| 摘要 |
PURPOSE:To make handleability excellent in the preparation of a film and the formation of base paper and to enhance printing grade and printing durability by setting the thickness, surface center line average roughness and heat shrinkage factor of a polyester film containing a butylene terephthalate unit in a specific amount or more to specific ranges. CONSTITUTION:Polyester contains 50mol.% or more of a butylene terephthalate unit necessarily and the remaining component thereof is composed of one or more kind of a unit other than the butylene terephthalate unit. The necessary thickness of a film is 0.5 - 8mum, pref., 0.5 - 5mum. In order to perforate the film uniformly and rapidly, the heat shrinkage factor of the film after treatment at 150 deg.C for 3min must be at least 5 - 30% in one direction of the film. The surface center line average roughness of the film is 0.02 - 0.5mum, pref., 0.02 - 0.3mum, further pref. 0.03 - 0.2mum. When the center line average roughness is below 0.02mum, workability is inferior and, when said roughness exceeds 0.5mum, resolving power and printing grade are made inferior. |
