Method for producing polarizing film, and polarizing film

A method for producing a polarizing film, comprising: a dyeing step for dyeing a PVA film with a dichroic dye; a stretching step in which uniaxial stretching is performed in an aqueous solution containing boric acid; and a drying step in which the boric acid concentration of the aqueous solution in the drawing step is 1-3 mass%, the total drawing ratio is 5.5-7.4 times, the total necking rate (A) represented by formula (1) is 57.5-61.0%, the necking rate (B) represented by formula (2) in the drawing step is 31.0-38.0%, and the necking rate (C) represented by formula (3) in the drying step is 9.8-16.5%. (A) = ((X1-X2)/X1) * 100 (1) (B) = {(Y1-Y2)/Y1} * 100 (2) (C) = {(Z1-X2)/Z1} * 100 (3) X1 represents the breadth (m) before the dyeing step; x2 represents the breadth (m) after the drying step; y1 represents the breadth (m) before the stretching step; y2 represents the breadth (m) after the stretching step; and Z1 represents the breadth (m) before the drying step. 偏振膜的制造方法，其包括：利用二色性染料对PVA膜进行染色的染色工序；在包含硼酸的水溶液中进行