Patent ID: 8512822

Claim:
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.