| 摘要 |
PURPOSE:To provide an ultra-thin film having an excellent handling property and a film-forming property and suitable as a raw material for capacitors, etc., by forming a specific readily slipping coating film on the surface of a specific biaxially oriented polyester film. CONSTITUTION:At least one surface of a crystallization orientation-non-finished film just after prepared by melt-forming a polyester such as preferably polyethylene terephthalate and subsequently orienting the formed film in a longitudinally mono-axial direction is coated with an aqueous coating solution containing the fine powder of an organic substance such as polystyrene having an average particle size of 0.05-0.3mum, dried, again oriented in a laterally mono-axial direction and subsequently subjected to a thermal treatment to provide a <=4mum thick ultra-thin film comprising a biaxially oriented polyester film having a density of formula: real density (g/cm<3>) - apparent density (g/cm<3>) = 0.003g/cm<3>, and having surface projections having heights of >=0.13mum in a rate of <=20 surface projections/mm<2> and an easily slipping coating film having a central line average roughness of 0.02-0.15mum and formed on at least one side of the polyester film. |
