Method for stretching polymer film, polarizing film and method for producing the same, polarizer, birefringenical film and liquid crystal display device

A method for stretching an optical polymer film comprising holding both edges of a continuously supplied polymer film by holding means, and imparting tension thereto while advancing said holding means in a longitudinal direction of the film,

• wherein a locus L1 of the holding means travels from a substantial holding initiation point to a substantial holding release point on one edge of the polymer film, a locus L2 of the holding means travels from a substantial holding initiation point to a substantial holding release point on the other edge of the polymer film, and a distance W exists between the two substantial holding release points,
• wherein |L2−L1| is a longitudinal distance measured when the first of the locus L1 or L2 arrives at its respective substantial holding release point, the distance being from the locus L1 or L2 which has not yet arrived at its respective substantial holding release point, to its respective substantial holding release point,
• and wherein |L2−L1| and W satisfy the following equation (1),
• maintaining the supporting property of the polymer film, stretching the film in the presence of a state in which the volatile content is 5% or more, and then, decreasing the volatile content while shrinking the film:
• |L2−L1|>0.4W (1).