Into a 500 ml-volume three-neck flask, 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 were charged. A catalytic amount of 2,2′-azobis(methyl 2-methylpropionate) was added thereto as a radical polymerization initiator, and polymerization was allowed to proceed at 80° C. for 6 hours in a nitrogen stream. The reaction solution was cooled and then poured in a large amount of heptane to precipitate a polymer. The crystal was collected by filtration and dissolved in propylene glycol monomethyl ether acetate, and heptane and methyl isobutyl ketone contained in the solution were removed by distillation under reduced pressure to obtain Polymer A-4 (1-ethoxyethyl acrylate/glycidyl methacrylate/benzyl methacrylate) as a propylene glycol monomethyl ether acetate solution.
