Optical film and method of manufacturing the same and display device including the same

1. An optical film comprising:

a polarizer; and

a protection film disposed on the polarizer and comprising a polymer having a glass transition temperature of greater than about 100° C.,

wherein the polymer is a terpolymer consisting of:

a first structural unit derived from styrene or a styrene derivative;

a second structural unit derived from maleimide, maleic anhydride, acrylonitrile, a derivative thereof or a combination thereof; and

a third structural unit derived from (meth)acrylate or a derivative thereof,

wherein refractive indices of the protection film satisfies the following inequations:

n z1 >n x1 =n y1 ,

wherein

n x1 denotes a refractive index at a slow axis of the protection film,

n y1 denotes a refractive index at a fast axis of the protection film, and

n z1 denotes a refractive index in a direction perpendicular to the slow axis and the fast axis of the protection film,

wherein retardations of the protection film satisfies the following inequations:

−60 nm≤ R o1 (550 nm)≤60 nm; and −200 nm ≤R th1 (550 nm)<−10 nm,

wherein

R o1 (550 nm) denotes an in-plane retardation of the protection film at 550 nanometers wavelength, and

R th1 (550 nm) denotes a thickness direction retardation of the protection film at 550 nanometers wavelength.

2. The optical film of claim 1 , wherein refractive indices of the protection film satisfies the following inequation:

n y1 >n x1 =n z1 ,

wherein

n x1 denotes a refractive index at a slow axis of the protection film,

n y1 denotes a refractive index at a fast axis of the protection film, and

n z1 denotes a refractive index in a direction perpendicular to the slow axis and the fast axis of the protection film.

3. The optical film of claim 2 , wherein retardations of the protection film satisfies the following inequations:

110 nm≤ R o1 (550 nm)≤300 nm; and −300 nm≤ R th1 (550 nm)≤0 nm,

wherein

R o1 (550 nm) denotes an in-plane retardation of the protection film at 550 nanometers wavelength, and

R th1 (550 nm) denotes a thickness direction retardation of the protection film at 550 nanometers wavelength.

4. The optical film of claim 1 , wherein the first structural unit is derived from styrene, a substituted or unsubstituted alkyl styrene, a substituted or unsubstituted aryl styrene, halogen styrene, a substituted or unsubstituted alkoxy styrene, a substituted or unsubstituted nitro styrene, a substituted or unsubstituted amino styrene, a substituted or unsubstituted carboxyl styrene, or a combination thereof.

5. The optical film of claim 1 , wherein the first structural unit, the second structural unit, and the third structural unit are included in an amount of about 10 mol % to about 50 mol %, about 10 mol % to about 40 mol %, and about 10 mol % to about 80 mol % based on the terpolymer, respectively.

6. The optical film of claim 1 , wherein the glass transition temperature of the polymer is in a range of about 110° C. to about 150° C.

7. The optical film of claim 1 , wherein the protection film is about 1.1 times to about 5.0 times elongated.

8. The optical film of claim 7 , wherein the protection film is biaxially elongated.

9. The optical film of claim 1 , wherein the protection film has a thickness ranging from about 5 micrometer to about 30 micrometer.

10. The optical film of claim 1 , wherein the polarizer and the protection film are bonded to each other.

11. The optical film of claim 1 , further comprising:

a compensation film disposed on the protection film,

wherein the compensation film is a λ/4 retardation film or a λ/2 retardation film.

12. The optical film of claim 11 , wherein refractive indices of the compensation film satisfies the following inequation:

n x2 >n y2 ; and n x2 >n z2 ,

wherein

n x2 denotes a refractive index at a slow axis of the compensation film,

n y2 denotes a refractive index at a fast axis of the compensation film, and

n z2 denotes a refractive index in a direction perpendicular to the slow axis and the fast axis of the compensation film.

13. A display device comprising

a display panel, and

the optical film of claim 1 .

14. A method of forming an optical film, the method comprising

preparing a polarizer,

melt-extruding a polymer having a glass transition temperature of greater than 100° C. and elongating the melt-extruded polymer to prepare a protection film, and

the protection film disposed on the polarizer,

wherein the polymer is a terpolymer consisting of:

a first structural unit derived from styrene or a styrene derivative;

a second structural unit derived from maleimide, maleic anhydride, acrylonitrile, a derivative thereof or a combination thereof; and

a third structural unit derived from (meth)acrylate or a derivative thereof,

wherein refractive indices of the protection film satisfies the following inequations:

n z1 >n x1 =n y1 ,

wherein

n x1 denotes a refractive index at a slow axis of the protection film,

ny y1 denotes a refractive index at a fast axis of the protection film, and

n z1 denotes a refractive index in a direction perpendicular to the slow axis and the fast axis of the protection film,

wherein retardations of the protection film satisfies the following inequations:

−60 nm≤ R o1 (550 nm)≤60 nm; and −200 nm≤ R th1 (550 nm)<−10 nm,

wherein

R o1 (550 nm) denotes an in-plane retardation of the protection film at 550 nanometers wavelength, and

R th1 (550 nm) denotes a thickness direction retardation of the protection film at 550 nanometers wavelength.

15. The method of claim 14 , wherein

the melt-extruding the polymer is performed at a temperature in a range of about 200° C. to about 350° C., and

the elongation of the polymer is performed at a temperature in a range of a glass transition temperature of the polymer ±30° C.

16. An optical film comprising:

a polarizer; and

a protection film disposed on the polarizer and comprising a polymer having a glass transition temperature of greater than about 100° C.,

wherein the polymer is a terpolymer consisting of:

a first structural unit derived from styrene or a styrene derivative;

a second structural unit derived from maleimide, maleic anhydride, acrylonitrile, a derivative thereof or a combination thereof; and

a third structural unit derived from (meth)acrylate or a derivative thereof,

wherein refractive indices of the protection film satisfies the following inequation:

n z1 >n x1 =n y1 ,

wherein

n x1 denotes a refractive index at a slow axis of the protection film,

n y1 denotes a refractive index at a fast axis of the protection film, and

n z1 denotes a refractive index in a direction perpendicular to the slow axis and the fast axis of the protection film.