A 500 ml three-necked flask was charged with 43.3 g (0.3 mol) of 1-ethoxyethyl acrylate, 25.6 g (0.18 mol) of glycidyl methacrylate, 21.2 g (0.12 mol) of benzyl methacrylate and 300 ml of methyl isobutyl ketone. A catalytic amount of 2,2′-azobis(methyl 2-methylpropionate) as a radical polymerization initiator was added to the mixture, and polymerization was performed in a nitrogen stream at 80° C. for six hours. The obtained reaction liquid was cooled, and poured in a large volume of heptane, thereby precipitating a polymer. The polymer crystal was collected by filtration, and dissolved in propylene glycol monomethyl ether acetate. The heptane and methyl isobutyl ketone contained in the solution were distilled off in vacuum, thereby obtaining a propylene glycol monomethyl ether acetate solution of polymer A-4 (1-ethoxyethyl acrylate/glycidyl methacrylate/benzyl methacrylate).
