Polarizing film and method for producing polarizing film
Provided is a polarizing film that is excellent in external appearance and can contribute to improving the display characteristics of an image display apparatus. A polarizing film of the present invention includes a polyvinyl alcohol-based resin film containing iodine. At least one surface side of the polyvinyl alcohol-based resin film includes a low-iodine layer.
1. A polarizing film, comprising a polyvinyl alcohol-based resin film dyed substantially with only iodine,
wherein at least one surface side of the polyvinyl alcohol-based resin film comprises a low content iodine layer.
2. The polarizing film according to claim 1 , wherein the polyvinyl alcohol-based resin film has a thickness of 7 μm or less.
3. The polarizing film according to claim 1 , wherein a surface of the polyvinyl alcohol-based resin film on the low content iodine layer side has an anisotropic reflection determined from the following equation (1) at a wavelength of 680 nm of 1.50 or less:
anisotropic reflection= Rc/Rp (1)
where:
Rp represents a reflectance in the transmission axis direction of the polarizing film, and
Rc represents a reflectance in the absorption axis direction of the polarizing film.
4. A manufacturing method for the polarizing film of claim 1 , the manufacturing method comprising bringing a treatment liquid containing a water-soluble antioxidant into contact with at least a surface of a polyvinyl alcohol-based resin membrane dyed with the iodine.
5. The manufacturing method according to claim 4 , wherein the water-soluble antioxidant contains at least any one kind of ascorbic acid, thiosulfuric acid, and salts thereof.
6. The manufacturing method according to claim 4 , wherein the treatment liquid has an absorbance of light having a wavelength of 350 nm of substantially zero.
7. The manufacturing method according to claim 4 , wherein the polyvinyl alcohol-based resin membrane comprises a polyvinyl alcohol-based resin layer formed on a resin substrate.
8. An image display apparatus, comprising the polarizing film of claim 1 ,
wherein the polarizing film is arranged so that a surface on the low content iodine layer side of the polarizing film is on a viewer side.
9. A manufacturing method for a polarizing film comprising a polyvinyl alcohol-based resin film dyed substantially with only iodine, wherein at least one surface side of the polyvinyl alcohol-based resin film comprises a low content iodine layer, the manufacturing method comprising:
bringing a treatment liquid containing a water-soluble antioxidant into contact with at least a surface of a polyvinyl alcohol-based resin membrane dyed with the iodine;
subjecting the polyvinyl alcohol-based resin membrane to underwater stretching,
wherein the treatment with the water-soluble antioxidant is performed after the underwater stretching.
10. A manufacturing method for a polarizing film comprising a polyvinyl alcohol-based resin film dyed substantially with only iodine, wherein at least one surface side of the polyvinyl alcohol-based resin film comprises a low content iodine layer, the manufacturing method comprising:
bringing a treatment liquid containing a water-soluble antioxidant into contact with at least a surface of a polyvinyl alcohol-based resin membrane dyed with the iodine;
stretching the polyvinyl alcohol-based resin membrane by adopting only an in-air stretching mode,
wherein the treatment liquid has a temperature of 50° C. or more.