Aqueous dispersion of acrylic urethane composite resin particles, aqueous coating composition, method of forming coating film, and method of forming multilayer coating film

An aqueous coating composition comprising an aqueous dispersion of acrylic urethane composite resin (AB) particles comprising:

• a urethane resin portion (A) produced from constituent components including a compound (a1) having a secondary amino group and an alkoxysilyl group and an isocyanate group-containing urethane prepolymer (a2);
• an acrylic resin portion (B) produced from constituent components including a compound (b) having a polymerizable unsaturated group and having no hydroxyl group or one hydroxyl group, and
• further containing at least one resin selected from the group consisting of an acrylic resin (C) and a polyester resin (D), wherein
• the compound (a1) having a secondary amino group and an alkoxysilyl group is produced from constituent components including a compound (a11) containing a primary amino group and an alkoxysilyl group and a polymerizable unsaturated group-containing compound (a12), and the isocyanate group-containing urethane prepolymer (a2) is produced from constituent components including a polyisocyanate component (a21) and a polyol component (a22).