Optical film, polarizing plate including the same, and liquid crystal display including the same

1. An optical film comprising:

a protective layer; and

a contrast improving layer;

wherein the contrast improving layer comprises a first resin layer and a second resin layer facing the first resin layer, the second resin layer and the first resin layer being sequentially stacked from the protective layer, wherein the second resin layer has a lower index of refraction than the first resin layer,

the first resin layer has a patterned portion with at least two embossed optical patterns and a flat section between and adjacent to the at least two embossed optical patterns, the patterned portion being in at least some region of the first resin layer facing the second resin layer and satisfying Equation 1,

a corresponding one of the embossed optical patterns having a base angle θ of about 75° to about 90°, and

the second resin layer comprising a metal complex salt dye and/or an organic black dye, the metal complex salt dye comprising a black dye in an absence of the organic black dye:

about 1< P/W ≤about 10,  Equation 1

wherein, in Equation 1, P is a pitch (unit: μm) of the patterned portion, and W is a maximum width (unit: μm) of a corresponding one of the embossed optical patterns, and

wherein the second resin layer has a light transmittance of about 50% to about 92% at a wavelength of 550 nm.

2. The optical film according to claim 1 , wherein the corresponding one of the embossed optical patterns has an aspect ratio (H1/W) of about 0.1 to about 10, wherein H1 is a maximum height (unit: μm) of the corresponding one of the embossed optical patterns.

3. The optical film according to claim 1 , wherein the metal complex salt dye and/or the organic black dye is comprised in an amount of about 0.01 wt % to about 10 wt % in the second resin layer.

4. The optical film according to claim 1 , wherein the metal complex salt dye and/or the organic black dye has an average particle diameter (D50) of about 1 nm to about 30 nm.

5. The optical film according to claim 4 , wherein a ratio of the average particle diameter (D50) of the metal complex salt dye and/or the organic black dye to the maximum width W of the embossed optical pattern, and a ratio of the average particle diameter (D50) of the metal complex salt dye and/or the organic black dye to a width of the flat section are each about 1:300 to about 1:800.

6. The optical film according to claim 1 , wherein the metal complex salt dye comprises a black dye containing chromium (Cr), nickel (Ni), cobalt (Co), or copper (Cu).

7. The optical film according to claim 6 , wherein the metal complex salt dye comprises a black dye containing chromium.

8. The optical film according to claim 1 , wherein the metal complex salt dye comprises an azo-based dye.

9. The optical film according to claim 1 , wherein the metal complex salt dye comprises an azo-based dye having a C 6 to C 20 monocyclic or polycyclic aromatic functional group.

10. The optical film according to claim 1 , wherein the metal complex salt dye comprises an azo-based dye containing chromium and a C 6 to C 20 monocyclic or polycyclic aromatic functional group, has an average particle diameter (D50) of about 1 nm to about 30 nm, and is comprised in an amount of about 0.01 wt % to about 10 wt % in the second resin layer.

11. The optical film according to claim 1 , wherein the organic black dye comprises a first dye having a maximum absorption wavelength of about 430 nm to about 450 nm, a second dye having a maximum absorption wavelength of about 510 nm to about 530 nm, and a third dye having a maximum absorption wavelength of about 590 nm to about 610 nm.

12. The optical film according to claim 11 , wherein each of the first dye, the second dye, and the third dye comprises an azo-based dye.

13. The optical film according to claim 12 , wherein the first dye is represented by Formula 1; the second dye is represented by Formula 2; and the third dye is represented by Formula 3:

14. The optical film according to claim 1 , wherein the first resin layer is adhesive.

15. The optical film according to claim 1 , wherein the embossed optical pattern has a trapezoidal, rectangular, and/or square-shaped cross-sectional shape.

16. A polarizing plate comprising:

a polarizing film; and

the optical film according to claim 1 , the optical film being on a light exit surface of the polarizing film.

17. A liquid crystal display comprising the polarizing plate according to claim 16 .