Cellulose ester film

Abstract

A cellulose ester film is disclosed which comprises a polyhydric alcohol ester, which is an ester of one or more kinds of monocarboxylic acids with an aliphatic polyhydric alcohol, wherein the cellulose ester film has a water vapor transmission rate of from 20 to 260 g/m 2 ·24 hours measured under conditions of 25° C. and 90% RH.

1 - 9 . (canceled)  
   
   
       10 . A method for manufacturing a polarizing plate comprising a polarizing film and a cellulose ester film provided on the surface of the polarizing film, the method comprising the steps of: 
 providing a dope containing cellulose ester and a polyhydric alcohol ester, the polyhydric alcohol ester being an ester of one or more kinds of monocarboxylic acids with an aliphatic polyhydric alcohol and having a molecular weight of from 300 to 1500;    casting the dope on a support to form a film;    peeling the film from the support;    drying the peeled film in a tenter to obtain a cellulose ester film; and    providing the cellulose ester film on both surfaces of a polarizing film,    wherein the cellulose ester film has a water vapor transmission rate of from 20 to 260 g/m 2 ·24 hours measured under conditions of 25° C. and 90% RH (relative humidity), and the cellulose ester film has a retention property of from 0.0 to 2.0%.    
   
   
       11 . The method of  claim 10 , wherein at the casting step, the temperature of the support is 0 to 50° C.  
   
   
       12 . The method of  claim 10 , wherein when the film is peeled from the support, the film has residual solvent content of 10 to 120%.  
   
   
       13 . The method of  claim 10 , wherein the drying in the tenter is carried out at a temperature of 40 to 140° C.  
   
   
       14 . The method of  claim 10 , between the dope providing step and the casting step, further comprising a step of filtering the dope through a filter medium.  
   
   
       15 . The method of  claim 14 , wherein the absolute filtration accuracy of the filter medium is from 0.001 to 0.008 mm.  
   
   
       16 . The method of  claim 15 , wherein the absolute filtration accuracy of the filter medium is from 0.003 to 0.006 mm.  
   
   
       17 . The method of  claim 10 , wherein the cellulose ester film contains the polyhydric alcohol ester in an amount of 5 to 20% by weight based on the weight of cellulose ester.  
   
   
       18 . The method of  claim 10 , wherein the monocarboxylic acid has an aromatic ring or a cycloalkyl ring in its molecular structure.  
   
   
       19 . The method of  claim 10 , wherein the aliphatic polyhydric alcohol has a hydroxyl group number of from 2 to 20.  
   
   
       20 . The method of  claim 10 , wherein the cellulose ester film has a thickness of from 10 to 65 μm.  
   
   
       21 . The method of  claim 10 , wherein the aliphatic polyhydric alcohol is represented by the following formula (1):  
       (R 1 )—(OH)n  formula (1)  
     wherein R 1  represents an n-valent aliphatic group; and n represents an integer of not less than 2.  
   
   
       22 . The method of  claim 21 , wherein the n-valent aliphatic group is selected from an alkylene group, an alkenylene group, an alkynylene group, a cycloalkylene group and an alkanetriyl group.  
   
   
       23 . The method of  claim 10 , wherein the polyhydric alcohol ester has an aromatic ring or a cycloalkyl ring in the molecule, the total number of the aromatic ring or the cycloalkyl ring being not less than 3.  
   
   
       24 . The method of  claim 23 , wherein the polyhydric alcohol ester has an aromatic ring and a cycloalkyl ring in the molecule, a total number of the aromatic ring and the cycloalkyl ring being not less than 3.  
   
   
       25 . The method of  claim 10 , wherein the cellulose ester film is subjected to an alkali saponification.  
   
   
       26 . The method of  claim 10 , wherein the monocarboxylic acid is a straight chained or branched fatty acid group having a carbon atom number of from 1 to 32.  
   
   
       27 . The method of  claim 10 , wherein the polyhydric alcohol ester has a molecular weight of from 350 to 750.  
   
   
       28 . The method of  claim 10 , wherein the cellulose ester film satisfies the following formula:  
         P≦ 1−sin 2 (2θ 1 )·sin 2 ( nR   0 /λ)  
     wherein θ 1  (radian) is a value obtained from θ 0 ° which is an angle of the mechanical direction of the film with respect to the delayed phase axis direction, plane R 0  is a retardation in plane of film, and λ is a wavelength (nm) of light used for measuring the three dimensional refractive indices for obtaining R 0  and θ 1 .  
   
   
       29 . A liquid crystal display comprising a liquid crystal cell and a polarizing plate provided on both sides of the liquid crystal cell, wherein the polarizing plate is manufactured according to the method of  claim 10.