Method for improving smoothness of film formed from thermosetting liquid coating composition

The present invention provides a method for improving the smoothness of a film formed from a thermosetting liquid coating composition, comprising making adjustments in the application and heat curing of the coating composition onto a substrate, in such a manner that, at a temperature at which the thermal fluidity of the film reaches a maximum before the start of the curing reaction, the film has a storage modulus G' of about 0.5 to about 20 Pa at a stress of 0.5 Pa and a frequency of 0.1 Hz, a loss modulus G'' of about 1.0 to about 20 Pa at a stress of 0.5 Pa and a frequency of 0.1 Hz, and a ratio of the storage modulus G' to the loss modulus G'' (G'/G'') of about 0.3 to about 1.0.