POLYVINYL-ALCOHOL-BASED FILM, METHOD FOR MANUFACTURING SAME, POLARIZING FILM, AND POLARIZING PLATE

摘要

The present invention is a polyvinyl-alcohol-based film obtained by forming a film of a film-forming material containing a polyvinyl-alcohol-based resin (A), the polyvinyl-alcohol-based film satisfying expression (1), where Xa is the true stress when the polyvinyl-alcohol-based film is immersed for 0.5 minutes at 56°C in a 5 wt% aqueous solution of boric acid (initial state), then drawn by a factor of 2.5 from the initial state at a drawing speed of 70 mm/sec in the aqueous solution of boric acid, and Xc is the true stress when the polyvinyl-alcohol-based film is subsequently drawn by a factor of 4.3 from the initial state in the aqueous solution of boric acid while drawing is continued. A polarizing film having excellent optical characteristics can therefore be obtained without increasing the draw ratio, the drawing time can thereby be reduced relative to the prior art, effects such as enhanced productivity are obtained, and effects such as reduced load on a drawing device due to increased film tension from high drawing, or reduced breakage due to high drawing are obtained. (1): 5.0 ≤ Xc/Xa ≤ 9.0