Microcapsule composition for electrophoretic displays

Abstract

The present invention provides: a microcapsule composition for electrophoretic displays; a production process for the microcapsule composition for the electrophoretic displays; a production process for a sheet for the electrophoretic displays; and a handling method for microcapsules for the electrophoretic displays; wherein the microcapsule composition contains microcapsules and, when used for the electrophoretic displays, can make them as excellent as conventional in various performances (e.g. longtime stability of displaying, respondability of displaying, contrast, and number of times of display rewritability) and, particularly above all, can make the electrophoretic displays exhibit a very high performance as to the contrast. The present invention composition is a composition used for preparation of a coating liquid and comprises an aqueous medium and microcapsules for the electrophoretic displays, wherein the microcapsules include a shell and a dispersion that is capsuled in the shell, wherein the dispersion includes a solvent and electrophoretic fine particles that are dispersed in the solvent; with the composition being characterized by: being a product as obtained without involving the step of drying the microcapsules; and having a microcapsule content of 30 to 80 weight %.

What is claimed is:  
     
         1 . A microcapsule composition for electrophoretic displays, which is a composition used for preparation of a coating liquid and comprises an aqueous medium and microcapsules for the electrophoretic displays, wherein the microcapsules include a shell and a dispersion that is capsuled in the shell, wherein the dispersion includes a solvent and electrophoretic fine particles that are dispersed in the solvent; 
 with the microcapsule composition:    being a product as obtained without involving the step of drying the microcapsules; and    having a microcapsule content of 30 to 80 weight %.    
     
     
         2 . A microcapsule composition according to  claim 1 , wherein the microcapsules have a volume-average particle diameter of 30 to 150 μm and a particle diameter distribution by volume such that: not less than 80 volume % of the microcapsules are present within the particle diameter range of ±40% of the maximum-peak particle diameter around the maximum-peak particle diameter.  
     
     
         3 . A microcapsule composition according to  claim 1 , wherein the total content of the microcapsules and the aqueous medium in the composition is not less than 90 weight %.  
     
     
         4 . A production process for a microcapsule composition for electrophoretic displays, wherein the microcapsule composition includes an aqueous medium and microcapsules for the electrophoretic displays, wherein the microcapsules include a shell and a dispersion that is capsuled in the shell, wherein the dispersion includes a solvent and electrophoretic fine particles that are dispersed in the solvent; 
 with the production process comprising: 
 the dispersing step of dispersing the electrophoretic fine particles into the solvent; and  
 the microcapsuling step of capsuling an electrophoretic fine particle dispersion into the shell in the presence of the aqueous medium, thereby obtaining a preparation liquid including the microcapsules and the aqueous medium, wherein the electrophoretic fine particle dispersion is obtained in the dispersing step;  
   wherein: 
 the composition having a microcapsule content of 30 to 80 weight % is obtained without involving the step of drying the microcapsules.  
   
     
     
         5 . A production process according to  claim 4 , which further comprises: 
 the wet classification step of treating the preparation liquid to classify the microcapsules; and    the concentration step of reducing the aqueous medium from a dispersion resultant from the classification step, thereby concentrating the dispersion.    
     
     
         6 . A production process according to  claim 5 , wherein the preparation liquid to be used in the wet classification step has a microcapsule concentration of not more than 15 weight %.  
     
     
         7 . A production process for a sheet for electrophoretic displays, which comprises the steps of: coating a coating liquid containing a microcapsule composition for the electrophoretic displays; and drying the resultant coating film; thereby producing the sheet for the electrophoretic displays; 
 with the production process:    using, as the composition, the microcapsule composition as recited in  claim 1;  and    further comprising the step of preparing the coating liquid by mixing the composition in such an amount that the coating liquid will have a microcapsule content of 25 to 65 weight %.    
     
     
         8 . A handling method for microcapsules for electrophoretic displays, wherein the microcapsules include a shell and a dispersion that is capsuled in the shell, wherein the dispersion includes a solvent and electrophoretic fine particles that are dispersed in the solvent, in which handling method the microcapsules are handled in the form of a microcapsule composition such that: the microcapsules are present in an aqueous medium; and the microcapsule composition has a microcapsule content of 30 to 80 weight %.