| 摘要 |
PURPOSE:To get rid of dimensional change and to decrease the difference of expansion coefficient to the temp. and humidity inside the face, by forming a flexible disk using a polyester film whose surface roughness, anisotropy inside the face of temp. expansion coefficient and humidity expansion coefficient, longitudinal shrinkage factor and lateral shrinkage factor are specific values. CONSTITUTION:A polyester film whose average surface roughness Ra on the center line of the film is 0.003-0.015mum, anisotropy inside the face of temp. expansion coefficient is 6X10<-6>/ deg.C or less, anisotropy inside the face of humidity expansion coefficient is 3X10<-6>/%RH or less, longitudinal shrinkage factor when held at 60 deg.C and 80%RH for 72hr is 0.05-0.2% and lateral shrinkage factor is 0.05-0.5% larger than said longitudinal shrinkage factor, is used. This polyester is an aromatic polyester represented by polyethylene terephthalate and biaxial drawing is thereon carried out. So-called balanced polyester film whose mechanical characteristic are balanced is used. It is preferable that the thickness of the film is 30-80mum. |
