| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method for polarizing film capable of improving durability of the polarizing film by subjecting a polarizing film base body to fixing treatment in a boric acid potassium iodide soln. having a specified liquid compsn. ratio of boric acid concn./potassium iodide concn. SOLUTION: A transparent polyvinylalcohol(PVA) resin film F having 20 to 100μm thickness as a polarizing film substrate is released from a releasing coil 22 to successively travel through a swelling tank 10, dyeing tank 12, stretching tank 14, fixing tank 16, washing tank 18 and drying furnace 20 and wound on a winding coil 24. In the fixing tank 16, polyiodine in the dyed and stretched PVA resin film F is first fixed. The liquid compsn. of the fixing tank 16 is controlled to 10 to 30 ratio of the boric acid concn./potassium iodide (KI) concn. In this case, the KI concn. is controlled to 0.1 to 0.4wt.% to 3wt.% of the boric acid concn. |
