Highly transparent (with a total light transmittance of 87%; haze 2%) and smooth-surfaced, polyethylene naphthalate (PEN) film has excellent heat stability (thermal shrinkage at 150 deg C×30 mins. is MD/TD 0.1% and 0.0% respectively; at 200 deg C×10 mins., thermal shrinkage is 0.3% for both MD and TD).