Method for producing polarizer
A method for producing a polarizer ( 20 ) comprises the steps of: (A) stretching a polyvinyl alcohol-based resin layer ( 10 ) to obtain a stretched layer ( 14 ); (B) immersing the stretched layer ( 14 ) in a dyeing liquid ( 23 ) containing iodine to obtain a dyed layer ( 18 ) in which absorbance thereof determined from a tristimulus value Y is from 0.4 to 1.0 (transmittance T=40% to 10%); and (C) removing a part of iodine adsorbed in the dyed layer ( 18 ) so that the absorbance of the dyed layer ( 18 ) decreases by 0.03 to 0.7, provided that the absorbance of the dyed layer ( 18 ) is controlled so that it does not become less than 0.3.
1. A polarizer comprising a stretched layer of polyvinyl alcohol-based resin including iodine adsorbed therein;
wherein said layer of polyvinyl alcohol-based resin has a thickness of 0.4 to 7 μm and includes polymer chains oriented substantially in a given direction being the direction of stretching, said polymer chain including a crystallized portion of polyvinyl alcohol-based resin oriented substantially in said given direction, and said layer of polyvinyl alcohol-based resin surrounding the crystallized portion of said polyvinyl alcohol-based resin is amorphous; and
wherein said iodine adsorbed in said layer of polyvinyl alcohol-based resin is present in said layer of polyvinyl alcohol-based resin in the form of polyiodine ion complex adsorbed to the crystallized portion of said layer of polyvinyl alcohol-based resin, whereby the polarizer exhibits an absorbance in the range of from 0.3 to 0.4 and said polyiodine ion complex adsorbed to the crystallized portion of said layer of polyvinyl alcohol-based resin provides the polarizer with dichrosim within a visible light range.
2. A polarizer in accordance with claim 1 , wherein said polyiodine ion complex is adsorbed to said crystallized portion of said polymer chain in the form of I 3 − or I 5 − .
3. A polarizer in accordance with claim 2 , wherein said polyiodine ion complex is adsorbed to the said crystallized portion of said polymer chain in a relatively large amount.
4. A polarizer in accordance with claim 1 , wherein the said layer of polyvinyl alcohol-based resin has a crystallization degree in the range of from 20 to 50%.
5. A polarizer in accordance with claim 4 , wherein the crystallization degree is in the range of from 32 to 50%.
6. The polarizer in accordance with claim 1 , wherein the said stretched layer has a thickness in the range of from 0.6 to 5 μm.
7. A laminate of the polarizer in accordance with claim 1 and a support layer whereon the resin layer was formed and that has been stretched with the polyvinyl alcohol-based resin layer.