Outstandingly durable and heat-resistant polarising element, polarising plate and image-display device, and polarising-element production method

A method of manufacturing a polarizer comprising at least a dyeing process, a cross-linking process, a stretching process, and a washing process;

• the dyeing process being performed by immersing a polyvinyl alcohol based film in an aqueous dyeing solution having an iodine concentration in a range of 0.05 wt. % to 0.2 wt. % (percent by weight), a potassium iodide concentration in a range of 0.2 wt. % to 1.5 wt. %, and a temperature in a range of 20° C. to 40° C. (degrees Celsius) for 150 seconds to 300 seconds;
• the cross-linking process being performed by immersing the polyvinyl alcohol based film in an aqueous cross-linking solution having a boron concentration in a range of 0.36 wt. % to 0.83 wt. %, a potassium iodide concentration in a range of 4 wt. % to 7 wt. %, and a temperature in a range of 15° C. to 60° C. (degrees Celsius) for 30 seconds to 120 seconds;
• at least one kind of zinc salt selected from a group consisting of zinc chloride, zinc iodide, zinc sulfate, zinc nitrate, and zinc acetate being included in at least one of the aqueous dyeing solution, the aqueous cross-linking solution, and a separate aqueous zinc salt processing solution in a concentration of 0.4 wt. % to 7.0 wt. %;
• and
• the washing process being performed by immersing the PVA based film in pure water having a temperature of 25° C. to 30° C. (degrees Celsius) for 10 seconds to 30 seconds.