Actinic-ray-curable coating composition

A method for forming a coating film, comprising:

• applying an active energy ray-curable coating composition as an uppermost layer to a substrate to form an uncured coating film;
• and
• irradiating the uncured coating film with active energy rays to cure the coating film,
• wherein the active energy ray-curable coating composition comprises:
• (A) a polymerizable unsaturated group(s)-containing acrylic resin having a weight average molecular weight in the range of 5,000 to 30,000:
• (B) a urethane (meth)acrylate having a weight average molecular weight in the range of 1.000 or more but less than 5,000 and containing an average of two to four polymerizable unsaturated groups per molecule;
• (C) a polymerizable unsaturated compound having a weight average molecular weight in the range of 200 or more but less than 1,000 and containing an average of two to nine polymerizable unsaturated groups per molecule;
• and
• (D) a photopolymerization initiator,
• wherein the molecular weight between crosslinks of a cured coating film obtained by applying the active energy ray-curable coating composition is in the range of 300 to 900 g/mol, and
• wherein a gloss of a surface coated with the coating film measured based on the specular gloss (60 degrees) according to JIS K5600-4-7 (1999) is 70 or more, on the condition that the surface coated with the coating film is prepared by applying the active energy ray-curable coating composition to an acrylonitrile-butadiene-styrene substrate, acrylonitrile-ethylene-styrene substrate or acrylonitrile-styrene-acrylate substrate to a film thickness of 30 μm using an air spray, setting the substrate at room temperature for 2 minutes and then preheating at 80° C. for 3 minutes, and performing UV irradiation using a metal halide lamp.