Ammonia → Silicon tetramethoxide

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The fine particles used were composite inorganic fine particles of silica and titania (average particle diameter: 100 nm). The fine particles were produced in the following manner according to the method disclosed in Production Example and Example of JP-A-7-2520. 140 g of methanol, 260 g of isopropanol and 100 g of aqueous ammonia (25% by weight) were charged in a 4-L glass reactor equipped with stirring blades to prepare a reaction solution, which was stirred while the temperature of the reaction solution was maintained to 40° C. 542 g of silicon tetramethoxide (Si(OMe)4, Methyl Silicate 39, a trade name, produced by Colcoat Co., Ltd.) was charged in a 3-L conical flask, and 195 g of methanol and 28 g of a 0.1% by weight aqueous solution of hydrochloric acid (obtained by diluting 35% hydrochloric acid, produced by Wako Pure Chemical Industries, Ltd. with water to 1/1,000) were added thereto under stirring, followed by further stirring for about 10 minutes. Subsequently, a solution obtained by diluting 300 g of titanium tetraisopropoxide (Ti(O-i-Pr)4, A-1 (TPT), a trade name, produced by Nippon Soda Co., Ltd.) with 634 g of isopropanol was added thereto to obtain a transparent uniform solution (copolycondensate of silicon tetraalkoxide and titanium tetraalkoxide). 1,699 g of the uniform solution and 480 g of aqueous ammonia (25% by weight) were simultaneously added dropwise to the aforementioned reaction solution over 2 hours at a small dropping rate in the initial stage, which was gradually increased toward the final stage. After completing the dropwise addition, the resulting cohydrolyzate was filtered and dried at 50° C. to remove the organic solvents, and it was then dispersed in water to obtain fine particles having a concentration of 10% by weight and a refractive index of 1.56.

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