Toyobo Co., Ltd.

Shunichiro Baba

Shoji Deguchi

A cavity-containing polyester film is disclosed, including a layer (layer A) which has therein cavities, and layers (layers B) which each include a polyester resin containing inorganic particles and which are laminated, respectively, over both surfaces of the layer A. The layer A includes a composition including a polyester resin and a polypropylene resin. The polypropylene resin satisfies requirements of: (1) the melt flow rate (MFR) ranges from 1.0 to 10 g/10-minutes (at a temperature of 230° C. under a load of 2.16 kg); (2) the deflection temperature is 85° C. or higher under load (at a bending stress of 0.45 MPa); and (3) the weight-average molecular weight Mw ranges from 200,000 to 450000 (measured by gel permeation chromatography (GPC)); and the molecular weight distribution ranges from 2 to 6 (being represented as the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn of the polypropylene resin (Mw/Mn)).

Cavity-containing polyester film and method for producing same

A cavity-containing polyester film is disclosed, including a layer (layer A) which has therein cavities, and layers (layers B) which each include a polyester resin containing inorganic particles and which are laminated, respectively, over both surfaces of the layer A. The layer A includes a composition including a polyester resin and a polypropylene resin. The polypropylene resin satisfies requirements of: (1) the melt flow rate (MFR) ranges from 1.0 to 10 g/10-minutes (at a temperature of 230° C. under a load of 2.16 kg); (2) the deflection temperature is 85° C. or higher under load (at a bending stress of 0.45 MPa); and (3) the weight-average molecular weight Mw ranges from 200,000 to 450,000 (measured by gel permeation chromatography (GPC)); and the molecular weight distribution ranges from 2 to 6 (being represented as the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn of the polypropylene resin (Mw/Mn)).

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Osaka, Japan

Shunichiro Baba