Polarizer, method of manufacturing the same, polarizing plate, optical film, and image display

Abstract

A polarizer of the invention comprises a polyvinyl alcohol-based film which is at least dyed with at least iodine and uniaxially stretched, having a single transmittance of 43% or more, a polarizing efficiency of 99.9% or more, and a dichroic ratio of 30 or more, wherein the dichroic ratio is calculated from a parallel transmittance (Tp) and a crossed transmittance (Tc) at a wavelength of 440 nm, and have good hue.

1 . A polarizer, comprising a polyvinyl alcohol-based film which is at least dyed with at least iodine and uniaxially stretched, having
 a single transmittance of 43% or more, a polarizing efficiency of 99.9% or more, and   a dichroic ratio of 30 or more, wherein the dichroic ratio is calculated from a parallel transmittance (Tp) and a crossed transmittance (Tc) at a wavelength of 440 nm according to the following formula:
   dichroic ratio={log 10 (1 /k   2 )}/{log 10 (1 /k   1 )}, where 
     k   1 =½·√{square root over ( )}2×[( Tp+Tc ) 1/2 +( Tp−Tc ) 1/2   ] and    
     k   2 =½·√{square root over ( )}2×[( Tp+Tc ) 1/2 −( Tp−Tc ) 1/2 ] 
   
       and a potassium content is of 0.2 to 0.6% by weight. 
     
     
         2 . The polarizer according to  claim 1 , wherein an iodine content is of 1.5 to 2.5% by weight. 
     
     
         3 . A polarizing plate, comprising the polarizer according to  claim 1  and a transparent protective film provided on at least one side of the polarizer. 
     
     
         4 . The polarizing plate according to  claim 3 , wherein
 a single transmittance is of 43% or more, a polarizing efficiency is of 99.9% or more, and   a dichroic ratio is of 30 or more, wherein the dichroic ratio is calculated from a parallel transmittance (Tp) and a crossed transmittance (Tc) at a wavelength of 440 nm according to the following formula:
   dichroic ratio={log 10 (1 /k   2 )}/{log 10 (1 /k   1 )}, where 
     k   1 =½·√{square root over ( )}2×[( Tp+Tc ) 1/2 +( Tp−Tc ) 1/2   ] and    
     k   2 =½·√{square root over ( )}2×[( Tp+Tc ) 1/2 −( Tp−Tc ) 1/2 ]. 
   
     
     
         5 . An optical film, comprising the polarizer according to  claim 1  and at least one other optical layer laminated with the polarizer or the polarizing plate. 
     
     
         6 . An image display, comprising at least one piece of the polarizer according to  claim 1 .