A curable resin composition comprising: an acetoacetyl functional unsaturated polyester comprising a branched molecular skeleton containing olefinically unsaturated functional groups therein and acetoacetyl functional groups chemically bonded to the branched molecular skeleton, wherein the acetoacetyl functional unsaturated polyester is the reaction product of: (a) reacting by esterification (i) a carboxylic acid component, at least a portion of which carboxylic acid component includes one or more unsaturated di- or poly-basic carboxylic acid, with (ii) an alcohol component, at least a portion of which alcohol component includes one or more di- or poly-basic alcohol, wherein the carboxylic acid component or the alcohol component additionally contains one or more tri- or poly-basic carboxylic acids or alcohols, thereby forming an unsaturated polyester having a hydroxyl value of 350 mg KOH/g or more and having a branched molecular skeleton containing olefinically unsaturated functional groups therein, wherein the molar equivalent ratio of the alcohol component to the carboxylic acid component is 1.5:1 or more; and (b) reacting the unsaturated polyester formed in step (a) with alkyl acetoacetate by transesterification; wherein the molar equivalent ratio of hydroxyl groups in the unsaturated polyester to ester groups in the alkyl acetoacetate ranges from 1.01:1 to 1.2:1; wherein the acetoacetyl functional unsaturated polyester further has a hydroxyl value of between 5 and 80 mg KOH/g, wherein the hydroxyl value is measured according to Standard GB/T 12008.3-2009; and wherein the acetoacetyl functional unsaturated polyester contains: 3 wt% to 6 wt% of the olefinically unsaturated functional groups, relative to the total weight of the acetoacetyl functional unsaturated polyester; and at least 20 wt% of the acetoacetyl functional groups, relative to the total weight of the acetoacetyl functional unsaturated polyester. an acetoacetyl functional unsaturated polyester comprising a branched molecular skeleton containing olefinically unsaturated functional groups therein and acetoacetyl functional groups chemically bonded to the branched molecular skeleton, wherein the acetoacetyl functional unsaturated polyester is the reaction product of: (a) reacting by esterification (i) a carboxylic acid component, at least a portion of which carboxylic acid component includes one or more unsaturated di- or poly-basic carboxylic acid, with (ii) an alcohol component, at least a portion of which alcohol component includes one or more di- or poly-basic alcohol, wherein the carboxylic acid component or the alcohol component additionally contains one or more tri- or poly-basic carboxylic acids or alcohols, thereby forming an unsaturated polyester having a hydroxyl value of 350 mg KOH/g or more and having a branched molecular skeleton containing olefinically unsaturated functional groups therein, wherein the molar equivalent ratio of the alcohol component to the carboxylic acid component is 1.5:1 or more; and (b) reacting the unsaturated polyester formed in step (a) with alkyl acetoacetate by transesterification; (a) reacting by esterification (i) a carboxylic acid component, at least a portion of which carboxylic acid component includes one or more unsaturated di- or poly-basic carboxylic acid, with (ii) an alcohol component, at least a portion of which alcohol component includes one or more di- or poly-basic alcohol, wherein the carboxylic acid component or the alcohol component additionally contains one or more tri- or poly-basic carboxylic acids or alcohols, thereby forming an unsaturated polyester having a hydroxyl value of 350 mg KOH/g or more and having a branched molecular skeleton containing olefinically unsaturated functional groups therein, wherein the molar equivalent ratio of the alcohol component to the carboxylic acid component is 1.5:1 or more; and (i) a carboxylic acid component, at least a portion of which carboxylic acid component includes one or more unsaturated di- or poly-basic carboxylic acid, with (ii) an alcohol component, at least a portion of which alcohol component includes one or more di- or poly-basic alcohol, (b) reacting the unsaturated polyester formed in step (a) with alkyl acetoacetate by transesterification; wherein the molar equivalent ratio of hydroxyl groups in the unsaturated polyester to ester groups in the alkyl acetoacetate ranges from 1.01:1 to 1.2:1; wherein the acetoacetyl functional unsaturated polyester further has a hydroxyl value of between 5 and 80 mg KOH/g, wherein the hydroxyl value is measured according to Standard GB/T 12008.3-2009; and wherein the acetoacetyl functional unsaturated polyester contains: 3 wt% to 6 wt% of the olefinically unsaturated functional groups, relative to the total weight of the acetoacetyl functional unsaturated polyester; and 3 wt% to 6 wt% of the olefinically unsaturated functional groups, relative to the total weight of the acetoacetyl functional unsaturated polyester; and at least 20 wt% of the acetoacetyl functional groups, relative to the total weight of the acetoacetyl functional unsaturated polyester.