Retardation film, polarizing plate comprising same, and liquid crystal display device comprising same

1. A retardation film comprising a composition or a cured product thereof, the composition comprising:

an acrylate-based resin having a glass transition temperature (Tg) of 120° C. or more;

a retardation adjusting agent comprising a styrene monomer; and

a triazine-based birefringence adjusting agent,

wherein the triazine-based birefringence adjusting agent is present in an amount of more than 5 parts by weight and 15 parts by weight or less, based on 100 parts by weight of the acrylate-based resin.

2. The retardation film of claim 1 , wherein a dichroism value of the triazine-based birefringence adjusting agent in a wavelength region of 200 nm to 400 nm satisfies the following Equation 1:

0.01≤|α e −α 0 |≤0.05  [Equation 1]

in Equation 1,

α e is an extinction coefficient of an extraordinary ray, and

α 0 is an extinction coefficient of an ordinary ray.

3. The retardation film of claim 1 , wherein the acrylate-based resin having a glass transition temperature of 120° C. or more has one or more monomers in an acrylate molecular chain selected from the group consisting of an N-substituted maleimide structure, a lactone ring structure, and a glutarimide structure.

4. The retardation film of claim 1 , wherein the retardation adjusting agent is present in an amount of 15 parts by weight to 80 parts by weight based on 100 parts by weight of the acrylate-based resin.

5. The retardation film of claim 1 , wherein the retardation film satisfies the following Equations 2 and 3:

0.7≤ R in (450)/ R in (550)≤1.0  [Equation 2]

1.0≤ R in (650)/ R in (550)≤1.1  [Equation 3]

in Equations 2 and 3,

R in (450) is a retardation in the in-plane direction at a wavelength of 450 nm and a value of ((n x −n y )×d,

n x is the refractive index of the retardation film surface in the slow axis direction,

n y is the refractive index of the retardation film surface in the fast axis direction, and

d is the thickness of the retardation film.

6. The retardation film of claim 1 , wherein the retardation film satisfies the following Equations 4 and 5:

0 nm≤ R in (550)≤300 nm  [Equation 4]

40 nm≤ R th (550)≤300 nm  [Equation 5]

In Equations 4 and 5,

R in (550) is a retardation in the in-plane direction at a wavelength of 550 nm and a value of (n x −n y )×d,

R th (550) is a retardation in the thickness direction at a wavelength of 550 nm and a value of {n z −(n x +n y )/2}×d,

n x is the refractive index of the retardation film surface in the slow axis direction,

n y is the refractive index of the retardation film surface in the fast axis direction,

n z is the refractive index of the retardation film in the thickness direction, and

d is the thickness of the retardation film.

7. The retardation film of claim 1 , wherein the retardation film has a thickness of 10 μm to 100 μm.

8. The retardation film of claim 1 , wherein the composition has a glass transition temperature of 115° C. or more.

9. The retardation film of claim 1 , wherein the retardation film has the wavelength dispersion property of 0.1 to 1.0.

10. A polarizing plate comprising:

a polarizer; and

the one or more retardation films of claim 1 .

11. The polarizing plate of claim 10 , wherein a polarizer protection film is attached onto one surface of the polarizer, and

the retardation film is attached onto a surface opposite to the surface of the polarizer onto which the polarizer protection film is attached.

12. A liquid crystal display device comprising:

a liquid crystal cell;

an upper polarizing plate provided on an upper part of the liquid crystal cell;

a lower polarizing plate provided on a lower part of the liquid crystal cell; and

a backlight unit provided on a lower part of the lower polarizing plate,

wherein at least one of the upper polarizing plate and the lower polarizing plate comprises: a polarizer; and the retardation film of claim 1 disposed on one surface of the polarizer.

13. The liquid crystal display device of claim 12 , wherein the upper polarizing plate comprises: the polarizer; and the retardation film, and

the retardation film is disposed so as to face the liquid crystal cell.

14. The liquid crystal display device of claim 12 , wherein the lower polarizing plate comprises: the polarizer; and the retardation film, and

the retardation film is disposed so as to face the backlight unit.