| 摘要 |
PURPOSE:To keep slip properties and to obtain a film having excellent surface scraping resistance, by setting skin thickness of at least one face and the ratio of surface average roughness and skin thickness in a specific ranges. CONSTITUTION:Skin thickness (d) of at least one face and ratio (Ra/d) of film surface average roughness Ra(nm) and d(nm) of a biaxially oriented film whose main components are polyester and a composition comprising of internally deposited particles and/or inert particles, are in the ranges of 50-800nm and 0.03-0.3 respectively. In this film, if the skin thickness is smaller than the above described range, the scraping resistance becomes worse and if this is larger, the slip properties become worse. If the ratio Ra/d is smaller than the above described range, the slip properties become worse and if the ratio is larger, the scraping resistance becomes worse. These tendencies are not desirable. To prepare this film, pellets containing a specific polyester and inert particles and/or internally deposited particles are fed in a melt extruder after these pellets are sufficiently dried and extruded from a slit-shaped die into a sheet-shape, which is cooled and solidified on a casting roll to prepare an undrawn film, which is then oriented by means of biaxial drawing. |
