| 摘要 |
PURPOSE:To obtain a biaxially stretched polyester film for forming excellent in formability, thickness evenness, heat resistance and surface gloss from a polyester film having specific charcteristics. CONSTITUTION:In polyester constituting a film having characteristics represented by formula [wherein Gs(60 deg.) is the glossiness of a film, X100 is a fine crystal size (A) measured by X-ray diffraction and F100 is strength (average value in the longitudinal and lateral directions of a film ; kg/mm<2>) at the time of 100% elongation in a 150 deg.C atmosphere], the ratio of polyethylene terephthalate is pref. 50mol.% or more, further pref. 70mol.% or more. When the ratio of polyethylene terephthalate is below 50mol.%, no pref. effect is obtained because the strength and heat resistant of a film are lowered. Further, it is also pref. to add fine org. or inorg. particles in order to impart easy slip properties and surface gloss to the film and, as fine particles, it is especially pref. to mainly use fine silicon oxide particles in order to impart desired surface gloss efficiently. |
