Optical compensation film, polarizing plate and liquid crystal display

Abstract

An optical compensation film wherein: (i) molecules of a liquid crystalline compound are oriented in a manner that an average tilt angle of the compounds is not more than 4 degrees; (ii) the orientation is fixed; (iii) Ro(λ) values are: at wavelength 589 nm: 40-130 nm; at 600 nm: 35-125 nm; and at 630 nm: 35-120 nm; (iv) Rt(λ) valuea are 120-400 nm in λ range of 500-630 cm; and (v) Values of Ro(589), Ro(600) and Ro(630) satisfy the following formulae: 1.0<B<7.0 B =( Ro (589)− Ro (630))/( Ro (600)− Ro (630)).

1 . A polarizing plate comprising: (i) an optical: compensation film and (ii) a polarizing film or a polarizing element, wherein an angle between an in-plane delayed phase axis of the optical compensation film and an absorbing axis of the polarizing film or of the polarizing element is 85-95 degrees,
 wherein the optical compensation film comprises a support exhibiting optical biaxiality, on which at least one optically anisotropic layer is provided,   wherein:
 (i) the optically anisotropic layer is formed by orienting molecules of a liquid crystalline compound in a manner that an average tilt angle of the molecules is not more than 4 degrees followed by fixing the orientation of the liquid crystal molecules; 
 (ii) in-plane retardation values of the optical compensation film Ro(λ) given by Formula (1) are as follows,
   Ro(589): 40-130 nm 
   Ro(600): 35-125 nm 
   Ro(630): 35-120 nm; 
 
   (iii) an out-of-plane retardation value in a thickness direction of the optical compensation film Rt(λ) represented by Formula (2) is in the range of 120-400 nm when measured at wavelengths of 500-630 nm; and   (iv) Ro(589), Ro(600) and Ro(630) satisfy Formula (3),
     Ro λ(λ)=( nx (λ)− ny (λ))× d   Formula (1) 
     Rt (α)=(( nx (λ)+ ny (λ))/2 −nz (λ))× d   Formula (2) 
   1.0<B<7.0  Formula (3) 
   B=(Ro(589)−Ro(630))/(Ro(600)−Ro(630)) nx(λ) representing a refractive index in a x direction which gives a maximum refractive index in the plane of the optical compensation film; ny(λ) representing a refractive index in a y direction which is orthogonal to the x direction in the plane of the optical compensation film; nz(λ) representing a refractive index in the thickness direction of the optical compensation film;   λ representing a wavelength (nm) at which each measurement is carried out; and   d representing a thickness (nm) of the optical compensation film.   
     
     
         2 . A vertically aligned ECB type liquid crystal display having the polarizing plate of  claim 1  on one surface or on both surfaces of a liquid crystal cell of the liquid crystal display. 
     
     
         3 . A vertically aligned ECB type liquid crystal display having the polarizing plate of  claim 1  on one surface or on both surfaces of a liquid crystal cell of the liquid crystal display wherein So(λ) and C(λ) satisfy Formulae (9)−(12):
   0.21 ×C (589)< So ( 589 )<0.66 ×C (589)  Formula (9)     0.22 <Ps (λ)/ Pc (λ)<1.75  Formula (10)       Ps (λ)=( So (λ)/ So (589)1)×100  Formula (11)       Pc (λ)= C (λ)/ C (589)−1)×100  Formula (12)   So(λ) representing a sum of in-plane retardation values (Ro(λ)) of:
 (i) the polarizing films or the polarizing elements of the polarizing plates of  claim 1  provided on one surface or both surfaces of the said liquid crystal cell; 
 (ii) the optical compensation films in the polarizing plates; and 
 (iii) the liquid crystal cell, 
   C(λ) representing a product of a birefringence Δn(λ) and a thickness of the liquid crystal cell, Δn(λ)×d; and   λ representing a wavelength in a range of 500-670 nm.