| 摘要 |
PURPOSE:To manufacture a laminated polyester film of superior flame-retardant properties and of no lowered physical properties by making at least a three-layer film and providing layers each having a specified amount of phosphorus atom content different from its adjacent layer. CONSTITUTION:A coextruded film is composed of at least three layers of linear polyester, and the thickness of respective layers is 1mu or more, and the phosphorus atom content is different by 1000ppm or more compared with an adjacent layer, and forms a uniaxially or biaxially oriented polyester laminated film. As for the linear polyester constituting respective layers of the film, although polyester or repeating unit of polyethylene terephthalate is mainly used, any material which can be made into a film or oriented can be used, regardless of its formation. The limiting viscosity of linear polyester is 0.4 to 1.0. If the limiting viscosity is under 0.4, strength is easily lowered as a laminated film, while if more than 1.0, melting viscosity is too high and fluidity or the like is damaged. |
