COATING RESIN COMPOSITION, COATING COMPOSITION PRODUCED BY USING THE RESIN COMPOSITION, ITS APPLICATION AND METHOD FOR FORMING COATING FILM

PROBLEM TO BE SOLVED: To obtain a coating composition capable of forming a coating film having improved acid resistance and scratch resistance. SOLUTION: A star-formed polyester oligomer (A) containing blocked hydroxyl groups on the terminals of >=3 branches radially extended from an imaginary center is used as an oligomer containing blocked hydroxyl groups in a coating composition comprising a combination of a blocked hydroxyl group, an epoxy group and an acid anhydride group. The polyester oligomer (A) has a number-average molecular weight of 300-2,500, a weight-average molecular weight of 300-5,000 and a weight-average molecular weight/number-average molecular weight ratio of 1-2. Another component to be used in the resin composition is a vinylpolymerization oligomer consisting of an oligomer containing epoxy group and/or acid anhydride group and having a numberaverage molecular weight of 1,000-10,000, a weight-average molecular weight of 1,000-40,000 and a weight-average molecular weight/number-average molecular weight ratio of 1-4 and containing 1.5-5.0mol of the functional groups in total per 1kg of the resin. The ratio of the polyester oligomer A to the vinyl-polymerizable oligomer B (A/B) is 1/(1-19).