Zirconium oxide-titanium oxide composite sol and production method thereof

1. A zirconium oxide-titanium oxide composite sol comprising zirconium oxide-titanium oxide composite nanoparticles dispersed in a dispersion medium;

wherein the zirconium oxide-titanium oxide composite nanoparticles have a ZrO 2 /TiO 2 composition ratio of 95/5 to 50/50, and a primary particle diameter of 10 nm or less,

both zirconium oxide and titanium oxide contained in the zirconium oxide-titanium oxide composite nanoparticles have an amorphous crystal structure, and

the dispersion medium is a polar dispersion medium.

2. The zirconium oxide-titanium oxide composite sol according to claim 1 , wherein the composite sol has a haze value of 20% or less.

3. A method for producing a zirconium oxide-titanium oxide composite sol comprising zirconium oxide-titanium oxide composite nanoparticles dispersed in a dispersion medium, the method comprising:

(1) step 1 of mixing a zirconium salt solution and a titanium salt solution so that the ZrO 2 /TiO 2 composition ratio in terms of oxide is 95/5 to 50/50, thereby obtaining a mixed solution;

(2) step 2 of adding a base to the mixed solution to thereby obtain a zirconium-titanium composite hydroxide;

(3) step 3 of dispersing the zirconium-titanium composite hydroxide in a polar dispersion medium to thereby obtain a dispersion;

(4) step 4 of adding an acid to the dispersion to thereby obtain an acid dispersion; and

(5) step 5 of heating the acid dispersion under reflux at 90 to 120° C. to thereby obtain a zirconium oxide-titanium oxide composite sol.