Colored composite microparticles, process for producing the colored composite microparticles, colorant, color filter and ink for ink-jet printing

Abstract

There are provided colored composite microparticles having a fine primary particle diameter and exhibiting a high tinting strength, an excellent dispersibility and an excellent light fastness; a process for producing the colored composite microparticles; and a dispersion of the colored composite microparticles. The colored composite microparticles are composite particles comprising silica and an organic pigment in which the silica is enclosed in the organic pigment and contained in an amount of 0.001 to 9% by weight (calculated as Si) based on the weight of the composite particles. The coloring composition for color filters is prepared by dispersing a colorant for color filters comprising the colored composite microparticles in a coloring composition base material, whereas the ink for ink-jet printing is prepared by dispersing a colorant for inks for ink-jet printing comprising the colored composite microparticles in an ink base solution. The colored composite microparticles have a high tinting strength and are excellent in dispersibility and light fastness, and therefore, can be suitably used in various applications such as ordinarily used paints, printing inks, etc., irrespective of an aqueous system or a solvent system.

1 . Colored composite microparticles comprising silica and an organic pigment, wherein the silica is enclosed in the organic pigment and contained in an amount of 0.001 to 9% by weight, calculated as Si, based on a weight of the colored composite microparticles. 
     
     
         2 . Colored composite microparticles according to  claim 1 , wherein the microparticles have a number-average particle diameter of not more than 200 nm and a volume-average particle diameter of not more than 200 nm. 
     
     
         3 . A dispersion comprising a solvent and the colored composite microparticles as defined in  claim 1  which are dispersed in the solvent. 
     
     
         4 . A dispersion according to  claim 3 , wherein the solvent is water, a water-soluble organic solvent or a mixed solvent of water and the water-soluble organic solvent. 
     
     
         5 . A dispersion according to  claim 3 , wherein the solvent is an organic solvent. 
     
     
         6 . A process for producing the colored composite microparticles as defined in  claim 1 , comprising the steps of:
 adding a surface modifying agent to silica particles;   mixing the surface modifying agent and the silica particles under stirring to coat surface of the silica particles with the surface modifying agent;   then adding an organic pigment to the silica particles coated with the surface modifying agent;   mixing the organic pigment and the coated silica particles under stirring to adhere the organic pigment onto surface of the coated silica particles, thereby obtaining composite particles; and   dissolving out a part of the silica particles and at least a part of the surface modifying agent, which are contained in the resultant composite particles, with an alkali solution.   
     
     
         7 . A colorant for color filters, comprising the colored composite microparticles as defined in  claim 1 . 
     
     
         8 . A coloring composition for color filters, comprising a coloring composition base material and the colorant for color filters as defined in  claim 7  which is dispersed in the base material. 
     
     
         9 . A coloring composition for color filters according to  claim 8 , wherein the colorant for color filters is contained in an amount of 3 to 300 parts by weight based on 100 parts by weight of the coloring composition base material. 
     
     
         10 . A coloring composition for color filters, comprising a solution of a transparent resin containing an acid group, a latent acid group or both of the acid group and the latent acid group, and the coloring composition for color filters as defined in  claim 8  which is dispersed in the transparent resin solution. 
     
     
         11 . A coloring composition for color filters according to  claim 10 , wherein the colorant for color filters contained in the composition has a number-average dispersed particle diameter of 1 to 200 nm and a volume-average dispersed particle diameter of 1 to 200 nm. 
     
     
         12 . A coloring composition for color filters according to  claim 10 , further comprising a photo-radical polymerization initiator and a polyfunctional monomer containing two or more ethylenically unsaturated double bonds. 
     
     
         13 . A coloring composition for color filters according to  claim 10 , further comprising a photo-acid generator. 
     
     
         14 . A color filter comprising a film-shaped product formed from the coloring composition for color filters as defined in  claim 10 . 
     
     
         15 . A color filter according to  claim 14 , wherein the color filter has a light transmittance in each color transmission range of not less than 75%, and a contrast of not less than 800. 
     
     
         16 . A colorant for inks for ink-jet printing, comprising the colored composite microparticles as defined in  claim 1 . 
     
     
         17 . An ink for ink-jet printing, comprising an ink base solution, and the colorant for inks for ink-jet printing as defined in  claim 16  which is dispersed in the ink base solution. 
     
     
         18 . An ink for ink-jet printing according to  claim 17 , wherein the colorant for inks for ink-jet printing is contained in an amount of 1 to 20% by weight based on a weight of the ink base solution.