Optical film, method for producing the same, polarizing plate and image display device

Abstract

Optical film having a transparent support and optical functional layer as the outermost layer. The optical functional layer is on or above the transparent support; has a thickness of 50-250 nm; and contains low refractive index fine particles having a refractive index of ≦1.45 and arranged substantially in a line on a surface of the optical functional layer on the opposite side of the transparent support, high refractive index fine particles having a refractive index of ≧1.55 and unevenly distributed in a lower part of the optical functional layer on the side of the transparent support, and a fluorine-containing compound.

1 . An optical film, comprising:
 a transparent support; and   an optical functional layer as the outermost layer of the optical film, the optical functional layer being provided on or above the transparent support,   wherein the optical functional layer has a thickness of 50 nm or more and not more than 250 nm;   the optical functional layer contains low refractive index fine particles having a refractive index of not more than 1.45, high refractive index fine particles having a refractive index of 1.55 or more, and a fluorine-containing compound;   the low refractive index fine particles are arranged substantially in a line on a surface of the optical functional layer on the opposite side of the transparent support; and   the high refractive index fine particles are unevenly distributed in a lower part of the optical functional layer on the side of the transparent support.   
     
     
         2 . The optical film according to  claim 1 ,
 wherein the optical functional layer contains the low refractive index fine particles in a range of from 5% by mass to 15% by mass with respect to the entire solid content of the optical functional layer.   
     
     
         3 . The optical film according to  claim 1 ,
 wherein the optical functional layer contains the high refractive index fine particles in a range of from 30% by mass to 50% by mass with respect to the entire solid content of the optical functional layer.   
     
     
         4 . The optical film according to  claim 1 ,
 wherein the low refractive index fine particles are silica fine particles or hollow silica fine particles.   
     
     
         5 . The optical film according to  claim 1 ,
 wherein a ratio of [(P Lu /P Lt )×100] is 200% or more,   in which P Lt  represents an average particle packing factor of the low refractive index fine particles in the whole layer of the optical functional layer; and   P Lu  represents an average particle packing factor of the low refractive index fine particles in the 30% thickness in an upper part of the optical functional layer on the opposite side of the transparent support.   
     
     
         6 . The optical film according to  claim 1 ,
 wherein a ratio of [(P Hd /P Ht )×100] is 120% or more,   in which P Ht  represents an average particle packing factor of the high refractive index fine particles in the whole layer of the optical functional layer; and   P Hd  represents an average particle packing factor of the high refractive index fine particles in the 50% thickness in a lower part of the optical functional layer on the side of the transparent support.   
     
     
         7 . The optical film according to  claim 1 ,
 wherein the low refractive index fine particles are surface-modified with a fluorine atom-free silane coupling agent.   
     
     
         8 . The optical film according to  claim 1 ,
 wherein the high refractive index fine particles are oxide fine particles of at least one element selected from the group consisting of aluminum, zirconium, titanium, zinc, germanium, indium, tin, antimony and cerium.   
     
     
         9 . A polarizing plate, comprising:
 the optical film according to  claim 1  as a protective film for the polarizing plate.   
     
     
         10 . An image display device, comprising:
 the optical film according to  claim 1 .   
     
     
         11 - 16 . (canceled)