or less than 700 MPa.

20. The method of claim 13 , further comprising:

bending the display panel and the window member with respect to a bending axis extending in one direction.