Clear coating composition for an automobile and method of forming a multi-layer coating film using the same

A clear coating composition for an automobile, comprising a hydroxyl group-containing acrylic resin and a polyfunctional isocyanate compound, wherein:

• the hydroxyl group-containing acrylic resin is a hydroxyl group-containing acrylic resin obtained by using hydroxyalkyl (meth) acrylate having a hydroxyalkyl group with 4 to 9 carbon atoms as a monomer;
• at least 60 mass % of the total amount of the polyfunctional isocyanate compound is an isocyanate compound having an isocyanurate structure;
• and
• the clear coating composition is prepared such that the clear coating composition includes 25 to 50 mass % of a soft segment part with respect to a total solid content of the hydroxyl group-containing acrylic resin and the polyfunctional isocyanate compound, a ratio of a soft segment part derived from a lactone-containing monomer with respect to the total solid content of the hydroxyl group-containing acrylic resin and the polyfunctional isocyanate compound is not more than 4.5 mass %, a content ratio of the soft segment part in the hydroxyl-group containing acrylic resin is 7 to 30 mass % with respect to the solid content of the hydroxyl group-containing acrylic resin, a content ratio of the soft segment part in the polyfunctional isocyanate compound is not greater than 60 mass % with respect to the solid content of the polyfunctional isocyanate compound, and that a dynamic glass transition temperature of a cured coating film obtained from the clear coating composition is within a range of 30 to 60° C., the soft segment part being represented by the formula (1) below:
• —(CH2)n— (1)
• wherein n represents an integer of 4 or more, and the soft segment part being present in a main chain or in a cross-linking chain in the clear coating composition.