Process for formation of multi-layered coating film

A process for formation of a multi-layered coating film, which sequentially comprises the following steps (1)-(4):

• (1) a step of coating an organic solvent-based first colored coating composition (A) on an object to be coated to form an uncured first colored coating film,
• (2) a step of coating an organic solvent-based second colored coating composition (B) on the uncured first colored coating film formed in the step (1) to form an uncured second colored coating film,
• (3) a step of coating a clear coating composition (C) on the uncured second colored coating film formed in the step (2) to form a clear coating film, and
• (4) a step of heating the uncured first colored coating film, the uncured second colored coating film and the uncured clear coating film formed in the steps (1)-(3) to cure these three films simultaneously;
• wherein the organic solvent-based first colored coating composition (A) is a coating composition containing (a1) a polyester resin containing a hydroxyl group, which contains a straight-chain alkylene group having a carbon number of 4 or more in the molecule in a content of 1.0-8.0 mol per 1 kg of a solid content of the polyester resin (a1), has a hydroxyl group value in a range of 30-160 mgKOH/g and has a number-average molecular weight in a range of 1,000-6,000, and (a2) a melamine resin;
• and
• the organic solvent-based second colored coating composition (B) is a coating composition containing (b1) an acrylic resin containing a hydroxyl group, which has a hydroxyl group value in a range of 40-200 mgKOH/g and has a weight-average molecular weight in a range of 3,000-15,000, (b2) a melamine resin having a content rate of a mononuclear melamine of 40 mass % or more, and (b3) an acid catalyst.