Hollow Silica Microparticles, Compositions for Forming Transparent Coating Film Containing the Same, and Substrate Having Transparent Coating Film

Abstract

Hollow silica microparticles suppress whitening of a transparent coating film and show excellent abrasion resistance and adhesiveness. The microparticles having the average particle diameter of 5 to 300 nm and the specific surface area of 50 to 1500 m2/g, and also having an outer shell in which cavities are formed. The microparticles lose the weight by 1.0 W % or more at a temperature range from 200° C. to 500° C. when measured by the thermogravimetry (TG), and the microparticles have a positive DTA peak at the temperature range when measured by the differential thermogravimetric analysis (DTA).

1 . Hollow silica microparticles having an average particle diameter of 5 to 300 nm when measured by the dynamic light scattering method, and a specific surface area of 50 to 1500 m 2 /g, and also having an outer shell in which cavities are formed, wherein the microparticles lose the weight by 1.0 W % or more at a temperature in the range from 200° C. to 500° C. when measured by the thermogravimetry (TG). 
     
     
         2 . The hollow silica microparticles according to  claim 1 , wherein the microparticles have a positive DTA peak when measured by the differential thermogravimetric analysis (DTA) at a temperature in the range from 200° C. to 500° C. 
     
     
         3 . The hollow silica microparticles according to  claim 1 , wherein the hollow silica microparticles have an organic group directly bonded to a silicon atom on a surface thereof. 
     
     
         4 . The hollow silica microparticles according to  claim 3 , wherein the organic group is at least one selected from the group consisting of saturated or unsaturated hydrocarbon groups having 1 to 18 carbon atoms and halogenated hydrocarbon groups having 1 to 18 carbon atoms. 
     
     
         5 . A method of producing the hollow silica microparticles according to  claim 1 , the method comprising the steps of:
 preparing an organosol in which hollow silica microparticles are dispersed with the silica concentration of 1 to 70 W %; and   adding a silane compound and an alkali catalyst to the organosol at a temperature in the range from 30° C. to 300° C. to react the silane compound to the hollow silica microparticles under the condition where a quantity of water against the added silica (the hollow silica microparticles) is in the range from 0.1 to 50 W %.   
     
     
         6 . The method of producing hollow silica microparticles according to  claim 5 , wherein a quantity of added silane compound is in the range from 1 to 50 weight portions against 100 weight portions of the hollow silica microparticles, and a quantity of added alkali catalyst is in the range from 20 to 2,000 ppm against the organosol. 
     
     
         7 . Compositions for forming a transparent coating film, wherein the composition contains the hollow silica microparticles according to  claim 1  and a binder. 
     
     
         8 . A transparent film-coated substrate, wherein the substrate has a transparent coating film prepared by curing the composition for forming a transparent coating film according to  claim 7 . 
     
     
         9 . The hollow silica microparticles according to  claim 4 , wherein the hollow silica microparticles have an organic group expressed by the following general formula (1) or general formula (2), and the microparticles lose the weight by 1.5 W % or more at a temperature in the range from 200° C. to 500° C. when measured by the thermogravimetry (TG):
   —R—OC(═O)CCH 3 ═CH 2   General formula (1)   (R: A bivalent hydrocarbon group having 1 to 12 carbon atoms)
   —R—OC(═O)CH═CH 2   General formula (2) 
   (R: A bivalent hydrocarbon group having 1 to 12 carbon atoms)   
     
     
         10 . The hollow silica microparticles according to  claim 4 , wherein the hollow silica microparticles have the organic group expressed by the following general formula (3):
   —R—C n F a H b   General formula (3)   (a+b=2n+1, n is an integer of 1 to 3, while R is a bivalent hydrocarbon group having 1 to 12 carbon atoms).   
     
     
         11 . The compositions for forming a transparent coating film according to  claim 7 , wherein a surface charge (Q A ) of the hollow silica microparticles contained in the compositions for forming a transparent coating film is in the range from 5 to 20 μeq/g. 
     
     
         12 . The compositions for forming a transparent coating film according to  claim 11 , wherein a concentration (C PA )of the hollow silica microparticles contained in the compositions for forming a transparent coating film is in the range from 0.1 to 20 W % and a concentration(C M ) of the binder as a solid component is in the range from 1 to 50 W %, and a solvent is a polar one. 
     
     
         13 . The compositions for forming a transparent coating film according to  claim 7 , wherein the compositions for forming a transparent coating film contain the hollow silica microparticles with the surface charge (Q A ) in the range from 5 to 20 μeq/g and also contain metal oxide microparticles with the surface charge (Q B ) in the range from 51 to 150 μeq/g, and a value of difference between the surface charge (Q B ) of the metal oxide microparticles and the surface charge (Q A ) of the hollow silica microparticles [(Q B )-(Q A )] is in the range from 20 to 100 μeq/g. 
     
     
         14 . The compositions for forming a transparent coating film according to  claim 13 , wherein a concentration (C PA ) of the hollow silica microparticles contained in the compositions for forming a transparent coating film is in the range from 0.1 to 20 W %, a concentration (C PB ) of the metal oxide microparticles is in the range from 0.1 to 20 W %, a concentration (C M ) of the binder as a solid component is in the range from 1 to 50 W %, and a solvent is a polar one. 
     
     
         15 . A transparent film-coated substrate having a having a transparent film (with the thickness of 100 nm to 10000 nm) prepared by curing the compositions for forming a transparent film according to  claim 11  formed on a surface thereof, wherein the hollow silica microparticles are unevenly distributed and dispersed in the outer side from the middle point of the transparent film in the depth direction. 
     
     
         16 . The transparent film-coated substrate according to  claim 15 , wherein the hollow silica microparticles are unevenly distributed and dispersed in the single-layered state or in the multilayered state. 
     
     
         17 . A transparent film-coated substrate having a transparent film (with the thickness of 100 nm to 10000 nm) prepared by curing the compositions for forming a transparent film according to  claim 13 , wherein the hollow silica microparticles are unevenly distributed and dispersed in the outer side from the middle point of the transparent film in the depth direction, and the metal oxide microparticles are unevenly distributed and dispersed in the inner side from the middle point in the depth direction. 
     
     
         18 . The transparent film-coated substrate according to  claim 17 , wherein the hollow silica microparticles are unevenly distributed and dispersed in the single-layered state or in the multilayered state, and also the metal oxide microparticles are unevenly distributed and dispersed in the single-layered state or in the multilayered state. 
     
     
         19 . Hollow silica microparticles having an average particle diameter of 5 to 300 nm when measured by the dynamic light scattering method, and a specific surface area of 50 to 1500 m 2 /g, and also having an outer shell in which cavities are formed, wherein the hollow silica microparticles lose the weight by 1.0 W % or more at a temperature in the range from 200° C. to 500° C. when measured by the thermogravimetry (TG), the hollow silica microparticles have a positive DTA peak at the temperature range when measured by the differential thermogravimetric analysis (DTA) and also have an organic group directly bonded to a silicon atom on a surface thereof, and the surface charge (Q A ) is in the range from 5 to 20 μeq/g. 
     
     
         20 . A method of producing the hollow silica microparticles according to  claim 1 , the method comprising the steps of:
 preparing an organosol with the silica concentration of 1 to 70 W % in which hollow silica microparticles are dispersed in an organic solvent; and   adding a silane compound and/or a multifunctional acrylic acid ester resin having a hydrophobic functional group, and an alkali catalyst to the organosol to react the silane compound to the hollow silica microparticles under the condition that a quantity of water is in the range from 0.1 to 50 W % against a quantity of silica blended therein.