Optical film and display device comprising the same

1. An optical film comprising:

a base film including a base and first and second lens pattern portions, which protrude from a surface of the base in a first direction and spaced apart from each other in a second direction orthogonal to the first direction; and

a cover film disposed on the base film,

wherein:

the first lens pattern portion includes a first surface, a first side surface, which extends from one side of the first surface to the surface of the base, and a second side surface, which extends from the other side of the first surface and the surface of the base,

the second lens pattern portion includes a second surface, a third side surface, which extends from one side of the second surface to the surface of the base, and a fourth side surface, which extends from the other side of the second surface and the surface of the base,

an angle between an imaginary line, which is drawn from a point of contact between the second side surface and the first surface and a point of contact between the third side surface and the surface of the base, and the surface of the base is less than about 50 degrees, and

the surface of the base is exposed extending in the second direction between a first point of contact between the second side surface and the surface of the base and a second point of contact between the third side surface and the surface of the base continuously along at least a substantial length defining the surface of the base.

2. The optical film of claim 1 , wherein a refractive index of the base film is lower than a refractive index of the cover film.

3. The optical film of claim 1 , wherein a difference between a refractive index of the cover film and a refractive index of the base film is about 0.03 to about 0.2.

4. The optical film of claim 1 , wherein a distance from a point of contact between the second side surface and the surface of the base to a point of contact between the third side surface and the surface of the base is proportional to a height of the first lens pattern portion and inversely proportional to the angle.

5. The optical film of claim 1 , wherein the cover film comprises first and second engraved pattern portions, which contact the first and second lens pattern portions.

6. The optical film of claim 1 , wherein when the base film has a refractive index of about 1.2 to about 1.6, the cover film has a refractive index of about 1.5 to about 2, and the angle is about 40 degrees or lower.

7. An optical film comprising:

a cover film in which first and second engraved pattern portions are defined and spaced apart from each other,

wherein:

the first engraved pattern portion includes a first surface, a first side surface, which extends from one side of the first surface to a surface of the cover film, and a second side surface, which extends from the other side of the first surface and the surface of the cover film,

the second engraved pattern portion includes a second surface, a third side surface, which extends from one side of the second surface to the surface of the cover film, and a fourth side surface, which extends from the other side of the second surface and the surface of the cover film,

an angle between an imaginary line, which is drawn from a point of contact between the second side surface and the first surface and a point of contact between the third side surface and the surface of the cover film,

the surface of the cover film is less than about 50 degrees, and

the surface of the cover film is exposed extending in a direction parallel to opposing major surface planes defining the cover film between a first point of contact between the second side surface and the surface of the cover film and a second point of contact between the third side surface and the surface of the cover film continuously along at least a substantial length defining the surface of the cover film.

8. The optical film of claim 7 , wherein a refractive index of the cover film is about 1.53 to about 1.57.

9. The optical film of claim 7 , wherein a distance from a point of contact between the second side surface and the surface of the cover film to a point of contact between the third side surface and the surface of the cover film is greater than a value obtained by dividing a height of the first engraved pattern portion by a tangent value of the angle.

10. The optical film of claim 7 , further comprising:

a base film disposed on the surface of the cover film.

11. The optical film of claim 10 , further comprising:

an air layer filling gaps between the base film and the first and second engraved pattern portions.

12. The optical film of claim 11 , wherein a refractive index of the cover film is higher than a refractive index of the air layer.

13. A display device comprising:

a display panel; and

an optical film comprising a base film, including a base and first and second lens pattern portions, which protrude from a surface of the base in a first direction and spaced apart from each other in a second direction orthogonal to the first direction, and a cover film disposed on the base film and having a different refractive index from that of the base film,

wherein:

the first lens pattern portion includes a first surface, a first side surface, which extends from one side of the first surface to the surface of the base, and a second side surface, which extends from the other side of the first surface and the surface of the base,

the second lens pattern portion includes a second surface, a third side surface, which extends from one side of the second surface to the surface of the base, and a fourth side surface, which extends from the other side of the second surface and the surface of the base,

an angle between an imaginary line, which is drawn from a point of contact between the second side surface and the first surface and a point of contact between the third side surface and the surface of the base, and the surface of the base is less than about 50 degrees, and

the surface of the base is exposed extending in the first direction between a first point of contact between the second side surface and the surface of the base and a second point of contact between the third side surface and the surface of the base continuously along at least a substantial length defining the surface of the base.

14. The display device of claim 13 , wherein a distance from a point of contact between the second side surface and a surface of the cover film to a point of contact between the third side surface and the surface of the cover film is proportional to a height of the first lens pattern portion and inversely proportional to the angle.

15. The display device of claim 13 , wherein a distance from a point of contact between the second side surface and the surface of the cover film to a point of contact between the third side surface and the surface of the cover film is greater than a value obtained by dividing a height of the first engraved pattern portion by a tangent value of the angle.

16. The display device of claim 13 , wherein a refractive index of the cover film is higher than a refractive index of the base film.

17. The display device of claim 13 , wherein a refractive index of the cover film is about 1.53 to about 1.57 and a refractive index of the base film is about 1.42 to about 1.5.

18. The display device of claim 13 , wherein when the base film has a refractive index of about 1.2 to about 1.6 and the cover film has a refractive index of about 1.5 to about 2, the angle is about 40 degrees or lower.

19. The display device of claim 13 , wherein the first and second lens pattern portions are polygonal, semicircular, semielliptical in a cross-sectional view.

20. The display device of claim 13 , wherein the first and second lens pattern portions have an aspect ratio of about 0.5 to about 1.6.