Method for manufacturing polarizing film, polarizing film obtained by the method, and image display apparatus using the polarizing film
The present invention provides a method for manufacturing a polarizing film, by which, even when a wide raw film is used, it is possible to obtain a polarizing film that achieves excellent optical characteristics as well as uniformity in in-plane optical characteristics. The method includes the steps of dyeing a polymer film; stretching the dyed film; and drying the film that has undergone the dyeing and stretching steps while conveying the film with rolls. In the drying step, at least two rolls are used as the rolls and the film is dried under a condition that a ratio (R/W) of a distance (R) between the adjacent rolls to an initial width (W) of the polymer film is not less than 0.5 and not more than 4.0.
1. A method for manufacturing a polarizing film, the method comprising the steps of:
dyeing a polyvinyl alcohol film;
stretching the dyed film with a wet stretching method; and
drying the film that has undergone the dyeing and stretching steps while conveying the film with rolls,
wherein, in the drying step, at least two rolls are used as the rolls and the film is dried under a condition that a ratio (R/W) of a distance (R) between the adjacent rolls to an initial width (W) of the film is not less than 1.0 and not more than 4.0.
2. The method according to claim 1 , wherein, in the drying step, three or more rolls are used as the rolls, and said condition is satisfied where the distance (R) denotes a distance between at least one pair of the adjacent rolls selected from the three or more rolls.
3. The method according to claim 1 , wherein, in the drying step, at least 50% of the film is dried under said condition.
4. The method according to claim 1 , wherein, in the drying step, the film is conveyed with a tensile force being applied to the film.
5. The method according to claim 1 , wherein, in the drying step, the film is conveyed with a tensile force of that causes the film to be stretched about 1.0 to 1.3 times.
6. The method according to claim 1 , wherein the R/W ratio is not less than 1.0 and not more than 3.8.
7. The method according to claim 1 , wherein method manufactures a polarizing film having a standard deviation of less than 0.06 in the width direction.