To obtain the subject binder having excellent adhesion to plastic films such as a polyester, nylon, polyethylene or polypropylene by including a terpenic resin and a polyurethane resin.

This binder is obtained by including (A) a terpenic resin (e.g. α-pinene or β-pinene) and (B) a polyurethane resin as principal components. The weight ratio A/B of the components A to B is preferably (1/99) to (70/30). The component A having 500-2,000 weight-average molecular weight is preferably used. The component B is prepared by reacting a polymeric diol with a diisocyanate compound, a chain extender and a chain terminator. The binder is used as a resin solution and is preferably regulated to 15-60 wt.% concentration of the resin solid content and 50-100,000 cP viscosity at 25°C.