| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a white polyester film improved in hiding power, heat resistance, and long-term storage stability, wherein the average titanium dioxide concentration in the film is specified, and the melting point of the film is specified. SOLUTION: In the white polyester film, the average titanium dioxide concentration in the film is 5-50 wt.%, the melting point of the film is 246-270 deg.C, and the melting subpeak of the film is 120-220 deg.C. It is desirable that the polyester has a diethylene glycol content of at most 5 wt.% and a terminal carboxyl content of 25-65 eq/t. Further, it is desirable that the film has an intrinsic viscosity of 0.45-0.75 dl/g and a degree of orientation of 0.3-0.7. It is desirable to add, in addition to the titanium dioxide particles, 0.005-0.5 wt.% at least one type of particles optionally selected from internal particles, inorganic particles, organic particles, and like particles having a mean particle diameter of 0.01-10μm. The titanium dioxide used is desirably rutile type one having a mean particle diameter of 0.1-0.5μm.</p> |
