| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol-based film having a uniform degree of crystallization in the surface and thickness direction of the film, excellent in optical uniformity and suitable for a stock roll of a polarizing film, and a method for producing the same. SOLUTION: This polyvinyl alcohol-based film is provided by having 30-70μm thickness, and the refractive index (a) of a film surface without making a contact with a casting drum in its production process, the refractive index (b) of the middle part in its thickness direction of the inside of the film and the refractive index (c) of the film surface making a contact with the casting drum in its production process satisfy the following formulae (1) and (2). The formula (1): ¾a-c¾≤0.02 ---(1), The formula (2): a≤b≤c -------(2), [wherein, (a) and (c) are values measured at positions going into the inside of the film by a film thickness (μm) x 0.1 thickness portion from the surface of the film]. COPYRIGHT: (C)2006,JPO&NCIPI |
