PURPOSE: To enhance a heat sealing strength of a covering film by applying a heat sealable acrylatepolymer paint or vinylidene chloride polymer paint to a primer coating surface covering at least one surface of a substrate layer made of a polyolefiln film.

CONSTITUTION: The heat sealable packaging film comprises a substrate layer made of a polyolefin film. The layer is longitudinally oriented. A primer paint is applied to at least one surface of the layer. The primer has a flow transition point (Tg) of 0 to 50°C. A film structure is laterally oriented. A heat sealable layer is existed on the primer coated film. The heat sealable layer is an acrylate polymer or vinylidene chloride polymer. When the primer paint is used between the layer and the heat sealable overcoating paint, an adhesion force of an unexpected high level is obtained. In addition, the primer has excellent transparency, and heat sealing strength of the overcoating paint is improved.