Retardation film, method for manufacturing the same, and liquid crystal display device including the same

1. A retardation film for an IPS (in-plane switching) mode liquid crystal display, comprising:

1) an acryl-based film, and

2) a coating layer of a negative C type cellulose-based material that includes a repeating unit of the following Formula 1,

wherein an in-plane retardation value of the entire retardation film that is represented by the following Equation 1 is 50 to 300 nm, a thickness retardation value of the entire retardation film that is represented by the following Equation 2 is 10 to 190 nm, and a N z (R th /R in ) value that is a ratio of the thickness retardation value to the in-plane retardation value is less than 1,

wherein Rs are the same as or different from each other, and each independently selected from —H, —CH 3 , —CH 2 CH(OH)CH 3 , —CH 2 CH 2 OH, and —CH 2 CH 3 , and n is 100 to 300,

R in =( n x − n y )× d   [Equation 1]

R th =( n z − n y )× d   [Equation 2]

n x is the refractive index in the direction in which the refractive index is the highest in the plane of the film,

n y is the refractive index in the vertical direction in respects to n x in the plane of the film,

n z is a thickness refractive index, and

d is a thickness of the film.

2. The retardation film according to claim 1 , wherein 1) the acryl-based film includes an acryl-based polymer.

3. The retardation film according to claim 2 , wherein the acryl-based polymer is an acryl-based copolymer that includes an acryl-based monomer and an aromatic vinyl monomer.

4. The retardation film according to claim 3 , wherein the acryl-based copolymer further includes a maleic anhydride-based or a maleimide-based monomer.

5. The retardation film according to claim 1 , wherein 1) the acryl-based film includes a rubber component.

6. The retardation film according to claim 5 , wherein the rubber component is selected from the group consisting of an acryl rubber, a rubber-acryl-based graft type core-shell polymer, and a mixture thereof.

7. The retardation film according to claim 1 , wherein in 1) the acryl-based film an in-plane retardation value that is represented by Equation 1 is 50 to 300 nm, and a thickness retardation value that is represented by Equation 2 is 50 to 300 nm.

8. The retardation film according to claim 1 , wherein 2) the negative C type material includes methyl cellulose (MC), hydroxy propyl methyl cellulose (HPMC), hydroxyl ethyl methyl cellulose (HEMC), or ethyl cellulose (EC).

9. The retardation film according to claim 1 , wherein in 2) the coating layer of the negative C type material an in-plane retardation value that is represented by Equation 1 is −5 to 5 nm, and a thickness retardation value that is represented by Equation 2 is −20 to −200 nm

10. The retardation film according to claim 1 , wherein the thickness of 2) the coating layer of the negative C type material is more than 0 μm and 50 μm or less.

11. The retardation film according to claim 1 , wherein the thickness of the retardation film for the IPS mode liquid crystal display is 20 to 80 μm.

12. The retardation film according to claim 1 , further comprising a buffer layer between 1) the acryl-based film, and 2) the coating layer of the negative C type material.

13. The retardation film according to claim 12 , wherein the buffer layer includes a compound that is selected from the group consisting of an acrylate polymer, a methacrylate polymer, and an acrylate/methacrylate copolymer.

14. The retardation film according to claim 12 , wherein the thickness of the buffer layer is 0.1 to 5 μm.

15. An IPS (in-plane switching) mode liquid crystal display comprising:

one or more retardation films for an IPS (in-plane switching) mode liquid crystal display according to claim 1 .

16. An integrated polarizing plate for an IPS (in-plane switching) mode liquid crystal display, comprising:

a polarizing film, and

the retardation film according to claim 1 on one side or both sides of the polarizing film as a protective film.

17. An IPS (in-plane switching) mode liquid crystal display comprising:

the integrated polarizing plate for an IPS (in-plane switching) mode liquid crystal display of claim 16 .

18. A method for manufacturing a retardation film for an IPS (in-plane switching) mode liquid crystal display, comprising:

a) preparing an acryl-based film, and

b) coating a negative C type cellulose-based material that includes a repeating unit of the following Formula 1 on at least one side of the acryl-based film,

wherein in the retardation film an in-plane retardation value of the entire retardation film that is represented by the following Equation 1 is 50 to 300 nm, a thickness retardation value of the entire retardation film that is represented by the following Equation 2 is 10 to 190 nm, and a N z (R th /R in ) value that is a ratio of the thickness retardation value to the in-plane retardation value is less than 1,

wherein Rs are the same as or different from each other, and each independently selected from —H, —CH 3 , —CH 2 CH(OH)CH 3 , —CH 2 CH 2 OH, and —CH 2 CH 3 , and n is 100 to 300,

R in =( n x − n y )× d   [Equation 1]

R th =( n z − n y )× d   [Equation 2]

n x is the refractive index in the direction in which the refractive index is highest in the plane of the film,

n y is the refractive index in the vertical direction in respects to n x in the plane of the film,

n z is a thickness refractive index, and

d is a thickness of the film.

19. The method for manufacturing a retardation film according to claim 18 , further comprising, after the step a), forming a buffer layer on at least one side of the acryl-based film.

20. The method for manufacturing a retardation film according to claim 18 , wherein 2) the negative C type material includes methyl cellulose (MC), hydroxy propyl methyl cellulose (HPMC), hydroxyl ethyl methyl cellulose (HEMC), or ethyl cellulose (EC).