Polyimide-based composite film and display device comprising same

1. A polyimide-based composite film, which comprises a base film comprising a polyimide-based resin; and a functional layer disposed on the base film,

wherein when the side of the functional layer located opposite to the side in contact with the base film is referred to as a first side and when the side of the base film in contact with the functional layer is referred to as a second side, the leveling index represented by the following Equation 1 is 0.11 to 0.7:

Leveling

⁢

⁢

index

=

Sz

⁢

⁢

2

-

Sz

⁢

⁢

1

Sz

⁢

⁢

2

+

Sz

⁢

⁢

1

[

Equation

⁢

⁢

1

]

wherein Sz1 is the Sz roughness (μm) of the first side, and Sz2 is the Sz roughness (μm) of the second side,

wherein the functional layer comprises an organic resin, and the organic resin is at least one selected from the group consisting of an acrylate-based monomer, a urethane acrylate-based oligomer, and an epoxy acrylate-based oligomer,

wherein the base film further comprises a filler, and the filler has a particle diameter of 0.05 μm to 0.9 μm, and

wherein the functional layer further comprises an inorganic filler, and the inorganic filler has a particle diameter of 1 nm to 100 nm.

2. The polyimide-based composite film of claim 1 , wherein the Sz2 is 0.01 μm to 5 μm, and Sz1 is 0.01 μm to 4 μm.

3. The polyimide-based composite film of claim 1 , wherein the Sz2 is 0.05 μm to 4 μm, and Sz1 is 0.05 μm to 3 μm.

4. The polyimide-based composite film of claim 1 , wherein the Sz2 is 0.1 μm to 4 μm, and Sz1 is 0.1 μm to 3 μm.

5. The polyimide-based composite film of claim 1 , wherein the leveling index is 0.11 to less than 0.65.

6. The polyimide-based composite film of claim 1 , wherein the filler is at least one selected from the group consisting of barium sulfate, silica, and calcium carbonate.

7. The polyimide-based composite film of claim 1 , wherein the functional layer has a thickness of 2 μm to 10 μm, and the FT represented by the following Equation 2 is less than 0.7:

FT

=

Sz

⁢

⁢

2

Th

[

Equation

⁢

⁢

2

]

wherein Th is the thickness (μm) of the functional layer.

8. The polyimide-based composite film of claim 7 , wherein the FT is 0.14 to 0.6.

9. The polyimide-based composite film of claim 1 , wherein the surface polarity index (SP) represented by the following Equation 3 is 1/40 or more:

SP

=



A

⁢

⁢

1

-

A

⁢

⁢

2



A

⁢

⁢

1

+

A

⁢

⁢

2

[

Equation

⁢

⁢

3

]

wherein A1 is the contact angle of the first side, and A2 is the contact angle of the second side.

10. The polyimide-based composite film of claim 1 , wherein the functional layer has an elongation of 2% or more.

11. The polyimide-based composite film of claim 1 , which a haze of 3% or less, a yellow index of 5 or less, a modulus of 5 GPa or more, and a transmittance of 80% or more.

12. A display device, which comprises a display panel; and a cover window disposed on the display panel,

wherein the cover window comprises a base film; and a functional layer disposed on the base film, and when the side of the functional layer located opposite to the side in contact with the base film is referred to as a first side and when the side of the base film in contact with the functional layer is referred to as a second side, the leveling index represented by the above Equation 1 is 0.11 to 0.7:

Leveling

⁢

⁢

index

=

Sz

⁢

⁢

2

-

Sz

⁢

⁢

1

Sz

⁢

⁢

2

+

Sz

⁢

⁢

1

[

Equation

⁢

⁢

1

]

wherein Sz1 is the Sz roughness (μm) of the first side, and Sz2 is the Sz roughness (μm) of the second side,

wherein the base film further comprises a filler, and the filler has a particle diameter of 0.05 μm to 0.9 μm, and

wherein the functional layer further comprises an inorganic filler, and the inorganic filler has a particle diameter of 1 nm to 100 nm.