Optical film, polarizing plate including the optical film, and liquid crystal display apparatus including the polarizing plate

1. An optical film comprising:

a protective layer; and

a contrast ratio improvement layer comprising 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 a lower surface of the protective layer,

wherein the second resin layer has a refractive index greater than that of the first resin layer,

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

a corresponding one of the embossed optical patterns has a base angle (θ) of about 75° to about 90°,

the first resin layer optionally comprises a metal complex salt dye and/or an organic black dye, and

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

1< P/W≤ 10,  Expression 1

wherein, in Expression 1,

P is a pitch (unit: μm) of the patterned portion, and

W is a maximum width (unit: μm) of the 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 of 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.

3. The optical film of 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 first resin layer.

4. The optical film of 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 100 nm.

5. The optical film of claim 1 , wherein the metal complex salt dye is the black dye, and the metal complex salt dye contains chromium (Cr), nickel (Ni), cobalt (Co), or copper (Cu).

6. The optical film of claim 5 , wherein the black dye contains chromium.

7. The optical film of claim 1 , wherein the metal complex salt dye is a metal azo-based dye.

8. The optical film of claim 1 , wherein the metal complex salt dye is an azo-based dye having a C 6 -C 20 monocyclic or multicyclic aromatic functional group.

9. The optical film of claim 1 , wherein the metal complex salt dye is an azo-based dye containing chromium and having a C 6 -C 20 monocyclic or multicyclic aromatic functional group, has an average particle diameter (D50) of about 1 nm to about 100 nm, and is comprised in an amount of about 0.01 wt % to about 10 wt % with respect to a total weight of the first resin layer.

10. The optical film of claim 1 , wherein the metal complex salt dye is an azo-based dye containing chromium and having a C 6 -C 20 monocyclic or multicyclic aromatic functional group, has an average particle diameter (D50) of about 1 nm to about 100 nm, and is comprised in an amount of about 0.01 wt % to about 10 wt % with respect to a total weight of the second resin layer.

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

13. The optical film of claim 11 , 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 of claim 1 , wherein the first resin layer is adhesive.

15. The optical film according to claim 1 , wherein at least one of the embossed optical patterns has a trapezoidal, a rectangular, or square-shaped cross-sectional shape.

16. The optical film of claim 1 , wherein, when a space between a corresponding one of the embossed optical patterns and an immediately adjacent embossed optical pattern is defined as a first zone in the second resin layer, and

a space between a virtual surface connecting first surfaces, which are top surfaces of the embossed optical patterns spaced apart from each other, and a lower surface of the protective layer is defined as a second zone in the second resin layer,

the metal complex salt dye and/or the organic black dye is comprised in both the first zone and the second zone.

17. The optical film of claim 1 , wherein, when a space between the corresponding one of the embossed optical patterns and an immediately adjacent embossed optical pattern is defined as a first zone in the second resin layer, and

a space between a virtual surface connecting first surfaces, which are top surfaces of the embossed optical patterns spaced apart from each other, and a lower surface of the protective layer is defined as a second zone in the second resin layer,

the metal complex salt dye and/or the organic black dye is comprised in the first zone and not comprised in the second zone.

18. A polarizing plate comprising:

a polarizing film; and

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

19. A liquid crystal display apparatus comprising the polarizing plate of claim 18 .