Patent ID: 8829080

Claim:
A coating agent comprising: core-shell type resin particles (A) comprising a shell layer comprising a urethane resin (a1), which comprises an aliphatic cyclic structure with 2000 to 5500 mmol/kg relative to the total amount of the urethane resin (a1) and at least one functional group selected from the group consisting of a carboxyl group and a carboxylate group, and a core layer comprising a vinyl polymer (a2) which is a (meth)acrylic acid ester copolymer having 50 to 150 mmol/kg of a tertiary amino group relative to the total amount of the core-shell type resin particles (A); a compound (B) comprising an epoxy group and an alkoxysilyl group; and a water-based medium, wherein the core-shell type resin particles (A) is obtained by reacting polyols including a carboxyl group-containing polyol (a1-1) and an aliphatic cyclic structure-containing polyol (a1-2) with polyisocyanate containing an aliphatic cyclic structure-containing polyisocyanate (a-3) to yield an aqueous dispersion of the urethane resin (a1); and then in the aqueous dispersion, polymerizing a vinyl monomer containing a vinyl monomer having a basic nitrogen atom-containing group to yield the vinyl polymer (a2), and the vinyl polymer (a2) is obtained by polymerizing vinyl monomers including a (meth)acrylic acid ester monomer containing a tertiary amino group, and the amount of the (meth)acrylic acid ester monomer containing a tertiary amino group is in the range of 0.1 to 10 mass % relative to the total amount of the vinyl monomer used in the production of the vinyl polymer (a2).