Method for producing zirconia-coated titanium oxide fine particles, zirconia-coated titanium oxide fine particles, and use thereof

Zirconia-coated titanium oxide fine particles comprising:

• titanium oxide fine particles satisfying Requirement (a) below;
• and
• zirconia coating layers covering the titanium oxide fine particles and satisfying Requirement (b) below,
• wherein the zirconia-coated titanium oxide fine particles as a whole satisfy Requirement (c) below and have an average particle size of 3 to 50 nm;
• Requirement (a):
• The titanium oxide fine particles contain 60 mass % or more of Ti in terms of the mass of TiO2 and at least one metal element selected from the group consisting of Al, Zr, Sb, Zn, Ni, Fe, Ba, Mg, Sn, Si, and V;
• Requirement (b):
• The amount of the zirconia coating layers per 100 parts by mass of the titanium oxide fine particles is 1 to 50 parts by mass in terms of the mass of ZrO2;
• Requirement (c):
• When the average particle size and the color fading rate of the titanium oxide fine particles are represented by D1 and PA1, respectively, and the average particle size and the color fading rate of the zirconia-coated titanium oxide fine particles are represented by D4 and PA4, respectively, D4/D1 is 0.8 to 1.2 and PA4/PA1 is 0.4 or less.