OPTICAL FILM, PRODUCTION METHOD OF THE SAME, POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an optical film and a production method of the optical film, which is thin, shows improvement in homogeneity of film thickness, and suppresses fluctuation of retardation in a plane direction associated with an environmental humidity change.SOLUTION: The optical film has a film thickness of 20 to 60 μm and satisfies the following expressions (1) to (3). They are: (1) PV(whole surface)≤0.5 μm; (2) 2.5>PV(MD)/PV(TD)≥0.8; and (3)&Dgr;Re(30-80)<3nm. In the expressions, (PV(whole surface) represents an average in ten locations of a whole PV value that is a difference between the maximum and the minimum in the film thickness at all points within each circular region; PV(MD) represents an average in ten locations of a longitudinal PV value that is a difference between the maximum and the minimum in the film thickness at all points on a diameter in a film conveyance direction within each circular region; PV(TD) represents an average in ten locations of a transverse PV value that is the difference between the maximum and the minimum of the film thickness at all points on a diameter in a direction orthogonal to the film conveyance direction within each circular region; and &Dgr;Re(30-80) represents an absolute value of a difference between Re(30%) at a relative humidity of 30% and Re(80%) at a relative humidity of 80%.