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|1. (WO2018199139) POLYVINYL ALCOHOL FILM, POLARIZING FILM AND POLARIZING PLATE, AND POLYVINYL ALCOHOL FILM PRODUCTION METHOD|
|Applicants:||THE NIPPON SYNTHETIC CHEMICAL INDUSTRY CO., LTD.
|Title:||POLYVINYL ALCOHOL FILM, POLARIZING FILM AND POLARIZING PLATE, AND POLYVINYL ALCOHOL FILM PRODUCTION METHOD|
A polyvinyl alcohol film which has an excellent balance of swelling properties and stretching properties during polarizing film manufacture, does not result in rupture during thin polarizing film production, and enables obtaining a polarizing film that exhibits high polarization performance and has few color irregularities, a polarizing film and polarizing plate using said polyvinyl alcohol film, and a polyvinyl alcohol film production method are provided. This polyvinyl alcohol film is elongate and 5-60 μm thick, and is characterized by satisfying all of the expressions (A) to (C) below when ΔnMDA is defined as the birefringence in the length direction (MD) of a first surface, ΔnMDB is defined as the birefringence in the length direction (MD) of a second surface, and ΔnMDC is defined as the birefringence of the center portion in the thickness direction. (A)... 1.0 ≤ ΔnMDA / ΔnMDB ≤ 1.5 (B)... ΔnMDB - ΔnMDC ≥ 0.2×10-3 (C)...ΔnMDA≥3.0×10-3